Characterization and expression pattern of KIFC1-like kinesin gene in the testis of the Macrobrachium nipponense with discussion of its relationship with structure lamellar complex (LCx) and acroframosome (AFS)

Spermiogenesis is a developmental process undergoing continuous differentiation to drive a diploid spermatogonium towards a haploid sperm cell. This striking transformation from spermatogonium to spermatozoa is made possible by the stage-specific adaption of cytoskeleton and associated molecular motor proteins. KIFC1 is a C-terminal kinesin motor found to boast essential roles in acrosome biogenesis and nuclear reshaping during spermiogenesis in rat. To explore its functions during the same process in Macrobrachium nipponense, we have cloned and sequenced the cDNA of a mammalian KIFC1 homologue (termed mn-KIFC1) from the total RNA of the testis. The 2,296 bp mn-KIFC1 cDNA contained a 87 bp 5' untranslated region, a 211 bp 3' untranslated region and a 1,998 bp open reading frame. Protein alignment demonstrated that mn-KIFC1 had 37.7, 58.7, 38.4, 37.2, 38.9 and 37.8% identity with its homologues in Salmo salar, Eriocheir sinensis, Homo sapiens, Mus musculus, Danio rerio and Xenopus laevis respectively. The phylogenetic tree revealed that mn-KIFC1 is most related to E. Sinensis KIFC1 among the examined species. Tissue expression analysis showed the presence of mn-KIFC1 in the testis, hepatopancreas, gill, muscle and heart. In situ hybridization showed that the mn-KIFC1 mRNA was localized at the periphery of the nuclear membrane and in the proacrosomal vesicle in early and middle spermatids. In late spermatids and spermatozoa, mn-KIFC1 was expressed in the acrosome and in the spike. In situ hybridization also indicated that KIFC1 works together with lamellar complex (LCx) and acroframosome (AFS) to drive acrosome formation and cellular transformation. LCx and AFS have both been previously proved to have essential roles during spermiogenesis in M. nipponense. In conclusion, the expression of mn-kifc1 at specific stages of spermiogenesis suggests a role in cellular transformations in M. nipponense.