Complete sequencing of the mouse pseudoautosomal region from three inbred strains reveals it to be the most rapidly evolving 'chromosome'.

Kasahara T., Mekada K., Abe K., Ashworth A., Kato T.

The pseudoautosomal region (PAR) of mammalian sex chromosomes is a small region of sequence identity shared by the X and Y chromosomes that allows pairing, crossover, recombination, and proper segregation of sex chromosomes. Although the mouse PAR sequence was largely a mystery, we have recently obtained the complete PAR sequences of the C57BL/6J and CAST/EiJ strains. Here, we report the complete PAR sequence of a Japanese wild mouse-derived strain, MSM/Ms, and compare the PARs of the three strains. There are considerable differences in the size of PARs between strains (MSM/Ms PAR is only about 20% the length of C57BL/6J PAR) and numerous amino acid substitution variants were found in the PAR genes. High GC-content exons and short introns are common features of the PAR genes and are likely a consequence of maintaining the functions of the encoded proteins during rapid evolution of the mouse PAR, whose recombination frequency in male meiosis is ∼100 times higher than the autosomal average.

Proceedings of the Japan Academy, Series B

48593