This research was supported by grants from NSFC Emergency Management Project (Grant No. 81741004), the National Natural Science Foundation of China (Grant No. 81860272), the Major Research Plan of the Provincial Science and Technology Foundation of Guangxi (Grant No. AB16380219), the China Postdoctoral Science Foundation Grant (Grant No. 2018M630993), and the Guangxi Natural Science Foundation (Grant No. 2018GXNSFAA281067).

Ethical approval was granted by the Joint Chinese University of Hong Kong&#8213;New Territories East Cluster Clinical Research Ethics Committee (Reference Number: 2013.055)
1. PCR amplification
<ol>
	<li>Prior to starting, remove PCR buffer mix, sample diluent and DNA samples (both test and reference DNA) (see the Table of Materials) from the -20 &#176;C freezer and keep them at room temperature for 20&#8211;30 min to make sure all reagents and DNA are fully thawed. Vortex and briefly spin down before use.</li>
	<li>Measure the concentration of the DNA samples using a spectrophotometer (see Table of Materials). The DNA concentration should be 25 ng/&#181;L; dilute with sample diluent to the appropriate concentration if required. 
	NOTE: The DNA should be extracted and purified to remove interfering substances, such as proteins and high salt concentrations. Non-degraded, high-quality DNA should be used for subsequent PCR amplification and analysis (A260/A280: 1.8&#8211;2.0 and A260/A230: &#62;1.0).</li>
	<li>Label wells of a PCR plate or 0.2 mL PCR tubes to identify reference and tested DNA samples.</li>
	<li>Calculate the number of PCR reactions required for the test samples, 2 reference samples and negative control sample. Prepare PCR Master Mix by adding 15 &#181;L of PCR buffer mix, 2.6 &#181;L of sample diluent and 0.4 &#181;L of polymerase for each reaction. 
	NOTE: A negative control using sample diluent is essential to monitor the PCR performance. Prepare the PCR master mix at room temperature, do NOT pipette on ice. The PCR buffer mix is viscous. Mix the tube and then briefly spin down prior to use.</li>
	<li>Vortex the PCR master mix from step 1.4 for 10&#8211;20 s and spin down. Slowly dispense 18 &#181;L of the mixture into each well or tube.</li>
	<li>Vortex and spin down the DNA samples. Pipette 2 &#181;L of each DNA into the appropriate well or tube for a final PCR volume of 20 &#181;L. Mix by pipetting up and down 5 times. 
	NOTE: The total amount of DNA per reaction should be 50&#8211;100 ng. DNA amounts greater than 150 ng per 20 &#181;L PCR reaction may result in a poor amplification of large repeat alleles. For lower concentrated DNAs, the amount of sample diluent in the PCR master mix can be replaced by DNA solution.</li>
	<li>Seal the plate with adhesive plate sealer, or with tube caps.</li>
	<li>Place the sealed PCR plate or tubes in the thermal cycler with heated lid. Run the program with the following settings: 95 &#176;C for 5 min, followed by 25 cycles of denaturing at 98 &#176;C for 35 s, annealing at 59 &#176;C for 35 s, and extension at 72 &#176;C for 4 min; a final step at 72 &#176;C for 10 min. Hold the PCR products at 4 &#176;C in the cycler until removal for further processing.</li>
	<li>After PCR amplification, purify and analyze the products immediately, or store at +2 to +8 &#176;C overnight. Alternatively, the product can be stored for up to 30 days at -30 to -16 &#176;C.</li>
</ol>
2. Purification of the PCR Products
<ol>
	<li>Preheat the incubator shaker to 65 &#176;C.</li>
	<li>For each PCR reaction, add 80 &#181;L of 1x TE buffer (see the Table of Materials) to the 20 &#181;L of each PCR product from section 1.</li>
	<li>Transfer the sample mixture into a PCR clean-up plate (see Table of Materials) using a multichannel pipette.</li>
	<li>Keep the plate uncovered and place it into the incubator shaker, and incubate at 65 &#176;C while shaking at 1,200 rpm for 10 min.</li>
	<li>After incubation, set the vacuum instrument at 250 mbar (or 25 kPa, 188 mmHg, 7.4 in Hg) and aspirate the solution through the filter for 15 min. Wells should have no liquid remaining.</li>
	<li>Cool the incubator shaker down to 25 &#176;C.</li>
	<li>After the first aspiration, turn off the vacuum and add 50 &#181;L of 1x TE buffer to each well. Do not mix. Aspirate the solution for 10 min using the vacuum settings in step 2.5.</li>
	<li>Dry the bottom of the filter plate by pressing it firmly on a stack of paper towels.</li>
	<li>Add 20 &#181;L of 1x TE buffer into the bottom center of each well. Place the plate in the incubator shaker and incubate at 25 &#176;C while shaking at 1,200 rpm for 5 min.</li>
	<li>After incubation, transfer &#62;15 &#181;L of each purified PCR DNA from step 2.9 to a fresh 96-well PCR plate. The purified DNA can be analyzed directly, or alternatively can be stored at -30 to -16 &#176;C until required.</li>
</ol>
3. Fragment Sizing of PCR Products
<ol>
	<li>Prior to starting, allow DNA dye concentrate, DNA gel matrix, DNA marker, DNA ladder and purified DNA samples from step 2 to equilibrate to room temperature for 30 min.</li>
	<li>Set up the priming station.
	<ol>
		<li>Replace the syringe (see Table of Materials) when using a new batch of reagents.</li>
		<li>Adjust the base plate, and release the lever of the syringe clip and slide it up to the top position.</li>
	</ol>
	</li>
	<li>Start the sizing software (see Table of Materials) and prepare the gel-dye mix.</li>
	<li>Vortex dye concentrate for 10 s and spin down. Add 25 &#956;L of the dye to a gel matrix vial. Vortex the mixed solution well and spin down.
	<ol>
		<li>Transfer the gel-dye mix to a spin filter. Place the spin filter in a microcentrifuge and spin for 10 min at room temperature at 1,500 x g &#177; 20%. 
		NOTE: Protect the solution with dye from light and store at 4 &#176;C after use. The gel-dye mix can be used for about 15 chips once prepared. Allow the gel-dye mix to equilibrate to room temperature for 30 min each time before use.</li>
	</ol>
	</li>
	<li>Load the gel-dye mix.
	<ol>
		<li>Insert a new DNA chip on the priming station. Add 9 &#956;L of gel-dye mix into the well marked with &#8220;G&#8221;. Please ensure the plunger is positioned at the 1 mL mark and then close the priming station.</li>
		<li>Press the syringe plunger down until it is held by the clip. Wait for exactly 30 s then release the clip. Wait for 5 s, and then slowly pull the plunger back to the 1 mL position.</li>
		<li>Open the priming station and add 9 &#956;L of gel-dye mix into the wells marked with &#8220;G&#8221;.</li>
	</ol>
	</li>
	<li>Add 5 &#956;L of marker into the well marked with the ladder symbol and also add 5 &#956;L of marker into each of the 12 sample wells. Do not leave any wells empty.</li>
	<li>Add 1 &#181;L of DNA ladder into the well marked with the ladder symbol. Add 1 &#181;L of PCR product (used wells) from step 3.1 or 1 &#181;L of ultrapure water (unused wells) into each of the 12 sample wells. Put the chip horizontally in the adapter of vortex mixer and vortex for 1 min at the indicated setting (2,400 rpm).</li>
	<li>Insert the chip in the bioanalyzer instrument and run the chip in the instrument within 5 min.</li>
	<li>After the assay is complete, immediately remove the used chip from the instrument.</li>
	<li>Slowly add 350 &#956;L of deionized water into one of the wells of the electrode cleaner. Open the lid of the bioanalyzer and place the electrode cleaner into it. Close the lid and incubate for about 10 s. Open the lid and remove the electrode cleaner. Wait another 10 s to allow the water on the electrodes to evaporate and then close the lid.</li>
</ol>
4. Analyze the Fragment Sizing Results
NOTE: The reference samples should be amplified and analyzed by the same thermal cycler and bioanalyzer in the same batch with the unknown samples.
<ol>
	<li>After the bioanalyzer run completes, export the peak data from each run as a .csv table file for subsequent analysis.</li>
	<li>Start the analysis software and open the exported .csv peak table file from step 4.1.</li>
	<li>Through the QC menu tab, review the regression line fitted to the four points (shown as blue diamonds on the plot) from the two reference samples. The R2 value of the regression line should be &#62;0.98 (typical values exceed 0.999).</li>
	<li>Through the Results menu tab, check the repeat size of each sample whose fragment length(s) is automatically plotted against the linear regression standard curve derived from the reference samples. The software also provides the classification of each sample according to different guidelines.</li>
	<li>Through the Export menu tab, export the result report for each sample with the repeat numbers and diagnostic classification, as well as a summary of sample information and QC report for each run. 
	NOTE: Analysis software allows the use of custom classification guidelines, such as American College of Medical Genetics (ACMG) or Clinical Molecular Genetics Society/ European Society of Human Genetics (CMGS/ESHG) guidelines, as well as predefined classification criteria.</li>
</ol>

