To test this hypothesis, 5-week-old Epha2<sup>+/+</sup> and Epha2<sup>+/-</sup> mice (n = 8 per group) were exposed to repeated below-threshold doses of UV-B radiation (0.0125-0.05 J/cm<sup>2</sup>), before development of Epha2-mediated cataract.
Ephrin type-A receptor 2 (EPHA2) and one of its ligands, ephrin-A5 (EFNA5), have been associated with loss of eye lens transparency, or cataract, - an important cause of visual impairment.
Due to this complex expression pattern and the promiscuous interactions between Eph receptors and ephrin ligands, as well as their complex bidirectional signaling pathways, cataracts in ephrin-A5(-/-) or EphA2(-/-) lenses may arise from loss of function or abnormal signaling mechanisms.
Micro-fluidic PCR amplification followed by targeted amplicon (exon) next-generation (deep) sequencing of EPHA2 (17-exons) afforded high read-depth coverage (1000x) for > 82% of reads in the cataract case-control panel (161 cases, 64 controls) and > 70% of reads in the post-mortem lens panel (35 clear lens pairs, 22 cataract lens pairs).
Mis-localization of two of the mutant proteins in epithelial cells suggests that some disease-causing mutations in EPHA2 likely affect lens epithelial cell homeostasis and contribute to cataract.
In this study, for the first time, a population-based approach was used to investigate the frequency of disease causing mutations in the EPHA2 gene in inherited cataract cases in South-Eastern Australia.
We used logistic regression with robust standard errors to examine the association between cataract and the EPHA2 SNPs, adjusting for age, sex and location.
Our results provide the first report of multiple EPHA2cataract mutations contributing to the destabilization of the receptor and causing the loss of cell migration activity.
The known cataract gene in this region (EPHA2) does not harbour mutations in this family, suggesting that at least one additional gene for cataract is present in this region.