CONNOLLY, M.H.*; HALL, B.K.; Dalhousie University, Halifax, NS; Dalhousie University, Halifax, NS: More than skin deep: tracing heat shock protein-90 expression to pigment and skeletal variation in Danio rerio

More genetic variation is present than normally expressed in the phenotype, due in part to canalization. Using embryonic zebrafish (Danio rerio), this �hidden� variation is being explored in the context of genetic assimilation by investigating the role of heat shock protein-90 (Hsp90), a cytosolic chaperone that interacts with transcription factors, mediating multiple developmental pathways. Following a 37°C heat shock during early somitogenesis (1 hour heat shock, targeting 5-12S), phenotypic variability was noted in the lower trunk and tail bud regions, where somite development was reduced or ceased prematurely. Furthermore, in situ hybridization shows that hsp90 is localized to this region 24 hours after heat shock, indicating its potential role in coordinating somitic fate. Phenotypic variation was traced among 250 individuals to further elucidate the degree of change. Here, phenotypic variation is expressed in adult pigment pattern and axial skeleton development as heat-treated fish display discontinuous melanophore stripes. In addition, bone-specific staining indicates increased variation in the shape and number of posterior skeletal elements with an increase in the number of caudal vertebrae and decrease in the number of caudal fin rays. Similarly, natural variation among zebrafish pigment patterns is accentuated with heat shock treatment creating a foundation for a selection regime and a basis for genetic assimilation. This work was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) grant to BKH.