Date: Monday, October 14, 2002
Time: 3:15-4:15pm
Place: 318 DBRT

Speaker: Thomas S. Vihtelic, Research Assistant Professor

From: Center for Zebrafish Research, Department of Biological Sciences
University of Notre Dame

Title: Animal Model for Genetic Analysis of the Vertebrate Visual System

Abstract
Zebrafish is a powerful model system for the genetic dissection of vertebrate developmental processes. Zebrafish development occurs rapidly and the structural organization of the adult retina and lens is achieved by 72 hours post-fertilization (pf). Furthermore, in the adult fish, all the retinal neuron types, including the rod and cone photoreceptors, are continuously generated from spatially distinct populations of retinal stem cells. Genetic and molecular strategies are being employed to identify and characterize genes critical for eye development and that function in the adult retina.

Vertebrate lens development is characterized by the morphological transformation of the embryonic anterior surface ectoderm into the differentiated lens epithelial and primary fiber cells. Three zebrafish mutant lines exhibiting defects in lens development were identified in a chemical mutagenesis screen by examination for changes in eye or pupil size at 5 days pf. Histological, immunohistochemical and tissue transplantation techniques demonstrated defects in the arrested lens and disrupted lens mutants are restricted to the lens tissue. In contrast, the lens opacity associated with increased epithelial cell proliferation in the lens opaque (lop) mutants is accompanied by photoreceptor cell degeneration.

Teleost fish possess the ability to regenerate retinal neurons. To characterize the adult stem cells that underlie the regeneration response, a protocol utilizing intense light treatment to cause photoreceptor cell death was developed. The light-induced regeneration response is characterized by a rapid increase in cell proliferation within the inner nuclear layer (INL) of the retina. The INL proliferating cells migrate to the photoreceptor layer and differentiate into rods and the different cone cell types. The neuronal cell proliferation and migration is accompanied by complex changes in the Muller glial cells, which undergo changes in gene expression and may transdifferentiate to a neuronal cell phenotype.