A new dysferlin gene mutation in a Portuguese family with Miyoshi myopathy

Dysferlinopathies are autosomal recessive muscular dystrophies caused by mutations in the dysferlin gene (DYSF). A 33-year-old man was born to a non-consanguineous couple. At the age of 25 he stared to feel weakness of the distal lower limbs and also experienced episodes of rhabdomyolysis. Electromyography showed a myopathic pattern, and muscle biopsy revealed dystrophic changes with absence of dysferlin. Genetic analysis was positive for a mutation in the c3367_3368del DYSF gene (p.Lys1123GLUFS*2). After 8 years of disease evolution the symptomatology worsened. This is the first report of this mutation of the DYSF gene identified in a non-consanguineous Portuguese family, studied over 8 years. We believe the mutation is responsible for the Miyoshi myopathy. Disease progression cannot be predicted in either the patient or carrier family because there are no similar cases previously described in the literature.

Functions of Vertebrate Ferlins

Ferlins are multiple-C2-domain proteins involved in Ca2+-triggered membrane dynamics within the secretory, endocytic and lysosomal pathways. In bony vertebrates there are six ferlin genes encoding, in humans, dysferlin, otoferlin, myoferlin, Fer1L5 and 6 and the long noncoding RNA Fer1L4. Mutations in DYSF (dysferlin) can cause a range of muscle diseases with various clinical manifestations collectively known as dysferlinopathies, including limb-girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy. A mutation in MYOF (myoferlin) was linked to a muscular dystrophy accompanied by cardiomyopathy. Mutations in OTOF (otoferlin) can be the cause of nonsyndromic deafness DFNB9. Dysregulated expression of any human ferlin may be associated with development of cancer. This review provides a detailed description of functions of the vertebrate ferlins with a focus on muscle ferlins and discusses the mechanisms leading to disease development.