Name: dual immunofluorescence of &#947;h2ax and 53bp1 in human peripheral lymphocytes
Uploaded: 2023-07-14T12:00:00
Description: Watch this Scientific Journal Video about Dual Immunofluorescence of Î³H2AX and 53BP1 in Human Peripheral Lymphocytes at JoVE.com

We are grateful to the whole blood donors and all the health personnel who took the blood samples.

The study was approved by the ethical committee of Pisa University, and informed and signed consent was obtained from each donor.
1. Formation of &#947;H2AX and 53BP1 foci
<ol>
	<li>Preparation of samples and mutagenic treatment
	<ol>
		<li>Collect whole blood samples by venipuncture from healthy adult individuals in blood collection (e.g., Vacutainer) tubes containing lithium heparin as an anticoagulant.</li>
		<li>In order to guarantee proper blood sample preserva...

<ol>
	<li>Chatterjee, N., Walker, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+DNA+damage,+repair+and+mutagenesis.">Mechanisms of DNA damage, repair and mutagenesis.</a> Environmental and Molecular Mutagenesis. 58 (5), 235-263 (2017).</li><li>Aleksandrov, R., Hristova, R., Stoynov, S., Gospodinov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chromatin+response+to+double-strand+DNA+breaks+and+their+repair.">The chromatin response to double-strand DNA breaks and their repair.</a> Cells. 9 (8), 1853 (2020).</li><li>Jackson, S. P., Bartek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+DNA-damage+response+in+human+biology+and+disease.">The DNA-damage response in human biology and disease.</a> Nature. 461 (7267), 1071-1078 (2009).</li><li>Dickey, J. S., 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=H2AX:+functional+roles+and+potential+applications.">H2AX: functional roles and potential applications.</a> Chromosoma. 118 (6), 683-692 (2009).</li><li>Her, J., Bunting, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+cells+ensure+correct+repair+of+DNA+double-strand+break.">How cells ensure correct repair of DNA double-strand break.</a> Journal of Biological Chemistry, Thematic Minireview. 293 (27), 10502-10511 (2018).</li><li>Kuo, L. K., Yang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=&#947;-H2AX+-+A+novel+biomarker+for+DNA+double-strand+breaks.">&#947;-H2AX - A novel biomarker for DNA double-strand breaks.</a> In Vivo. 22 (3), 305-310 (2008).</li><li>B&#225;rtov&#225;, E., Legartova, S., Dundr, M., Such&#225;nkov&#225;, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+role+of+the+53BP1+protein+in+genome+protection:+structural+and+functional+characteristics+of+53BP1-dependent+DNA+repair.">A role of the 53BP1 protein in genome protection: structural and functional characteristics of 53BP1-dependent DNA repair.</a> Aging. 11 (8), 2488-2511 (2019).</li><li>Popp, H. D., Brendel, S., Hofman, W., Fabarius, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunofluorescence+microscopy+of+&#947;H2AX+and+53BP1+for+analyzing+the+formation+and+repair+of+DNA+double-strand+breaks.">Immunofluorescence microscopy of &#947;H2AX and 53BP1 for analyzing the formation and repair of DNA double-strand breaks.</a> Journal of Visualized Experiments. (129), 56617 (2017).</li><li>Jezkova, 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=Particles+with+similar+LET+values+generate+DNA+breaks+of+different+complexity+and+reparability:+a+high-resolution+microscopy+analysis+of+&#947;H2AX/53BP1+foci.">Particles with similar LET values generate DNA breaks of different complexity and reparability: a high-resolution microscopy analysis of &#947;H2AX/53BP1 foci.</a> Nanoscale. 10, 1162-1179 (2018).</li><li>Scarpato, R., 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=Kinetics+of+nuclear+phosphorylation+(&#947;-H2AX)+in+human+lymphocytes+treated+in+vitro+with+UVB,+bleomycin+and+mitomycin+C.">Kinetics of nuclear phosphorylation (&#947;-H2AX) in human lymphocytes treated in vitro with UVB, bleomycin and mitomycin C.</a> Mutagenesis. 28 (4), 465-473 (2013).</li><li>Im, K., Mareninov, S., Diaz, M. F. P., Yong, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+introduction+to+performing+immunofluorescence+staining.">An introduction to performing immunofluorescence staining.</a> Methods in Molecular Biology. 1897, 299-311 (2019).</li><li>Sanderson, M. J., Smith, I., Parker, I., Bootman, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fluorescence microscopy. 10, (2014).</li><li>Jamur, M. C., Oliver, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+fixatives+for+immunostaining.">Cell fixatives for immunostaining.