Sutcliffe, Maxine J.; (1990) Y chromosome effects on the kinetics of spermatogenesis in the developing mouse. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The mammalian Y chromosome has a fundamental role in the control of primary sex determination, diverting the undifferentiated bi-potential gonad to form a testis. In addition, the Y chromosome has been implicated in a number of other male-specific functions. This study aims to provide additional details of the function of the Y chromosome in spermatogenesis during development. A quantitative analysis of germ cells in XOSxrb mice compared to their XY±Sxrb sibs, during the first two post-natal weeks, investigated the function of the spermatogenesis gene Spy. The spermatogenesis gene was shown to act on the survival and proliferation of early differentiating A spermatogonia by five days after birth. By a quantitative analysis of germ cells in XOSxra and XYSxra mice - the latter identified by DNA analysis - throughout puberty, it was shown that there was no pre-meiotic cell loss. Cell degeneration was first observed at metaphase I in XOSxra testes, but earlier, at pachytene, in XYSxra mice. XYSxra testes are mosaic for normal and defective germ cell patches. The 'pairing site' hypothesis of Miklos (1974) states that there is a correlation between the number of 'unsaturated' pairing sites and the extent of spermatogenic impairment. It is suggested that the earlier spermatogenic breakdown in XYSxra testes, results from the presence of two unpaired univalents (as opposed to one in XOSxra) with the consequent increased number of 'unsaturated' sites. The XSxra chromosome was provided with a pairing partner - the chromosomal product, derived from XY* mice - which could satisfy at least some of the pairing sites, without adding Y long arm material. The germ cells in XSxraYdel testes overcame the block at Ml seen in XOSxra mice, and proceeded to sperm. All sperm, however, were abnormal, confirming previous findings that a sperm morphology gene (Smy), present on the long arm, is essential for fertility.

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