GUCY2EP and Cone rod dystrophy: This work provides a detailed characterization of cone dysmorphology and rod and cone photoreceptor loss in cpfl9 mice, which carry a novel mutant allele of Gucy2e. The mild cone-rod dystrophy disease phenotype exhibited by this mouse model may make it attractive for testing therapeutic interventions designed to mitigate the human retinal diseases caused by GUCY2D mutations.