FUNCTIONAL-ANALYSIS OF PAIRED BOX MISSENSE MUTATIONS IN THE PAX6 GENE

Mutations in the human PAX6 gene produce various phenotypes, including aniridia, Peters' anomaly, autosomal dominant keratitis and familial foveal dysplasia, The various phenotypes may arise from different muta tions in the same gene, To test this theory, we performed a functional analysis of two missense mutations in the paired domain: the R26G mut ation, previously reported in a case of Peters' anomaly, and an unrepo rted I87R mutation, which we identified in a patient with aniridia. Wh ile both the R26 and the I87 positions are conserved in the paired box es of all known PAX genes, X-ray crystallography has shown that only R 26 makes contact with DNA, We showed that the R26G mutant failed to bi nd a subset of paired domain binding sites but, surprisingly, bound ot her sites and successfully transactivated promoters containing those s ites, In contrast, the I87R mutant had lost the ability to bind DNA at all tested sites and failed to transactivate promoters, Our data supp ort the haploid-insufficiency hypothesis of aniridia, and the hypothes is that R26G is a hypomorphic allele.