Changes of gonadotropin-releasing hormone receptor 2 during the anadromous spawning migration in Coilia nasus.

Jin-Rong Duan,Dong-Po Xu,Yan-Feng Zhou,Da-Peng Li,Di-An Fang,Pao Xu,Kai Liu,Min-Ying Zhang

doi:10.1186/s12861-016-0142-9

Jin-Rong Duan, Dong-Po Xu + Show 6 more

Open Access

https://doi.org/10.1186/s12861-016-0142-9

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Abstract

BackgroundAn increase in the activity of the pituitary-gonad axis (PG-axis) and gonad development are essential for the onset of spawning migration in teleosts. In the fish Coilia nasus, gonad development and spawning migration up the Yangtze River occurs by the end of each summer. We hypothesized that gonadotropin releasing hormones receptor 2 (GnRH-R2), which together produce a signal that interacts with the PG-axis, may help to regulate spawning migration processes.ResultsIn this regard, we (1) characterized the gonadosomatic index (GSI) in the anadromous fish C. nasus; (2) analyzed the GnRH-R2 mRNA expression levels in ovary and brain, and concentrations in the serum; and (3) identified the GnRH-R2 protein distribution in the brain and ovaries. We found strong relationships between all of these indices.ConclusionsThe results indicate that GnRH-R2 could act together to promote spawning during the anadromous migration. There is some evidence that the GnRH-R2 gene expression levels and protein distributions change in association with the migratory behavior.

Highlights

An increase in the activity of the pituitary-gonad axis (PG-axis) and gonad development are essential for the onset of spawning migration in teleosts
There was a gradual increase in the serum gonadotropin-releasing hormone (GnRH)-R2 concentrations from the onset to multiplication, and a sharp increase to the highest concentration of gonadotropin releasing hormones receptor 2 (GnRH-R2) observed during maturation; after the mature stage, significantly high levels of GnRH-R2 were maintained during the spawning and spawned stages, and there was a sharp decrease for the rest stage
The present study shows that gene expression of GnRH-R2 was elevated in association with the activation of the pituitary–gonad axis (PG)-axis, during the upstream migration of C. nasus (Fig. 4)

Summary

Introduction

An increase in the activity of the pituitary-gonad axis (PG-axis) and gonad development are essential for the onset of spawning migration in teleosts. In the fish Coilia nasus, gonad development and spawning migration up the Yangtze River occurs by the end of each summer. We hypothesized that gonadotropin releasing hormones receptor 2 (GnRH-R2), which together produce a signal that interacts with the PG-axis, may help to regulate spawning migration processes. The hypothalamic neutrohormone, gonadotropin-releasing hormone (GnRH), helps to regulate gonad function and spawning migration behaviors in fish [3,4,5,6]. Even though nearly 30 years have passed, in fish species, the distribution of GnRH-Rs in cells and tissues, their regulation, and their functions remain elusive. The characterization of GnRH-R gene expression in a single species would help to clarify the mechanisms that regulate GnRH functions [19].

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