<ol>
	<li>Verkerk, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+gene+(FMR-1)+containing+a+CGG+repeat+coincident+with+a+breakpoint+cluster+region+exhibiting+length+variation+in+fragile+X+syndrome.">Identification of a gene (FMR-1) containing a CGG repeat coincident with a breakpoint cluster region exhibiting length variation in fragile X syndrome.</a> Cell. 65, 905-914 (1991).</li><li>Fu, Y. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+of+the+CGG+repeat+at+the+fragile+X+site+results+in+genetic+instability:+resolution+of+the+Sherman+paradox.">Variation of the CGG repeat at the fragile X site results in genetic instability: resolution of the Sherman paradox.</a> Cell. 67, 1047-1058 (1991).</li><li>Antar, L. N., Li, C., Zhang, H., Carroll, R. C., Bassell, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+functions+for+FMRP+in+axon+growth+cone+motility+and+activity-dependent+regulation+of+filopodia+and+spine+synapses.">Local functions for FMRP in axon growth cone motility and activity-dependent regulation of filopodia and spine synapses.</a> Molecular and Cellular Neurosciences. 32, 37-48 (2006).</li><li>Didiot, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+G-quartet+containing+FMRP+binding+site+in+FMR1+mRNA+is+a+potent+exonic+splicing+enhancer.">The G-quartet containing FMRP binding site in FMR1 mRNA is a potent exonic splicing enhancer.</a> Nucleic Acids Research. 36, 4902-4912 (2008).</li><li>Bechara, E. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+function+for+fragile+X+mental+retardation+protein+in+translational+activation.">A novel function for fragile X mental retardation protein in translational activation.</a> PLoS Biology. 7, e16 (2009).</li><li>Ascano, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMRP+targets+distinct+mRNA+sequence+elements+to+regulate+protein+expression.">FMRP targets distinct mRNA sequence elements to regulate protein expression.</a> Nature. 492, 382-386 (2012).</li><li>Kenny, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MOV10+and+FMRP+regulate+AGO2+association+with+microRNA+recognition+elements.">MOV10 and FMRP regulate AGO2 association with microRNA recognition elements.</a> Cell Reports. 9, 1729-1741 (2014).</li><li>Oberle, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instability+of+a+550-base+pair+DNA+segment+and+abnormal+methylation+in+fragile+X+syndrome.">Instability of a 550-base pair DNA segment and abnormal methylation in fragile X syndrome.</a> Science. 252, 1097-1102 (1991).</li><li>Hagerman, R., Lauterborn, J., Au, J., Berry-Kravis, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fragile+X+syndrome+and+targeted+treatment+trials.">Fragile X syndrome and targeted treatment trials.</a> Results and Problems in Cell Differentiation. 54, 297-335 (2012).</li><li>Hatton, D. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autistic+behavior+in+children+with+fragile+X+syndrome:+prevalence,+stability,+and+the+impact+of+FMRP.">Autistic behavior in children with fragile X syndrome: prevalence, stability, and the impact of FMRP.</a> American Journal of Medical Genetics Part A. 140A, 1804-1813 (2006).</li><li>Mattei, J. F., Mattei, M. G., Aumeras, C., Auger, M., Giraud, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=X-linked+mental+retardation+with+the+fragile+X.+A+study+of+15+families.">X-linked mental retardation with the fragile X. A study of 15 families.</a> Human Genetics. 59, 281-289 (1981).</li><li>Backes, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cognitive+and+behavioral+profile+of+fragile+X+boys:+correlations+to+molecular+data.">Cognitive and behavioral profile of fragile X boys: correlations to molecular data.</a> American Journal of Medical Genetics. 95, 150-156 (2000).</li><li>Nolin, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fragile+X+analysis+of+1112+prenatal+samples+from+1991+to+2010.">Fragile X analysis of 1112 prenatal samples from 1991 to 2010.</a> Prenatal Diagnosis. 31, 925-931 (2011).</li><li>Nolin, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+of+the+fragile+X+CGG+repeat+in+females+with+premutation+or+intermediate+alleles.">Expansion of the fragile X CGG repeat in females with premutation or intermediate alleles.</a> American Journal of Human Genetics. 72, 454-464 (2003).</li><li>Fernandez-Carvajal, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+of+an+FMR1+grey-zone+allele+to+a+full+mutation+in+two+generations.">Expansion of an FMR1 grey-zone allele to a full mutation in two generations.</a> Journal of Molecular Diagnostics. 11, 306-310 (2009).</li><li>Terracciano, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+to+full+mutation+of+a+FMR1+intermediate+allele+over+two+generations.">Expansion to full mutation of a FMR1 intermediate allele over two generations.</a> European Journal of Human Genetics. 12, 333-336 (2004).</li><li>Garcia-Arocena, D., Hagerman, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+understanding+the+molecular+basis+of+FXTAS.">Advances in understanding the molecular basis of FXTAS.</a> Human Molecular Genetics. 19, R83-R89 (2010).</li><li>Juncos, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+clinical+findings+in+the+fragile+X-associated+tremor+ataxia+syndrome+(FXTAS).">New clinical findings in the fragile X-associated tremor ataxia syndrome (FXTAS).</a> Neurogenetics. 12, 123-135 (2011).</li><li>Hagerman, R. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intention+tremor,+parkinsonism,+and+generalized+brain+atrophy+in+male+carriers+of+fragile+X.">Intention tremor, parkinsonism, and generalized brain atrophy in male carriers of fragile X.</a> Neurology. 57, 127-130 (2001).</li><li>Conway, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Premature+ovarian+failure+and+FMR1+gene+mutations:+an+update.">Premature ovarian failure and FMR1 gene mutations: an update.</a> Annales d'endocrinologie. 71, 215-217 (2010).</li><li>Conway, G. S., Hettiarachchi, S., Murray, A., Jacobs, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fragile+X+premutations+in+familial+premature+ovarian+failure.">Fragile X premutations in familial premature ovarian failure.