Abstract
Abstract: :
Purpose: ROSA 3 transgenic mice carry the coding sequence of bacterial ß-galactosidase under the control of an undefined murine promoter. Previously, we described the apparent restricted expression of this reporter in ganglion cells of the retina. These studies were extended to confirm the ganglion cell-specific expression of this gene and to examine the pattern of expression in other neurons of the CNS. Methods: Ganglion cell specific expression was determined by co-localizing ß-galactosidase activity and neurotracer fluorogold (FG). The tracer was localized to ganglion cells via retrograde transport after injection into the superior colliculus (SC). Changes in enzyme levels after damage to ganglion cells were monitored by histochemistry and ELISA assays. Neuronal expression in the brain was determined by histochemistry. Results: Reporter enzyme activity and protein levels decrease in retinas subjected to treatments that cause retinal ganglion cell death including, optic nerve crush and intravitreal injections of the glutamate analog NMDA. Injection of FG into the SC of ROSA 3 mice leads to nearly complete labeling of ganglion cells in the retina. Subsequent histochemistry for enzyme activity showed that 100% of ß-galactosidase positive cells in the ganglion cell layer were FG positive, but only ∼70% of FG positive cells expressed this transgene. Transgene expression in the brain was limited. Prominently labeled cells included the CA1 pyramidal neurons of the hippocampus and purkinje neurons of the cerebellum. Conclusion: The ROSA 3 locus is expressed in a sub-set of retinal ganglion cells and in select neurons in the brain, suggesting a functional and molecular similarity between some ganglion cells and other neurons of the CNS. Efforts are underway to identify the DNA sequences that control ROSA 3 expression, starting with the characterization of the transgene integration site in the mouse genome.
Keywords: 415 ganglion cells • 323 apoptosis/cell death • 316 animal model