This study was carried out in the Center for the Study of Mitochondrial Pediatric Diseases (http://www.mitopedia.org), funded by the Mariani Foundation. VT is a member of the European Reference Network for Rare Neuromuscular Diseases (ERN EURO-NMD).

NOTE: The use of human fibroblasts may require ethical approval. Fibroblasts used in this study were derived from MD patients and stored in the Institutional biobank in compliance with ethical requirements. Informed consent was provided for the use of the cells. Perform all cell culture procedures under a sterile laminar flow cabinet at room temperature (RT, 22-25 &#176;C). Use sterile-filtered solutions suitable for cell culture and sterile equipment. Grow all cell lines in a humidified incubator at 37 &#176;C with 5% C...

<ol>
	<li>Gorman, G. 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=Mitochondrial+diseases.">Mitochondrial diseases.</a> Nature Reviews. Disease Primers. 2, (2016).</li><li>DiMauro, S., Davidzon, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+DNA+and+disease.">Mitochondrial DNA and disease.</a> Annals of Medicine. 37 (3), 222-232 (2005).</li><li>El-Hattab, A. W., Craigen, W. J., Scaglia, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+DNA+maintenance+defects.">Mitochondrial DNA maintenance defects.</a> Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease. 1863 (6), 1539-1555 (2017).</li><li>Stewart, J. B., Chinnery, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dynamics+of+mitochondrial+DNA+heteroplasmy:+implications+for+human+health+and+disease.">The dynamics of mitochondrial DNA heteroplasmy: implications for human health and disease.</a> Nature Reviews Genetics. 16 (9), 530-542 (2015).</li><li>King, M. P., Attardi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+cells+lacking+mtDNA:+repopulation+with+exogenous+mitochondria+by+complementation.">Human cells lacking mtDNA: repopulation with exogenous mitochondria by complementation.</a> Science. 246 (4929), 500-503 (1989).</li><li>Trounce, I., Neill, S., Wallace, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytoplasmic+transfer+of+the+mtDNA+nt+8993+T--&gt;G+(ATP6)+point+mutation+associated+with+Leigh+syndrome+into+mtDNA-less+cells+demonstrates+cosegregation+with+a+decrease+in+state+III+respiration+and+ADP/O+ratio.">Cytoplasmic transfer of the mtDNA nt 8993 T--&gt;G (ATP6) point mutation associated with Leigh syndrome into mtDNA-less cells demonstrates cosegregation with a decrease in state III respiration and ADP/O ratio.</a> Proceedings of the National Academy of Sciences of the United States of America. 91 (18), 8334-8338 (1994).</li><li>Jun, A. S., Trounce, I. A., Brown, M. D., Shoffner, J. M., Wallace, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+transmitochondrial+cybrids+to+assign+a+complex+I+defect+to+the+mitochondrial+DNA-encoded+NADH+dehydrogenase+subunit+6+gene+mutation+at+nucleotide+pair+14459+that+causes+Leber+hereditary+optic+neuropathy+and+dystonia.">Use of transmitochondrial cybrids to assign a complex I defect to the mitochondrial DNA-encoded NADH dehydrogenase subunit 6 gene mutation at nucleotide pair 14459 that causes Leber hereditary optic neuropathy and dystonia.</a> Molecular and Cellular Biology. 16 (3), 771-777 (1996).</li><li>Dunbar, D. R., Moonie, P. A., Zeviani, M., Holt, I. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+I+deficiency+is+associated+with+3243G:C+mitochondrial+DNA+in+osteosarcoma+cell+cybrids.">Complex I deficiency is associated with 3243G:C mitochondrial DNA in osteosarcoma cell cybrids.</a> Human Molecular Genetics. 5 (1), 123-129 (1996).</li><li>Pye, 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=Production+of+transmitochondrial+cybrids+containing+naturally+occurring+pathogenic+mtDNA+variants.">Production of transmitochondrial cybrids containing naturally occurring pathogenic mtDNA variants.</a> Nucleic Acids Research. 34 (13), 95 (2006).</li><li>Bacman, S. R., Nissanka, N., Moraes, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+18+-+Cybrid+technology.">Chapter 18 - Cybrid technology.</a> Methods in Cell Biology. 155, 415-439 (2020).</li><li>Rucheton, B., 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=Homoplasmic+deleterious+MT-ATP6/8+mutations+in+adult+patients.">Homoplasmic deleterious MT-ATP6/8 mutations in adult patients.</a> Mitochondrion. 55, 64-77 (2020).</li><li>Xu, 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=Identification+of+a+novel+variant+in+MT-CO3+causing+MELAS.">Identification of a novel variant in MT-CO3 causing MELAS.</a> Frontiers in Genetics. 12, 638749 (2021).</li><li>Habbane, 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=Human+Mitochondrial+DNA:+Particularities+and+diseases.">Human Mitochondrial DNA: Particularities and diseases.