Mutation of the EPHA2 tyrosine-kinase domain dysregulates cell pattern formation and cytoskeletal gene expression in the lens

Genetic variations in ephrin type-A receptor 2 (EPHA2) have been associated with inherited and age-related forms of cataract in humans. Here we have characterized the eye lens phenotype and transcript profile of germline Epha2 knock-in mutant mice homozygous for either a missense variant associated with age-related cataract in humans (Epha2-Q722) or a novel insertion-deletion mutation (Epha2-indel722) that were both located within the tyrosine-kinase domain of EPHA2. Whole-mount confocal imaging of clear lenses from Epha2-indel722 mice on a fluorescent reporter background revealed misalignment of epithelial-to-fiber cell meridional-rows at the lens equator and severe disturbance of Y-suture formation at the lens poles, whereas, Epha2-Q722 lenses displayed mild disturbance of posterior sutures. Immunofluorescent labeling showed that EPHA2 was mostly localized to lens fiber cell membranes with some sub-membrane localization observed in Epha2-Q722 lenses and diffuse membrane and perinuclear localization in Epha2-indel722 lenses. Immunoprecipitation/blotting studies indicated that EPHA2 formed strong complexes with Src kinase but not with catenin beta 1 or cadherin 2 and was mostly serine phosphorylated in the lens. RNA-sequencing analysis revealed differential expression of several cytoskeleton-associated genes in Epha2-mutant and Epha2-null lenses including strong downregulation of Lgsn and Clic5. Collectively, our data suggest that mutations within the tyrosine-kinase domain of EPHA2 result in lens cell patterning defects and dysregulated expression of several cytoskeletal proteins. Overall design: mRNA profiles from seven day old lenses of wild type (WT), EPHA2 null, and EPHA2 mutant mice