</a> Lancet. 346, 309-310 (1995).</li><li>Van Esch, H., Buekenhout, L., Race, V., Matthijs, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Very+early+premature+ovarian+failure+in+two+sisters+compound+heterozygous+for+the+FMR1+premutation.">Very early premature ovarian failure in two sisters compound heterozygous for the FMR1 premutation.</a> European Journal of Medical Genetics. 52, 37-40 (2009).</li><li>Bourgeois, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+fragile+X+premutation+disorders:+expanding+the+psychiatric+perspective.">A review of fragile X premutation disorders: expanding the psychiatric perspective.</a> Journal of Clinical Psychiatry. 70, 852-862 (2009).</li><li>Farzin, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autism+spectrum+disorders+and+attention-deficit/hyperactivity+disorder+in+boys+with+the+fragile+X+premutation.">Autism spectrum disorders and attention-deficit/hyperactivity disorder in boys with the fragile X premutation.</a> Journal of Developmental and Behavioral Pediatrics. 27, S137-S144 (2006).</li><li>Hantash, F. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR1+premutation+carrier+frequency+in+patients+undergoing+routine+population-based+carrier+screening:+insights+into+the+prevalence+of+fragile+X+syndrome,+fragile+X-associated+tremor/ataxia+syndrome,+and+fragile+X-associated+primary+ovarian+insufficiency+in+the+United+States.">FMR1 premutation carrier frequency in patients undergoing routine population-based carrier screening: insights into the prevalence of fragile X syndrome, fragile X-associated tremor/ataxia syndrome, and fragile X-associated primary ovarian insufficiency in the United States.</a> Genetics in Medicine. 13, 39-45 (2011).</li><li>Kraan, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR1+allele+size+distribution+in+35,000+males+and+females:+a+comparison+of+developmental+delay+and+general+population+cohorts.">FMR1 allele size distribution in 35,000 males and females: a comparison of developmental delay and general population cohorts.</a> Genetics in Medicine. 20 (12), 1627-1634 (2018).</li><li>Saul, R. A., Tarleton, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR1-Related+Disorders.">FMR1-Related Disorders.</a> GeneReviews. , (2012).</li><li>Amos Wilson, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consensus+characterization+of+16+FMR1+reference+materials:+a+consortium+study.">Consensus characterization of 16 FMR1 reference materials: a consortium study.</a> Journal of Molecular Diagnostics. 10, 2-12 (2008).</li><li>Kwok, Y. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validation+of+a+robust+PCR-based+assay+for+quantifying+fragile+X+CGG+repeats.">Validation of a robust PCR-based assay for quantifying fragile X CGG repeats.</a> Clinica Chimica Acta. 456, 137-143 (2016).</li><li>Rousseau, F., Rouillard, P., Morel, M. L., Khandjian, E. W., Morgan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevalence+of+carriers+of+premutation-size+alleles+of+the+FMRI+gene--and+implications+for+the+population+genetics+of+the+fragile+X+syndrome.">Prevalence of carriers of premutation-size alleles of the FMRI gene--and implications for the population genetics of the fragile X syndrome.</a> American Journal of Human Genetics. 57, 1006-1018 (1995).</li><li>Tassone, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR1+CGG+allele+size+and+prevalence+ascertained+through+newborn+screening+in+the+United+States.">FMR1 CGG allele size and prevalence ascertained through newborn screening in the United States.</a> Genome Medicine. 4, 100 (2012).</li><li>Dombrowski, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Premutation+and+intermediate-size+FMR1+alleles+in+10572+males+from+the+general+population:+loss+of+an+AGG+interruption+is+a+late+event+in+the+generation+of+fragile+X+syndrome+alleles.">Premutation and intermediate-size FMR1 alleles in 10572 males from the general population: loss of an AGG interruption is a late event in the generation of fragile X syndrome alleles.</a> Human Molecular Genetics. 11, 371-378 (2002).</li><li>Cronister, A., Teicher, J., Rohlfs, E. M., Donnenfeld, A., Hallam, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevalence+and+instability+of+fragile+X+alleles:+implications+for+offering+fragile+X+prenatal+diagnosis.">Prevalence and instability of fragile X alleles: implications for offering fragile X prenatal diagnosis.</a> Obstetrics and Gynecology. 111, 596-601 (2008).</li><li>Hayward, B. E., Kumari, D., Usdin, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+assays+for+the+fragile+X-related+disorders.">Recent advances in assays for the fragile X-related disorders.</a> Human Genetics. 136, 1313-1327 (2017).</li><li>Seltzer, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevalence+of+CGG+expansions+of+the+FMR1+gene+in+a+US+population-based+sample.">Prevalence of CGG expansions of the FMR1 gene in a US population-based sample.</a> American Journal of Medical Genetics Part B Neuropsychiatrics Genetics. 259B, 589-597 (2012).</li><li>Hayward, B. E., Usdin, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assays+for+determining+repeat+number,+methylation+status,+and+AGG+interruptions+in+the+Fragile+X-related+disorders.">Assays for determining repeat number, methylation status, and AGG interruptions in the Fragile X-related disorders.</a> Methods in Molecular Biology. , 49-59 (1942).</li><li>Orrico, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosaicism+for+full+mutation+and+normal-sized+allele+of+the+FMR1+gene:+a+new+case.">Mosaicism for full mutation and normal-sized allele of the FMR1 gene: a new case.</a> American Journal of Medical Genetics. 78, 341-344 (1998).</li><li>Schmucker, B., Seidel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosaicism+for+a+full+mutation+and+a+normal+size+allele+in+two+fragile+X+males.">Mosaicism for a full mutation and a normal size allele in two fragile X males.</a> American Journal of Medical Genetics. 84, 221-225 (1999).</li></ol>