</a> Biomedicines. 9 (10), 1364 (2021).</li><li>Legati, 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=Current+and+new+Next-Generation+Sequencing+approaches+to+study+mitochondrial+DNA.">Current and new Next-Generation Sequencing approaches to study mitochondrial DNA.</a> The Journal of Molecular Diagnostics. 23 (6), 732-741 (2021).</li><li>Boerwinkle, E., Xiong, W. J., Fourest, E., Chan, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+typing+of+tandemly+repeated+hypervariable+loci+by+the+polymerase+chain+reaction:+application+to+the+apolipoprotein+B+3'+hypervariable+region.">Rapid typing of tandemly repeated hypervariable loci by the polymerase chain reaction: application to the apolipoprotein B 3' hypervariable region.</a> Proceedings of the National Academy of Sciences of the United States of America. 86 (1), 212-216 (1989).</li><li>Lawless, C., Greaves, L., Reeve, A. K., Turnbull, D. M., Vincent, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+rise+and+rise+of+mitochondrial+DNA+mutations.">The rise and rise of mitochondrial DNA mutations.</a> Open Biology. 10 (5), 200061 (2020).</li><li>Wallace, D. 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=Mitochondrial+DNA+mutation+associated+with+Leber's+hereditary+optic+neuropathy.">Mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy.</a> Science. 242 (4884), 1427-1430 (1988).</li><li>Holt, I. J., Harding, A. E., Morgan-Hughes, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deletions+of+muscle+mitochondrial+DNA+in+patients+with+mitochondrial+myopathies.">Deletions of muscle mitochondrial DNA in patients with mitochondrial myopathies.</a> Nature. 331 (6158), 717-719 (1988).</li><li>Chomyn, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelet-mediated+transformation+of+human+mitochondrial+DNA-less+cells.">Platelet-mediated transformation of human mitochondrial DNA-less cells.</a> Methods in Enzymology. 264, 334-339 (1996).</li><li>Sazonova, M. 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=Cybrid+models+of+pathological+cell+processes+in+different+diseases.">Cybrid models of pathological cell processes in different diseases.</a> Oxidative Medicine and Cellular Longevity. 2018, 4647214 (2018).</li><li>Tarrago-Litvak, 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=The+inhibition+of+mitochondrial+DNA+polymerase+gamma+from+animal+cells+by+intercalating+drugs.">The inhibition of mitochondrial DNA polymerase gamma from animal cells by intercalating drugs.</a> Nucleic Acids Research. 5 (6), 2197-2210 (1978).</li><li>Swerdlow, R. 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=Mitochondria,+cybrids,+aging,+and+Alzheimer's+disease.">Mitochondria, cybrids, aging, and Alzheimer's disease.</a> Progress in Molecular Biology and Translational Science. 146, 259-302 (2017).</li><li>Ghosh, S. 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=Use+of+cytoplasmic+hybrid+cell+lines+for+elucidating+the+role+of+mitochondrial+dysfunction+in+Alzheimer's+disease+and+Parkinson's+disease.">Use of cytoplasmic hybrid cell lines for elucidating the role of mitochondrial dysfunction in Alzheimer's disease and Parkinson's disease.</a> Annals of the New York Academy of Sciences. 893, 176-191 (1999).</li><li>Buneeva, O., Fedchenko, V., Kopylov, A., Medvedev, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+dysfunction+in+Parkinson's+disease:+focus+on+mitochondrial+DNA.">Mitochondrial dysfunction in Parkinson's disease: focus on mitochondrial DNA.</a> Biomedicines. 8 (12), 591 (2020).</li><li>Weidling, I. W., 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=Mitochondrial+DNA+manipulations+affect+tau+oligomerization.">Mitochondrial DNA manipulations affect tau oligomerization.</a> Journal of Alzheimer's disease: JAD. 77 (1), 149-163 (2020).</li><li>Ferreira, I. 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=Bioenergetic+dysfunction+in+Huntington's+disease+human+cybrids.">Bioenergetic dysfunction in Huntington's disease human cybrids.</a> Experimental Neurology. 231 (1), 127-134 (2011).</li><li>Cruz-Berm&#250;dez, 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=Spotlight+on+the+relevance+of+mtDNA+in+cancer.">Spotlight on the relevance of mtDNA in cancer.</a> Clinical &amp; Translational Oncology. 19 (4), 409-418 (2017).</li><li>Patel, T. 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=European+mtDNA+variants+are+associated+with+differential+responses+to+cisplatin,+an+anticancer+drug:+implications+for+drug+resistance+and+side+effects.">European mtDNA variants are associated with differential responses to cisplatin, an anticancer drug: implications for drug resistance and side effects.</a> Frontiers in Oncology. 9, 640 (2019).</li></ol>

