Different distributions of homologous chromosomes in adult human Sertoli cells and in lymphocytes signify nuclear differentiation.

Using whole chromosome painting probes for human chromosomes 3,7,8,13,17 and 21 and X and the probe pHY2.1 for the Y chromosome coupled with fluorescent in situ hybridization (FISH) analysis, the distribution of chromosomes is reported in nuclei of Sertoli cells of the adult testis and in stimulated blood lymphocytes. The distribution of chromosomes in the two cell types is significantly different. A strong tendency for each pair of homologues to pair is inferred from the observation of only a single detectable signal in the majority of Sertoli cell nuclei. The sex chromosomes, by contrast, give two clearly separated signals. Interphase nuclei in dividing blood lymphocytes, analysed as controls, also show mainly two separated signals for all non-acrocentric autosomal pairs, but acrocentric pairs no. 13 and 21 show some tendency to associate, probably reflecting satellite association.