A report on 528 intragenic deletions detected in DMD and BMD patients by an Italian collaborative study.

The results of a collaborative study involving about one third of the total DMD and BMD cases living in the Italian territory are reported. The analysis of the breakpoint frequency by intron revealed significant differences among regional groups of DMD patients (for introns 2, 11 and 50 in Sardinia and for introns 9 and 45 in northeastern Italy), whereas no regional differences were observed among regional groups of BMD patients. These differences involve the same Italian regions which previous studies, performed by different markers, identified as "genetically differentiated". The data support the possibility of a differential distribution among populations of some intronic sequences, facilitating the origin of deletion breakpoints within the dystrophin gene.

Patterns of deletions of the dystrophin gene in different European populations.

The distribution of deletion breakpoints in the dystrophin gene was studied in a series of subjects belonging to different European populations. The data, obtained from the literature or directly from the present study, refer to population samples from France, Finland, Germany, Italy, Netherlands, Switzerland, and U.K. (England, Scotland, Wales). In total, 1516 breakpoints were assigned to different introns, 359 in the region encompassing the first 40 exons and 1157 (76%) in the distal part of the gene. Intron 7 appears to be equally involved as the starting or ending breakpoint, whereas intron 44 is involved mostly as a starting breakpoint. Breakpoint distribution by intron seems to differ in different populations, reaching statistical significance in the case of introns 44, 49, and 53. This finding suggests that some intronic sequences might contain preferential breakpoints that might vary in different populations, possibly as a consequence of genetic drift.