The pattern of gene expression in eukaryotic cells is strongly influenced by interactions with neighboring cells. When cell-cell interactions are perturbed, changes in cellular gene activity are often observed. In the vertebrate retina, inherited or acquired rod and cone degeneration results in disruption of normal interactions between photoreceptors and their support cells, the Müller cells. Under these conditions many genes such as the glial intermediate filament protein (GFAP) gene, ciliary neurotrophic factor (CNTF) gene and basic fibroblast growth factor (bFGF) gene are upregulated in neighboring Müller cells.
We use techniques such as single cell RT-PCR and differential display to study changes in gene expression patterns in Müller cells. A major goal of our current research is to elucidate the molecular mechanisms responsible for transcriptional activation, and to determine the extracellular inductive signal and the signal transduction pathways involved. Our recent cell transfection studies and experiments with GFAP-lacZ transgenic mice suggest that GFAP gene activation in Müller cells is regulated by a cell type-specific, inducible enhancer, and that GFAP gene is activated through the JAK-STAT pathway. The work on gene regulation is crucial for development of strategies for using Müller cell-specific promoters to test the biological effects of growth factors and cytokines in animals models of retinal degeneration, and more importantly for designing cell type-specific vectors for targeted delivery in gene therapy.
A second project is concerned with molecular cloning, regulation and function of neurotransmitter transporters --- a family of membrane proteins that are involved in the uptake of neurotransmitters. We are particularly interested in the role of taurine and glutamate transporters in retinal ischemia and glutamate neurotoxicity. We have already cloned and characterized GABA, taurine and glutamate transporters from retina. We have also localized the transporters to specific retinal cell types, and shown that phosphorylation may play a key role in regulating transporter function.
Publications:
Lu, S.C., Y. Bao, Z-Z. Huang, V.P. Sarthy and R. Kannan (1999) Regulation of g-glutamylcysteine synthetase subunit gene expression in retinal Müller cells by oxidative stress. Invest. Ophthalmol. Vis. Sci. 40: 1776-1782.
Sarthy, V., S. Brodjian, K. Dutt, B. Kennedy, R. French and J. Crabb (1998) Establishment and characterization of a retinal Müller cell line. Invest. Ophthalmol. Vis. Sci. 39: 212-216.
Smith, S.B., S. Brodjian, S. Patel and V. Sarthy (1997) Glial fibrillary acidic protein in the early stages of the photoreceptor cell degeneration of the mivit/mivit (vitiligo) mice. Exp. Eye Res. 64: 645-650.
Vinnakota, S., X. Qian, H. Egal, V. Sarthy and H.K. Sarkar (1997) Molecular characterization and in situ localization of a mouse retinal taurine transporter. J. Neurochem. 69: 2238-2250.
