Characterization of the Xp21-23 region in the wood lemming, a region involved in XY sex reversal

The wood lemming (Myopus schisticolor) harbors two types of X chromosome, a normal X and a variant X, designated X*. The X* chromosome contains a muta tion that causes XY sex reversal. We have previously demonstrated that the Xp21-23 region is deleted from X* and is associated with XY sex reversal. T o further analyze the deleted region, we have constructed and characterized seven X chromosome- and region-specific recombinant DNA libraries. Further , we have screened mouse fetal gonad cDNA libraries with the microdissected Xp21-23 DNA as a probe in an attempt to identify homologous and expressed sequences from the deletion. Fourteen positive clones were isolated, and se quence analyses showed that ten of these contained identical sequences homo logous to mouse gamma -satellite sequences. One of the remaining four was p erfectly homologous to the mouse gene Ccth (chaperonin containing t-complex polypeptide 1, eta subunit). Southern blot indicated that the Ccth cDNA wa s located on the X chromosome, not deleted from the X* but closely linked t o the deletion region. Although the role of the Ccth containing region in s ex determination of the wood lemming requires additional studies, the isola tion of the mouse Ccth gene by the deletion Xp21-23 probe could be importan t since this gene is mainly expressed in testis. J. Exp. Zool. 290:551-557, 2001. (C) 2001 Wiley-Liss, Inc.