A polymorphic and hypervariable locus in the pseudoautosomal region of the CBA/H mouse sex chromosomes.

We have identified a genomic locus (DXYH1) that is polymorphic and hypervariable within the CBA/H colony. Using a panel of C57BL/6 x Mus spretus backcross offspring, it was mapped to the distal end of the X chromosome. Pseudoautosomal inheritance was demonstrated through three generations of CBA/H x CBA/H and CBA/H x C57BL/6 crosses and confirmed through linkage to the Sxr locus in X/Y Sxr x 3H1 crosses. Meiotic recombination frequencies place DXYH1 similar 28% into the pseudoautosomal region from the boundary. The de novo generation of CBA/H variant DXYH1 restriction fragment length polymorphisms during spermatogenesis is suggestive of the germline instability associated with hypermutable human minisatellites. The absence of DXYH1-related sequences in Mus spretus provides DNA sequence evidence to support the observed failure of X-Y pairing during meiosis and consequent hybrid infertility in C57BL/6 x Mus spretus male F1 offspring.