Condensation behavior of the human x chromosome in male germ cells and Sertoli cells examined by flourescence in situ hybridisation

The chromatin condensation behavior of the human x chromosome has been studied by FISH analysis in germ cells and Sertoli cells of the adult testes. Comparisons are made with previous findings for the human Y chromosome and for chromosome 7. In meiotic prophase, the X chromosome can be seen to extend greatly at zygotene and to contract through pachytene into the sex vesicle. Such extension, which has also been noted for the human Y chromosome at this state of meiosis, could be a prerequisite for XY pairing crossing-over. In patients with {open_quotes}Sertoli-cell-only{close_quotes} syndrome, the sex chromosomes, by in situ hybridization analysis, appear extremely contracted compared with their normal extended state seen in adult Sertoli cells of fertile men. By contrast, the state of expansion of chromosome 7 in Sertoli cells appears identical for sterile and fertile testes. This could suggest an association between gene-controlled germ cell losses and failure of expansion of the sex chromosome axes. The variable patterns of extension and contraction for the X and Y chromosome axes in germ cells and Sertoli cells might provide underlying clues to pattern of expression noted for sex-linked genes in the human testis.