Dass Brinda, Tardif Steve, Park Ji Yeon, Tian Bin, Weitlauf Harry M, Hess Rex A, Carnes Kay, Griswold Michael D, Small Christopher L, Macdonald Clinton C
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20374-9. doi: 10.1073/pnas.0707589104. Epub 2007 Dec 12.
Polyadenylation, the process of eukaryotic mRNA 3' end formation, is essential for gene expression and cell viability. Polyadenylation of male germ cell mRNAs is unusual, exhibiting increased alternative polyadenylation, decreased AAUAAA polyadenylation signal use, and reduced downstream sequence element dependence. CstF-64, the RNA-binding component of the cleavage stimulation factor (CstF), interacts with pre-mRNAs at sequences downstream of the cleavage site. In mammalian testes, meiotic XY-body formation causes suppression of X-linked CstF-64 expression during pachynema. Consequently, an autosomal paralog, tauCstF-64 (gene name Cstf2t), is expressed during meiosis and subsequent haploid differentiation. Here we show that targeted disruption of Cstf2t in mice causes aberrant spermatogenesis, specifically disrupting meiotic and postmeiotic development, resulting in male infertility resembling oligoasthenoteratozoospermia. Furthermore, the Cstf2t mutant phenotype displays variable expressivity such that spermatozoa show a broad range of defects. The overall phenotype is consistent with a requirement for tauCstF-64 in spermatogenesis as indicated by the significant changes in expression of thousands of genes in testes of Cstf2t(-/-) mice as measured by microarray. Our results indicate that, although the infertility in Cstf2t(-/-) males is due to low sperm count, multiple genes controlling many aspects of germ-cell development depend on tauCstF-64 for their normal expression. Finally, these transgenic mice provide a model for the study of polyadenylation in an isolated in vivo system and highlight the role of a growing family of testis-expressed autosomal retroposed variants of X-linked genes.
聚腺苷酸化是真核生物mRNA 3'末端形成的过程，对基因表达和细胞活力至关重要。雄性生殖细胞mRNA的聚腺苷酸化不同寻常，表现出增加的可变聚腺苷酸化、减少的AAUAAA聚腺苷酸化信号使用以及降低的下游序列元件依赖性。切割刺激因子（CstF）的RNA结合成分CstF-64在切割位点下游的序列处与前体mRNA相互作用。在哺乳动物睾丸中，减数分裂XY体的形成导致粗线期X连锁的CstF-64表达受到抑制。因此，一个常染色体旁系同源物tauCstF-64（基因名Cstf2t）在减数分裂及随后的单倍体分化过程中表达。我们在此表明，在小鼠中靶向破坏Cstf2t会导致精子发生异常，特别是破坏减数分裂和减数分裂后发育，导致雄性不育，类似于少弱畸精子症。此外，Cstf2t突变体表型表现出可变的表达性，使得精子显示出广泛的缺陷。整体表型与tauCstF-64在精子发生中的需求一致，这通过微阵列测量Cstf2t(-/-)小鼠睾丸中数千个基因表达的显著变化得以表明。我们的结果表明，尽管Cstf2t(-/-)雄性的不育是由于精子数量少，但控制生殖细胞发育多个方面的多个基因的正常表达依赖于tauCstF-64。最后，这些转基因小鼠为在孤立的体内系统中研究聚腺苷酸化提供了一个模型，并突出了一个不断增加的睾丸表达的X连锁基因常染色体反转录变体家族的作用。
