Experimental assessment of novel PAX6 splicing mutations in two Chinese families with aniridia

Aniridia is a rare, congenital ocular disorder caused by the mutations of the paired box gene-6 (PAX6) (OMIM 607108), which encodes a highly conserved transcriptional regulator. In order to investigate the clinical characterizations and genetic defects of two Chinese families affected with aniridia, we recruited the family members and 200 ethnically matched controls. The entire exons and flanking intronic sequences of the PAX6 gene (NG_008679.1) were analyzed and effects of variants on splicing were assessed in silico and in vitro using exon trapping assay with pET01. The donor site (c.1183 + 1G > A) mutation identified in family 1 would result in a complete skipping of exon 12 and cause a frameshift and run-on translation past the normal termination codon, creating an enlarged PAX6 protein with extended COOH-terminal domain. Novel c.1033-1_1033delinsCT mutation was detected in family 2. This mutation provoked both complete exon 12 skipping and partial skipping of exon 12 deleting 7 bp. This would lead to a frameshift translation and the introduction of pre-mature termination code, which resulted in severely truncated PAX6 protein likely to be degraded. Our study further expands the spectrum of genetic pathology underlying PAX6.