Genomic organization and single-nucleotide polymorphism map of desmuslin, a novel intermediate filament protein on chromosome 15q26.3

The desmuslin gene was localized to chromosome 15q26.3 by electronic screening of the human DNA sequence database. Primer pairs were designed to amplify the 5 exons of the desmuslin gene in 11 overlapping DNA segments. The desmuslin gene was screened for mutations in 71 patients with various forms of myopathy for which there was no known cause. In this analysis, 10 common and 2 rare amino acid altering single-nucleotide polymorphisms were identified, all of which were seen in a control population of individuals thus making these unlikely causes of the phenotype. Interestingly, one of the single-nucleotide polymorphisms found in a patient resulted in a premature stop codon in the first exon. The nonsense mutation was also detected in the patient's unaffected father and one unaffected control; it was detected in 0.44% (2/454) of unrelated chromosomes and is therefore predicted to have a homozygous frequency of 0.002%.No causative mutations were found in the desmuslin gene. However, the single-nucleotide polymorphisms mapped in this study represent a well-mapped group that can be used for disequilibrium studies of this region of chromosome 15q26.3.Dystrophin and its associated proteins are thought to be involved in the anchoring of the muscle cell membrane to the extracellular matrix [1], and the absence of many of these proteins can lead to the phenotype of muscular dystrophy [2]. The dystrophin-associated protein complex (DAPC) consists of several subgroups of protein complexes, each associated either directly or indirectly with dystrophin. The sarcoglycans are four transmembrane proteins [3] that are organized by a fifth protein called sarcospan [4]. This complex is thought to be involved in signalling at the cell membrane [5]. A second subcomplex, known as the dystroglycan complex [6], interacts directly with dystrophin in the cytoplasm and laminin in the extracellular matrix, thus providing a structural link between the inside and the outside of the cell. A third