A 556 kb deletion in the downstream region of the PAX6 gene causes familial aniridia and other eye anomalies in a Chinese family

Abstract

Purpose: The paired box gene 6 (PAX6) on human chromosome 11p13 is an essential transcription factor for eye formation in animals. Mutations in PAX6 can lead to varieties of autosomal-dominant ocular malformations with aniridia as the major clinical signs. Known genetic alterations causing haplo-insufficiency of PAX6 include nonsense mutations, frame-shift mutations, splicing errors, or genomic deletions. The purpose of this study was to identify genetic defects as the underlying cause of familial aniridia in a large Chinese family.

Methods: All exons of PAX6 in the proband were sequenced by the Sanger sequencing technique. The genome of the proband was evaluated by a microarray-based comparative genomic hybridization (aCGH). Quantitative real-time PCR was applied to verify the abnormal aCGH findings in the proband and to test five other family members.

Results: There were no detectable pathogenic mutations in the exons of PAX6 in the proband. The aCGH analysis showed two copies of PAX6 but revealed a 566 kb hemizygous deletion of chromosome 11p13, including four annotated genes doublecortin domain containing 1 (DCDC1), DnaJ homolog subfamily C member 24 (DNAJC24), IMP1 inner mitochondrial membrane(IMMP1L), andelongation factor protein 4 (ELP4) downstream of PAX6. Quantitative real-time PCR verified the deletion in the proband and further identified the deletion in a blind fashion in four affected family members but not in the one with a normal phenotype.

Conclusions: The 566 kb hemizygous deletion of chromosome 11p13 downstream of PAX6 should be the cause of the familial aniridia in this Chinese family, although two copies of PAX6 are intact. aCGH evaluation should be applied if there is a negative result for the mutation detection of PAX6 in patients with aniridia.

Figure 1

Pedigree of the family in this study. Squares and circles indicated males and females respectively. The symbols in black represent the affected members. The asterisks indicate those subjects who participated in this study. The arrow indicates the proband. The square with a line indicated a deceased individual.

Figure 2

The 556 kb genomic deletion of chromosome 11p13. This deletion harbors four annotated genes, DCDC1, DNAJC24, IMMP1L, and ELP4.

Figure 3

qPCR analysis result. An example of the qPCR amplification plot showed a single copy of the test gene, ELP4, in the affected individuals compared to the two copies of this gene in the reference DNA.