Université Paris VII, Paris, France.
Desmin is a muscle-specific intermediate filament that is encoded by a gene assigned to human chromosome 2q35. Desmin-related myopathies are inherited disorders characterized by an intrasarcoplasmic accumulation of desmin. Recently, the knockout of the desmin gene was shown to generate a myopathic syndrome in transgenic mice, suggesting that functional abnormality of desmin may generate similar clinical symptoms in mouse and human. To determine the potential role of the desmin gene in a well-defined desmin-related myopathy (autosomal dominant form of Fardeau), human desmin cDNAs obtained from affected and unaffected individuals were cloned, sequenced and compared. No obvious mutation was detected. A BssHII restriction fragment length polymorphism (RFLP) was identified in exon 6 of the desmin gene. This RFLP was associated with a previously identified EcoRV RFLP in exon 4 to generate a tetra-allelic system, which was tested for linkage to the desmin-related myopathy in three families. The human desmin gene was localized within an 11-cM interval on chromosome 2q using a panel of radiation hybrids. This 11-cM region was clearly excluded by linkage analysis in the three desmin-related myopathy families using a set of highly polymorphic microsatellite markers. These results suggest that the desmin gene is not primarily involved in this disease.