Pituitary Gonadotropin Gene Expression During Induced Onset of Postsmolt Maturation in Male Atlantic Salmon: and Tissue Culture Studies

Overview

Journal Front Endocrinol (Lausanne)

Specialty Endocrinology

Date 2022 Apr 4

PMID 35370944

Authors

Diego Crespo

Kai Ove Skaftnesmo

Erik Kjaerner-Semb

Ozlem Yilmaz

Birgitta Norberg

Sara Olausson

Petra Vogelsang

Jan Bogerd

Lene Kleppe

Rolf B Edvardsen

Eva Andersson

Anna Wargelius

Tom J Hansen

Per Gunnar Fjelldal

Rudiger W Schulz

Affiliations

Soon will be listed here.

Abstract

Precocious male maturation causes reduced welfare and increased production costs in Atlantic salmon () aquaculture. The pituitary produces and releases follicle-stimulating hormone (Fsh), the gonadotropin triggering puberty in male salmonids. However, little is known about how Fsh production is regulated in Atlantic salmon. We examined, and , transcriptional changes of gonadotropin-related genes accompanying the initial steps of testis maturation, in pituitaries of males exposed to photoperiod and temperature conditions promoting maturation (constant light and 16°C). Pituitary , and transcripts increased in maturing males (gonado-somatic index > 0.1%). RNA sequencing (RNAseq) analysis using pituitaries from genetically similar males carrying the same genetic predisposition to mature, but differing by responding or not responding to stimulatory environmental conditions, revealed 144 differentially expressed genes, ~2/3rds being up-regulated in responders, including and other pituitary hormones, steroid-related and other puberty-associated transcripts. Functional enrichment analyses confirmed gene involvement in hormone/steroid production and gonad development. In studies, whole pituitaries were exposed to a selection of hormones and growth factors. Gonadotropin-releasing hormone (Gnrh), 17β-estradiol (E) and 11-ketotestosterone (11-KT) up-regulated and , while was up-regulated by Gnrh but down-regulated by 11-KT in pituitaries from immature males. Also pituitaries from maturing males responded to Gnrh and sex steroids by increased and transcript levels, but expression remained unchanged. Growth factors (inhibin A, activin A and insulin-like growth factor 1) did not change , or transcript levels in pituitaries either from immature or maturing males. Additional pituitary studies on candidates identified by RNAseq showed that these transcripts were preferentially regulated by Gnrh and sex steroids, but not by growth factors, and that Gnrh/sex steroids were less effective when incubating pituitaries from maturing males. Our results suggest that a yet to be characterized mechanism up-regulating expression in the salmon pituitary is activated in response to stimulatory environmental conditions prior to morphological signs of testis maturation, and that the transcriptional program associated with this mechanism becomes unresponsive or less responsive to most stimulators once males had entered pubertal developmental .

Citing Articles

Loss of Fshr Prevents Testicular Maturation in Atlantic Salmon (Salmo salar L.).

Andersson E, Schulz R, Almeida F, Kleppe L, Skaftnesmo K, Kjaerner-Semb E Endocrinology. 2024; 165(4).

PMID: 38298132 PMC: 10878062. DOI: 10.1210/endocr/bqae013.

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