Abstract
Abstract: :
Purpose: NeuroD is a basic helix–loop–helix (bHLH) transcription factor that in the adult teleost retina is expressed in cells of the rod photoreceptor lineage (Hitchcock and Ochocinska, ARVO Abstract 2003). The purpose of this investigation is to characterize the spatial and temporal expression pattern of neuroD in the developing retina of the zebrafish. Methods: In situ hybridization using DIG–labeled riboprobes was performed in zebrafish embryos between 25 and 76 hours post fertilization (hpf). Bromodeoxyuridine (BrdU) was used to label mitotically active cells in these animals by briefly soaking them in 5mM BrdU and 15%DMSO in embryo rearing solution. Results: The expression of neuroD begins at 31hpf in a cluster of cells in the precocious ventronasal patch. Between 31hpf and 48hpf, neuroD expression expands from the vetronasal patch through the developing layers of the retina. At 48hpf and beyond, when the three nuclear layers are formed, neuroD is expressed in the inner and the outer nuclear layers. In the INL, neuroD is expressed in putative amacrine cells and INL progenitors, characterized by their neuroepithelial morphology. In the ONL, neuroD is expressed in developing cone photoreceptors, and rod precursors, identified by double labeling with neuroD and BrdU. Conclusions:In early retinal development neuroD defines the cellular origin of the precocious ventral patch of rod photoreceptors. At later embryonic stages the cellular pattern of neuroD expression appears similar to that observed in the adult teleost retina.
Keywords: retinal development • gene/expression • retina