Hsp 90α and Hsp 90β Genes Are Present in the Zebrafish and Are Differentially Regulated in Developing Embryos

Abstract

We have employed a polymerase chain reaction-based cloning strategy to demonstrate that both hsp 90α and hsp 90β genes are present in the zebrafish. The fact that zebrafish represents the most primitive vertebrate in which hsp 90 genes have been isolated to date has allowed us to determine that the duplication event which generated the hsp 90α and hsp 90β genes occurred shortly before the emergence of the teleosts from the rest of the vertebrate lineage. In expression studies using Northern blot analysis, hsp 90β mRNA was found to be present at control temperatures throughout normal embryonic development whereas hsp 90α mRNA was barely detectable. Upon heat shock, hsp 90α mRNA levels increased dramatically in all developmental stages examined. The levels of hsp 90β mRNA increased 2-3 fold during heat shock of early stage embryos. Thus, the hsp 90α gene is strongly upregulated during heat shock in zebrafish embryos whereas expression of the hsp 90β gene appears to be weakly induced.