A successful strategy for preimplantation genetic diagnosis of myotonic dystrophy using multiplex fluorescent PCR

The most common form of inherited muscular dystrophy in adults is myotonic dystrophy (DM), an autosomal-dominant disease caused by the expansion of an unstable CTG repeat sequence in the 3 ' untranslated region of the myotoni n protein kinase (DMPK) gene. Expanded (mutant) CTG repeat sequences are re fractory to conventional PCR, but alleles with a number of repeats within t he normal range can be readily amplified and detected. Preimplantation gene tic diagnosis (PGD) of DM has been successfully applied. However, a misdiag nosis using the reported protocol was recently documented. Two new PCD prot ocols for DM have been developed which utilise multiplex fluorescent PCR. I deally a linked polymorphic marker, APOC2, is amplified in addition to the normal DMPK alleles, thus providing a backup diagnostic result. However, th e two couples reported in the present study were not fully informative at t he APOC2 locus and so an unlinked short tandem repeat (STR) marker, D21S141 4, was substituted. The highly polymorphic nature of the D21S1414, DMPK and APOC2 loci means that a very simple genetic fingerprint can be generated b y analyses of these loci. This allows most DNA contaminants to be detected. Contamination is a significant problem for PGD and is the primary reason f or the inclusion of D21S1414 and APOC2 in this protocol. This paper reports the: first clinical experience and pregnancies following PGD For DM using a multiplex fluorescent PCR protocol. Copyright (C) 2001 John Wiley Br Sons , Ltd.