The presence of transposable elements (TEs) was suggested by us two years ago to explain the familial occurrence of Duchenne muscular dystrophy (DMD) through paternal lines in 4 families among 454 who had been ascertained in our center [Zatz et al., 19911. The possible involvement of transposons would also explain the genealogy reported by Miciak et al. [19921 in which 3 DMD affected boys, linked through paternal lines, carry different mutations. Our hypothesis was that the presence ofTEs could be responsible in some families for a greater predisposition for the occurrence of pathogenetic deletions, duplications, or mutations but which would be difficult to be detected in isolated cases or when transmitted through maternal lines. We also suggested that the presence of TEs could offer an alternative explanation for the observation of intronic nonpathogenic and pathogenic deletions in normal and affected members of the same families.
Therefore, we read with great interest the recent report of Pizzuti et al. [19921 about the finding of a transposon-like element in the deletion-prone region of the dystrophin gene. The authors describe the molecular analysis of 2 deletions (among 13 DMD patients with deletions of exon 44 only) in one of the dystrophin hotspots and the involvement of a transposable sequence in