</a> Methods in Molecular Biology. , 55-61 (2010).</li><li>Jamur, M. C., Oliver, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Permeabilization+of+the+cell+membrane.">Permeabilization of the cell membrane.</a> Methods in Molecular Biology. 588, 63-66 (2010).</li><li>Hecht, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bleomycin:+New+perspectives+on+the+mechanism+of+action.">Bleomycin: New perspectives on the mechanism of action.</a> Journal of Natural Products. 63, 158-168 (2000).</li><li>Fei, P., El-Deiry, W. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=P53+and+radiation+responses.">P53 and radiation responses.</a> Oncogene. 22, 5774-5783 (2003).</li><li>Mahaney, B. L., Meek, K., Lees-Miller, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repair+of+ionizing+radiation-induced+DNA+double-strand+breaks+by+non-homologous+end-joining.">Repair of ionizing radiation-induced DNA double-strand breaks by non-homologous end-joining.</a> Biochemical Journal. 417 (3), 639-650 (2009).</li><li>Palla, V., 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=Gamma-H2AX:+Can+it+be+established+as+a+classical+cancer+prognostic+factor.">Gamma-H2AX: Can it be established as a classical cancer prognostic factor.</a> Tumor Biology. 39 (3), 1010428317695931 (2017).</li><li>Markov&#224;, E., Hillert, L., Malmgren, L., Persson, B. R. R., Belyaev, I. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwaves+from+GSM+mobile+telephones+affect+53BP1+and+gamma-H2AX+foci+in+human+lymphocytes+from+hypersensitive+and+healthy+persons.">Microwaves from GSM mobile telephones affect 53BP1 and gamma-H2AX foci in human lymphocytes from hypersensitive and healthy persons.</a> Environmental Health Perspectives. 113 (9), 1172-1177 (2005).</li><li>Scarpato, R., 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=Nuclear+damage+in+peripheral+lymphocytes+of+obese+and+overweight+Italian+children+as+evaluated+by+the+&#947;-H2AX+focus+assay+and+micronucleus+test.">Nuclear damage in peripheral lymphocytes of obese and overweight Italian children as evaluated by the &#947;-H2AX focus assay and micronucleus test.</a> The FASEB Journal. 25 (2), 685-693 (2018).</li><li>Shanbhag, N. 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=Early+neuronal+accumulation+of+DNA+double-strand+breaks+in+Alzheimer's+disease.">Early neuronal accumulation of DNA double-strand breaks in Alzheimer's disease.</a> Acta Neuropathologica Communication. 7 (1), 77 (2019).</li><li>Lassmann, 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=In+vivo+formation+of+gamma-H2AX+and+53BP1+DNA+repair+foci+in+blood+cells+after+radioiodine+therapy+of+differentiated+thyroid+cancer.">In vivo formation of gamma-H2AX and 53BP1 DNA repair foci in blood cells after radioiodine therapy of differentiated thyroid cancer.</a> Journal of Nuclear Medicine. 51 (8), 1318-1325 (2010).</li><li>Derlin, T., 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=Assessment+of+&#947;-H2AX+and+53BP1+foci+in+peripheral+blood+lymphocytes+to+predict+subclinical+hematotoxicity+and+response+in+somatostatin+receptor-targeted+radionuclide+therapy+for+advanced+gastroenteropancreatic+neuroendocrine+tumors.">Assessment of &#947;-H2AX and 53BP1 foci in peripheral blood lymphocytes to predict subclinical hematotoxicity and response in somatostatin receptor-targeted radionuclide therapy for advanced gastroenteropancreatic neuroendocrine tumors.</a> Cancers (Basel). 13 (7), 1516 (2021).</li><li>Djuzenova, C. S., 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=Radiosensitivity+in+breast+cancer+assessed+by+the+histone+&#947;-H2AX+and+53BP1+foci.">Radiosensitivity in breast cancer assessed by the histone &#947;-H2AX and 53BP1 foci.</a> Radiation Oncology. 24, 8-98 (2013).</li><li>Atkinson, J., Bezak, E., Kempson, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+DNA+double-strand+breaks+-+are+we+there+yet.">Imaging DNA double-strand breaks - are we there yet.</a> Nature Reviews in Molecular Cell Biology. 23, 579-580 (2022).</li></ol>

Immunofluorescence analysis of &#947;H2AX and 53BP1 foci is a suitable method for assessing genomic damage in interphase nuclei of a cell system. This procedure has several critical points that can affect the outcome of the experiments, mainly, the agents used in fixation and permeabilization, the type of antibodies and their dilution factors, and the concentration of the mutagen.
The maintenance of protein integrity is fundamental since the immunofluorescence method expects to identify antige...