The authors have nothing to disclose.

FXS is the second most common cause of intellectual impairment after trisomy 21, accounting for nearly one-half of X-linked mental retardation30, which may affect approximately 1 in 4,000 males and 1 in 8,000 females. More importantly, nearly 1 in 250&#8211;1,000 females carry a premutation, and this frequency is 1 in 250&#8211;1,600 in males26,31,32,33. Since the risk o...

Fragile X syndrome (FXS) and Fragile X associated disorders, e.g., tremor and ataxia syndrome (FX-TAS), and primary ovarian insufficiency (FX-POI) are mainly caused by cytosine-guanine-guanine (CGG) trinucleotide repeat expansion in the 5&#8217; untranslated region (UTR) of the Fragile X mental retardation-1 (FMR1) gene on Xq27.31,2. The FMR1 encoded protein (FMRP) is a polyribosome-associated RNA-binding protein that functions in neuronal development and synaptic plasticity by regulating alternative splicing, stability, and dendritic transport of mRNA or modulating synthesis of partial postsynaptic proteins3,4,5,6,7.
The dynamic variation with a CGG repeat size of &#62;200 is described as full mutation, which induces the aberrant hypermethylation and subsequent transcriptional silencing of the FMR1 promoter8. The resulting absence or lack of the FMRP protein disrupts normal neuronal development and causes FXS9, characterized by various clinical symptoms, including moderate to severe intellectual disability, developmental delay, hyperactive behaviors, poor contacts and autistic manifestations10,11,12. The presentation in female FXS patients is generally milder than that in males. The CGG repeat size ranging from 55 to 200 and 45 to 54 are classified as premutation and intermediate status, respectively. Due to the high degree of instability, the CGG repeat size in a premutation or intermediate allele presumably expands when transmitted from parents to offspring13,14. Thus, carriers with premutation alleles are at high risk of having children affected with FXS because of the repeat expansion, and in some cases, intermediate alleles can expand their repeat size to the full mutation range over two generations15,16. Furthermore, males with premutation also convey increased risk of developing late-onset FX-TAS17,18,19, while premutation females are predisposed for both FX-TAS and FX-POI20,21,22. Recently, it has been reported that autistic spectrum disorders with developmental delay and problems in social behaviors are presented in children with premutation FMR1 alleles23,24.
To determine the exact CGG repeat size is of great significance for classification and prediction of the FXS and Fragile X-associated disorders25,26. Historically, the CGG repeat region-specific polymerase chain reaction (PCR) with fragment sizing plus Southern blot analysis have been the gold standard for molecular profiling of the FMR1 CGG repeat27. However, traditional specific PCR is less sensitive to large premutations with more than 100 to 130 repeats and is incapable of amplifying full mutations27,28. Furthermore, capillary electrophoresis on a traditional genetic analyzer for repeat sizing fails to detect FMR1 PCR products with more than 200 CGG repeats. The Southern blot analysis enables differentiation of a wider range of repeat size, from normal to full mutation repeat numbers, and has been widely used for confirming full mutations (in males) and differentiating heterozygous alleles with a full mutation from apparently homozygous alleles with normal repeat sizes (in females). However, the resolution for quantifying the repeats is limited. More importantly, this step-by-step testing strategy is labor-intensive, time-consuming, and cost-ineffective.
Here, we present an accurate and robust PCR-based method for quantification of the CGG repeats of FMR1. The first step of this test is PCR amplification of the repeat sequences in the 5&#8217;UTR of the FMR1 promoter using Fragile X PCR kit. The PCR products are purified and fragment sizing is performed on a microfluidic capillary electrophoresis instrument, and subsequent interpretation of the number of CGG repeats using the analysis software by referencing standards with known repeats based on the rationale that PCR fragment length is directly proportional to the number of CGG repeats. The PCR system include reagents that facilitate the amplification of the highly GC-rich trinucleotide repeat region. This PCR-based assay is reproducible and capable of identifying all ranges of CGG repeats of FMR1 promoters. This is a cost-effective method that can find wide application in molecular diagnosis and screening of FXS and Fragile X-related disorders with less turn-around time and investment in equipment and thus, can be utilized in a broader spectrum of clinical laboratories.

