Gene changes in Duchenne muscular dystrophy: Comparison of multiplex PCR and multiplex ligation-dependent probe amplification techniques

Background: Duchenne muscular dystrophy (DMD) is a common X-linked recessive neuromuscular disorder, affecting 1 in 3,500 live male births. About 65% of cases are caused by deletions; ~5% to 8%, by duplication; and the remaining, by point mutations of the dystrophin gene. The frequency of complex rearrangements (double-deletion and non-contiguous duplications) is reported to be 4%.
Aim: In this study, we examined the usefulness of multiplex ligation-dependent probe amplification (MLPA) for screening of deletion and duplication mutations in a group of DMD/ BMD (Becker muscular dystrophy) patients from India.
Patients and Methods: We analyzed 180 patients referred from all over India, by both multiplex PCR technique (22 exons) and MLPA (all 79 exons).
Results and Conclusion: By multiplex PCR, deletions were detected in 90 (50%) patients. MLPA studies in these cases detected 3 additional deletions, 16 (8.9%) duplications and 2 point mutations. MLPA is useful to verify absence of deletions/ duplications in all 79 exons. This sets the stage to look for point mutations using RNA- or DNA-based tests because of the availability of the drug PTC124. Also, the extent of the deletions and duplications could be more accurately defined by MLPA. The delineation of the precise extent of deletion helps in deciding whether exon-skipping technique would be useful as therapy.

Keywords
Deletions, Duchenne muscular dystrophy, duplications, dystrophin gene, multiplex ligation-dependent probe amplification