Donald J. Zack, M.D., Ph.D.
Associate Professor of Ophthalmology and Neuroscience
Room 809, Maumenee Building
Molecular Approaches to the Study of Retinal Development and Function
Regulation of rhodopsin gene expression: The goal of this project is to understand the molecular basis of retinal development using regulation of rhodopsin gene expression as a model system. We are interested in the mechanisms which determine retinal cell fate, i.e. determine whether a particular multipotential retinal progenitor cell will become, for example, a photoreceptor, ganglion cell, or bipolar cell. What are the molecular mechanisms that determine which visual pigment an individual photoreceptor will express? More specifically, which cis-acting DNA regulatory sequences and trans-acting regulatory factors are involved? Which other genes share the same regulatory elements? Are there "master" regulatory factors analogous to the muscle system's myo-D which control a number of different photoreceptor-specific genes? These questions are being explored experimentally using transgenic mice, gel mobility shift assays, DNase I footprinting, protein purification, in vitro transcription analysis, and DNA and yeast one-hybrid cloning. Among the transcription factors that we have cloned by this approach is Cone Rod Homeobox (CRX), which regulates the expression of a number of photoreceptor-specific genes and is mutated in several forms of retinal degeneration. The definition of retina-specific promoters is making possible targeted expression of altered genes to the retina, as well as the development of inducible promoter systems. This is facilitating the generation of animal models of human retinal disease and may have implications for future attempts towards gene therapy, particularly in light of the finding that mutations in the rhodopsin gene are responsible for some forms of the human retinal degeneration retinitis pigmentosa.
Neurotrophic factors and retinal degeneration: In collaboration with Drs. Ruben Adler and Peter Campochiaro , we are utilizing a variety of approaches to analyze the mechanisms by which neurtrophic factors promote photoreceptor survival in a number of animal models of retinal degeneration.
Molecular biology of ganglion cells and glaucoma: Ganglion cells serve as the output pathway from the retina and are involved in initial signal processing. Glaucoma is a disease that kills ganglion cells, and there is evidence that certain subsets are more sensitive than others. We are using molecular biology approaches to explore the mechanism by which ganglion cells die. In collaboration with Dr. Harry Quigley, we have shown that ganglion cells in an animal model of glaucoma can die by apoptosis. We are examining the role of genes which have already been implicated in apoptosis. We are also developing retinal cDNA based microarrays to study gene expression changes associated with glaucoma, as well as in a number of other retinal diseases.