CRYSTALLIN GENES--STRUCTURE, ORGANIZATION, EXPRESSION, AND EVOLUTION

National Eye Institute

Investigators

Linked publications & trials

Abstract

We have been studying crystallins, the abundant water-soluble proteins responsible for the optical properties of the eye lens as a model of tissue-specific gene expression. Crystallins are particularly interesting since they are often expressed in non-lens tissues at lower concentration where they have enzymatic or other non-refractive functions. Within this fiscal year we have published our findings that myocilin mRNA is present in human intact and organ-cultured mouse trabecular meshwork, but not in human primary TM cell cultures. Myocilin mRNA could be induced from the TM cell cultures by TGFbeta, dexamethasone or mechanical stretch. We have also continued to characterize a mouse corneal epithelial cell line that proliferates under permissive conditions and that slows its growth rate and increases aldehyde gene expression under nonpermissive conditions for cell growth. Transgenic mice expressing truncate forms of Pax-6 in the lens were shown to have altered lens morphology were made and the results published. We also produced transgenic mice showing that the enhancer-independent alphaB-crystallin promoter is active specifically in the lens and corneal epithelium, linking lens and corneal gene expression to a small proximal promoter fragment utilizing Pax-6 and retinoic receptors. Lens expression started in the embryo, while corneal expression was not detected until one month after birth. We published our findings that betaB2-crystallin mRNA and protein are expressed in the retina, brain and testis of mice, establishing that this crystallin is not lens-specific and suggesting that it has a yet to be discovered non-refractive function. Current experiments this year have resulted in the cloning of the rabbit aldehyde dehydrogenase 1 cDNA and gene, and the initiation of promoter studies of the aldehyde dehydrogenase 1 promoter. Also accepted for publication is our characterization of the scallop aldehyde dehydrogenase/omega crystallin. It was found to be an inactive, dimeric member of the aldehyde dehydrogenase family that does not bind NAD or NADP. It is expressed mainly in the lens, next in the cornea, and to a much lesser extent in several non-eye tissues. We have also cloned the scallop omega-crystallin gene and shown that its promoter is active in mammalian cells. Sequence data and transfection tests indicate that the transcription factor, CREB/CREM, is important for omega-crystallin promoter activity, and suggest that Pax-6 may also play a role in its activation.