A REASSESSMENT OF Y-CHROMOSOMAL BEHAVIOR IN GERM-CELLS AND SERTOLI CELLS OF THE MOUSE AS REVEALED BY IN-SITU HYBRIDIZATION

In situ hybridisation experiments were carried out to reappraise the s tate of condensation of the Y chromosome in germ cells and Sertoli cel ls of the mouse. Previous work had suggested that all testicular cells showed a condensed Y chromosome prior to the adult stage. We now demo nstrate that, although the Y chromosome is condensed in pre-pubertal S ertoli cells, it is greatly expanded in primordial germ cells (gonocyt es). An expanded Y-signal is first seen in Sertoli cell nuclei at or a round day 21 of postnatal development, coinciding with the first appea rance of spermatids in the germinal epithelium.