Gene expression profiles of prohibitin in testes of Octopus tankahkeei (ot-phb) revealing its possible role during spermiogenesis.

Prohibitin is essential for intracellular homeostasis and stabilization of mitochondrial respiratory chain complexes. To explore its functions during spermiogenesis of Octopus tankahkeei (O. tankahkeei), we have cloned and sequenced the cDNA of this mammalian PHB homologue (termed ot-PHB) from the testes of O. tankahkeei. The 1165 bp ot-phb cDNA contains a 100 bp 5' UTR, a 882 bp open reading frame and a 183 bp 3' UTR. The putative ot-PHB protein owns a transmembrane domain from 6 to 31 amino acid (aa) and a putative PHB domain from 26 to 178 aa. Protein alignment demonstrated that ot-PHB had 73.3, 73.6, 74.0, 75.1, and 45.4% identity with its homologues in Homo sapiens, Mus muculus, Danio rerio, Xenopus tropicalis and Trypanosoma brucei, respectively. Tissue distribution profile analysis revealed its presence in all the tissues examined. In situ hybridization in spermiogenic cells demonstrated that ot-phb was expressed moderately at the beginning of the spermiogenesis. The abundance of transcripts increased in intermediate spermatids and in drastically remodeling final spermatids. In mature spermatozoa, the residuary transcripts concentrated around the chondriosomal mantle where mitochondria assemble around. In summary, the expression of ot-phb during spermiogenesis implicates a potential function of this protein during mitochondrial ubiquitination. It is the first time to implicate the role of prohibitin in cephalopod spermiogenesis.