The development of preimplantation genetic diagnosis for myotonic dystrophy using multiplex fluorescent polymerase chain reaction and its clinical application

Preimplantation genetic diagnoses (PGD) for single gene defects require con siderable time and resources for the standardization of polymerase chain re actions that are rapid, sensitive and reliable. Developing tests for the tr inucleotide repeat diseases, where the expansion of unstable repeats produc es the phenotypes, are particularly complex. One of these disorders is myot onic dystrophy where, at present, diagnosis at the single cell level relies on the detection of the normal alleles from both the affected and unaffect ed parent. The incorporation of short tandem repeat polymorphisms in the as say can give additional information to improve the accuracy of diagnosis. W e have developed a multiplex fluorescent reaction for myotonic dystrophy an d one of two closely mapped, highly heterozygous, short tandem repeats (D19 S219 and D19S559) on chromosome 19 to reduce the possibility of misdiagnosi s due to contamination, act as a control for allelic drop-out and maximize the number of embryos genotyped. This protocol was designed as a general di agnosis for myotonic dystrophy, using the most informative of the two polym orphisms for each couple. Subsequently this approach was used in a PGD trea tment cycle.