The mtDNA has a very high mutation rate compared to nDNA because of the lack of protective histones and its location close to the respiratory chain, which exposes the molecule to damaging oxidative effects not efficiently counteracted by the repair systems16. The first pathogenic mtDNA mutations were identified in 198817,18, and since then, a large number of mutations have been described. NGS technology is a relevant approach to screen the...

Mitochondrial disorders (MDs) are a group of multisystem syndromes caused by an impairment in mitochondrial functions due to mutations in either nuclear (nDNA) or mitochondrial (mtDNA) DNA1. They are among the most common inherited metabolic diseases, with a prevalence of 1:5,000. mtDNA-associated diseases follow the rules of mitochondrial genetics: maternal inheritance, heteroplasmy and threshold effect, and mitotic segregation2. Human mtDNA is a double-stranded DNA circle of 16.6 kb, which contains a short control region with sequences needed for replication and transcription, 13 protein-coding genes (all subunits of the respiratory chain), 22 tRNA, and 2 rRNA genes3.
In healthy individuals, there is one single mtDNA genotype (homoplasmy), whereas more than one genotype coexists (heteroplasmy) in pathological conditions. Deleterious heteroplasmic mutations must overcome a critical threshold to disrupt OXPHOS and cause diseases that can affect any organ at any age4. The dual genetics of OXPHOS dictates inheritance: autosomal recessive or dominant and X-linked for nDNA mutations, maternal for mtDNA mutations, plus sporadic cases both for nDNA and mtDNA.
At the beginning of the mitochondrial medicine era, a landmark experiment by King and Attardi5 established the basis to understand the origin of a mutation responsible for an MD by creating hybrid cells containing nuclei from tumor cell lines in which mtDNA was entirely depleted (rho0 cells) and mitochondria from patients with MDs. Next-generation sequencing (NGS) techniques were not available at that time, and it was not easy to determine whether a mutation was present in the nuclear or mitochondrial genome. The method, described in 1989, was then used by several researchers working in the field of mitochondrial medicine6,7,8,9; a detailed protocol has been recently published10, but no video has been made yet. Why should such a protocol be relevant nowadays when NGS could precisely and rapidly identify where a mutation is located? The answer is that cybrid generation is still the state-of-the-art protocol to understand the pathogenic role of any novel mtDNA mutation, correlate the percentage of heteroplasmy with the severity of the disease, and perform a biochemical investigation in a homogeneous nuclear system in which the contribution of the autochthonous nuclear background of the patient is absent11,12,13.
This protocol describes how to obtain cytoplasts from confluent, patient-derived fibroblasts grown in 35 mm Petri dishes. Centrifugation of the dishes in the presence of cytochalasin B allows the isolation of enucleated cytoplasts, which are then fused with rho0 cells in the presence of polyethylene glycol (PEG). The resulting cybrids are then cultivated in selective medium until clones arise. The representative results section shows an example of molecular characterization of the resulting cybrids to prove that the mtDNA is identical to that of the donor patients&#39; fibroblasts and that the nDNA is identical to the nuclear DNA of the tumoral rho0 cell line.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5-Bromo-2&#39;-Deoxyuridine</td>
			<td>Sigma-Aldrich (Merck)</td>
			<td>B5002-500MG</td>
			<td></td>
		</tr>
		<tr>
			<td>6 well Plates</td>
			<td>Corning</td>
			<td>3516</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well Plates</td>
			<td>Corning</td>
			<td>3596</td>
			<td></td>
		</tr>
		<tr>
			<td>Blood and Cell Culture DNA extraction kit</td>
			<td>QIAGEN</td>
			<td>13323</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Beckman Coulter</td>
			<td>Avanti J-25</td>
			<td>7,200 rcf, 37 &#176;C</td>
		</tr>
		<tr>
			<td>Centrifuge bottles, 250 mL</td>
			<td>Beckman Coulter</td>
			<td>356011</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytochalasin B from Drechslera dematioidea</td>
			<td>Sigma-Aldrich (Merck)</td>
			<td>C2743-200UL</td>
			<td></td>
		</tr>
		<tr>
			<td>Dialyzed FBS</td>
			<td>Gibco</td>
			<td>26400-036 100mL</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM High Glucose (w/o L-Glutamine W/Sodium Pyruvate)</td>
			<td>EuroClone</td>
			<td>ECB7501L</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Phosphate Buffered Saline - PBS (w/o Calcium w/o Magnesium)</td>
			<td>EuroClone</td>
			<td>ECB4004L</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol Absolute Anhydrous</td>
			<td>Carlo Erba</td>
			<td>414601</td>
			<td></td>
		</tr>
		<tr>
			<td>FetalClone III (Bovine Serum Product)</td>
			<td>Cytiva - HyClone Laboratories</td>
			<td>SH30109.03</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass pasteur pipettes</td>
			<td>VWR</td>
			<td>M4150NO250SP4</td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted Research Microscope For Live Cell Microscopy</td>
			<td>Nikon</td>
			<td>ECLIPSE TE200</td>
			<td></td>
		</tr>
		<tr>
			<td>JA-14 Fixed-Angle Aluminum Rotor</td>
			<td>Beckman Coulter</td>
			<td>339247</td>
			<td></td>
		</tr>
		<tr>
			<td>Laboratory autoclave Vapormatic 770</td>
			<td>Labotech</td>
			<td>29960014</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine 200 mM (100x)</td>
			<td>EuroClone</td>
			<td>ECB 3000D</td>
			<td></td>
		</tr>
		<tr>
			<td>Minimum Essential Medium MEM</td>
			<td>Euroclone</td>
			<td>ECB2071L</td>
			<td></td>
		</tr>
		<tr>
			<td>MycoAlert Mycoplasma Detection Kit</td>
			<td>Lonza</td>
			<td>LT07-318</td>
			<td></td>
		</tr>
		<tr>
			<td>PEG (Polyethylene glicol solution)</td>
			<td>Sigma-Aldrich (Merck)</td>
			<td>P7181-5X5ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (solution 100x)</td>
			<td>EuroClone</td>
			<td>ECB3001D</td>
			<td></td>
		</tr>
		<tr>
			<td>Primo TC Dishes 100 mm</td>
			<td>EuroClone</td>
			<td>ET2100</td>
			<td></td>
		</tr>
		<tr>
			<td>Primo TC Dishes 35 mm</td>
			<td>EuroClone</td>
			<td>ET2035</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Pyruvate 100 mM</td>
			<td>EuroClone</td>
			<td>ECM0542D</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Nikon</td>
			<td>SMZ1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin 2.5% in HBSS</td>
			<td>EuroClone</td>
			<td>ECB3051D</td>
			<td></td>
		</tr>
		<tr>
			<td>Uridine</td>
			<td>Sigma-Aldrich (Merck)</td>
			<td>U3003-5G</td>
			<td></td>
		</tr>
	</tbody>
</table>

