ZFIN ID: ZDB-PUB-060124-23
Gene duplication and separation of functions in alphaB-crystallin from zebrafish (Danio rerio)
Smith, A.A., Wyatt, K., Vacha, J., Vihtelic, T.S., Samuel Zigler, J. Jr, Wistow, G.J., and Posner, M.
Date: 2006
Source: The FEBS journal   273(3): 481-490 (Journal)
Registered Authors: Posner, Mason, Vihtelic, Thomas
Keywords: none
MeSH Terms:
  • Alternative Splicing*
  • Amino Acid Sequence
  • Animals
  • Cloning, Molecular
  • Electrophoresis, Gel, Two-Dimensional
  • Electrophoresis, Polyacrylamide Gel
  • Gene Duplication*
  • Gene Expression Regulation
  • Humans
  • Molecular Sequence Data
  • Phylogeny
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Alignment
  • Temperature
  • Time Factors
  • Zebrafish/genetics*
  • alpha-Crystallin B Chain/genetics*
  • alpha-Crystallin B Chain/physiology*
PubMed: 16420472 Full text @ FEBS J.
We previously reported that zebrafish alphaB-crystallin is not constitutively expressed in nervous or muscular tissue and has reduced chaperone-like activity compared with its human ortholog. Here we characterize the tissue expression pattern and chaperone-like activity of a second zebrafish alphaB-crystallin. Expressed sequence tag analysis of adult zebrafish lens revealed the presence of a novel alpha-crystallin transcript designated cryab2 and the resulting protein alphaB2-crystallin. The deduced protein sequence was 58.2% and 50.3% identical with human alphaB-crystallin and zebrafish alphaB1-crystallin, respectively. RT-PCR showed that alphaB2-crystallin is expressed predominantly in lens but, reminiscent of mammalian alphaB-crystallin, also has lower constitutive expression in heart, brain, skeletal muscle and liver. The chaperone-like activity of purified recombinant alphaB2 protein was assayed by measuring its ability to prevent the chemically induced aggregation of alpha-lactalbumin and lysozyme. At 25 degrees C and 30 degrees C, zebrafish alphaB2 showed greater chaperone-like activity than human alphaB-crystallin, and at 35 degrees C and 40 degrees C, the human protein provided greater protection against aggregation. 2D gel electrophoresis indicated that alphaB2-crystallin makes up approximately 0.16% of total zebrafish lens protein. Zebrafish is the first species known to express two different alphaB-crystallins. Differences in primary structure, expression and chaperone-like activity suggest that the two zebrafish alphaB-crystallins perform divergent physiological roles. After gene duplication, zebrafish alphaB2 maintained the widespread protective role also found in mammalian alphaB-crystallin, while zebrafish alphaB1 adopted a more restricted, nonchaperone role in the lens. Gene duplication may have allowed these functions to separate, providing a unique model for studying structure-function relationships and the regulation of tissue-specific expression patterns.