<i>Mus poschiavinus</i> Y Chromosome in the C57BL/6J Murine Genome Causes Sex Reversal

Abstract

When the Y chromosome from Mus poschiavinus (Y POS ) is transferred onto the C57BL/6J genome, XY individuals develop as females with two ovaries, or as hermaphrodites. No XY individual develops normal testes. Although C57BL/6J-Y POS XY females are rarely fertile, most hermaphrodites with normal male genitalia sire offspring. Thus, the Mus poschiavinus Y chromosome carries a form of the Y-linked testis-determining locus different from that present in the C57BL/6J inbred strain. This gene interacts abnormally with autosomal or X-linked testis-determining loci of the C57BL/6J genome to prevent normal testicular differentiation. Divergence of the Y-linked testis-determining gene may be involved in mammalian speciation.