RPE65 and retinal degeneration: Further evidence to support this was provided by cross breeding RhoT4R dogs with the Rpe65−/− dog to produce RhoT4R/+ Rpe65−/− dogs which lack 11-cis-retinal chromophore (due to the lack of Rpe65 function) and thus have only unliganded mutant rod opsin (i.e., have a lack of rod opsin combined with 11-cis-retinal) and show a greatly accelerated rate of retinal degeneration compared to RhoT4R/+Rpe65+/+ dogs (see details on the Rpe65−/− dog below) [21].