title: Changes in the expression of pituitary gonadotropin subunits during reproductive cycle of multiple spawning female chub mackerel Scomber japonicus.
abstract: The endocrine regulation of reproduction in a multiple spawning fish with an asynchronous-type ovary remains largely unknown. The objectives of this study were to monitor changes in the mRNA expression of three gonadotropin (GtH) subunits (GPα, FSHβ, and LHβ) during the reproductive cycle of the female chub mackerel Scomber japonicus. Cloning and subsequent sequence analysis revealed that the cDNAs of chub mackerel GPα, FSHβ, and LHβ were 658, 535, and 599 nucleotides in length and encoded 117, 115, and 147 amino acids, respectively. We applied a quantitative real-time PCR assay to quantify the mRNA expression levels of these GtH subunits. During the seasonal reproductive cycle, FSHβ mRNA levels remained high during the vitellogenic stages, while GPα and LHβ mRNA levels peaked at the end of vitellogenesis. The expression of all three GtH subunits decreased during the post-spawning period. These results suggest that  follicle-stimulating hormone (FSH) is involved in vitellogenesis, while luteinizing hormone (LH) functions during final oocyte maturation (FOM). Both GPα and FSHβ mRNA levels remained high during the FOM stages of the spawning cycle and increased further just after spawning. Thus, FSH synthesis may be strongly activated just after spawning to accelerate vitellogenesis in preparation for the next spawning. Alternatively, LHβ mRNA levels declined during hydration and then increased after ovulation. This study demonstrates that chub mackerel are a good model for investigating GtH functions in multiple spawning fish.
authors: Laboratory of Marine Biology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors: Mitsuo
authors: M
authors: Nyuji
authors: Sethu
authors: S
authors: Selvaraj
authors: Hajime
authors: H
authors: Kitano
authors: Hirofumi
authors: H
authors: Ohga
authors: Michio
authors: M
authors: Yoneda
authors: Akio
authors: A
authors: Shimizu
authors: Kensuke
authors: K
authors: Kaneko
authors: Akihiko
authors: A
authors: Yamaguchi
authors: Michiya
authors: M
authors: Matsuyama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics; D005786:Gene Expression Regulation; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics; D006065:Gonadotropins, Pituitary / Q000737:chemistry / Q000235:genetics*; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D010053:Ovary / Q000502:physiology; D010473:Perciformes / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology*; D010802:Phylogeny; D021122:Protein Subunits / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D014818:Vitellogenesis / Q000235:genetics / Q000502:physiology
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D037201:Follicle Stimulating Hormone, beta Subunit; D015292:Glycoprotein Hormones, alpha Subunit; D006065:Gonadotropins, Pituitary; D037101:Luteinizing Hormone, beta Subunit; D021122:Protein Subunits; D012333:RNA, Messenger