Allelic forms of mouse transcobalamin 2

Transcobalamin 2 is the only vitamin B12-binding protein found in mouse serum. Two allelic forms of mouse transcobalamin 2 are described. The two forms differ in their mobilities on polyacrylamide gel electrophoresis. The slowly migrating form has been found in serum from 25 inbred mouse strains. The more rapidly migrating form was detected in 3 inbred mouse strains (NZB, ST/bJ, and CPB-WV). Both parental variants were expressed in F₁ progeny of appropriate interstrain crosses, showing codominant expression of the transcobalamin 2 alleles. In backcrosses between F₁ and parental individuals, the two electrophoretic variants were inherited as single Mendelian traits. The strain distribution pattern of the two variants in recombinant inbred lines likewise suggested a single-gene mode of inheritance and indicated a lack of close linkage with a number of genetic loci on chromosomes 1, 2, 4, 5, 6, 7, 9, 12, 14, 15, and 17. We propose the symbol Tcn-2 for the polymorphic gene locus coding for transcobalamin 2 in the mouse and Tcn-2 ^s and Tcn-2 ^f for the two alleles.