Genomic Structure and Expression Sites of Three Gonadotropin-Releasing Hormone Genes in One Species

Abstract

In the teleost fish, Haplochromis burtoni, gonadotropinreleasing hormone (GnRH) peptide has been localized to three distinct regions in the brain. Each GnRH population is associated with expression of a distinct cDNA as previously described. Here we report the complete genomic sequences encoding these three forms and compare their structural organization, putative regulatory elements, and expression patterns in the body. All three genes share a common structure of four exons: the first exon encodes the 5Ј untranslated region; the second exon encodes the signal sequence, GnRH decapeptide, and the 5Ј end of the GnRH-associated peptide (GAP); the third exon consists entirely of GAP coding sequence; and the fourth exon encodes the 3Ј end of GAP and the 3Ј untranslated region. Each of the three GnRH genes has been shown previously to have a distinct spatial expression pattern in the brain, and here we use reverse transcription and cDNA amplification to demonstrate that each gene is expressed in the body. The gene encoding the releasing form, 5Ser 8 6GnRH, is expressed in the heart, liver, spleen, kidney, and testis, as well as in the preoptic area. The 5His 5 Trp 7 Tyr 8 6GnRH gene is expressed in the testis as well as in the midbrain. The 5Trp 7 Leu 8 6GnRH gene is expressed in the testis and the terminal nerve area. We examined the 500 bp upstream of exon 1 in all three H. burtoni genes and identified putative binding sites for glucocorticoid receptor, androgen receptor, and progesterone receptor, as well as the transcription factors Ap-1 and Sp-1. The genomic sequence encoding the terminal nerve form of GnRH (i.e., 5Trp 7 Leu 8 6GnRH) in H. burtoni is remarkably similar to that encoding the presumed releasing form of GnRH in salmonids, especially in the 3Ј intergenic region. Taken together with phylogenetic and mRNA localization data in salmonids, these data suggest that the gene encoding the releasing form of GnRH in salmonids may not yet be described.

The GnRH system in the European sea bass (Dicentrarchus labrax)

“…However, the respective projections of the different cell groups remained unknown. The results of our in situ hybridization study confirm the differential expression of the three forms by showing that sGnRH mRNA is mainly detected in the olfactory bulbs, sbGnRH mRNAs in the preoptic area and cGnRH II in the synencephalon, as shown in other perciforms (White et al 1995, Gothilf et al 1996, Okuzawa et al 1997, Parhar 1997, Parhar et al 1998, White & Fernald 1998. Because of the high similarity in the primary sequences of the three corresponding GnRH decapeptides, it was decided to generate antibodies against recombinant GAPs.…”

Heterogeneous nuclear ribonucleoprotein A/B and G inhibits the transcription of gonadotropin-releasing-hormone 1

“…2C). Since multiple transcription initiation sites for GnRH1 have been found in other species (Dong et al, 1996(Dong et al, , 1993Kepa et al, 1992;Radovick et al, 1990;Von Schalburg and Sherwood, 1999), we predicted that there might be more transcription initiation sites than previously predicted (White and Fernald, 1998). To avoid missing any upstream sequence, we included the sequence corresponding to the GnRH1 mRNA 5′ untranslated region to the translation start codon (+165).…”

Gonadotropin-Releasing Hormone Receptor in the TeleostHaplochromis burtoni: Structure, Location, and Function1

“…Like GnRH (10,35,36), GnRH-R mRNA is found in many tissues outside the nervous system. In H. burtoni, the kidney and testes show relatively greater abundance of GnRH-R mRNA.…”

“…In H. burtoni, the kidney and testes show relatively greater abundance of GnRH-R mRNA. The roles of both GnRH (10,36) and GnRH-R in the kidney are unknown. Also, in rats GnRH-R mRNA is found in the adrenals, but not the kidney (33), whereas in fish the renal system is inseparable from the kidney, suggesting that the current data reflect a role for the renal system rather than the kidneys.…”