The Pde6b-null rat has a rapidly progressive retinal degeneration with near complete loss of photoreceptor cells by 2-months of age [15], which makes it ideal for evaluation of post-transplant donor cell integration (i.e., the lack of host photoreceptor cells at the time of transplantation mitigates concerns pertaining to donor cell antigen transfer [26–28]). The gene discussed is PDE6B; the disease is retinal degeneration.