Assignment of the canine myosin Va gene (MYO5A) to chromosome 30q14 by fluorescence in situ hybridization and radiation hybrid mapping.

Myosin Va belongs to the unconventional myosin family that has been identified in many non-muscle tissues of vertebrates and invertebrates. All known myosins bind actin and produce mechanical force through ATP hydrolysis. Myosin Va is only expressed in melanocytes and in cells of the neuronal system (Mercer et al., 1991). In melanocytes it is part of the melanosome transport complex (Wu et al., 1997). Mutations in the MYO5A gene cause the dilute phenotype in mice that is generally associated with severe neurological disorders (Mercer et al., 1991), the dilute-opisthotonus rat mutant (Futaki et al., 2000), and in human the rare Griscelli syndrome with neurological impairment (Pastural et al., 1997; Ménasche et al., 2000). This autosomal recessive disorder results in a phenotype with pigmentary dilution of skin and hair, the presence of large clumps of pigment in hairshafts and an accumulation of melanosomes in melanocytes in addition to neurological defects. The MYO5A gene has been located on HSA 15q21→q22 and on the homologous mouse and rat chromosomes 8 and 9, respectively (Hasson et al., 1996; Ohuo et al., 1996). In dogs affected with black hair follicular dysplasia (BHFD) abnormal hair follicles showing clumps of melanosomes in the hair matrix and an abnormal shape of the hairshaft are also observed (Schmutz et al., 1998). Therefore, MYO5A might be a suitable candidate gene for this canine disorder. To facilitate future linkage studies we report here the assignment of the canine MYO5A gene to CFA30q14 by FISH and RH mapping.