DNA damage is continuously induced by agents that can be endogenous, such as ROS generated by cellular oxidative metabolism, or exogenous, both chemicals and physical1. Among the most harmful lesions, double-strand breaks (DSBs) play a fundamental role in contributing to genomic instability, since they cause chromosome aberrations that in turn can initiate the carcinogenesis process. Thus, cells are provided with complex and efficient mechanisms of DSBs repairing2.
When a DSB occurs, the cell triggers the DNA damage response (DDR) where, together with the MRE11/RAD50/NBS1 complex, ATM or ATR kinases are recruited to activate other proteins that slow down or stop the cell cycle3. An essential target of these kinases is histone H2AX, which is phosphorylated on Ser-139 within a few megabases from the DSBs (namely &#947;H2AX), thereby allowing the recruitment of several repair factors such as, among others, BRCA1 and p53 binding protein 1 (53BP1)3. Later, one pathway among homologous recombination (HR), non-homologous end joining (NHEJ), or single-strand annealing (SSA) is triggered to repair the DSBs4,5. Therefore, 53BP1 is involved in dictating the choice between HR or NHEJ, mainly promoting the activation of NHEJ rather than HR6. Moreover, both the phosphorylated form of H2AX histone and 53BP1 can form foci at the sites of DSBs. As these foci persist until the integrity of the double strand is restored, assessing the appearance/disappearance of &#947;H2AX or 53BP1 foci within a time interval is considered a useful method to evaluate the occurrence and repair of DSBs in a cell system6,7. However, according to the molecular processes above described, since &#947;H2AX and 53BP1 foci are expected to co-localize near the DSBs during DDR8,9, it can be useful to detect concurrently the presence of these markers in a dual immunofluorescence.
Thus, the aim of this manuscript was to evaluate the suitability of the simultaneous quantification of &#947;H2AX and 53BP1 foci to assess the genomic damage induced in human peripheral lymphocytes by the radiomimetic agent bleomycin. Using the same methodology, we also attempted to delineate repair kinetics of bleomycin-induced DSBs according to a previously set up experimental procedure10.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AlexaFluor 568 goat anti-mouse IgG (&#947;1)</td>
			<td>Invitrogen</td>
			<td>A21124</td>
			<td>53BP1 secondary antibody</td>
		</tr>
		<tr>
			<td>Bleoprim</td>
			<td>Sanofi</td>
			<td></td>
			<td>bleomycin sulfate (mutagen)</td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin solution 100X</td>
			<td>Euroclone</td>
			<td>ECB3001D</td>
			<td>antibiotics for culture medium</td>
		</tr>
		<tr>
			<td>PBS 10X</td>
			<td>Termofisher</td>
			<td>14200075</td>
			<td>Phosphate-buffered saline</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Euroclone</td>
			<td>EC20180L</td>
			<td>Fetal Bovine Serum for immunofluorescence</td>
		</tr>
		<tr>
			<td>Goat anti-rabbit IgG (H+L) DyLight 488 Coniugated</td>
			<td>Termofisher</td>
			<td>#35552</td>
			<td>&#947;H2AX secondary antibody</td>
		</tr>
		<tr>
			<td>Mouse anti-53BP1 monoclonal antibody</td>
			<td>Merck</td>
			<td>MAB 3802</td>
			<td>53BP1 primary antibody</td>
		</tr>
		<tr>
			<td>Labophot 2</td>
			<td>Nikon</td>
			<td></td>
			<td>Fluorescence microscope</td>
		</tr>
		<tr>
			<td>P-histone H2AX (Ser139) rabbit antibody</td>
			<td>Cell Signaling</td>
			<td>#2577</td>
			<td>&#947;H2AX primary antibody</td>
		</tr>
		<tr>
			<td>Phytohemoagglutinin</td>
			<td>Termofisher</td>
			<td>R30852801</td>
			<td>component of culture medium</td>
		</tr>
		<tr>
			<td>Prolong gold antifade reagent with DAPI</td>
			<td>Cell Signaling</td>
			<td>#8961</td>
			<td>Antifade solution with DAPI for counterstaining</td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Euroclone</td>
			<td>ECB9006L</td>
			<td>Culture medium</td>
		</tr>
		<tr>
			<td>Triton-X100</td>
			<td>Sigma</td>
			<td>T9284</td>
			<td>Nonionic detergent for permeabilization</td>
		</tr>
	</tbody>
</table>

