title: Mechanistically distinct mouse models for CRX-associated retinopathy.
abstract: Cone-rod homeobox (CRX) protein is a "paired-like" homeodomain transcription factor that is essential for regulating rod and cone photoreceptor transcription. Mutations in human CRX are associated with the dominant retinopathies Retinitis Pigmentosa (RP), Cone-Rod Dystrophy (CoRD) and Leber Congenital Amaurosis (LCA), with variable severity. Heterozygous Crx Knock-Out (KO) mice ("+/-") have normal vision as adults and fail to model the dominant human disease. To investigate how different mutant CRX proteins produce distinct disease pathologies, we generated two Crx Knock-IN (K-IN) mouse models: Crx(E168d2) ("E168d2") and Crx(R90W) ("R90W"). E168d2 mice carry a frameshift mutation in the CRX activation domain, Glu168del2, which is associated with severe dominant CoRD or LCA in humans. R90W mice carry a substitution mutation in the CRX homeodomain, Arg90Trp, which is associated with dominant mild late-onset CoRD and recessive LCA. As seen in human patients, heterozygous E168d2 ("E168d2/+") but not R90W ("R90W/+") mice show severely impaired retinal function, while mice homozygous for either mutation are blind and undergo rapid photoreceptor degeneration. E168d2/+ mice also display abnormal rod/cone morphology, greater impairment of CRX target gene expression than R90W/+ or +/- mice, and undergo progressive photoreceptor degeneration. Surprisingly, E168d2/+ mice express more mutant CRX protein than wild-type CRX. E168d2neo/+, a subline of E168d2 with reduced mutant allele expression, displays a much milder retinal phenotype, demonstrating the impact of Crx expression level on disease severity. Both CRX([E168d2]) and CRX([R90W]) proteins fail to activate transcription in vitro, but CRX([E168d2]) interferes more strongly with the function of wild type (WT) CRX, supporting an antimorphic mechanism. E168d2 and R90W are mechanistically distinct mouse models for CRX-associated disease that will allow the elucidation of molecular mechanisms and testing of novel therapeutic approaches for different forms of CRX-associated disease.
authors: Ph.D. program in Molecular Genetics and Genomics, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Nicholas M
authors: NM
authors: Tran
authors: College of Arts & Sciences, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Alan
authors: A
authors: Zhang
authors: Department of Ophthalmology and Visual Sciences, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Xiaodong
authors: X
authors: Zhang
authors: Department of Ophthalmology and Visual Sciences, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Julie B
authors: JB
authors: Huecker
authors: Department of Ophthalmology and Visual Sciences, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Anne K
authors: AK
authors: Hennig
authors: Ph.D. program in Molecular Genetics and Genomics, Washington University in Saint Louis, Saint Louis, Missouri, United States of America ; Department of Ophthalmology and Visual Sciences, Washington University in Saint Louis, Saint Louis, Missouri, United States of America ; Department of Developmental Biology, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.
authors: Shiming
authors: S
authors: Chen
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D016368:Frameshift Mutation; D018398:Homeodomain Proteins / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D057130:Leber Congenital Amaurosis / Q000235:genetics* / Q000473:pathology; D051379:Mice; D010641:Phenotype; D017949:Retinal Cone Photoreceptor Cells; D012162:Retinal Degeneration / Q000235:genetics; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000473:pathology; D015534:Trans-Activators / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins; D015534:Trans-Activators; C109288:cone rod homeobox protein