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

Abstract

GnRH acts via GnRH receptors (GnRH-R) in the pituitary to cause the release of gonadotropins that regulate vertebrate reproduction. In the teleost fish, Haplochromis burtoni, reproduction is socially regulated through the hypothalamus-pituitary-gonadal axis, making the pituitary GnRH-R a likely site of action for this control. As a first step toward understanding the role of GnRH-R in the social control of reproduction, we cloned and sequenced candidate GnRH-R complementary DNAs from H. burtoni tissue. We isolated a complementary DNA that predicts a peptide encoding a G protein-coupled receptor that shows highest overall identity to other fish type I GnRH-R (goldfish IA and IB and African catfish). Functional testing of the expressed protein in vitro confirmed high affinity binding of multiple forms of GnRH. Localization of GnRH-R messenger RNA using RT-PCR revealed that it is widely distributed in the brain and retina as well as elsewhere in the body. Taken together, these data suggest that this H. burtoni GnRH receptor probably interacts in vivo with all three forms of GnRH. (Endocrinology 142: [1737][1738][1739][1740][1741][1742][1743] 2001)

The puzzling phylogeography of the haplochromine cichlid fishAstatotilapia burtoni

“…The origin of the Basel laboratory strain (LAB) is less clear, as it forms the sister clade to all samples from the northern and central basins (except the more basal Kalemie [KKA] sample). Since several decades, A. burtoni is a laboratory model for various research fields such as developmental biology, neurobiology, genetics and genomics, and behavioral biology (see, e.g., Baldo et al., 2011; Diepeveen et al., 2013; Dijkstra et al., 2017; Egger et al., 2017; Hofmann, 2003; Juntti et al., 2016; Lang et al., 2006; Robison et al., 2001; Salzburger et al., 2008; Santos et al., 2014; Theis et al., 2012; Wickler, 1962). Given the high population structure and deep divergence among several clades in A. burtoni , different populations and/or laboratory strains might also vary with regard to the trait(s) under study.…”

“…Phylogenetically, A. burtoni is nested with the “modern haplochromines” as one of several sister lineages to the Lake Malawi assemblage and the Lake Victoria region superflock (Meyer, Matschiner, & Salzburger, 2015; Salzburger et al., 2005). The species is among the five African cichlids to have a complete reference genome sequence (Brawand et al., 2014) and constitutes one of the most important cichlid model species in various fields of research, including developmental biology, neurobiology, genetics and genomics, and behavioral biology (see, e.g., Baldo, Santos, & Salzburger, 2011; Diepeveen, Roth, & Salzburger, 2013; Dijkstra et al., 2017; Egger, Roesti, Bohne, Roth, & Salzburger, 2017; Hofmann, 2003; Juntti et al., 2016; Lang et al., 2006; Robison et al., 2001; Salzburger et al., 2008; Santos et al., 2014; Theis, Salzburger, & Egger, 2012; Wickler, 1962). …”

Expression of tachykinin3 and related reproductive markers in the brain of the African cichlid fish Astatotilapia burtoni

“…We identified two tac3 genes from the highly social African cichlid fish Astatotilapia burtoni. Aspects of both the GnRH and kisspeptin systems in this species are previously described (Chen & Fernald, 2006;Flanagan et al, 2007;Grone, Maruska, Korzan, & Fernald, 2010;Robison et al, 2001;White & Fernald, 1998a, 1998b, as well as a suite of other neuroendocrine signaling molecules (Maruska & Fernald, 2018). Both the female reproductive cycle and male dominance hierarchy in A. burtoni are associated with changes in the GnRH and kisspeptin systems (Foran & Bass, 1999;Greenwood & Fernald, 2004;Grone et al, 2010;Grone, Carpenter, Lee, Maruska, & Fernald, 2012;Maruska & Fernald, 2013;Soma, Francis, Wingfield, & Fernald, 1996), with important consequences for reproductive behaviors and physiology.…”

Ovaprim abrogates expression of GnRH receptor- II in the Indian catfish

“…It is well established that in vertebrates, gonadotropin-releasing hormones (GnRH) act via GnRH receptors on target organs to regulate reproduction (Robinson et al, 2001). Thus, regulation of fish reproductive fecundity can be elucidated by analyzing the interaction and effect of GnRH analogs, such as ovaprim, on GnRH receptors.…”