The rapidly evolving Pem homeobox gene and Agtr2, Ant2, and Lamp2 are closely linked in the proximal region of the mouse X chromosome.

The Pem gene encodes a homeodomain-containing protein expressed in reproductive tissue that may function as a transcription factor regulating spermatogenesis and sperm maturation. We have mapped the Pem gene to the proximal end of the mouse X chromosome, placing it within the Hprt region. Based on the mapping of Pem and other loci in three separate Mus musculus x Mus spretus backcross panels, we established the order of markers within this segment of the Hprt region as: Agtr2-Pem-Ant2-DXMit50-Lamp2-DXMit49. In contrast to some other regions of the X chromosome, which have been rearranged during the evolution of mammals, we show that the order of gene loci within this Hprt region is conserved in mice and human. The finding that the mouse Ant2 and Pem loci are tightly linked suggests that human ANT2 may be useful as a marker for isolating the human PEM gene, which has been impervious to cloning by conventional hybridization methods because of its rapid evolution. Copyright 1997 Academic Press.