ORGANIZATION OF THE Y-CHROMOSOME IN TESTIS CELLS OF FETAL, SUBADULT AND ADULT MICE AS DETERMINED BY IN-SITU HYBRIDIZATION

In order to reveal the time-course of decondensation of the Y chromoso me in Sertoli cells, testes preparations of fetal, subadult and adult laboratory mice in different developmental stages were hybridized in s itu with biotinylated probe pY353/B, which binds along the entire long arm of the mouse Y chromosome. All fetal and subadult testicular cell s exhibited tightly compacted hybridization signals, indicating highly condensed Y chromosomes. Diffuse signals, indicating decondensation o f the Y chromosome were found for the first time in the structurally d ifferentiated Sertoli cells of 35 to 40 day old animals. Since this co incides with the appearance of mature sperm nuclei, a correlation betw een decondensation of the Y chromosome and its activity in sperm matur ation and/or sperm motility can be presumed.