An ultramicroscopic study on the distribution of Muller cell processes in the outer retinal layers of the zebrafish

Abstract

The zebrafish, Brachydanio rerio, is a good model for studying the development of various organs. We have assayed the distribution pattern of Muller cell processes in zebrafish retinas by electron microscopy. In the outer nuclear (ON) layer, multiple Layers of Muller cell processes were present along both sides of the large pyramidal endings of the synaptic terminals. We found that the inner segments (ISs) of the zebrafish photoreceptors (PRs), including the cones, double cones and rods, were arranged in different planes, and that the Muller cell processes formed multilayered sheaths around virtually all PR compartments except their outer segments. Thus, Muller cell processes beyond the outer limiting membrane (OLM) are more easily observed in zebrafish retina than in the retinas of other species. To our knowledge, this is the first study to show the exact ultrastructural distribution of Muller cell processes around the OLM and the PR layer in zebrafish retina. (c) 2005 Elsevier GmbH. All rights reserved.