Abstract
BackgroundNuclear morphogenesis is one of the most fundamental cellular transformations taking place during spermatogenesis. In rodents, a microtubule-based perinuclear structure, the manchette, and a C-terminal kinesin motor KIFC1 are believed to play crucial roles in this process. Spermatogenesis in Octopus tankahkeei is a good model system to explore whether evolution has created a cephalopod prototype of mammalian manchette-based and KIFC1-dependent sperm nuclear shaping machinery.Methodology/Principal FindingsWe detected the presence of a KIFC1-like protein in the testis, muscle, and liver of O. tankahkeei by Western Blot. Then we tracked its dynamic localization in spermatic cells at various stages using Immunofluorescence and Immunogold Electron Microscopy. The KIFC1-like protein was not expressed at early stages of spermatogenesis when no significant morphological changes occur, began to be present in early spermatid, localized around and in the nucleus of intermediate and late spermatids where the nucleus was dramatically elongated and compressed, and concentrated at one end of final spermatid. Furthermore, distribution of the motor protein during nuclear elongation and condensation overlapped with that of the cephalopod counterpart of manchette at a significant level.Conclusions/SignificanceThe results support the assumption that the protein is actively involved in sperm nuclear morphogenesis in O. tankahkeei possibly through bridging the manchette-like perinuclear microtubules to the nucleus and assisting in the nucleocytoplasmic trafficking of specific cargoes. This study represents the first description of the role of a motor protein in sperm nuclear shaping in cephalopod.
Highlights
Spermatogenesis is a highly-ordered developmental process beginning in the testis with proliferation and differentiation of spermatogonia, incorporating mitotic and meiotic divisions, and ending up with spermiogenesis which witnesses dramatic structural, functional and morphological changes transforming spermatids towards mature spermatozoa [1,2,3]
The motor protein KIFC1 was initially identified in mouse embryonic brain
The presence of this motor protein in these tissues is consistent with the tissue distribution pattern of KIFC1 in mouse [47] but not with that in the Chinese mitten crab [48]
Summary
Spermatogenesis is a highly-ordered developmental process beginning in the testis with proliferation and differentiation of spermatogonia, incorporating mitotic and meiotic divisions, and ending up with spermiogenesis which witnesses dramatic structural, functional and morphological changes transforming spermatids towards mature spermatozoa [1,2,3]. The morphological transformations involved in the differentiation of spermatid are dependent on dedication of various cellular elements including cytoskeleton network and associated molecular motor proteins [5,6,7,8]. At specific stages during spermiogenesis, a bundle of microtubules in the distolateral region of cytoplasm will transiently assemble around the nucleus to form a special structure called the manchette, which is believed to be indispensable for acquisition of the final nuclear morphology [7,11,12] and delivery of molecules to centriole and tail [13,14,15]. A microtubule-based perinuclear structure, the manchette, and a C-terminal kinesin motor KIFC1 are believed to play crucial roles in this process. Spermatogenesis in Octopus tankahkeei is a good model system to explore whether evolution has created a cephalopod prototype of mammalian manchette-based and KIFC1-dependent sperm nuclear shaping machinery
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