Abstract
Purpose: :
Retinal waves in the developing vertebrate retina influence both the size and complexity of retinal ganglion cell (RGC) dendrites and RGC axon target refinement. Acetylcholine delivery onto nicotinic acetylcholine receptors (nAchRs) partly modulate these effects. We report altered expression of nAchR subunits in both healthy and glaucomatous adult mouse retinas.
Methods: :
Pooled whole retinas from DBA/2J or C57BL/6J mice at young (2-3M), adult (12M) and elderly (16-18M) age groups were prepared for Gene-Chip analysis. Globes were fixed in formaldehyde and sectioned for immunofluorescense (IF). Sectioned retinas were subjected to Trilogy(Cell Marque, CA) antigen retrieval and labeled with antibodies against nicotinic acetylcholine receptor alpha 6 subunit (Chrna6). Brain, retina and RGC-5 cell line lysates were analyzed by western blot (WB) for Chrna6 expression. Quantitative trait locus analysis (QTL) was utilized to obtain gene cellular signatures.
Results: :
Chrna6 expression is enriched in the RGC layer. Using bioinformatic tools in GeneNetwork (genenetwork.org), Chrna6 had a cellular expression signature for retinal ganglion cells with a high correlation to Thy1 (r=0.65), a well recognized RGC marker. Chrna6 protein was detected by WB in whole retina and RGC-5 cell line lysates. Gene array data analayzed with Affymetrix Microarray Suite 5.0 demonstrate decreased Chrna6 expression in aged, glaucomatous DBA2/J retinas compared to young, non-glaucomatous DBA2/J retinas and to age-matched C57/Bl6 non-glaucomatous controls. Adult C3H retinas, which lack photoreceptors, maintain Chrna6 expression in the RGC layer.
Conclusions: :
Chrna6 is highly expressed in the mouse retina RGC layer. WB analysis of RGC-5 cell line lysates and quantitative trait locus analysis provide additional support for Chrna6 as an RGC marker. Chrna6 expression decreases with glaucomatous RGC changes in the DBA/2J mouse model, providing more support for Chrna6 as a RGC marker. High expression of RGC Chrna6 in the absence of photoreceptors is suggestive that Chrna6 expression by RGCs is independent of photoreceptor derived stimuli.
Keywords: aging • ganglion cells • nerve fiber layer