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1 July 2000 Unique Expression of Gonadotropin-I and -II Subunit Genes in Male and Female Red Seabream (Pagrus major) During Sexual Maturation
Koichiro Gen, Koichi Okuzawa, Balasubramanian Senthilkumaran, Hideki Tanaka, Shunsuke Moriyama, Hirohiko Kagawa
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Abstract

Two distinct gonadotropins (GTHs) have been demonstrated in a number of teleost fishes. Although the physiological roles of GTHs have been extensively studied in salmonids, little is known about their biological functions in nonsalmonid fishes. In this study, to elucidate the role of GTH-I and GTH-II in reproduction, we cloned the α-glycoprotein subunit (αGSU) and gonadotropin β subunits (Iβ and IIβ) of red seabream using the 5′- and 3′-RACE methods and used these cDNA probes to reveal changes in mRNA levels of each subunit during sexual maturation of both male and female red seabream. The nucleotide sequences of αGSU, Iβ, and IIβ are 629, 531, and 557 base pairs long, encoding peptides of 117, 120, and 146 amino acids, respectively. The deduced amino acid sequence of each mature subunit showed high homology with those of other teleosts. Northern blot analysis showed that Iβ mRNA levels of males increase in association with gonadal development, whereas those of females remain low throughout sexual maturation, indicating sexual dimorphism in the expression pattern of Iβ. In contrast, IIβ mRNA levels of both sexes are maintained at high levels from the beginning of gametogenesis to spawning season. These results are different than those of salmonids and suggest that GTH-I may have important roles in male, but not female, gametogenesis. GTH-II may be involved in regulation of early and late gametogenesis in both male and female red seabream.

Koichiro Gen, Koichi Okuzawa, Balasubramanian Senthilkumaran, Hideki Tanaka, Shunsuke Moriyama, and Hirohiko Kagawa "Unique Expression of Gonadotropin-I and -II Subunit Genes in Male and Female Red Seabream (Pagrus major) During Sexual Maturation," Biology of Reproduction 63(1), 308-319, (1 July 2000). https://doi.org/10.1095/biolreprod63.1.308
Received: 29 November 1999; Accepted: 1 February 2000; Published: 1 July 2000
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