<table><tbody><tr><td>Agilent 2100 Bioanalyzer instrument: 0.2 mL PCR tubes</td><td>Axygen</td><td>PCR-02D-C</td><td></td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: 1x TE buffer, pH 8.0, Rnase-free</td><td>Ambion</td><td>AM9849</td><td></td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: 2100 Bioanalyzer instrument</td><td>Agilent</td><td>G2939AA</td><td></td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: 96-well PCR Plate</td><td>Thermo Fisher</td><td>AB0800</td><td></td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: Electrode cartridge</td><td>Agilent</td><td></td><td>Supplies equipment of the 2100 Bioanayzer instrument</td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: IKA vortex mixer</td><td>Agilent</td><td></td><td>Supplies equipment of the 2100 Bioanayzer instrument</td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: Sizing software 2100 Expert software</td><td>Agilent</td><td></td><td>Supplies equipment of the 2100 Bioanayzer instrument</td></tr><tr><td>Agilent 2100 Bioanalyzer instrument: Test chips</td><td>Agilent</td><td></td><td>Supplies equipment of the 2100 Bioanayzer instrument</td></tr><tr><td>Agilent DNA 7500 kit</td><td>Agilent</td><td>5067-1506</td><td>For Fragment sizing</td></tr><tr><td>Agilent DNA 7500 kit: DNA 7500 Ladder (yellow cap)</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: DNA 7500 Markers (green cap)</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: DNA chips</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: DNA Dye Concentrate (blue cap)</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: DNA Gel Matrix Vial (red cap)</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: Electrode Cleaner</td><td>Agilent</td><td></td><td>In kit: Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: Spin Filter</td><td>Agilent</td><td></td><td>Supplies of Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Agilent DNA 7500 kit: Syringe</td><td>Agilent</td><td></td><td>Supplies of Agilent DNA 7500 kit (catalog number: 5067-1506)</td></tr><tr><td>Chip priming station</td><td>Agilent</td><td>5065-4401</td><td>Supplies equipment of the 2100 Bioanayzer instrument</td></tr><tr><td>Cubee Mini-centrifuge</td><td>GeneReach</td><td>aqbd-i</td><td></td></tr><tr><td>Filter plate vacuum Manifold: MultiScreenHTS Vacuum Manifold</td><td>Merck Millipore</td><td>MSVMHTS00</td><td>Vacuum instrument for Filter plate vacuum Manifold for PCR product purification</td></tr><tr><td>Filter plate vacuum Manifold: Silicone stopper</td><td>Merck Millipore</td><td>XX2004718</td><td>Filter plate vacuum Manifold</td></tr><tr><td>Filter plate vacuum Manifold: Vacuum pump</td><td>Merck Millipore</td><td>WP6122050</td><td>Filter plate vacuum Manifold</td></tr><tr><td>Filter plate vacuum Manifold: Waste collection vessel</td><td>Merck Millipore</td><td>XX1004705</td><td>Filter plate vacuum Manifold</td></tr><tr><td>FragilEase Fragile X PCR kit</td><td>PerkinElmer</td><td>3101-0010</td><td>For PCR amplification</td></tr></tbody></table>

a robust polymerase chain reaction-based assay for quantifying cytosine-guanine-guanine trinucleotide repeats in fragile x mental retardation-1 gene

Fragile X syndrome (FXS) and associated disorders are caused by expansion of the cytosine-guanine-guanine (CGG) trinucleotide repeat in the 5&#8217; untranslated region (UTR) of the Fragile X mental retardation-1 (FMR1) gene promoter. Conventionally, capillary electrophoresis fragment analysis on a genetic analyzer is used for the sizing of the CGG repeats of FMR1, but additional Southern blot analysis is required for exact measurement when the repeat number is higher than 200. Here, we present an accurate and robust polymerase chain reaction (PCR)-based method for quantification of the CGG repeats of FMR1. The first step of this test is PCR amplification of the repeat sequences in the 5&#8217;UTR of the FMR1 promoter using a Fragile X PCR kit, followed by purification of the PCR products and fragment sizing on a microfluidic capillary electrophoresis instrument, and subsequent interpretation of the number of CGG repeats by referencing standards with known repeats using the analysis software. This PCR-based assay is reproducible and capable of identifying the full range of CGG repeats of FMR1 promoters, including those with a repeat number of more than 200 (classified as full mutation), 55 to 200 (premutation), 46 to 54 (intermediate), and 10 to 45 (normal). It is a cost-effective method that facilitates classification of the FXS and Fragile X-associated disorders with robustness and rapid reporting time.

The sizing results of the premutation female reference sample (NA20240, repeat sizes of 30 and 80) and the full mutation female reference sample (NA20239, repeat sizes of 20 and 200) are shown in Figure 1A and Figure 1B, respectively. Typically, two marker peaks (lower marker 50 base pairs [bp] and upper marker 10,380 bp) are included in the fragment size profile. There is usually a primer complex peak with a size of nearly 95 bp. Through the reference sample, a...

Watch this Scientific Journal Video about A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene at JoVE.c

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

An accurate and robust polymerase chain reaction-based assay for quantifying cytosine-guanine-guanine trinucleotide repeats in the Fragile X mental retardation-1 gene facilitates molecular diagnosis and screening of Fragile X syndrome and Fragile X-related disorders with shorter turn-around time and investment in equipment.

Fragile X syndrome (FXS) and associated disorders are caused by expansion of the cytosine-guanine-guanine (CGG) trinucleotide repeat in the 5&#8217; ...

a-robust-polymerase-chain-reaction-based-assay-for-quantifying

Research

JoVE Journal

Genetics

7.8K Views.  Jinan University. Deze kosteneffectieve methode kan brede toepassingen vinden in moleculaire diagnose en screening van FXS en Fragile X-gerelateerde aandoeningen. Het is snel in doorlooptijd en minder investeringen in apparatuur. Onze pcr-gebaseerde test kan de classificatie van het volledige spectrum van de FXS en Fragile X-geassocieerde aandoeningen vergemakkelijken, inclusief tussenliggende, premutatie en volledige mutatie met robuustheid en snelle rapportagetijd.De procedure zal worden aangetoond do...

