Zhang Yong, Liu Hong, Li Wei, Zhang Zhengang, Shang Xuejun, Zhang David, Li Yuhong, Zhang Shiyang, Liu Junpin, Hess Rex A, Pazour Gregory J, Zhang Zhibing
Department of Dermatology, Tongji Hospital affiliated to Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Department of Obstetrics&Gynecology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
Department of Obstetrics&Gynecology, Virginia Commonwealth University, Richmond, VA, 23298, USA; School of Public Health, Wuhan University of Science and Technology, Wuhan, Hubei 430060, China.
Dev Biol. 2017 Dec 1;432(1):125-139. doi: 10.1016/j.ydbio.2017.09.023. Epub 2017 Sep 28.
Intraflagellar transport (IFT) is an evolutionarily conserved mechanism essential for the assembly and maintenance of most eukaryotic cilia and flagella. In mice, mutations in IFT proteins have been shown to cause several ciliopathies including retinal degeneration, polycystic kidney disease, and hearing loss. However, little is known about its role in the formation of the sperm tail, which has the longest flagella of mammalian cells. IFT27 is a component of IFT-B complex and binds to IFT25 directly. In mice, IFT27 is highly expressed in the testis. To investigate the role of IFT27 in male germ cells, the floxed Ift27 mice were bred with Stra8-iCre mice so that the Ift27 gene was disrupted in spermatocytes/spermatids. The Ift27: Stra8-iCre mutant mice did not show any gross abnormalities, and all of the mutant mice survived to adulthood. There was no difference between testis weight/body weight between controls and mutant mice. All adult homozygous mutant males examined were completely infertile. Histological examination of the testes revealed abnormally developed germ cells during the spermiogenesis phase. The epididymides contained round bodies of cytoplasm. Sperm number was significantly reduced compared to the controls and only about 2% of them remained significantly reduced motility. Examination of epididymal sperm by light microscopy and SEM revealed multiple morphological abnormalities including round heads, short and bent tails, abnormal thickness of sperm tails in some areas, and swollen tail tips in some sperm. TEM examination of epididymal sperm showed that most sperm lost the "9+2″ axoneme structure, and the mitochondria sheath, fibrous sheath, and outer dense fibers were also disorganized. Some sperm flagella also lost cell membrane. Levels of IFT25 and IFT81 were significantly reduced in the testis of the conditional Ift27 knockout mice, and levels of IFT20, IFT74, and IFT140 were not changed. Sperm lipid rafts, which were disrupted in the conditional Ift25 knockout mice, appeared to be normal in the conditional Ift27 knockout mice. Our findings suggest that like IFT25, IFT27, even though not required for ciliogenesis in somatic cells, is essential for sperm flagella formation, sperm function, and male fertility in mice. IFT25 and IFT27 control sperm formation/function through many common mechanisms, but IFT25 has additional roles beyond IFT27.
鞭毛内运输（IFT）是一种进化上保守的机制，对于大多数真核生物的纤毛和鞭毛的组装与维持至关重要。在小鼠中，IFT蛋白的突变已被证明会导致多种纤毛病，包括视网膜退化、多囊肾病和听力丧失。然而，对于其在精子尾部形成中的作用却知之甚少，精子尾部是哺乳动物细胞中最长的鞭毛。IFT27是IFT-B复合体的一个组成部分，直接与IFT25结合。在小鼠中，IFT27在睾丸中高度表达。为了研究IFT27在雄性生殖细胞中的作用，将携带floxed Ift27基因的小鼠与Stra8-iCre小鼠杂交，从而使Ift27基因在精母细胞/精子细胞中被破坏。Ift27:Stra8-iCre突变小鼠未表现出任何明显异常，所有突变小鼠均存活至成年。对照小鼠和突变小鼠的睾丸重量/体重之间没有差异。所有接受检查的成年纯合突变雄性均完全不育。睾丸的组织学检查显示，在精子形成阶段生殖细胞发育异常。附睾中含有圆形的细胞质团块。与对照相比，精子数量显著减少，其中只有约2%的精子活力仍显著降低。通过光学显微镜和扫描电子显微镜对附睾精子进行检查，发现了多种形态异常，包括圆形头部、短而弯曲的尾部、某些区域精子尾部厚度异常以及某些精子的尾部尖端肿胀。对附睾精子进行透射电子显微镜检查显示，大多数精子失去了“9+2”轴丝结构，线粒体鞘、纤维鞘和外致密纤维也紊乱无序。一些精子鞭毛还失去了细胞膜。在条件性Ift27基因敲除小鼠的睾丸中，IFT25和IFT81的水平显著降低，而IFT20、IFT74和IFT140的水平未发生变化。在条件性Ift25基因敲除小鼠中被破坏的精子脂筏，在条件性Ift27基因敲除小鼠中似乎是正常的。我们的研究结果表明，与IFT25一样，IFT27尽管不是体细胞纤毛发生所必需的，但对于小鼠精子鞭毛的形成、精子功能和雄性生育能力至关重要。IFT25和IFT27通过许多共同机制控制精子的形成/功能，但IFT25除了IFT27之外还有其他作用。
