Multi-Allelic Interactions of Glaucoma and Anterior Segment Dysgenesis-Associated Genes in the Pathogenesis of Primary Congenital Glaucoma

Abstract

Purpose : Primary congenital glaucoma (PCG) is an autosomal recessive disease that occurs due to developmental defects in the anterior chamber angle and trabecular meshwork. The resulting resistance to aqueous humor outflow raises the intraocular pressure and damages the optic nerve. PCG exhibits considerable genetic heterogeneity, and the known mutation spectrum does not explain the entire genetic basis of this disease. As anterior segment dysgenesis (ASD) and PCG share overlapping phenotypes, we determined the involvement of ASD-associated genes in PCG pathogenesis.

Methods : A large cohort of PCG cases (n=586) and ethnically matched controls (n=1758) were screened by deep sequencing with a customized gene panel comprising of known ASD-associated genes using the Ion Ampliseq chemistry. A combination of GATK and Haploview softwares was used for variant analysis. The identified variants were validated by Sanger sequencing. Pathogenicity of the variants was determined through SIFT, PolyPhen2 and Mutation Taster scores. Ingenuity Pathway Analysis (IPA) was used for network and pathway analyses.

Results : We identified 71 novel and rare pathogenic variants in 123 (20.9%) PCG cases across the ASD genes: FBN1, HMX1, LMX1B, MAF, PITX3, PRDM5, RAX, SIX1, SIX6, SLC4A11, SOX2, TRIM44, VAX1 and WT1. The affected amino-acid residues were conserved across multiple species and the variants were either absent or rarely observed in our controls and global databases. We also identified 52 significantly associated polymorphisms conferring risk to PCG. These genes shared similar molecular functions and were involved in the regulation of Wnt and Hedgehog signaling and cell growth and survival pathways (Akt/PI3K/NfkB). Moreover, we detected co-occurrence of pathogenic variants between ASD and PCG candidate genes in 63 cases (10.75%) indicating potential multi allele interactions and possible dysregulation of multiple pathways in PCG.

Conclusions : Our results expand the mutation spectrum of PCG with the identification of pathogenic variants in ASD genes and suggest their potential involvement in PCG. Our observations on the co-occurrences of pathogenic variants in ASD and PCG candidate genes suggest gene-gene interactions in PCG pathogenesis.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.