Evolution of Molecular Investigations on Sturgeon Sex Determination and Most Recent Developments in DNA Methylation with a Focus on the Siberian Sturgeon

Sturgeon aquaculture is largely based around females due to caviar production. In the absence of sexual dimorphism and differentiated gonads in juveniles, the gender sorting of sturgeon is carried out at about 2–3 years old depending on rearing conditions, which increases farming costs. Identification of a molecular sex determination mechanism or of a molecular sex marker could lead to earlier sex identification. For decades scientists have developed different methods and approaches to identify a way in which sturgeon can be sexed. In this chapter we gather together the different approaches employed: heterogametic sex chromosome identification, random identification of molecular polymorphisms, transcriptome sequencing, and targeting sequences of interest. We have included our own results from juvenile and adult Siberian sturgeon on the inter simple sequence repeat (ISSR) with the support of hierarchical cluster analysis and on the expression of genes known to be involved in sex differentiation, Foxl2, So9, Igf1, and Fgf9. To date, no sex marker has been identified following these methods. We also present the advantages of DNA methylation to assess gene expression regulation, which opens up new perspectives in sex determination and differentiation research in fish. The first investigation of DNA methylation of DMRT1 using MS-HRM technology in sturgeon will conclude this chapter.