Analysis of retinal ganglion cell subtypes across six different inbred mouse strains

Purpose Retinal ganglion cells (RGCs) are the principal conduits responsible for propagating visual stimuli from the retina to visual centers in the brain. The loss of RGCs leads to visual deficits following trauma or in diseases such as glaucoma. Mouse models are consistently used to investigate root causes for RGC loss. This study quantifies the total number of RGCs and selected RGC subtypes across six strains of inbred mice used in ophthalmic research. Methods Six mouse strains (C57BL/6J, BALB/cByJ, 129X1/SvJ, A/J, CBA/CaJ, and CAST/EiJ) were selected to represent genetic diversity across the mouse genome. Normal retinas were immunostained for POU6F2, BRN3A, SATB2, OPN4, SMI32, and TO-PRO-3. Cells positively labeled for POU6F2, BRN3A, and SATB2 were quantified using an automated deep learning tool, RGCode. Cells labeled with OPN4, SMI32, and TO-PRO-3 were quantified using the Fiji software. Results We found statistically significant differences in the quantity (Mean±SEM) and percentage of different RGCs across the inbred mouse strains. The total number of RGCs per retina ranged from 39,961±838 in CAST/EiJ to 53,872±1864 in 129X1/SvJ (p<0.005). Global BRN3A counts ranged from 34,572±494 in CAST/EiJ to 44,253±798 in C57BL/6J (p<0.005). SATB2 counts ranged from 9944±384 in BALB/cByJ to 15,872±1196 in CBA/CaJ (p<0.005). OPN4 density ranged from 110±7 cells/mm2 in CAST/EiJ to 164±13 cells/mm2 in 129X1/SvJ (p<0.05). Differences in SMI32 density were not significant across all strains, with densities ranging from 183±14 cells/mm2 in A/J to 279±12 cells/mm2 in C57BL/6J (not significant). Conclusions There is a significant variation in total RGC counts and RGC subtypes across the different mouse strains. When working with different strains of mice, it is important to consider this strain-based variation before drawing conclusions from experimental data.