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HAVBRUK2-Stort program for havbruksforskning

MATUREWEL - Welfare gains based on revealing molecular roles of Vgll3a in salmon puberty

Alternative title: MATUREWEL - Forbedret dyrevelferd basert på økt kunnskap om molekylære roller og funksjoner til vgll3a i laksens kjønnsmodning

Awarded: NOK 7.7 mill.

Increased knowledge on salmon puberty can improve welfare in salmon farming Salmon entering puberty early grow less than fish that stay immature longer. This is a problem for the aquaculture industry because early maturation results in small salmon with low quality that are more susceptible to diseases and have problems with the physiological processes that enable adaptation to seawater. This causes financial losses for the farming companies, and reduces the welfare of the salmon. The problem is greater in land-based fish farms, where water temperatures often are higher than in the sea, but due to climate changes, seawater temperatures are rising and making the problem worse. We have previously shown that a single gene – vgll3a – has a large effect on timing of maturation. The gene exists in two variants, one causing early and another causing late maturation, however, the mechanisms behind vgll3a’s control of puberty remain unknown. Both variants are present among the major farm strains, and to enable breeders to fully take advantage of the variant giving late maturation we need to improve our knowledge on the processes that are initiating puberty in salmon. In this project we will take advantage of the gene editing tool CRISPR to “knock out”, i.e. deactivate the vgll3a gene in salmon. This will aid in identifying the mechanisms behind the onset of puberty and the roles that vgll3a has in activating the process of maturation. Puberty is regulated by signaling molecules, so called endocrine signals, and our aim is to investigate which of these signals are connected to vgll3a and that starts – or alternatively inhibits – the onset of puberty. We will also use molecular techniques to identify which other genes, proteins and signaling molecules that are working together with vgll3a. Our goal is to develop a better understanding of which factors determine the timing of salmon puberty, so that this knowledge can be used to improve fish welfare in salmon aquaculture. So far in the project, we have followed vgll3a mutant salmon in the F1 generation, and we have observed that males lacking the vgll3a gene seem to have a delayed maturation under conditions that normally trigger high degree of maturation. These observations will be presented in the form of a master thesis as well as a scientific paper.

This project will elucidate the roles of Vgll3a in controlling timing of puberty in Atlantic salmon. In Atlantic salmon, time at maturity is a trait controlled to a large extent by a major effect locus with SNPs near or within vgll3a on chromosome 25, having alleles causing early (E) and late (L) onset of puberty. The function of Vgll3a is not well characterized in animals, however, the Vgll3 protein is associated with the Hippo signaling pathway, which is involved in controlling proliferation in various tissues, including gonads. Previous investigations have characterized cellular localization and gene regulation of vgll3 in male and female salmon gonads, and examined the possible connection to the Hippo pathway. In addition, we have identified genes in salmon pituitary and gonad tissues which are differentially regulated depending on vgll3a genotype. The mechanisms by which Vgll3a elicits its effects on maturation are currently unknown. However, we have results from pituitary and testis tissue culture experiments pointing to a mechanism mediated through the vgll3a L allele, involving secretion of one or more unidentified endocrine factors with the ability to inhibit pubertal activation in the pituitary. To elucidate the mechanisms by which Vgll3a modulates the pubertal timing, we aim to identify proteins interacting with Vgll3a, and identify downstream target genes, using gene-edited vgll3a knockout salmon lines as a model in combination with tissue and cell culture experiments. Using these approaches will also allow experiments to identify the currently unknown endocrine signaling responsible for inhibiting the onset of puberty in LL animals, potentially useful as biomarkers for late maturation, which will contribute to more precise breeding protocols for late maturation in salmon.

Publications from Cristin

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Funding scheme:

HAVBRUK2-Stort program for havbruksforskning