Kinesins in spermatogenesis.

Kinesins are essential for the proper function of many types of polar cells, including epithelial cells, neurons, and sperm. Spermatogenesis is closely associated with many different kinesins. These kinesins participate in several fundamental processes, including mitotic and meiotic division, essential organelle transport, and the biogenesis of peculiar structures for the formation of mature sperm. Kinesin-13, kinesin-8, and the chromokinesin families cooperate to ensure normal sister chromatid congression and segregation. The kinesin-8 family motor KIF18A, kinesin-12 motors PAKRP/kinesin12A and PAKRP1L/kinesin12B, and other kinesin-like motors are essential in the process of homologous chromosome pairing and in the separation to create haploid gametes. During spermiogenesis, the responsibility of a handful of kinesin members lies in the maturation of spermatids into mature, motile, and intact spermatozoa. Such roles are completed upon the release of viable and functional sperm into the lumen of seminiferous tubules. In this process, KIFC1, KIF5C, KRP3A, and KRP3B may be involved in acrosome biogenesis; KIFC1, KIFC5, CHO2, KIF17b, and KIF3A probably contribute to nuclear shaping; KIF17b, KIF3A, and KLC3 are implicated in the tail formation process; and KIF20 and KRP3 likely participate in sperm translocation. KIF17b also exhibited postmeiosis transcriptional activities that are critical for the dramatic alterations observed in nuclear and cytoplasmic structures. This review summarizes the roles of kinesins during mitosis, meiosis, and spermiogenesis, and proposes several important issues for further investigation.