Video: A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

Modified Terminal Restriction Fragment Analysis for Quantifying Telomere Length Using In-gel Hybridization

There are several different techniques for measuring telomere length, each with their own advantages and disadvantages. The traditional approach, Telomere Restriction Fragment (TRF) analysis, utilizes a DNA hybridization technique whereby genomic DNA samples are digested with restriction enzymes, leaving behind telomere DNA repeats and some sub-telomeric DNA. These are separated by agarose gel electrophoresis, transferred to a filter membrane and hybridized to oligonucleotide probes tagged with either chemiluminescence or radioactivity to visualize telomere restriction fragments. This approach, while requiring a larger quantity of DNA than other techniques such as PCR, can measure the telomere length distribution of a population of cells and allows measurement expressed in absolute kilobases. This manuscript demonstrates a modified DNA hybridization procedure for determining telomere length. Genomic DNA is first digested with restriction enzymes (that do not cut telomeres) and separated by agarose gel electrophoresis. The gel is then dried and the DNA is denatured and hybridized in situ to a radiolabeled oligonucleotide probe. This in situ hybridization avoids loss of telomere DNA and improves signal intensity. Following hybridization, the gels are imaged utilizing phosphor screens and the telomere length is quantified using a graphing program. This procedure was developed by the laboratories of Drs. Woodring Wright and Jerry Shay at the University of Texas Southwestern1,2. Here, we present a detailed description of this procedure, with some modifications.

In this article, a detailed protocol for quantifying telomere length using a modified terminal restriction fragment analysis is discussed that provides fast and efficient direct measurement of telomere length. This technique can be applied to a variety of cell sources of DNA for quantifying telomere length.

There are several different techniques for measuring telomere length, each with their own advantages and disadvantages. The traditional approach, Telomere ...

Cancer Research

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment

Complement receptor 1 (CR1), a transmembrane glycoprotein that plays a key role in the innate immune system, is expressed on many cell types, but especially on red blood cells (RBCs). As a receptor for the complement components C3b and C4b, CR1 regulates the activation of the complement cascade and promotes the phagocytosis of immune complexes and cellular debris, as well as the amyloid-beta (A&#946;) peptide in Alzheimer's disease (AD). Several studies have confirmed AD-associated single nucleotide polymorphisms (SNPs), as well as a copy-number variation (CNV) in the CR1 gene. Here, we describe an innovative method for determining the length polymorphism of the CR1 receptor. The receptor includes three domains, called long homologous repeats (LHR)-LHR-A, LHR-C, and LHR-D-and an n domain, LHR-B, where n is an integer between 0 and 3. Using a single pair of specific primers, the genetic material is used to amplify a first fragment of the LHR-B domain (the variant amplicon B) and a second fragment of the LHR-C domain (the invariant amplicon). The variant amplicon B and the invariant amplicon display differences at five nucleotides outside of the hybridization areas of said primers. The numbers of variant amplicons B and of invariant amplicons is deduced using a quantitative tool (high-resolution melting (HRM) curves), and the ratio of the variant amplicon B to the invariant amplicon differs according to the CR1 length polymorphism. This method provides several advantages over the canonical phenotype method, as it does not require fresh material and is cheaper, faster, and therefore applicable to larger populations. Thus, the use of this method should be helpful to better understand the role of CR1 isoforms in the pathogenesis of diseases such as AD.

Here, we describe an innovative method to determine complement receptor 1 (CR1) length polymorphisms for use in several applications, particularly the assessment of susceptibility to diseases such as Alzheimer&#39;s disease (AD). This method could be useful to better understand the role of CR1 isoforms in the pathogenesis of AD.

Complement receptor 1 (CR1), a transmembrane glycoprotein that plays a key role in the innate immune system, is expressed on many cell types, but ...

High Sensitivity 5-hydroxymethylcytosine Detection in Balb/C Brain Tissue

DNA hydroxymethylation is a long known modification of DNA, but has recently become a focus in epigenetic research. Mammalian DNA is enzymatically modified at the 5th carbon position of cytosine (C) residues to 5-mC, predominately in the context of CpG dinucleotides. 5-mC is amenable to enzymatic oxidation to 5-hmC by the Tet family of enzymes, which are believed to be involved in development and disease. Currently, the biological role of 5-hmC is not fully understood, but is generating a lot of interest due to its potential as a biomarker. This is due to several groundbreaking studies identifying 5-hydroxymethylcytosine in mouse embryonic stem (ES) and neuronal cells. Research techniques, including bisulfite sequencing methods, are unable to easily distinguish between 5-mC and 5-hmC . A few protocols exist that can measure global amounts of 5-hydroxymethylcytosine in the genome, including liquid chromatography coupled with mass spectrometry analysis or thin layer chromatography of single nucleosides digested from genomic DNA. Antibodies that target 5-hydroxymethylcytosine also exist, which can be used for dot blot analysis, immunofluorescence, or precipitation of hydroxymethylated DNA, but these antibodies do not have single base resolution.In addition, resolution depends on the size of the immunoprecipitated DNA and for microarray experiments, depends on probe design. Since it is unknown exactly where 5-hydroxymethylcytosine exists in the genome or its role in epigenetic regulation, new techniques are required that can identify locus specific hydroxymethylation. The EpiMark 5-hmC and 5-mC Analysis Kit provides a solution for distinguishing between these two modifications at specific loci. The EpiMark 5-hmC and 5-mC Analysis Kit is a simple and robust method for the identification and quantitation of 5-methylcytosine and 5-hydroxymethylcytosine within a specific DNA locus. This enzymatic approach utilizes the differential methylation sensitivity of the isoschizomers MspI and HpaII in a simple 3-step protocol. Genomic DNA of interest is treated with T4-BGT, adding a glucose moeity to 5-hydroxymethylcytosine. This reaction is sequence-independent, therefore all 5-hmC will be glucosylated; unmodified or 5-mC containing DNA will not be affected. This glucosylation is then followed by restriction endonuclease digestion. MspI and HpaII recognize the same sequence (CCGG) but are sensitive to different methylation states. HpaII cleaves only a completely unmodified site: any modification (5-mC, 5-hmC or 5-ghmC) at either cytosine blocks cleavage. MspI recognizes and cleaves 5-mC and 5-hmC, but not 5-ghmC. The third part of the protocol is interrogation of the locus by PCR. As little as 20 ng of input DNA can be used. Amplification of the experimental (glucosylated and digested) and control (mock glucosylated and digested) target DNA with primers flanking a CCGG site of interest (100-200 bp) is performed. If the CpG site contains 5-hydroxymethylcytosine, a band is detected after glucosylation and digestion, but not in the non-glucosylated control reaction. Real time PCR will give an approximation of how much hydroxymethylcytosine is in this particular site. In this experiment, we will analyze the 5-hydroxymethylcytosine amount in a mouse Babl/C brain sample by end point PCR.

