Abstract
A previous study indicated that genetic information encoded on the mouse Y chromosome short arm (Yp) is required for efficient completion of the second meiotic division (that generates haploid round spermatids), restructuring of the sperm head, and development of the sperm tail. Using mouse models lacking a Y chromosome but with varying Yp gene complements provided by Yp chromosomal derivatives or transgenes, we recently identified the Y-encoded zinc finger transcription factors Zfy1 and Zfy2 as the Yp genes promoting the second meiotic division. Using the same mouse models we here show that Zfy2 (but not Zfy1) contributes to the restructuring of the sperm head and is required for the development of the sperm tail. The preferential involvement of Zfy2 is consistent with the presence of an additional strong spermatid-specific promotor that has been acquired by this gene. This is further supported by the fact that promotion of sperm morphogenesis is also seen in one of the two markedly Yp gene deficient models in which a Yp deletion has created a Zfy2/1 fusion gene that is driven by the strong Zfy2 spermatid-specific promotor, but encodes a protein almost identical to that encoded by Zfy1. Our results point to there being further genetic information on Yp that also has a role in restructuring the sperm head.
Highlights
The mouse Y chromosome has two copies of a gene, Zfy, which together with the closely related X chromosome linked Zfx, encode zinc finger transcription factors [1,2,3]
For our published study showing that Zfy1 and Zfy2 have an important role in promoting completion of the second meiotic division to form haploid spermatids [14] we added a minute sex chromosome (YÃX) [16, 17]) to the three XO models
Before assessing the effects of Zfy transgene additions on sperm morphogenesis we sought to establish: (1) whether the YÃX addition per se had any discernible effect on spermiogenic progression by comparing XEOSry with XEYÃXSry; and (2) whether the markedly increased haploid frequency associated with the YÃX addition in the context of Sxrb had any discernible effect on spermiogenic progression by comparing XESxrbO with XEYÃXSxrb
Summary
The mouse Y chromosome has two copies of a gene, Zfy, which together with the closely related X chromosome linked Zfx, encode zinc finger transcription factors [1,2,3]. They derive from an autosomal precursor that was added to the mammalian sex chromosomes via the pseudoautosomal region (PAR) subsequent to the separation of the marsupial and eutherian lineages [4, 5]. Zfy encodes a much more potent transcription factor than Zfy1 [9, 10] and has PLOS ONE | DOI:10.1371/journal.pone.0145398. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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