Genetic polymorphism of the vitamin D binding protein (Gc) in the musk shrew (Suncus murinus)

In the musk shrew (Suncus murinus), the electrophoretic bands in the post-albumin region were identified as vitamin D binding protein (Gc) by the [3H] vitamin D3 binding method. Three Gc phenotypes were distinguished from each other: a single faster band (Gc-A), a single slower band (Gc-B) and the double bands (Gc-AB). Results of mating experiments indicated that the Gc-A and Gc-B are controlled by two codominant alleles, Gca and Gcb at an autosomal locus (Gc), respectively. It was noticed that, in the Gc-AB phenotypes, the Gc-B band was constantly more intense than the Gc-A band in the protein staining. The same tendency was also observed between the homozygous Gc-A and Gc-B bands, and further, radioactivity of the Gc-B bound with [3H] vitamin D3 was about twofold higher than that of the Gc-A. These results suggest that the Gcb yields its protein product twofold more than the Gca. No cross-reaction between the shrew proteins and a rabbit anti-human Gc protein was observed.