The EpiMark 5-hmC and 5-mC Analysis Kit can be used to analyze and quantitate 5-methylcytosine and 5-hydroxymethylcytosine within a spe cific locus. The kit distinguishes 5-mC from 5-hmC by the addition of glucose to the hydroxyl group of 5-hmC via an enzymatic reaction utilizing &beta;-glucosyltransferase (T4-BGT). When 5-hmC occurs In the context of CCGG, this modification converts a cleavable MspI site to a non-cleavable site.

DNA hydroxymethylation is a long known modification of DNA, but has recently become a focus in epigenetic research.   Mammalian DNA is enzymatically ...

Neuroscience

Digital Polymerase Chain Reaction Assay for the Genetic Variation in a Sporadic Familial Adenomatous Polyposis Patient Using the Chip-in-a-tube Format

The quantitative analysis of human genetic variation is crucial for understanding the molecular characteristics of serious medical conditions, such as tumors. Because digital polymerase chain reactions (PCR) enable the precise quantification of DNA copy number variants, they are becoming an essential tool for detecting rare genetic variations, such as drug-resistant mutations. It is expected that molecular diagnoses using digital PCR (dPCR) will be available in clinical practice in the near future; thus, how to efficiently conduct dPCR with human genetic material is a hot topic. Here, we introduce a method to detect Adenomatous polyposis coli (APC) somatic mosaicism using dPCR with the chip-in-a-tube format, which allows eight dPCR reactions to be simultaneously conducted. Care should be taken when filling and sealing the reaction mixture on the chips. This article demonstrates how to avoid the over- and underestimation of positive partitions. Furthermore, we present a simple procedure for collecting the dPCR product from the partitions on the chips, which can then be used to confirm the specific amplification. We hope that this methods report will help promote the dPCR with the chip-in-a-tube method in genetic research.

Digital polymerase chain reaction (PCR) is a useful tool for the high-sensitivity detection of single nucleotide variants and DNA copy number variants. Here, we demonstrate key considerations for measuring rare variants in the human genome using digital PCR with the chip-in-a-tube format.

The quantitative analysis of human genetic variation is crucial for understanding the molecular characteristics of serious medical conditions, such as ...

Single Droplet Digital Polymerase Chain Reaction for Comprehensive and Simultaneous Detection of Mutations in Hotspot Regions

Droplet digital polymerase chain reaction (ddPCR) is a highly sensitive quantitative polymerase chain reaction (PCR) method based on sample fractionation into thousands of nano-sized water-in-oil individual reactions. Recently, ddPCR has become one of the most accurate and sensitive tools for circulating tumor DNA (ctDNA) detection. One of the major limitations of the standard ddPCR technique is the restricted number of mutations that can be screened per reaction, as specific hydrolysis probes recognizing each possible allelic version are required. An alternative methodology, the drop-off ddPCR, increases throughput, since it requires only a single pair of probes to detect and quantify potentially all genetic alterations in the targeted region. Drop-off ddPCR displays comparable sensitivity to conventional ddPCR assays with the advantage of detecting a greater number of mutations in a single reaction. It is cost-effective, conserves precious sample material, and can also be used as a discovery tool when mutations are not known a priori.

Here, we present a protocol to accurately quantify multiple genetic alterations of a target region in a single reaction using drop-off ddPCR and a unique pair of hydrolysis probes.

Droplet digital polymerase chain reaction (ddPCR) is a highly sensitive quantitative polymerase chain reaction (PCR) method based on sample fractionation ...

Evaluation of Colorectal Cancer Risk and Prevalence by Stool DNA Integrity Detection

Nowadays, stool DNA can be isolated and analyzed by several methods. The long fragments of DNA in stool can be detected by a qPCR assay, which provides a reliable probability of the presence of pre-neoplastic or neoplastic colorectal lesions. This method, called fluorescence long DNA (FL-DNA), is a fast, non-invasive procedure that is an improvement upon the primary prevention system. This method is based on evaluation of fecal DNA integrity by quantitative amplification of specific targets of genomic DNA. In particular, the evaluation of DNA fragments longer than 200 bp allows for detection of patients with colorectal lesions with very high specificity. However, this system and all currently available stool DNA tests present some general issues that need to be addressed (e.g., the frequency at which tests should be carried out and optimal number of stool samples collected at each timepoint for each individual). However, the main advantage of FL-DNA is the possibility to use it in association with a test currently used in the CRC screening program, known as the immunochemical-based fecal occult blood test (iFOBT). Indeed, both tests can be performed on the same sample, reducing costs and achieving a better prediction of the eventual presence of colorectal lesions.

The presented diagnostic FL-DNA kit is a time-saving and user-friendly method to determine the reliable probability of the presence of colorectal cancer lesions.

Nowadays, stool DNA can be isolated and analyzed by several methods. The long fragments of DNA in stool can be detected by a qPCR assay, which provides a ...

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding sites for transcriptional regulators to modulate gene expression. Alterations of CREs have been implicated in various diseases including cancer. While promoters and enhancers have been the primary CREs for studying gene regulation, very little is known about the role of silencer, which is another type of CRE that mediates gene repression. Originally identified as an adaptive immunity system in prokaryotes, CRISPR/Cas9 has been exploited to be a powerful tool for eukaryotic genome editing. Here, we present the use of this technique to delete an intronic silencer in the human RUNX1 gene and investigate the impacts on gene expression in OCI-AML3 leukemic cells. Our approach relies on electroporation-mediated delivery of two preassembled Cas9/guide RNA (gRNA) ribonucleoprotein (RNP) complexes to create two double-strand breaks (DSBs) that flank the silencer. Deletions can be readily screened by fragment analysis. Expression analyses of different mRNAs transcribed from alternative promoters help evaluate promoter-dependent effects. This strategy can be used to study other CREs and is particularly suitable for hematopoietic cells, which are often difficult to transfect with plasmid-based methods. The use of a plasmid- and virus-free strategy allows simple and fast assessments of gene regulatory functions.

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

Direct delivery of preassembled Cas9/guide RNA ribonucleoprotein complexes is a fast and efficient means for genome editing in hematopoietic cells. Here, we utilize this approach to delete a RUNX1 intronic silencer and examine the transcriptional responses in OCI-AML3 leukemic cells.