dual immunofluorescence of &#947;h2ax and 53bp1 in human peripheral lymphocytes

Double strand breaks (DSBs) are one of the most severe lesions that can occur in cell nuclei, and, if not repaired, they can lead to severe outcomes, including cancer. The cell is, therefore, provided with complex mechanisms to repair DSBs, and these pathways involve histone H2AX in its phosphorylated form at Ser-139 (namely &#947;H2AX) and p53 binding protein 1 (53BP1). As both proteins can form foci at the sites of DSBs, identification of these markers is considered a suitable method to study both DSBs and their kinetics of repair. According to the molecular processes that lead to the formation of &#947;H2AX and 53BP1 foci, it could be more useful to investigate their co-localization near the DSBs in order to set up an alternative approach that allows quantifying DSBs by the simultaneous detection of two DNA damage markers. Thus, this protocol aims to assess the genomic damage induced in human lymphocytes by the radiomimetic agent bleomycin through the presence of &#947;H2AX and 53BP1 foci in a dual immunofluorescence. Using this methodology, we also delineated the variation in the number of &#947;H2AX and 53BP1 foci over time, as a preliminary attempt to study the repair kinetics of bleomycin-induced DSBs.

Data obtained by the fluorescence microscope analysis of peripheral lymphocytes allow us to evaluate three main aspects: the effectiveness of bleomycin treatment in increasing the number of &#947;H2AX and 53BP1 foci (and thus of DSBs) due to its mutagenic effect, at what extent both foci co-localized at the site of DSBs, and the time-course of &#947;H2AX and 53BP1 foci to delineate the repair kinetics of bleomycin-induced DSBs. As expected, a very higher frequency of both &#947;H2AX and 53BP1 foci was observed between un...

Watch this Scientific Journal Video about Dual Immunofluorescence of Î³H2AX and 53BP1 in Human Peripheral Lymphocytes at JoVE.com

Dual Immunofluorescence of &#947;H2AX and 53BP1 in Human Peripheral Lymphocytes

This protocol presents a method to assess the formation and repair of DNA double-strand breaks through the simultaneous detection of &#947;H2AX and 53BP1 foci in interphase nuclei of bleomycin-treated human peripheral lymphocytes.

Double strand breaks (DSBs) are one of the most severe lesions that can occur in cell nuclei, and, if not repaired, they can lead to severe outcomes, ...

