A contravention of Ohno's law in mice.

The chloride channel gene, CLCN4, has been previously mapped to the X chromosome in humans. We isolated a cDNA clone for mouse Clcn4 and used this to map the gene in an interspecific backcross. This revealed the surprising finding that the gene maps to the X chromosome in Mus spretus but to chromosome 7 in C57BL/6 mice. This is the first example of a gene that contravenes Ohno's law--it is a gene unique to the X chromosome in one eutherian species but autosomal in another. The consequence of this chromosomal rearrangement is that the gene is lost by mendelian segregation in a subset of the male progeny of a (C57BL/6 x Mus spretus) x Mus spretus backcross.