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding ...

Single-cell Profiling of Developing and Mature Retinal Neurons

Highly specialized, but exceedingly small populations of cells play important roles in many tissues. The identification of cell-type specific markers and gene expression programs for extremely rare cell subsets has been a challenge using standard whole-tissue approaches. Gene expression profiling of individual cells allows for unprecedented access to cell types that comprise only a small percentage of the total tissue1-7. In addition, this technique can be used to examine the gene expression programs that are transiently expressed in small numbers of cells during dynamic developmental transitions8.
This issue of cellular diversity arises repeatedly in the central nervous system (CNS) where neuronal connections can occur between quite diverse cells9. The exact number of distinct cell types is not precisely known, but it has been estimated that there may be as many as 1000 different types in the cortex itself10. The function(s) of complex neural circuits may rely on some of the rare neuronal types and the genes they express. By identifying new markers and helping to molecularly classify different neurons, the single-cell approach is particularly useful in the analysis of cell types in the nervous system. It may also help to elucidate mechanisms of neural development by identifying differentially expressed genes and gene pathways during early stages of neuronal progenitor development.
As a simple, easily accessed tissue with considerable neuronal diversity, the vertebrate retina is an excellent model system for studying the processes of cellular development, neuronal differentiation and neuronal diversification. However, as in other parts of the CNS, this cellular diversity can present a problem for determining the genetic pathways that drive retinal progenitors to adopt a specific cell fate, especially given that rod photoreceptors make up the majority of the total retinal cell population11. Here we report a method for the identification of the transcripts expressed in single retinal cells (Figure 1). The single-cell profiling technique allows for the assessment of the amount of heterogeneity present within different cellular populations of the retina2,4,5,12. In addition, this method has revealed a host of new candidate genes that may play role(s) in the cell fate decision-making processes that occur in subsets of retinal progenitor cells8. With some simple adjustments to the protocol, this technique can be utilized for many different tissues and cell types.

A method for the isolation of single retinal cells and subsequent amplification of their cDNAs is described. Single-cell transcriptomics reveals the degree of cellular heterogeneity present in a tissue and uncovers new marker genes for rare cell populations. The accompanying protocol can be adjusted to suit many different cell types.

Highly specialized, but exceedingly small populations of cells play important roles in many tissues. The identification of cell-type specific markers and ...

Capturing Common Fragile Site Breaks by Native &#947;H2A.X ChIP

Replication stress induced by exposure to extrinsic agents can lead to DNA breaks at common fragile sites, which are regions in the genome known to be prone to structural instability. The &#947;H2A.X chromatin immunoprecipitation (ChIP) assay serves as a powerful tool in genotoxicity studies, as &#947;H2A.X phosphorylation is a well-established marker for DNA double-strand breaks. Traditional &#947;H2A.X ChIP assays, however, are often labor-intensive and involve multiple, time-consuming steps. In this study, we present a simplified yet effective method that combines subcellular fractionation with native ChIP to isolate &#947;H2A.X-associated complexes. This approach is particularly suitable for analyzing &#947;H2A.X-chromatin interactions with enhanced specificity and efficiency. Using subcellular fractionation, chromatin-unbound materials are effectively removed, resulting in a purified chromatin fraction. Subsequent micrococcal nuclease (MNase) digestion under mild conditions allows chromatin fragmentation while preserving physiological interactions between &#947;H2A.X and its associated protein complexes. This preservation is essential for studying native interaction partners involved in DNA damage response pathways. This optimized native ChIP protocol substantially reduces the time and labor associated with conventional &#947;H2A.X ChIP assays. The streamlined procedure not only simplifies the workflow but also yields highly reproducible results, making it particularly advantageous in settings where high-throughput processing of multiple samples is required. This method has broad applicability in studies focused on genome stability, DNA repair, and chromatin biology, where accurate and efficient detection of DNA damage sites is critical. By employing optimized protocols and streamlined steps, this method enables the detection of DNA damage at fragile sites with improved sensitivity and minimal sample handling, making it a valuable tool for studies on genome stability and DNA damage response.

We present a rapid and efficient method to detect common fragile site breaks through native &#947;H2A.X chromatin immunoprecipitation (ChIP). This approach significantly reduces both the time and labor associated with traditional &#947;H2A.X ChIP assays while maintaining high reproducibility and reliability of results.

Replication stress induced by exposure to extrinsic agents can lead to DNA breaks at common fragile sites, which are regions in the genome known to be ...

Biochemistry

Dissecting Cell-Autonomous Function of Fragile X Mental Retardation Protein in an Auditory Circuit by In Ovo Electroporation

Fragile X mental retardation protein (FMRP) is an mRNA-binding protein that regulates local protein translation. FMRP loss or dysfunction leads to aberrant neuronal and synaptic activities in fragile X syndrome (FXS), which is characterized by intellectual disability, sensory abnormalities, and social communication problems. Studies of FMRP function and FXS pathogenesis have primarily been conducted with Fmr1 (the gene encoding FMRP) knockout in transgenic animals. Here we report an in vivo method for determining the cell-autonomous function of FMRP during the period of circuit assembly and synaptic formation using chicken embryos. This method employs stage-, site-, and direction-specific electroporation of a drug-inducible vector system containing Fmr1 small hairpin RNA (shRNA) and an EGFP reporter. With this method, we achieved selective FMRP knockdown in the auditory ganglion (AG) and in one of its brainstem targets, the nucleus magnocellularis (NM), thus providing a component-specific manipulation within the AG-NM circuit. Additionally, the mosaic pattern of the transfection allows within-animal controls and neighboring neuron/fiber comparisons for enhanced reliability and sensitivity in data analyzing. The inducible vector system provides temporal control of gene editing onset to minimize accumulating developmental effects. The combination of these strategies provides an innovative tool to dissect the cell-autonomous function of FMRP in synaptic and circuit development.

Dissecting Cell-Autonomous Function of Fragile X Mental Retardation Protein in an Auditory Circuit by In Ovo Electroporation

Using in ovo electroporation, we devised a method to selectively transfect the auditory inner ear and cochlear nucleus in chicken embryos to achieve a cell-group-specific knockdown of fragile X mental retardation protein during discrete periods of circuit assembly.

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video