A PITX2 splice-site mutation in a family with Axenfeld-Rieger syndrome leads to decreased expression of nuclear PITX2 protein.

PURPOSE: Axenfeld-Rieger syndrome (ARS) is an autosomal dominant disorder characterized by ocular anterior segment abnormalities. In the current study, we describe clinical and genetic findings in a Chinese ARS pedigree.

METHODS

An ARS pedigree was recruited and patients were given comprehensive ophthalmic examinations and general physical examinations. DNA from the proband II:2 was used for exome sequencing. Sanger sequencing was utilized to identify and validate PITX2 variations. qPCR and western blotting were performed to detect PITX2 expression in immortalized peripheral blood lymphocytes.

RESULTS

All affected family members showed typical ocular abnormalities, including iris atrophy, corectopia, shallow anterior chamber, complete or partial angle closure, and advanced glaucoma. They also exhibited systemic anomalies, such as microdontia, hypodontia, and redundant periumbilical skin. A heterozygous splice-site variation c.390 + 1G > A in PITX2, which might lead to a truncated PITX2 protein (p.Val131IlefsX127), was found in the proband. Sanger sequencing validated that the variation completely co-segregated with the ARS phenotype within this family and was absent in 100 unrelated controls. Western blotting revealed that the nuclear PITX2 protein was significantly decreased in patients compared with controls. Nonetheless, there was no significant difference in the total PITX2 protein level, consistent with qPCR results showing no alteration in PITX2 mRNA levels in the patient group.

CONCLUSIONS

PITX2 c.390 + 1G > A (p.Val131IlefsX127) was a novel genetic etiology of the ARS pedigree. The mutation leads to decreased nuclear PITX2, indicating lower transcriptional activity.