Frmd4b (FERM domain containing 4B) encodes a GRP1 binding protein involved in scaffolding. This ENU-induced mutation, Tvrm222, was identified as a serine to proline substitution at amino acid 938 (S938P). Mice carrying this dominant mutation do not have any apparent phenotype, however, when the allele is present in mice carrying the Nr2e3rd7 mutation, Tvrm222 lessens the severity of the rd7-associated photoreceptor dysplasia. Nr2e3rd7 is a mouse model for enhanced S-cone syndrome. Mice homozygous for the rd7 allele exhibit white spots on the retina, a progressive loss of rod and cone cells, attenuated retinal vessels and a decrease in the thickness of the outer nuclear layer. This strain provides a mouse model for a less severe phenotype of enhanced S-cone syndrome.

These ENU-induced Tvrm222 mice carry a S938P mutation in the Frmd4b (FERM domain containing 4B) gene. Mice homozygous for the Nr2e3rd7 allele develop photoreceptor dysplasia and serve as a mouse model of enhanced S-cone syndrome. These combined Tvrm222 rd7 mice provide a milder phenotype of enhanced S-cone syndrome than rd7 alone.

This strain is hosted by NIH's MMRRC, which partners with JAX for the distribution of this and other strains. For additional information and to purchase, please visit the MMRRC site.