Chronic chemogenetic activation of the superior colliculus in glaucomatous mice: local and retrograde molecular signature

One important facet of the glaucoma pathology is axonal damage, which ultimately disrupts the connection between the retina and its postsynaptic targets. The concurrent loss of retrograde support interferes with the functionality and survival of the retinal ganglion cells (RGCs). Con-versely, previous research has shown that stimulation of neuronal activity in a primary retinal target area—i.e., the superior colliculus— promotes RGC survival in an acute mouse model of glaucoma. To build further on this observation, we applied repeated chemogenetics in the superior colliculus of a more chronic model of glaucoma—i.e., the microbead occlusion model—and per-formed bulk RNA sequencing on collicular lysates and isolated RGCs. Our study revealed that chronic target stimulation upon glaucomatous injury phenocopies the a priori expected molecular response: growth factors were pinpointed as essential transcriptional regulators both in the locally stimulated tissue and in distant, unstimulated RGCs. Strikingly, and although the RGC tran-scriptome revealed an enrichment of pro-survival signaling pathways, functional rescue of injured RGCs was not achieved. Overall design: In this experiment, we FACsorted retinal ganglion cells and collected lysates of superior colliculi of adult mice (+- 10 weeks old). Per tissue, 10-11 biological samples were used per experimental groups. Experimental groups included sham mice, mice subjected to ocular hypertension (microbead occlusion model), mice subjected to chronic DREADD (hM3Dq) stimulation in the colliculus and mice subjected to ocular hypertension and chronic DREADD stimulation in the colliculus. Libraries for the RGC samples were prepared with SmarSeq2, collicular samples with Lexogen Quantseq.