Lack of the steroid 15 alpha-hydroxylase gene (Cyp2a-4) in wild mouse strain Mus spretus: rapid evolution of the P450 gene superfamily.

Steroid 15 alpha-hydroxylase P450(15 alpha) and coumarin 7-hydroxylase P450coh genes Cyp2a-4 and Cyp2a-5 are members of the mouse P450 2A subfamily. Whereas Mus musclus domesticus strains contain both genes, wild mouse strain Mus spretus contains only Cyp2a-5. Evolutionarily, therefore, Cyp2a-5 is ancestral to Cyp2a-4. Moreover, the line to Cyp2a-4 descended as recently as 3 million years ago in an ancestral mouse. This evidence implies a rapid evolution of the P450 gene superfamily.