Molecular cloning, developmental expression, and hormonal regulation of zebrafish (Danio rerio) beta crystallin B1, a member of the superfamily of beta crystallin proteins

The cDNA sequence of beta crystallin B1 was determined from zebrafish (Dani o rerio) and compared to the corresponding genes of bovine, rat, chicken, h uman, and Xenopus, Multispecies comparison of superfamily diversity demonst rated beta crystallin B1 homology between zebrafish, bovine, chicken, and r at, but large distances to beta crystallin B2 and B3, Zebrafish cDNA has a size of 943 nucleotides and encodes a polypeptide of 233 amino acids. Zebra fish beta crystallin B1 shares 71.30, 75.86, and 71.00% similarities with b ovine, chicken, and rat beta crystallin B1, respectively. Northern blot ana lysis revealed a single 0.9-kb beta crystallin B1 transcript which was expr essed and progressively increased in the first 20 h of zebrafish embryogene sis. Whole-mount in situ hybridization revealed that the beta crystallin B1 transcript was only specifically expressed in the lens region of the eye. A starvation experiment revealed no variation in mRNA levels after 14 and 2 1 days. An experiment in which hormone was injected showed that the beta cr ystallin BI transcript first increased 24 h after the injection of insulin- like growth factor I, insulin-like growth factor II, or growth hormone, the n decreased 48 h after injection, The beta crystallin B1 transcript continu ously increased after insulin was injected. Taken together, our results ide ntify the early specific expression of beta crystallin B1 within the lens. Despite small differences, these results indicate that both the structure o f the beta crystallin B1 protein and its involvement with regulation by gro wth factors appear to have been remarkably conserved. (C) 2001 Academic Pre ss.