Meeting Abstract

66.5  Wednesday, Jan. 6  The Evolution of Sex Determination in Stickleback Fishes URTON, J.R.*; BRUNER, A.M.; MCCANN, S.R.; BALCELLS, R.; PEICHEL, C.L.; Fred Hutchinson Cancer Research Center; Fred Hutchinson Cancer Research Center; Fred Hutchinson Cancer Research Center; Fred Hutchinson Cancer Research Center; Fred Hutchinson Cancer Research Center cpeichel@fhcrc.org

Sex determination is critical to an individual’s fitness. But, the initial sex determination signal and sex chromosomes can vary between closely related species. To understand this evolutionary process, it is important to study closely related species with different sex chromosomes and sex determination signals. In the stickleback family (Gasterosteidae), at least five sex chromosome systems have evolved in the last 35 million years. It is possible that each stickleback species has evolved a different sex determination gene. Alternatively, all sticklebacks could share the same sex determination gene, which has been transposed to different sex chromosomes. To address these possibilities, we must identify the sex determination gene in each species. We are starting our search in the threespine stickleback (Gasterosteus aculeatus), which has an XX-XY sex chromosome system and numerous genetic and genomic tools available. Our past genetic mapping approaches to find the threespine stickleback sex determination gene have not proved feasible. Thus, we are using a Solexa/RNA-Seq approach to identify transcripts present at the earliest stage of male gonadal differentiation. We will identify X and Y chromosome genes that are expressed during this developmental period and screen candidate genes using a transgenic assay to see if expression in female (XX) embryos causes male phenotypic development. Once we identify the threespine stickleback sex determination gene, we can see if this gene is present in other stickleback species, and ultimately gain insight into the evolution of sex determination pathways in this family.