A G-protein-coupled receptor mediates neuropeptide-induced oocyte maturation in the jellyfish Clytia

Abstract

The reproductive hormones that trigger oocyte meiotic maturation and release from the ovary vary greatly between animal species. Identification of receptors for these Maturation Inducing Hormones (MIHs), and understanding how they initiate the largely conserved maturation process, remain important challenges. In hydrozoan cnidarians including the jellyfish Clytia hemisphaerica, MIH comprises neuropeptides released from somatic cells of the gonad. We identified the receptor (MIHR) for these MIH neuropeptides in Clytia using cell culture-based "deorphanization" of candidate oocyte-expressed GPCRs. MIHR mutant jellyfish generated using CRISPR-Cas9 had severe defects in gamete development or in spawning both in males and females. Female gonads, or oocytes isolated from MIHR mutants, failed to respond to synthetic MIH. Treatment with the cAMP analogue 5'Br-cAMP to mimic cAMP rise at maturation onset rescued meiotic maturation and spawning. Injection of inhibitory antibodies to Gα S into wild type oocytes phenocopied the MIHR mutants. These results provide the molecular links between MIH stimulation and meiosis initiation in hydrozoan oocytes. Molecular phylogeny grouped Clytia MIHR with a subset of bilaterian neuropeptide receptors including Neuropeptide Y, Gonadotropin Inhibitory Hormone, pyroglutamylated RFamide and Luqin, all upstream regulators of sexual reproduction. This identification and functional characterisation of a cnidarian peptide GPCR advances our understanding of oocyte maturation initiation and sheds light on the evolution of neuropeptidehormone systems. Non-standard Abbreviations: MIH -Maturation Inducing Hormone; GVBD -Germinal VesicleBreakdown.

Selective dephosphorylation by PP2A-B55 directs the meiosis I-meiosis II transition in oocytes

“…Intriguingly, although there is considerable conservation among the downstream phosphorylation steps associated with Cdk1 activation and meiotic progression, the upstream triggers of meiotic cell cycle resumption have diverged across evolution. For example, numerous species, including mammals, sea stars, and cnidarians (jellyfish), all utilize G protein-coupled receptors (GPCRs) that respond to hormonal signals and undergo communication with surrounding somatic ovarian cells to propagate signals (Jaffe and Norris, 2010;Quiroga Artigas et al, 2020;Tadenuma et al, 1992). However, the hormone/receptor pairs differ amongst species.…”

“…Patiria miniata ARPP19 was identified using the genomic resources at echinobase.org and previously published ovary transcriptomes (Kudtarkar and Cameron, 2017;Reich et al, 2015). Wild-type ARPP19 was amplified from first strand cDNA reverse transcribed from total ovary mRNA and cloned into pCS2+8.…”

Cellular pathways during spawning induction in the starlet sea anemoneNematostella vectensis

“…In cnidarians, light has been shown to have a fundamental role in regulating sexual reproduction. The spawning of the hydromedusa Clytia hemisphaerica and Cladonema pacificum is triggered by light-dark transition and is mediated by opsin photoreceptors from the GPCR family (Lamb et al, 2007; Quiroga Artigas et al, 2018; Quiroga Artigas et al, 2020). In the corals Acropora millepora and Acropora digitifera , the photopigment melanopsin, which belongs to the opsin family, is upregulated during the spawning night, possibly triggering different signaling cascades contributing to gamete release (Kaniewska et al, 2015; Rosenberg et al, 2017).…”

Molecular and cellular architecture of the larval sensory organ in the cnidarian Nematostella vectensis

“…We used previously published GPCR datasets of Crassostrea virginica, Platynereis dumerilii, Saccoglossus kovalevski and Drosophila melanogaster [61], as well as Homo sapiens GPCRs [62].…”