A proteome map of the zebrafish (Danio rerio) lens reveals similarities between zebrafish and mammalian crystallin expression

PURPOSE To characterize the crystallin content of the zebrafish lens using two-dimensional gel electrophoresis (2-DE). These data will facilitate future investigations of vertebrate lens development, function, and disease. METHODS Adult zebrafish lens proteins were separated by 2-DE, and the resulting spots were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). The relative proportion of each crystallin was quantified by image analysis, and phosphospecific staining was used to identify phosphorylated alpha-crystallins. The proportion of each crystallin in the soluble and insoluble fraction of the lens was also determined by resolving these lens fractions separately by 2-DE. RESULTS alpha-, beta-, and gamma-crystallins comprised 7.8, 36.0, and 47.2% of the zebrafish lens, respectively. While the alpha-crystallin content of the zebrafish lens is less than the amounts found in the human lens, the ratio of alphaA:alphaB crystallin is very similar. The phosphorylation pattern of zebrafish alphaA-crystallins was also similar to that of humans. The most abundant gamma-crystallins were the diverse gammaMs, comprising 30.5% of the lens. Intact zebrafish crystallins were generally more common in the soluble fraction with truncated versions more common in the insoluble fraction. CONCLUSIONS While the total alpha- and gamma-crystallin content of the zebrafish lens differs from that of humans, similarities in alpha-crystallin ratios and modifications and a link between crystallin truncation and insolubility suggest that the zebrafish is a suitable model for the vertebrate lens. The proteome map provided here will be of value to future studies of lens development, function, and disease.