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Scientific leaders: R. Guyomard (GABI), E. Quillet (GABI), Alexis Fostier (LPGP), Y. Guiguen (LPGP)
Technical leaders: Lionel Goardon, François Guyvarc’h, Lise-Anna Le Ven
Contact : Edwige Quillet

Start date: 2008      Planned duration: > 5 years

INRA research unit partners

• INRA - GABI-GenAqua
• INRA - LPGP, Rennes (including technical breeding and transgenic platforms)

Access conditions: Strain available in the framework of scientific collaborations with the INRA research units GABI and LPGP on a case-by-case basis (material transfer agreement (MTA) regarding the use of animals and derived tissues or cells).

Objectives

• Characterise, with the trout model, the origin and determinism (genetic and environmental) of spontaneous masculinisation, which adds to the main determinant contributed by the Y chromosome.
• Improve general knowledge about sex determinism in fish.
• Develop more sustainable methods of sex inversion (reducing the amount of masculinising hormones necessary to induce XX males in the production of the monosex female populations used in fish farming).

Experimental design

Main sex determinant
Monosex female (all XX) and male (all XY, obtained from producing YY individuals) strains have been used to analyse differential expression in male and female gonads undergoing differentiation, an analysis that has potentially identified the main sex determinant. The candidate sequence was located on the sex chromosome, and its linkage with the phenotypic sex was validated in a large number of individuals within the reference rainbow trout strain maintained at PEIMA (SY strain) before functional validations were performed (at LPGP), which validated the sdY gene as the main sex determinant in the species. The monosex strains served as controls in several stages of the project.

Minor determinants
A high-frequency strain was established, and then maintained, from crossings using spontaneous XX males. An isogenic strain with a high rate of spontaneous masculinisation was also identified. These breeders are used to form families with known genetic structure that are used in functional studies (development of gonadic differentiation, expression profiles, temperature effect, etc.) or genetic studies (QTL mapping and search for causal genes).