Molecular genetic analysis of the dystrophin locus

There are a variety of different strategies available for testing in DMD. In the absence of DNA samples from affected individuals and/or non-deletion DMD families, linkage analysis can be performed with suitable families. If the available PCR-based markers are informative, the segregation of the at risk X chromosome can usually be assigned with a high degree of accuracy. As depicted in the illustration below, many PCR-based short tandem repeat (STR) markers are available that are either intragenic or flanking the DMD locus. In certain situations, knowledge of the deletion region in affected males permits the determination of the carrier status of female relatives due to STR hemizygosity in the carrier females. PCR assay*.

DMD LINKAGE ANALYSIS STRATEGY

At risk females can be evaluated by a quantitative PCR fluorescent dosage analysis that reveals hemizygosity in DMD deletion carriers. This assay will detect about 98% of DMD deletion carriers. This test is performed in collaboration with the Molecular Diagnostic Lab, Hospital for Sick Children, Toronto. PCR assay*.

DMD DELETION ANALYSIS

CompGene performs a multiplex deletion analysis in males that evaluates 22 regions of the dystrophin locus. The evaluated regions account for approximately 99% of the deletions found in DMD affected males. MULTI I (9 exons) and MULTI II (13 exons) reactions are evaluated separately. Lanes 1 and 4 are from a normal control male while lanes 2 and 5, and lanes 3 and 6 are from DMD affected males. The arrowheads indicate the exons that have been deleted in the affected DMD males.

Deletion analysis in affected males. Multiplex analysis will detect 99% of deletions (70% of affected males). PCR assay*.