DYSF is a human gene encoding the protein dysferlin. Dysferlin is a large protein (2080 amino acids) found at the sarcolemma, or plasma membrane, of skeletal muscle cells. Its function is currently unknown, although its orthologous gene in the nematode Caenorhabditis elegans, fer-1, is involved in the fusion of membranous organelles during sperm formation. It is thus possible that dysferlin regulates the fusion of myoblasts (early muscle cells) during the formation of mature muscle cells, or myotubes, but to be honest this is little more than idle speculation.

Mutations in the DYSF gene result in three distinct forms of muscle disease: limb-girdle muscular dystrophy type 2B (LGMD-2B), Miyoshi myopathy, and a rare condition known as distal myopathy with anterior tibial onset. Each of these diseases is associated with a different pattern of muscle weakness, but they all have a few things in common: namely, a relatively late age of onset (average about 19 years), and a slow progression. Sufferers of these diseases frequently have completely normal muscle function for most of their teens, and then experience progressive weakness of the limb muscles during their late teens and early twenties. Most patients are confined to a wheelchair before the age of fifty, but there are always exceptions - one LGMD-2B patient I know remains an active (albeit slow) walker in his seventies. All in all, though, compared to horrors such as Duchenne muscular dystrophy these are quite benign diseases.

More vital statistics on the DYSF gene: in total it includes 55 exons spread out over more than 233,000 bases of genomic DNA. The mature mRNA generated from the gene contains a 6,243 base pair coding region, which encodes the 2,080 amino acids of the dysferlin protein followed by a stop codon.

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