A Hypothetical Ring Finger Protein is Differentially Expressed in Aging Monkey and Human Retina

Abstract

Abstract: : Purpose: Age related retinal changes are well documented, and include alterations in dark adaptation, accumulation of lipofuscin in cones and RPE, and increased level of apoptosis. Thses changes may also predispose to ARMD. Little is known of the molecular causes of these changes. We hypothesized that age-related differential gene expression may play a key role in age-related retinal changes, and may shed light on the molecular basis of age related retinal diseases. Methods: Human retina cDNA library clones were arrayed at high density on nylon membranes and screened with cDNA probes generated from mRNA from young (4 year old) and old (80 year old) human retinae. Clones showing a more than two fold difference in intersity were re-screened by southern blot analysis using cDNA probes prepared from mRNA from young (2-3 year old) and old (15-30 year old) rhesus monkey retinae. True age related changes were confirmed by two methods: 1. Northern analysis using multiple age samples from both monkey and human. 2. Real time quantitative rt-PCR (RQ-PCR). Results: Approximately 1.6% of the 55,368 retina expressed sequences examined showed age related changes between young and old human. Less than 0.2% of all clones showed changes in both human and monkeys. One clone revealed a roughly two fold change in young and old monkey retina. Sequence analysis of this clone showed 100% homology with a human ring finger protein. Northern blot analysis using multiple monkey tissue show that this gene is dominantly expressed in brain and retina. Northern analysis with mutliple age samples show that this gene changes two-fold, and by RQ-PCR, significantly declines nearly two-fold (35,000 v. 20,000; p=0.015). Conclusions: There are few true age-related gene expression changes. The age associated ring finger protein has the ring domain at the amino terminus, which suggests that it may be involved in protein-protein binding and interaction. We are currently studying its cellular localization and expression in vivo, to help better understand its function.

Keywords: aging • gene/expression