*3.4. Inclusion*/*Exclusion Criteria*

Monogenic models generated from a variety of sources were included in Table S1. However, in the case of conditional models, only those for which a germline null allele was reported in the MGI database that resulted in embryonic, prenatal, or postnatal lethality were included. We excluded the following models from Table S1: those for which a causative gene had ye<sup>t</sup> to be identified and for which complementation tests were unavailable; those requiring multiple genes for the presentation of the disease phenotype; those based on overexpressing transgenes; and those in which PR degeneration depended on experimental interventions, such as an altered diet, drug treatment, or exposure to bright illumination. Environmental influences on retinal diseases are very important and may a ffect the progression of PR cell loss, but models that depend on environmental conditions are challenging to compare because of the significant variation among the types of environmental perturbations and the methods used to apply them. We also excluded models that exhibited a reduction in the PR cell number during development but not a progressive loss with age, and those where IS and/or OS dysmorphology or reduction in length was observed without a loss of PR cells, as indicated by a reduction in nuclei number or ONL thickness within the time frame reported in the papers. Although these models were excluded from Table S1, examples are included in the Results.