The aim of this manuscript was to evaluate the suitability of the simultaneous quantification of Gamma H2AX and 53BP1 foci to assess the genomic damage induced in human peripheral lymphocytes by bleomycin. Several factors can cause double strand breaks. Cells are thus provided with several repair mechanisms, involving both Gamma H2AX and 53 Binding Protein 1, that can co-localize near the double strand break.After collecting whole blood samples, add 300 microliters of sample to a tube containing 4.7 milliliters of complete medium. Then add five micrograms per milliliter of bleomycin sulfate final concentration. For each sample, set up a negative control.Put the tube in a thermostat at 37 degrees Celsius for two hours. Centrifuge samples at 540 G for five minutes. Then add five milliliters of hypotonic solution to pellet.Then add 400 microliters of pre fixative solution in order to cause hemolysis. Centrifuge samples at 540 G for five minutes, then resuspend pellet in five milliliters of methanol at room temperature for at least 30 minutes to fix the cells. Centrifuge samples at 540 G for five minutes, then resuspend pellet in five milliliters of fixative solution.Repeat this step once more time. Centrifuge again at 540 G for five minutes, then aspire the supernatant leaving enough solution to resuspend pellet. Drop the resuspended cell pellet on the slides.Prepare the two solutions containing the anti-Gamma H2AX and the anti-53BP1 primary antibodies dissolved in blocking solution. Then wash slides two times in PBS 1X. Then keep slides for 30 minutes in blocking solution.Add to each slide 10 microliters of each of the two solutions containing the primary antibodies dissolved in blocking solution. Cover the slides with parafilm. Incubate at four degrees Celsius overnight.After the incubation, perform three washing in PBS 1X for five minutes. Prepare the two solutions containing the DyLight 488 and Alexa Fluor 568 secondary antibodies dissolved in blocking solution. Then add to each slide 10 microliters of each of the two solutions containing the secondary antibodies dissolved in blocking solution.Cover the slides with parafilm and incubate at room temperature for two hours. After this second incubation, perform three washing in PBS 1X for five minutes. Add 2.5 microliters of Antifade solution with DAPI on the cover slips before assembly to counter stain the nuclei.In order to assess foci kinetic, the procedure is the same as now described. The last phase is observation and quantification of foci. Human lymphocytes without Gamma H2AX and 53BP1 foci are shown in A, in B, and in C, human lymphocytes with different amounts of Gamma H2AX and 53BP1 foci are shown.It is observed a low level of foci co-localization. As expected, a very higher frequency of both Gamma H2AX and 53BP1 foci are observed between untreated untreated cells. Also, a large difference is observed in the number of foci of the two markers.The time course of Gamma H2AX and 53BP1 foci over time showed a different behavior although they contribute to the same function. Gamma H2AX and 53BP1 foci analysis has the ability to evaluate the cellular response in either exposure or pathological contexts. However, Gamma H2AX and 53BP1 dual immunofluorescence can lead to underestimate the true frequency of the event.

dual-immunofluorescence-h2ax-53bp1-human-peripheral

Research

JoVE Journal

Genetics

siRNA Transfection and EMSA Analyses on Freshly Isolated Human Villous Cytotrophoblasts

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend diseases related to pregnancy. In this protocol, human primary villous cytotrophoblasts freshly isolated from placentas through a standard DNase/trypsin protocol are microporated with small interfering RNA (siRNA). This approach provided greater efficiency for siRNA transfection when compared to a lipofection-based method. Transfected cells can subsequently be analyzed by standard Western blot within a time frame of 3-4 days post-transfection. In addition, using cultured primary villous cytotrophoblasts, Electrophoretic Mobility Shift Assay (EMSA) analysis was optimized and performed on extracts from days 1 to 4. The use of these cultured primary cells and the protocol described allow for an evaluation of the implication of specific genes and transcription factors in the process of villous cytotrophoblast differentiation into a syncytiotrophoblast-like cell layer. However, the limited time span allowable in culture precludes the use of methods requiring more time, such as generation of a stable cell population. Therefore testing of this cell population requires highly optimized gene transfer protocols.

This protocol describes a method for efficiently transfecting siRNA in freshly isolated human villous cytotrophoblasts using microporation and identifying DNA-protein complexes in these cells. Transfected cells can be monitored by Western blot and EMSA analyses during the 4-day culture time.

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend ...

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental changes. Considerable progress in our understanding of the tight connection between the circadian clock and most aspects of physiology has been made in the field over the last decade. However, unraveling the molecular basis that underlies the function of the circadian oscillator in humans stays of highest technical challenge. Here, we provide a detailed description of an experimental approach for long-term (2-5 days) bioluminescence recording and outflow medium collection in cultured human primary cells. For this purpose, we have transduced primary cells with a lentiviral luciferase reporter that is under control of a core clock gene promoter, which allows for the parallel assessment of hormone secretion and circadian bioluminescence. Furthermore, we describe the conditions for disrupting the circadian clock in primary human cells by transfecting siRNA targeting CLOCK. Our results on the circadian regulation of insulin secretion by human pancreatic islets, and myokine secretion by human skeletal muscle cells, are presented here to illustrate the application of this methodology. These settings can be used to study the molecular makeup of human peripheral clocks and to analyze their functional impact on primary cells under physiological or pathophysiological conditions.

Here, we describe settings to monitor in parallel circadian bioluminescence and the secretory activity of human islet cells and primary myotubes. For this, we employed lentiviral gene delivery of a luciferase core clock reporter, followed by in vitro synchronization and collection of outflow medium by continuous cell perifusion.

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental ...

