Eye lens regeneration and the crystallins in the adult newt, Notophthalmus viridescens.
Upon lens removal, the adult Eastern Spotted newt, Notophthalmus viridescens, has the capacity to regenerate an ocular lens. Crystallins, proteins characteristic of the vertebrate lens, were studied from normal and 3-month regenerated adult newt lenses. When separated by high-performance liquid chromatography (HPLC) or Sephadex G-200SF column chromatography, the crystallins from normal and regenerated lenses were fractionated into what appear to be the classical four groups: alpha, beta High, beta Low, and gamma. Upon further examination by immunoelectrophoresis, the first peak contains both alpha and beta crystallins. This study provides evidence that most of the crystallins from the regenerated lenses share biochemical properties with those of the normal lens crystallins based on their native molecular weight, isoelectric point, and the molecular wt of their constituent polypeptides, indicating that the fidelity of gene expression in reactivated iris tissue is high. Some differences are found between normal and regenerated lens crystallins and are most obvious in the beta-crystallin region: the proportion of beta crystallins is decreased in regenerated lenses when the total proteins are fractionated by column chromatography and some of the beta-crystallin polypeptide chains found in normal lenses are missing from regenerated lenses. Iris epithelial cells are normally withdrawn from the cell cycle and are synthesizing a tissue-specific product, melanin. After lentectomy these cells dedifferentiate, redifferentiate into lens cells, and their progeny then synthesize different tissue-specific proteins, crystallins. Little is known about the specific mechanism(s) for the activation of gene expression in eukaryotes, but the regenerating lens suggests itself as a good model in which to study this biological problem.
Borst
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Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine 19104.
McDevitt
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D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D007122:Immunoelectrophoresis; D007525:Isoelectric Focusing; D007526:Isoelectric Point; D007908:Lens, Crystalline / Q000502:physiology*; D008970:Molecular Weight; D009673:Notophthalmus viridescens; D012038:Regeneration
D003459:Crystallins