Multiplex Ligation-Dependent Probe Amplification in X-linked Recessive Muscular Dystrophy in Korean Subjects

Abstract

Purpose: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are similar genetic disorders whose patterns of mutation and disease phenotypes might be expected to show differences among different countries. We analyzed multiplex ligation-dependent probe amplification (MLPA) data in a large number of Korean patients with DMD/BMD.

Materials and methods: We obtained 130 positive MLPA results (86 DMD, 27 BMD, and 17 female carriers) from 272 candidates (237 clinically suspected patients and 35 possible female carriers) who took part in this study. We analyzed the mutation patterns among 113 patients diagnosed by MLPA and calculated deletion/duplication percentages from a total of 128 patients, including 15 patients who were diagnosed using methods other than MLPA. We also analyzed hot spot locations among the 130 MLPA-positive results.

Results: Most mutations were detected in a central hot spot region between exons 44 and 55 (80 samples, 60.6%). Unlike previous reports, a second frequently observed hot spot near the 5'-end was not distinctive. MLPA detected deletions in specific exons in 92 patients with DMD/BMD (71.8%) and duplications in 21 patients (16.4%).

Conclusion: Our MLPA study of a large number of Korean patients with DMD/BMD identified the most frequent mutation hot spot, as well as a unique hot spot pattern. DMD gene mutation patterns do not appear to show significant ethnic differences.

Keywords: Becker muscular dystrophy; Duchenne muscular dystrophy; female carrier; multiple ligation-dependent probe amplification.

Fig. 1. Asterisks (^*) show patients who were diagnosed with other neuromuscular diseases. Among them, 16 patients had unspecified myopathy. MLPA, multiple ligation-dependent probe amplification; DMD, Duchenne muscular dystrophy; BMD, Becker muscular dystrophy; del, deletion; dup, duplication.

Fig. 2. Plotting of mutations detected by MLPA. A significant hot spot region is visible between exons 44 and 55. The most common deletion site in patients with DMD is shown at exon 49–50 (7 cases, black indicator), followed by exons 46–47 (5 cases, white arrowhead), exon 45 and 51 (black arrowheads). The most common deletion site in patients with BMD is shown at exons 45–47 (7 cases, grey indicator). DMD, Duchenne muscular dystrophy; BMD, Becker muscular dystrophy; MLPA, multiple ligation-dependent amplification.

Fig. 3. Cumulative numbers of each exon showing deletion/duplication events. Numbers of subjects showing deletions/duplications in each exon were counted and plotted. For exon deletion, a significant hot spot region is visible between exons 44–55; the second most frequent hot spot is not significantly distinguishable. In the case of duplication, neither central nor proximal hot spot regions are clearly identifiable.