an in vitro approach to study mitochondrial dysfunction: a cybrid model

Deficiency of the mitochondrial respiratory chain complexes that carry out oxidative phosphorylation (OXPHOS) is the biochemical marker of human mitochondrial disorders. From a genetic point of view, the OXPHOS represents a unique example because it results from the complementation of two distinct genetic systems: nuclear DNA (nDNA) and mitochondrial DNA (mtDNA). Therefore, OXPHOS defects can be due to mutations affecting nuclear and mitochondrial encoded genes.
The groundbreaking work by King and Attardi, published in 1989, showed that human cell lines depleted of mtDNA (named rho0) could be repopulated by exogenous mitochondria to obtain the so-called &#34;transmitochondrial cybrids.&#34; Thanks to these cybrids containing mitochondria derived from patients with mitochondrial disorders (MDs) and nuclei from rho0 cells, it is possible to verify whether a defect is mtDNA- or nDNA-related. These cybrids are also a powerful tool to validate the pathogenicity of a mutation and study its impact at a biochemical level. This paper presents a detailed protocol describing cybrid generation, selection, and characterization.

Generating cybrids requires 3 days of laboratory work plus a selection period (~2 weeks) and additional 1-2 weeks for the growth of clones. The critical steps are the quality of cytoplasts and the selection period. The morphology of cybrids resembles that of the rho0 donor cells. Assignment of the correct mtDNA and nDNA in the cybrids is mandatory to confirm the identity of the cells. An example is given in Figure 2. In this case, we generated cybrids starting from fibroblasts der...

