POU4F1 and infection: In further characterization of the COI model, we examined the expression of RGC marker (Brn3) and reactivity of glia cells, which normally respond to tissue injury caused by physical trauma, chemicals, or infection.36 Our results have shown a significant decrease in Brn3a expression (measured by Western blot) as early as 3 to 5 days following TON, in agreement with previous Brn3 analyses in optic nerve–injured retinas.13,37 Furthermore and consistent with previous TON models,21,38,39 a similar microglia activation, represented by the increased Iba-1 expression, has been observed in our model.