Three Forms of Gonadotropin-Releasing Hormone in a Perciform Fish (Sparus Aurata): Complementary Deoxyribonucleic Acid Characterization and Brain Localization1

Abstract

Three forms of GnRH-salmon (sGnRH), seabream (sb-GnRH), and chicken (cGnRH-II)-have been described in the gilthead seabream (Sparus aurata) brain, and the cDNA encoding the sbGnRH precursor was recently isolated. In the present study, the cDNAs encoding the sGnRH and cGnRH-II were isolated and characterized, and the neurons producing the three GnRHs were localized in the seabream brain. Fragments of sGnRH and cGnRH-II cDNAs were amplified by polymerase chain reaction and used as probes to isolate the full-length cDNAs from a brain cDNA library. The cDNA encoding the cGnRH-II precursor is 573 nucleotides (nt) long, and the cDNA encoding the sGnRH precursor is 1971 nt in length with an unusually long 5' untranslated region. Specific single-strand DNA probes for in situ detection of mRNA were designed according to nonconserved regions among the three GnRH c-DNAs. Localization of GnRH mRNA-producing cells in the brain revealed five distinct populations of cells: sGnRH-producing cells in the ventromedial olfactory bulbs and the terminal nerve, sbGnRH-producing cells in the preoptic area and the ventral thalamus, and cGnRH-II-producing cells in the midbrain tegmentum. The discrete sites of expression of the three forms of GnRH indicate that only sbGnRH is directly involved in the control of gonadotropin secretion.

Gonadotropin-Releasing Hormone Analog and Sex Steroids Shorten Homing Duration of Sockeye Salmon in Lake Shikotsu

“…In salmonids, as well as in many vertebrate species, GnRH-immunoreactive fibers are widely distributed in the hypothalamus, the pituitary, and in various other brain areas (see Gothilf et al, 1996;Amano et al, 1997). It is hypothesized that GnRH regulates GTH secretion from the pituitary as a hypothalamic neurohormone and brain functions as a neuromodulator.…”

Isolation and characterisation of mRNA encoding the salmon- and chicken-II type gonadotrophin-releasing hormones in the teleost fish Rutilus rutilus (Cyprinidae)

“…To date, complete or partial cDNA sequences encoding salmon-type GnRH have been identified in Pagrus major (red seabream; Okuzawa et al 1994), Carassius auratus (goldfish; Lin & Peter 1996), Porichthys notatus (plainfin midshipman; Grober et al 1995), Sparus aurata (gilthead seabream; Gothilf et al 1996), Salmo salar (Atlantic salmon; Klungland et al 1992), Salvelinus fontinalis (brook trout; GeneBank accession no. X79712), Oncorhynchus tshawytscha (chinook salmon; GeneBank accession no.…”

“…The cDNA encoding the cGnRH-II precursor has been characterised in goldfish (Lin & Peter 1996), Haplochromis burtoni (African cichlid; GeneBank accession no. L27435), African catfish (Bogerd et al 1994) and Sparus aurata (Gothilf et al 1996).…”

Multiple GnRHs present in a teleost species are encoded by separate genes: analysis of the sbGnRH and cGnRH-II genes from the striped bass, Morone saxatilis

“…The architecture of the striped bass cGnRH-II gene is similar to that of all other GnRH genes Gothilf et al (1995Gothilf et al ( , 1996b; cichlid (Haplochromis burtoni) White et al (1995); red seabream (Pagrus major) Okuzawa et al (1994Okuzawa et al ( , 1997; African catfish (Clarius gariepinus) Bogerd et al (1994); goldfish (Carassius aurata) Lin & Peter (1996) and tree shrew (Tupaia glis belangeri) Kasten et al (1996).…”

“…Each of the three forms of GnRH has a restricted pattern of regional expression in the brain (White et al 1995, Gothilf et al 1996b) and appears to be regulated by hormones and environmental cues (Francis et al 1993, Gothilf et al 1997. These characteristics make the GnRH gene family an attractive model to study gene regulation.…”