A comparison of different lysis buffers to assess allele dropout from single cells for preimplantation genetic diagnosis
ABSTRACT Single cell polymerase chain reaction (PCR) for preimplantation genetic diagnosis (PGD) requires high efficiency and accuracy. Allele dropout (ADO), the random amplification failure of one of the two parental alleles, remains the most significant problem in PCR-based PGD testing since it can result in serious misdiagnosis for compound heterozygous or autosomal dominant conditions. A number of different strategies (including the use of lysis buffers to break down the cell and make the DNA accessible) have been employed to combat ADO with varying degrees of success, yet there is still no consensus among PGD centres over which lysis buffer should be used (ESHRE PGD Consortium, 1999). To address this issue, PCR amplification of three genes (CFTR, LAMA3 and PKP1) at different chromosomal loci was investigated. Single lymphocytes from individuals heterozygous for mutations within each of the three genes were collected and lysed in either alkaline lysis buffer (ALB) or proteinase K/SDS lysis buffer (PK). PCR amplification efficiencies were comparable between alkaline lysis and proteinase K lysis for PCR products spanning each of the three mutated loci (ΔF508 in CFTR 90% vs 88%; R650X in LAMA3 82% vs 78%; and Y71X in PKP1 91% vs 87%). While there was no appreciable difference between ADO rates between the two lysis buffers for the LAMA3 PCR product (25% vs 26%), there were significant differences in ADO rates between ALB and PK for the CFTR PCR product (0% vs 23%) and the PKP1 PCR product (8% vs 56%). Based on these results, we are currently using ALB in preference to PK/SDS buffer for the lysis of cells in clinical PGD. Copyright © 2001 John Wiley & Sons, Ltd.
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ABSTRACT: The Herlitz type of junctional epidermolysis bullosa (H-JEB) is a severe blistering disease affecting the skin and mucous membranes, and laminin 5 has been implicated as the candidate gene/protein system for most patients with H-JEB. In this study, we have examined a cohort of 14 families with H-JEB for mutations in the LAMB3 gene. Premature termination codon mutations were delineated in both alleles of each proband in all pedigrees. Interestingly, two recurrent mutations, R42X and R635X, were noted in over 50% of the mutant LAMB3 alleles. These nonsense mutations occurred at CpG dinucleotide sequences, suggesting hypermutability of 5-methylcytosine to thymine. Additional evidence suggested that R42X and R635X represent mutational hotspots. First, the inheritance of R635X in a homozygous individual on two different genetic backgrounds was demonstrated by haplotype analysis. Furthermore, in one family, R42X was shown to be inherited on the maternal allele which lacked this mutation, suggesting that it arose as a result of maternal germline mutation. Elucidation of these two hotspot mutations will facilitate screening of additional JEB patients for the underlying mutations.Human Molecular Genetics 03/1996; 5(2):231-7. · 7.69 Impact Factor
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ABSTRACT: Myotonic dystrophy (DM) or Steinert's disease is a progressive autosomal dominant disease characterized by increasing muscle weakness, myotonia, cataracts, and endocrine abnormalities such as diabetes and testicular atrophy. The gene for DM was cloned in 1992 and the mutation was shown to be an expanded trinucleotide (CTG) repeat. A polymerase chain reaction (PCR)-based assay was described soon after that would allow (prenatal) diagnosis of the disease. Based on these PCR assays, we have developed a method for carrying out single-cell PCR for DM. In preimplantation diagnosis, embryos obtained in vitro are checked for the presence or absence of a disease, after which only embryos shown to be free of the disease under consideration are returned to the mother. A single-cell assay was developed for preimplantation diagnosis in couples where one of the parents is afflicted with DM. Twenty intracytoplasmic sperm injection (ICSI) cycles were carried out in eight patients and between one and four embryos were replaced in 17 out of 20 cycles. Two of the patients became pregnant and have had prenatal diagnosis which has confirmed that they are unaffected.Prenatal Diagnosis 11/1997; 17(10):925-32. · 2.68 Impact Factor
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ABSTRACT: The first clinical application of preimplantation genetic diagnosis (PGD) was reported almost a decade ago. Since then, the range of genetic defects that can be detected at single cell level has increased dramatically. At the 13th Annual Meeting of ESHRE in Edinburgh in 1997, a PGD Consortium was formed to undertake the first systematic and long-term study of the efficacy and clinical outcome of PGD. We report here the first data collection covering the period of January 1997 to September 1998. Referral data on 323 couples have been collected for a variety of monogenic and chromosomal disorders, providing information about which patients, at risk for which genetic diseases, are interested in PGD. Data were collected on 392 PGD cycles, resulting in 302 embryo transfers and 66 clinical pregnancies. Because of the importance of follow-up of the children born after PGD, participating centres were asked to contribute data on the pregnancies achieved and the children born after PGD since the start of their PGD programme. Data on 82 pregnancies and 110 fetal sacs were collected, and information was available on 79 children. Finally, biopsy, fluorescence in-situ hybridization and polymerase chain reaction protocols were collected, clearly showing that no consensus exists on technical aspects such as which culture medium to use, and emphasizing the role the PGD Consortium could play in setting up guidelines for good laboratory practice. In conclusion, it is clear that the effort of gathering data on PGD cycles is worthwhile and will be continued in the future, preferably using electronic data collection.Human Reproduction 01/2000; 14(12):3138-48. · 4.67 Impact Factor