Optogenetic Random Mutagenesis Using Histone-miniSOG in C. elegans

Forward genetic screening in model organisms is the workhorse to discover functionally important genes and pathways in many biological processes. In most mutagenesis-based screens, researchers have relied on the use of toxic chemicals, carcinogens, or irradiation, which requires designated equipment, safety setup, and/or disposal of hazardous materials. We have developed a simple approach to induce heritable mutations in C. elegans using germline-expressed histone-miniSOG, a light-inducible potent generator of reactive oxygen species. This mutagenesis method is free of toxic chemicals and requires minimal laboratory safety and waste management. The induced DNA modifications include single-nucleotide changes and small deletions, and complement those caused by classical chemical mutagenesis. This methodology can also be used to induce integration of extrachromosomal transgenes. Here, we provide the details of the LED setup and protocols for standard mutagenesis and transgene integration.

Optogenetic Random Mutagenesis Using Histone-miniSOG in C. elegans

Genetically-encoded histone-miniSOG induces genome-wide heritable mutations in a blue&#160;light-dependent manner. This mutagenesis method is simple, fast, free of toxic chemicals, and well-suited for forward genetic screening and transgene integration.

Forward genetic screening in model organisms is the workhorse to discover functionally important genes and pathways in many biological processes. In most ...

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex is by far the most common pathway to initiate protein synthesis in eukaryotic cells, but stress-specific variations of this complex are now emerging. Purifying cap-binding proteins with an affinity resin composed of Agarose-linked m7GTP (a 5' mRNA cap analog) is a useful tool to identify factors involved in the regulation of translation initiation. Hypoxia (low oxygen) is a cellular stress encountered during fetal development and tumor progression, and is highly dependent on translation regulation. Furthermore, it was recently reported that human adult organs have a lower oxygen content (physioxia 1-9% oxygen) that is closer to hypoxia than the ambient air where cells are routinely cultured. With the ongoing characterization of a hypoxic eIF4F complex (eIF4FH), there is increasing interest in understanding oxygen-dependent translation initiation through the 5' mRNA cap. We have recently developed a human cell culture method to analyze cap-binding proteins that are regulated by oxygen availability. This protocol emphasizes that cell culture and lysis be performed in a hypoxia workstation to eliminate exposure to oxygen. Cells must be incubated for at least 24 hr for the liquid media to equilibrate with the atmosphere within the workstation. To avoid this limitation, pre-conditioned media (de-oxygenated) can be added to cells if shorter time points are required. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. This method allows the user to identify novel oxygen-regulated translation factors involved in cap-dependent translation.

Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex ...

Genome Editing and Directed Differentiation of hPSCs for Interrogating Lineage Determinants in Human Pancreatic Development

Interrogating gene function in self-renewing or differentiating human pluripotent stem cells (hPSCs) offers a valuable platform towards understanding human development and dissecting disease mechanisms in a dish. To capitalize on this potential application requires efficient genome-editing tools to generate hPSC mutants in disease-associated genes, as well as in vitro hPSC differentiation protocols to produce disease-relevant cell types that closely recapitulate their in vivo counterparts. An efficient genome-editing platform for hPSCs named iCRISPR has been developed through the TALEN-mediated targeting of a Cas9 expression cassette in the AAVS1 locus. Here, the protocols for the generation of inducible Cas9 hPSC lines using cells cultured in a chemically defined medium and a feeder-free condition are described. Detailed procedures for using the iCRISPR system for gene knockout or precise genetic alterations in hPSCs, either through non-homologous end joining (NHEJ) or via precise nucleotide alterations using a homology-directed repair (HDR) template, respectively, are included. These technical procedures include descriptions of the design, production, and transfection of CRISPR guide RNAs (gRNAs); the measurement of the CRISPR mutation rate by T7E1 or RFLP assays; and the establishment and validation of clonal mutant lines. Finally, we chronicle procedures for hPSC differentiation into glucose-responsive pancreatic &#946;-like cells by mimicking in vivo pancreatic embryonic development. Combining iCRISPR technology with directed hPSC differentiation enables the systematic examination of gene function to further our understanding of pancreatic development and diabetes disease mechanisms.

Protocols to generate hPSC mutant lines using the iCRISPR platform and to differentiate hPSCs into glucose-responsive &#946;-like cells are described. Combining genome editing technology with hPSC-directed differentiation provides a powerful platform for the systematic analysis of the role of lineage determinants in human development and disease progression.

