Gonadotropin-inhibitory hormone in teleosts: New insights from a basal representative, the eel

• Published in: General and comparative endocrinology Vol. 287; p. 113350
• Main Authors: Maugars, G., Pasquier, J., Atkinson, C., Lafont, A.-G., Campo, A., Kamech, N., Lefranc, B., Leprince, J., Dufour, S., Rousseau, K.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2020; Elsevier
• Subjects: Anguilla; Animals; Eels; Female; GnIH; GnRH-R; Gonadotropin subunits; Gonadotropin-Releasing Hormone; Gonadotropin-Releasing Hormone - antagonists & inhibitors; Life Sciences; NPVF; Phylogeny; Pituitary cell culture; Pituitary Gland; Pituitary Gland - metabolism; Pituitary hormones; Synteny; Tissue distribution; Pituitary cell culture; Pituitary hormones; Gonadotropin subunits; NPVF; GnIH; Synteny; Phylogeny; Tissue distribution; Anguilla; GnRH-R
• DOI: 10.1016/j.ygcen.2019.113350
• ISSN: 0016-6480

•A single gnih paralog has been conserved after the teleost 3R.•The gnih gene encodes three GnIH peptides in a basal teleost, the European eel.•Gnih mRNA is mostly expressed in the diencephalon in the eel.•Eel GnIH peptides inhibit the expression of lhβ, fshβ, gpα and gnrh-r2 in vitro. Since its discovery in birds, gonadotropin-inhibitory hormone (GnIH) has triggered investigation in the other groups of vertebrates. In the present study, we have identified a single gnih gene in the European eel (Anguilla anguilla), a representative species of a basal group of teleosts (Elopomorphs). We have also retrieved a single gnih gene in Osteoglossomorphs, as well as in more recently emerged teleosts, Clupeocephala. Phylogeny and synteny analyses allowed us to infer that one of the two gnih paralogs emerged from the teleost-specific whole genome duplication (TWGD or 3R), would have been lost shortly after the 3R, before the emergence of the basal groups of teleosts. This led to the presence of a single gnih in extant teleosts as in other vertebrates. Two gnih paralogs were still found in some teleost species, such as in salmonids, but resulting from the additional whole genome duplication that specifically occurred in this lineage (4R). Eel gnih was mostly expressed in the diencephalon part of the brain, as analyzed by quantitative real-time PCR. Cloning of eel gnih cDNA confirmed that the sequence of the GnIH precursor encoded three putative mature GnIH peptides (aaGnIH-1, aaGnIH-2 and aaGnIH-3), which were synthesized and tested for their direct effects on eel pituitary cells in vitro. Eel GnIH peptides inhibited the expression of gonadotropin subunits (lhβ, fshβ, and common a-subunit) as well as of GnRH receptor (gnrh-r2), with no effect on tshβ and gh expression. The inhibitory effect of GnIH peptides on gonadotropic function in a basal teleost is in agreement with an ancestral inhibitory role of GnIH in the neuroendocrine control of reproduction in vertebrates.