A novel Mr 77,000 protein of the XY body of mammalian spermatocytes: its localization in normal animals and in Searle's translocation carriers.

We describe a novel XY body protein of rat and mice pachytene spermatocytes called XY77. Biochemical characterization showed that protein XY77 (Mr 77,000; pH value 8.3) is present in meiotic but absent in postmeiotic stages of spermatogenesis. With the aid of an antibody against protein XY77 together with another specific for XY body-associated protein XY40 we also investigated the localization of these proteins in mice carrying Searle’s translocation, a reciprocal X-autosomal translocation. We show here that in these mice the distribution of both XY77 and XY40 is abnormal. Our results indicate that in Searle’s translocation alterations are not restricted to the translocated autosome, but also involve chromatin segments corresponding originally to the sex chromosomes X and Y.