Interrogating gene function in self-renewing or differentiating human pluripotent stem cells (hPSCs) offers a valuable platform towards understanding ...

Mapping Genome-wide Accessible Chromatin in Primary Human T Lymphocytes by ATAC-Seq

Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) is a method used for the identification of open (accessible) regions of chromatin. These regions represent regulatory DNA elements (e.g., promoters, enhancers, locus control regions, insulators) to which transcription factors bind. Mapping the accessible chromatin landscape is a powerful approach for uncovering active regulatory elements across the genome. This information serves as an unbiased approach for discovering the network of relevant transcription factors and mechanisms of chromatin structure that govern gene expression programs. ATAC-seq is a robust and sensitive alternative to DNase I hypersensitivity analysis coupled with next-generation sequencing (DNase-seq) and formaldehyde-assisted isolation of regulatory elements (FAIRE-seq) for genome-wide analysis of chromatin accessibility and to the sequencing of micrococcal nuclease-sensitive sites (MNase-seq) to determine nucleosome positioning. We present a detailed ATAC-seq protocol optimized for human primary immune cells i.e. CD4+ lymphocytes (T helper 1 (Th1) and Th2 cells). This comprehensive protocol begins with cell harvest, then describes the molecular procedure of chromatin tagmentation, sample preparation for next-generation sequencing, and also includes methods and considerations for the computational analyses used to interpret the results. Moreover, to save time and money, we introduced quality control measures to assess the ATAC-seq library prior to sequencing. Importantly, the principles presented in this protocol allow its adaptation to other human immune and non-immune primary cells and cell lines. These guidelines will also be useful for laboratories which are not proficient with next-generation sequencing methods.

Assay for Transposase-Accessible Chromatin coupled with high-throughput sequencing (ATAC-seq) is a genome-wide method to uncover accessible chromatin. This is a step-by-step ATAC-seq protocol, from molecular to the final computational analysis, optimized for human lymphocytes (Th1/Th2). This protocol can be adopted by researchers without prior experience in next-generation sequencing methods.

Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) is a method used for the identification of open (accessible) regions ...

Determining Genome-wide Transcript Decay Rates in Proliferating and Quiescent Human Fibroblasts

Quiescence is a temporary, reversible state in which cells have ceased cell division, but retain the capacity to proliferate. Multiple studies, including ours, have demonstrated that quiescence is associated with widespread changes in gene expression. Some of these changes occur through changes in the level or activity of proliferation-associated transcription factors, such as E2F and MYC. We have demonstrated that mRNA decay can also contribute to changes in gene expression between proliferating and quiescent cells. In this protocol, we describe the procedure for establishing proliferating and quiescent cultures of human dermal foreskin fibroblasts. We then describe the procedures for inhibiting new transcription in proliferating and quiescent cells with Actinomycin D (ActD). ActD treatment represents a straightforward and reproducible approach to dissociating new transcription from transcript decay. A disadvantage of ActD treatment is that the time course must be limited to a short time frame because ActD affects cell viability. Transcript levels are monitored over time to determine transcript decay rates. This procedure allows for the identification of genes and isoforms that exhibit differential decay in proliferating versus quiescent fibroblasts.

We describe a protocol for generating proliferating and quiescent primary human dermal fibroblasts, monitoring transcript decay rates, and identifying differentially decaying genes.

Quiescence is a temporary, reversible state in which cells have ceased cell division, but retain the capacity to proliferate. Multiple studies, including ...

ATAC-seq Assay with Low Mitochondrial DNA Contamination from Primary Human CD4+ T Lymphocytes

ATAC-seq has become a widely used methodology in the study of epigenetics due to its rapid and simple approach to mapping genome-wide accessible chromatin. In this paper we present an improved ATAC-seq protocol that reduces contaminating mitochondrial DNA reads. While previous ATAC-seq protocols have struggled with an average of 50% contaminating mitochondrial DNA reads, the optimized&#160;lysis buffer introduced in this protocol reduces mitochondrial DNA contamination to an average of 3%. This improved ATAC-seq protocol allows for a near 50% reduction in the sequencing cost. We demonstrate how these high-quality ATAC-seq libraries can be prepared from activated CD4+ lymphocytes, providing step-by-step instructions from CD4+ lymphocyte isolation from whole blood through data analysis. This improved ATAC-seq protocol has been validated in a wide range of cell types and will be of immediate use to researchers studying chromatin accessibility.

