Whole-Exome Sequencing of Congenital Glaucoma Patients Reveals rare and Hypermorphic Variants in GPATCH3

Abstract

Purpose : Congenital glaucoma (CG) is an inherited and severe optical neuropathy that originates from maldevelopment of the anterior segment of the eye. Genetically, this disease is heterogeneous and has a poorly understood genetic etiology. We sought to identify new genetic alterations underlying CG.

Methods : Whole-exome sequencing (WES) analysis was performed in 26 severe PCG cases with no CYP1B1 or MYOC mutations. A mutational screening of the proximal promoter and seven exons of the GPATCH3 gene was carried out in a second group of 170 patients. The pathogenicity of the identified variants was evaluated by segregation analysis, examination of transcriptional activity and subcellular localization of the recombinat protein variants. Inmunohistochemistry was used to asses the localization of the protein in the human eye. The biological function of GPATCH3 was investigated by morpholino-mediated knockdown and transient overexpression of the ortholog zebrafish gene.

Results : In one of the 26 patients we identified two rare, recessive and hypermorphic coding variants in GPATCH3, a gene of unidentified function, and 5% of a second group of 170 unrelated CG patients carried rare variants in this gene. The recombinant GPATCH3 protein activated in vitro the proximal promoter of CXCR4, a gene involved in embryo neural crest cell migration. The GPATCH3 protein was detected in human tissues relevant to glaucoma (e.g., ciliary body). This gene was expressed in the dermis, skeletal muscles, periocular mesenchymal-like cells and corneal endothelium of early zebrafish embryos. Morpholino-mediated knockdown and transient overexpression of gpatch3 led to varying degrees of goniodysgenesis and ocular and craniofacial abnormalities, recapitulating some of the features of zebrafish embryos deficient in the glaucoma-related genes pitx2 and foxc1.

Conclusions : Our data indicate that mild functional alteration of GPATCH3 may be involved in congenital glaucoma and provide evidence for the role of tis gene in ocular and craniofacial development.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.