Molecular cloning and sequence analysis of the cDNA for the putative β subunit of the type-II gonadotrophin from the European eel

Abstract

Oestradiol treatment enhances type-II gonadotrophin (GTH-II) synthesis in the European eel (Anguilla anguilla) at the silver stage. As a first step in studying the molecular mechanisms involved in this stimulation, we cloned and characterized the cDNA encoding the beta subunit of eel GTH-II. A cDNA library was constituted in lambda gt10 from oestradiol-treated eels. It was screened using an oligodeoxyribonucleotide mixed probe designed to be complementary to a highly conserved region of cDNAs from several LH-related beta subunits. Several clones were obtained and four were subcloned in pUC13 and sequenced. The longest clones comprised a 420 bp coding sequence, plus 5' and 3' untranslated regions of 36 and 172 bp respectively. Comparison with GTH-II from other teleost fish permitted the localization of the putative cleavage site of a 24 amino acid signal peptide. The resulting 116 amino acid apopeptide had well-conserved cysteine positions and a putative N-linked glycosylation site; homology was 70-80% with GTH-II from other fish, 45% with LH from mammals and birds, 38% with mammalian FSH and only 35% with fish GTH-I. Preliminary results indicated a strong positive effect of oestradiol treatment on the level of the putative GTH-II beta-subunit mRNA. This supports our proposal that the European eel provides a suitable model for studying the positive regulation of gonadotrophin synthesis by gonadal steroids.

Differential Regulation of Luteinizing Hormone and Follicle-Stimulating Hormone Expression during Ovarian Development and under Sexual Steroid Feedback in the European Eel

“…A European eel pituitary cDNA library constructed into λgt10 vector [23, 24] was used to amplify a partial FSHβ cDNA. Gene-specific primers (primer 2 and primer 4; table 1) were designed based on the nucleotide sequences of the Japanese eel (Anguilla japonica) FSHβ cDNA (GenBank accession No.…”

“…Negative feedback on LH was further evidenced in various teleosts [for reviews, see [4, 8]]. In contrast, other studies showed a positive feedback on LH, particularly when fish were treated at a juvenile stage: in European eel, injections of estradiol (E 2 ) induced an increase in pituitary LH content [9] and mRNA levels of GPα [10] and LHβ subunits [11]. This effect was also demonstrated not only in other juvenile teleosts but also in adult fish with variations according to the stage of the reproductive cycle [for reviews, see [4,5,6]].…”

“…In the present study, we cloned and sequenced the FSHβ subunit. This new tool, together with other previously developed molecular probes for the European eel [23, 24], allowed us to characterize the localization of FSH- and LH-expressing cells in the pituitary and to investigate the variations of LH and FSH subunits expression under hormonal treatments. We compared the expression of the two gonadotropins during the experimental ovarian development induced by gonadotropic treatment, as well as under the effect of steroid treatments (E 2 or T).…”

Blue gourami (Trichogaster trichopterus) gonadotropic beta subunits (I and II) cDNA sequences and expression during oogenesis

“…subunits of GtH-I and GtH-II have been cloned and sequenced in chum salmon, Onchorhynchus keta (Itoh et al 1988), masu salmon, Onchorhynchus masou (Kato et al 1993), goldfish, Carassius auratus (Yoshiura et al 1997), mummichog, Fundulus heteroclitus (Lin et al 1992), European eel, Anguilla anguilla (Querat et al 1990), baikal omul, Coregonus auumnalis migratorius (Trofimova & Belikov 1994), and gilthead seabream, Sparus aurata (Elizur et al 1996). The and subunits of GtH-I and/or GtH-II have been cloned and sequenced in common carp, Cyprinus carpio (Chang et al 1993), chum salmon (Sekine et al 1989), and Japanese eel, Anguilla japonica (Nagae et al 1996).…”

Molecular structures of glycoprotein hormones and functions of their carbohydrate components

“…Amino acid sequences of lutropin-f, from nine mammals [47,[68][69][70][71][72][73][74][75][76][77][78], choriogonadotropin-fl from three mammals [33,[79][80][81][82][83], bullfrog lutropin-,8 [84], chicken lutropin-,8 [85], and the ,-subunits of fish gonadotropin from four species [52,54,[86][87][88][89][90] have been reported and found to be highly similar. The amino acid sequence of follitropin-fl has been determined in six mammals [42,78,[91][92][93][94][95][96][97][98][99][100][101] and thyrotropin-,f in five mammals [31,43,[102][103][104][105][106][107][10...…”