| Octopus tankahkeei, belonging to the phylum mollusk, class cephalopoda and order octopoda, is an economically important species in the Eastern China Sea. The supply of this fishery product is excessively dependent on catching of the wild population because artificial breeding and culturing technique is sill limited on a pilot scale due to a number of problems resulting from the poor understanding of the fundamentals of the fertilization biology and developmental biology in this species.As one of the most drastic cytological transformation processes, spermatogenesis refers to the period where progenitor cells sequentially undergo mitotic and meiotic divisions, giving rive to, after a dramatic remodeling process, a mature sperm capable of fertilizing an egg. The morphologic characteristics of spermatogenesis in Octopus tankahkeei has been comprehensively described, however, the molecular mechanism underlying these structural reorganizations remain to be addressed.Microtubule is one component of the cytoskeletons network in eukaryotic cells and is tied to multiple cellular events. Kinesin is a group of highly related molecular motors driving cellular transport of various cargoes along microtubules though ATP hydrolysis and having a saying in physiological regulations. KIFC1 is a C-terminal kinesin moving towards the minus end of microtubules with pivotal roles in acrosome biogenesis and nuclear reshaping during spermiogenesis in some rodents.Based on multiple protein sequences alignment of KIFC1 homologues and using a combined method of degenerate and RACE PCR, we were able to identify a gene encoding a homologue of rat KIFC1 from the testis of Octopus tankahkeei and obtain its full-length cDNA. The 2229bp cDNA included a 1992 in-frame ORF corresponding to 663 continuous amino acids. The encoded polypeptide possessed the putative ATP-binding and microtubule-binding motifs and shared an overall similarity of 40%, 41%, 39% and 41% with its counterpart from human, rat, mouse and African clawed frog, respectively. Tissue expression analysis revealed ot-kifc1 was expressed in testis, gill and hepatopancreas, but not in other tissues examined. In situ hybridization result showed the ot-kifc1 message was hardly detectable in early spermatid, concentrated at the tail region of intermediate spermatid, abundant in spermatid undergoing dramatic elongation and compression, enriched at one end in final spermatids and disappeared in mature sperm. Immunofluorescence observation disclosed that the nucleoporin NUP62 was constantly localized on the nuclear envelope and occasionally scattered in the nucleus. Its distribution dynamics coincided with that of KIFC1 homologue on a significant level.In conclusion, the expression of ot-kfic1 at specific stages during spermiogenesis and the distribution correlation between KIFC1 homologue and NUP62 shed light on the potential functions of this motor in major cytological transformations. The KIFC1 homologue may connect to some macromolecular assembly on the nuclear membrane through interaction with NUP62 or other candidate mediator, thus providing the nuclear with direct shaping force or influencing the shaping process through indirect regulation. |
