Molecular cloning and localization of the luteinizing hormone subunit and glycoprotein hormone α subunit from Japanese anchovy Engraulis japonicus
Although Clupeiformes contain many economically important species, there is limited information on their reproductive physiology. To obtain more insight into reproductive mechanisms in clupeiform fishes, molecular cloning of the Japanese anchovy Engraulis japonicus luteinizing hormone (LH) and glycoprotein hormone α (GPHα) subunits, and immunocytochemistry of gonadotrophs in the pituitary using antisera raised against the synthetic peptides for both subunits were carried out. The cDNAs for LH and GPHα subunits consisted of 963 and 535 nucleotides encoding 141 and 122 amino acids, respectively. The deduced amino acid sequences of the E. japonicus LH subunit showed a 60% similarity to the Pacific herring Clupea pallasii LH subunit and 24–31% similarities to FSH subunits of other fish species. The E. japonicus GPHα subunit showed 52–57% similarities to anguilliform and cypriniform GPHα subunits. Both the subunits have typical structural characteristics of each subunit such as N-linked glycosylation sites, conserved cysteine residues and highly conserved short amino acid sequences. These results indicate that cDNAs cloned in this study encode the E. japonicus LH and GPHα subunits. Reverse-transcription polymerase chain reaction (RT-PCR) revealed that both the LH and GPHα subunit genes were abundantly expressed in the pituitary, and the GPHα subunit was observed to be weakly expressed in the extrapituitary tissues. Immunocytochemistry of the E. japonicus pituitary showed that cells that immunoreacted with antiserum against the LH subunit were distributed in the peripheral regions of proximal pars distalis, and these cells were also immunoreactive to antiserum against the GPHα subunit. An abundant number of both LH and GPHα cells in the pituitary of matured fish were observed, in comparison with immature fish. These results indicate that the E. japonicus LH is involved in the final reproductive maturation as well as those of other teleosts.
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Document Type: Regular Paper
Stock Assessment Division, National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa 236-8648, Japan
Coastal Fisheries and Aquaculture Division, National Research Institute of Fisheries Science, Fisheries Research Agency, Yokosuka, Kanagawa 238-0316, Japan
Publication date: 2010-08-01