We are interested in the mechanisms that direct development and degeneration of the central nervous system (CNS) of vertebrates. We are focussing our studies on the vertebrate retina, a relatively simple and well-characterized area of the CNS. We use genomics approaches to determine how the retina uses a large repetoire of genes to form this complex tissue of >60 neuronal cell types. To aid in these studies, we carry out lineage studies wherein we mark individual progenitor cells in vivo, and analyze the types of neurons produced. To study the function of regulatory genes, we have developed an electroporation method and a series of plasmids that promote the regulated expression of short hairpin RNAs, cDNA, or multiple genes and shRNA species. This method allows for relatively rapid assessment of gene function, including genetic epistasis. We also use this method to investigate the sequences that control the expression of regulatory genes, in order to place such genes into a regulatory network. To understand the connections among these neurons in retinal circuits, and more generally to discover the circuitry of CNS neurons, we have recently developed novel viral vectors which move transsynaptically in vivo.

We are also interested in the mechanisms that lead to the death of photoreceptors in the many inherited forms of human blindness. Through examination of gene expression changes that accompany photoreceptor death in murine models of the human diseases, retinitis pigmentosa, we have discovered that the metabolism of cone photoreceptors appears to be stressed to the point that the cells undergo autophagy. We have found that we can slow down the death of these cells through administration of insulin, whereas the death is accelerated if animals are depleted for insulin. In addition, we have found that delivery of the histone deacetylase 4 gene can slow down the autonomous death of mutant rod photoreceptors via stabilization of the hypoxia inducible factor 1 alpha. We are now investigating whether gene therapy approaches that follow from these findings might extend vision in animal models, with the goal of developing a therapy for humans.

References:
Cherry TJ, Trimarchi JM, Stadler MB, Cepko CL. Development and diversification of retinal amacrine interneurons at single cell resolution Proc Natl Acad Sci U S A. 2009 Jun 9;106(23):9495-500.

Chen, B and Cepko, C. HDAC4 regulates neuronal survival in normal and diseased retinas. Science, 323(5911):256-259 (2009).

Punzo C., Kornacker K., Cepko C.L. Stimulation of the insulin/mTOR pathway delays cone death in a mouse model of Retinitis Pigmentosa. Nature Neuroscience, 12(1):44-52. (2009).

Beier, K., Saunders, A., Oldenburg, I.A., Miyamichi, K., Akhtar, N., Luo, L., Whelan, S., Sabatini, BL., and Cepko, CL. Anterograde or retrograde transsynaptic labeling of CNS neurons with vesicular stomatitis virus vectors, Proc Natl Acad Sci U S A. In Press. (2011).