Watch this Scientific Journal Video about An In Vitro Approach to Study Mitochondrial Dysfunction: A Cybrid Model at JoVE.com

An In Vitro Approach to Study Mitochondrial Dysfunction: A Cybrid Model

Transmitochondrial cybrids are hybrid cells obtained by fusing mitochondrial DNA (mtDNA)-depleted cells (rho0 cells) with cytoplasts (enucleated cells) derived from patients affected by mitochondrial disorders. They allow the determination of the nuclear or mitochondrial origin of the disease, evaluation of biochemical activity, and confirmation of the pathogenetic role of mtDNA-related variants.

An In Vitro Approach to Study Mitochondrial Dysfunction: A Cybrid Model

Deficiency of the mitochondrial respiratory chain complexes that carry out oxidative phosphorylation (OXPHOS) is the biochemical marker of human ...

Cyber generation is still the state of the art protocol to understand the pathogenic role of any novel mitochondrial DNA mutation and to correlate the percentage of atriplasmy with the severity of the disease. This technique allows performing biochemical investigation in a homogeneous nuclear system, in which the contribution of the nuclear background of the patient is absent. This technique allows validating the pathogenicity of a mutation of the mitochondrial DNA.and makes it possible to study its impact at biochemical level Wash the 35 millimeter dishes containing the fibroblasts twice using two milliliters of 1X PBS without calcium and magnesium. Clean the outer surface of the dishes with 70%ethanol, and wait until the alcohol evaporates. Remove the lids from the dishes and the screw caps from the bottles.Place each dish without the lid upside down at the bottom of each 250 milliliter centrifuge bottle. Slowly add 32 milliliters of a nucleation medium to each bottle allowing the medium to enter the dish and come in contact with the cells. Remove any bubbles from the dishes using a long glass pasture pipette, curving the tip in a bunsen flame.Close each bottle with the screw cap, and transfer them to the centrifuge. Centrifuge for 20 minutes at 37 degrees Celsius and 8, 000 x G.Aspirate the medium from the bottles and discard it. Remove the dishes by inverting the bottles on a sterile gauze previously sprayed with 70%ethanol.Clean the outer surface of the dishes and their lids with 70%ethanol, and close the dishes after the ethanol evaporates. Before proceeding check for cytoplast formation using an inverted microscope for live cells. Look for extremely elongated fibroblasts due to the extrusion of their nuclei induced by cytochalasin.To each 35 millimeter dish add 1, 000, 143 row zero cells. Re-suspended in two milliliters of culture medium supplemented with 5%FBS. Leave the dishes for three hours in a humidified carbon dioxide incubator to settle the 143 row zero cells on the ghosts.After three hours of incubation, aspirate and discard the medium. Wash the adherence cells twice with two milliliters of DMEM high glucose medium without serum or MEM, then aspirate and discard the medium. Add 500 microliters of polyethylene glycol solution to the cells and incubate for exactly one minute.Aspirate and discard the polyethylene glycol solution. Wash the cells three times with two milliliters of DMEM high glucose without serum or with MEM. Add two milliliters of fusion medium, and incubate overnight in the incubator at 37 degrees Celsius with 5%carbon dioxide.Trypsinize the cells in the remaining culture dishes Count them and seed them into one or more Petri dishes Add 50 to 100 cells per dish in the supplemented culture until clones appear. Then let them grow for several days. Using a stereo microscope, pick up the clones from the Petri dish with cloning cylinders or a pipette tip.Try to avoid pooling different clones and transfer them to a 96 well plate, each well containing 200 microliters of supplemented culture medium. Cybrids were generated starting from fibroblasts derived from a patient carrying the heteroplasmic M2343A2G One of the most common mitochondrial DNA mutations associated with mitochondrial myopathy, encephalopathy lactic acidosis, and stroke-like episodes. Analysis of a variable number of tandem repeats showed that cyber DNA is identical to the row zero cells confirming the replacement of the patient's cyber DNA with the 143 B genome.Restriction fragment length polymorphism, or sequencing analyses, can be used to assess the presence of the mitochondrial DNA mutation and the heteroplasmy percentage. When attempting this protocol it is important to verify the correct genetic asset of the nucleon and mitochondrial DNA, as well as the mitochondrial DNA amount in the repopulated cybrids.

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JoVE Journal

Genetics

3.4K vistas.  Fondazione IRCCS Istituto Neurologico Carlo Besta. La generación cibernética sigue siendo el protocolo de vanguardia para comprender el papel patógeno de cualquier nueva mutación del ADN mitocondrial y correlacionar el porcentaje de atriplasmia con la gravedad de la enfermedad. Esta técnica permite realizar investigación bioquímica en un sistema nuclear homogéneo, en el que la aportación del fondo nuclear del paciente está ausente. Esta técnica permite validar la patogenicidad de una mutación del ADN mitocondrial.y permite ...