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. 2023 May 31:14:1180725.
doi: 10.3389/fphys.2023.1180725. eCollection 2023.

Identification and characterization of gonadotropin-releasing hormone (GnRH) in Zhikong scallop Chlamys farreri during gonadal development

Juyan Tang  1 , Mengqiang Yuan  1 , Jia Wang  2 , Qianqian Li  1 , Baoyu Huang  1 , Lei Wei  1 , Yaqiong Liu  1 , Yijing Han  1 , Xuekai Zhang  1 , Xiaona Wang  1 , Meiwei Zhang  1 , Xiaotong Wang  1
Affiliations

Identification and characterization of gonadotropin-releasing hormone (GnRH) in Zhikong scallop Chlamys farreri during gonadal development

Juyan Tang et al. Front Physiol. .

Abstract

Gonadotropin-releasing hormone (GnRH) controls synthesis of sex steroid hormones through hypothalamic-pituitary-gonadal (HPG) axis in vertebrates. But in mollusks, research on neuroendocrine control of gonadal function, such as the function of GnRH during gonadal development is limited. In this study, we investigated the morphology and structure of the nerve ganglia of Zhikong scallop Chlamys farreri by physiological and histological observations. We also cloned the ORF and studied the expression patterns of GnRH in the scallop. Tissue expression analysis showed that GnRH was highly expressed in parietovisceral ganglion (PVG). The in situ hybridization result further confirmed that GnRH mRNA only distributed in some good-sized neurons in the posterior lobe (PL) and some pint-sized neurons in the lateral lobe (LL). In addition, by examining the expression of GnRH during gonadal development in ganglia, we found GnRH displayed higher expression in the female scallops, and showed significant high expression at the growing stage of female scallops in PVG. This study would contribute to gaining insight into the mechanism underlying reproduction regulation by GnRH in the scallop and help to provide a better understanding of reproductive neuroendocrine in mollusks.

Keywords: Chlamys farreri; GnRH; gonadal development; in situ hybridization; nerve ganglia.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Nerve ganglion system of C. farreri. (A) morphological and (B) histological structure of CG and PG. (C) morphological and (D) histological observation of PVG. Abbreviations: RCN, region of central neuropile; RNB, region of neuron-cell bodies; AL, anterior lobe; LL, lateral lobe; PL, posterior lobe; OL, osphradium lobe.
FIGURE 2
FIGURE 2
Sequence and phylogenetic analysis of GnRH. (A) Sequence of Zhikong scallop GnRH. Yellow, signal peptide; purple pink, GnRH peptide; green, C-terminal glycine; red, cleavage site. (B) Alignment of GnRH peptides among vertebrates, echinoderms and mollusks. (C) Neighbor-joining phylogenetic tree of GnRH.
FIGURE 3
FIGURE 3
Tissue expressions and spatial localization of GnRH. (A) Relative expressions in different tissues. Abbreviations: Man, mantle; Gil, gill; Ova, ovary; Tes, testis; Kid, kidney, Hep, hepatopancreas; Amu, adduct muscle; Pvg, parietovisceral ganglion; Cpg, cerebral and pedal ganglia. (B) Localization of GnRH mRNA in PVG. (C-F): The enlarged areas in the red boxes corresponding to panel (B). Positive signals with an antisense probe are indicated in blue, and the cell nuclei are dyed red. Red arrows indicate good-sized neurons; pink arrows indicate pint-sized neurons.
FIGURE 4
FIGURE 4
Histological observation of gonads and temporal expression of GnRH in ganglia. (A) Sections of testis and ovary during different gonadal development. Abbreviations: M, testis; F, ovary; 1, proliferative stage; 2, growing stage; 3, mature stage. F, follicle; Sg, spermatogonium; Sc, spermatocyte; Sz, spermatozoon; Og, oogonium; Oc, oocyte; MO, mature oocyte. Relative expressions of GnRH in (B) PVG and (C) CPG.
See this image and copyright information in PMC

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