Indy (acronym for I'm Not Dead Yet) is a recently identified gene in Drosophila which, when made dysfunctional, leads to doubling of life span in the organism. This gene codes for a plasma membrane transporter (INDY) that mediates the cellular uptake of citric acid cycle intermediates. It is believed that disruption of the function of this gene reduces the availability of key metabolic intermediates to the cells for energy production and thus creates a metabolic condition similar to that of caloric restriction. However, it is not known whether the involvement of the indy gene function as a determinant of life span can be reproduced in organisms other than Drosophila. This would require selection of a suitable alternative model organism and identification of the gene in the organism that is the counterpart of Drosophila INDY. The purpose of the current project is to use C. elegans as a model system to address this novel and intriguing link between membrane transport and life span. Studies completed thus far show that C. elegans expresses three different transporters for citric acid cycle intermediates. Two of these transporters, ceNaDC2 and ceNaCT, play a significant role as determinants of life span. In addition, knockdown of ceNaCT produces a novel, hitherto unrecognized, phenotype with a reduced body size (""""""""lean"""""""" phenotype). There is also evidence to show that ceNaCT is the most likely counterpart of Drosophila INDY.
The specific aims of this project are: 1) analyze the tissue-specific expression patterns of ceNaDC2 and ceNaCT, 2) knockdown cenadc2 and cenact genes either independently or in combination using a modified RNAi technique and determine its influence on life span and body size, 3) inactivate each of these two genes by a reverse genetic approach to establish mutant lines and study the influence of heterozygous and homozygous knockout on life span and body size, 4) investigate the interaction of these genes with other known gerontogenes (e.g., daf-2, age-l, clk-1, and eat-2) as determinants of life span to understand the diversity and/or overlap of the signaling pathways involved in the modulation of life span by these genes, and 5) identify specific inhibitors/blockers for ceNaDC2 and ceNaCT and assess the influence of such inhibitors/blockers on the life span of the organism. These studies using a simple model organism will provide unequivocal evidence for the first time linking a membrane transport activity to life span and body size and for the interaction of the nadc2 and nact genes with other known gerontogenes as determinants of life span.
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