Lin Ying-Hung, Lin Yung-Ming, Wang Ya-Yun, Yu I-Shing, Lin Yi-Wen, Wang Yun-Han, Wu Ching-Ming, Pan Hsien-An, Chao Shin-Chih, Yen Pauline H, Lin Shu-Wha, Kuo Pao-Lin
Graduate Institute of Basic Medical Sciences, National Cheng Kung University, College of Medicine, Tainan, Taiwan.
Am J Pathol. 2009 May;174(5):1857-68. doi: 10.2353/ajpath.2009.080955. Epub 2009 Apr 9.
Septins belong to a family of polymerizing GTP-binding proteins that are required for many cellular functions, such as membrane compartmentalization, vesicular trafficking, mitosis, and cytoskeletal remodeling. One family member, septin12, is expressed specifically in the testis. In this study, we found septin12 expressed in multiple subcellular compartments during terminal differentiation of mouse germ cells. In humans, the testicular tissues of men with either hypospermatogenesis or maturation arrest had lower levels of SEPTIN12 transcripts than normal men. In addition, increased numbers of spermatozoa with abnormal head, neck, and tail morphologies lacked SEPT12 immunostaining signals, as compared with normal spermatozoa. To elucidate the role of septin12, we generated 129 embryonic stem cells containing a septin12 mutant allele with a deletion in the exons that encode the N-terminal GTP-binding domain. Most chimeras derived from the targeted embryonic stem cells were infertile, and the few fertile chimeras only produced offspring with a C57BL/6 background. Semen analysis of the infertile chimeras showed a decreased sperm count, decreased sperm motility, and spermatozoa with defects involving all subcellular compartments. The testicular phenotypes included maturation arrest of germ cells at the spermatid stage, sloughing of round spermatids, and increased apoptosis of germ cells. Electron microscopic examination of spermatozoa showed misshapen nuclei, disorganized mitochondria, and broken acrosomes. Our data indicate that Septin12 expression levels are critical for mammalian spermiogenesis.
Septin蛋白属于一类聚合的GTP结合蛋白家族，许多细胞功能都需要它们，如膜区室化、囊泡运输、有丝分裂和细胞骨架重塑。该家族成员之一septin12在睾丸中特异性表达。在本研究中，我们发现septin12在小鼠生殖细胞终末分化过程中在多个亚细胞区室中表达。在人类中，精子发生低下或成熟停滞的男性的睾丸组织中SEPTIN12转录本水平低于正常男性。此外，与正常精子相比，头部、颈部和尾部形态异常的精子数量增加，且缺乏SEPT12免疫染色信号。为了阐明septin12的作用，我们构建了129个胚胎干细胞，其含有一个septin12突变等位基因，该等位基因在编码N端GTP结合结构域的外显子中有缺失。大多数源自靶向胚胎干细胞的嵌合体不育，少数可育嵌合体仅产生具有C57BL/6背景的后代。对不育嵌合体的精液分析显示精子数量减少、精子活力下降，且精子存在涉及所有亚细胞区室的缺陷。睾丸表型包括生殖细胞在精子细胞阶段的成熟停滞、圆形精子细胞的脱落以及生殖细胞凋亡增加。精子的电子显微镜检查显示细胞核畸形、线粒体紊乱和顶体破裂。我们的数据表明Septin12表达水平对哺乳动物精子发生至关重要。
