Abstract
Abstract: :
Purpose: : Cell-specific markers are highly desirable in neurobiological studies of subsets of morphologically similar populations of neurons such as amacrine cells. In the course of screening transgenic mice recently generated in our lab, we have come across a line in which Enhanced Green Fluorescent Protein (EGFP) is expressed in a subset of amacrine cells in the inner nuclear layer (INL). The aim of this study was to characterize the amacrine cells based on their morphology and known immunological markers. Methods: Transgenic mice were generated by injecting a construct consisting of a 1.2 kb CD44 promoter and the EGFP gene. Retinas from transgenic animals were examined by confocal microscopy to screen for EGFP-positive cells. Subsequently, immunohistochemistry was preformed on 10µm frozen sections to determine the stratification pattern of the amacrine cells. Results: A subpopulation of amacrine cells was found to express EGFP in the retinas of CD44 - EGFP transgenic mice. The labeled cells had a density of 1499 ± 57.7 cells per mm2 and had axonal arborizations that extended laterally between 20-50 µm. When retinas were stained with anti-ChAT, the EGFP-axons could be seen to projecte to stratum 4 near the On-Starburst amacrine cell processes, and below band 3 that is labeled by antibodies against GLT-1. Also, these cells do not appear to be GABAergic since they did not co-localize with anti-GAD. Conclusion: The narrow-field amacrine cell that is labeled by EGFP in our transgenic mouse line stratifies is stratum 4. The lack of GAD co-localization in these cells, suggests that they are possibly glycinergic. The EGFP label should facilitate further characterization of these cells by allowing their targeting for electrophysiological and molecular studies.
Keywords: 312 amacrine cells • 557 retina: proximal(bipolar, amacrine, and ganglion cells) • 434 immunohistochemistry