Here, we present a protocol to perform an assay for transposase-accessible chromatin sequencing (ATAC-seq) on activated CD4+ human lymphocytes. The protocol has been modified to minimize contaminating mitochondrial DNA reads from 50% to 3% through the introduction of a new lysis buffer.

ATAC-seq has become a widely used methodology in the study of epigenetics due to its rapid and simple approach to mapping genome-wide accessible ...

Navigating MARRVEL, a Web-Based Tool that Integrates Human Genomics and Model Organism Genetics Information

Through whole-exome/genome sequencing, human geneticists identify rare variants that segregate with disease phenotypes. To assess if a specific variant is pathogenic, one must query many databases to determine whether the gene of interest is linked to a genetic disease, whether the specific variant has been reported before, and what functional data is available in model organism databases that may provide clues about the gene&#8217;s function in human. MARRVEL (Model organism Aggregated Resources for Rare Variant ExpLoration) is a one-stop data collection tool for human genes and variants and their orthologous genes in seven model organisms including in mouse, rat, zebrafish, fruit fly, nematode worm, fission yeast, and budding yeast. In this Protocol, we provide an overview of what MARRVEL can be used for and discuss how different datasets can be used to assess whether a variant of unknown significance (VUS) in a known disease-causing gene or a variant in a gene of uncertain significance (GUS) may be pathogenic. This protocol will guide a user through searching multiple human databases simultaneously starting with a human gene with or without a variant of interest. We also discuss how to utilize data from OMIM, ExAC/gnomAD, ClinVar, Geno2MP, DGV and DECHIPHER. Moreover, we illustrate how to interpret a list of ortholog candidate genes, expression patterns, and GO terms in model organisms associated with each human gene. Furthermore, we discuss the value protein structural domain annotations provided and explain how to use the multiple species protein alignment feature to assess whether a variant of interest affects an evolutionarily conserved domain or amino acid. Finally, we will discuss three different use-cases of this website. MARRVEL is an easily accessible open access website designed for both clinical and basic researchers and serves as a starting point to design experiments for functional studies.

Here, we present a protocol to access and analyze many human and model organism databases efficiently. This protocol demonstrates the use of MARRVEL to analyze candidate disease-causing variants identified from next-generation sequencing efforts.

Through whole-exome/genome sequencing, human geneticists identify rare variants that segregate with disease phenotypes. To assess if a specific variant is ...

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

Advances in sequencing technology have made whole-genome and whole-exome datasets more accessible for both clinical diagnosis and cutting-edge human genetics research. Although a number of in silico algorithms have been developed to predict the pathogenicity of variants identified in these datasets, functional studies are critical to determining how specific genomic variants affect protein function, especially for missense variants. In the Undiagnosed Diseases Network (UDN) and other rare disease research consortia, model organisms (MO) including Drosophila, C. elegans, zebrafish, and mice are actively used to assess the function of putative human disease-causing variants. This protocol describes a method for the functional assessment of rare human variants used in the Model Organisms Screening Center Drosophila Core of the UDN. The workflow begins with gathering human and MO information from multiple public databases, using the MARRVEL web resource to assess whether the variant is likely to contribute to a patient&#39;s condition as well as design effective experiments based on available knowledge and resources. Next, genetic tools (e.g., T2A-GAL4 and UAS-human cDNA lines) are generated to assess the functions of variants of interest in Drosophila. Upon development of these reagents, two-pronged functional assays based on rescue and overexpression experiments can be performed to assess variant function. In the rescue branch, the endogenous fly genes are &#34;humanized&#34;&#160;by replacing the orthologous Drosophila gene with reference or variant human transgenes. In the overexpression branch, the reference and variant human proteins are exogenously driven in a variety of tissues. In both cases, any scorable phenotype (e.g., lethality, eye morphology, electrophysiology) can be used as a read-out, irrespective of the disease of interest. Differences observed between reference and variant alleles suggest a variant-specific effect, and thus likely pathogenicity. This protocol allows rapid, in vivo assessments of putative human disease-causing variants of genes with known and unknown functions.

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

The goal of this protocol is to outline the design and performance of in vivo experiments in Drosophila melanogaster to assess the functional consequences of rare gene variants associated with human diseases.

Advances in sequencing technology have made whole-genome and whole-exome datasets more accessible for both clinical diagnosis and cutting-edge human ...