Mutations in PRSS56 are Associated with Primary Congenital Glaucoma

Abstract

Purpose : Primary congenital glaucoma (PCG) has been implicated to mutations in three candidate genes (CYP1B1, LTBP2 and TEK). But the overall mutation spectrum across these genes accounts for less than half of all PCG cases globally. Using a large panel of 180 genes that are involved in other forms of glaucoma and anterior segment anomalies, the present study was designed to probe their functional involvement in PCG.

Methods : The targeted gene panel (designed using the Ion Ampliseq designer) was used to screen PCG cases that did not harbor homozygous mutations in the PCG-associated genes (n=323) along with ethnically matched normal controls (n=1291). Screening was accomplished by deep sequencing on an Ion Proton platform using the Ion Ampliseq chemistry and the raw data was analyzed by GATK and imported to the Ion Reporter software (version 5.2) and aligned to the hg19 sequence for further analysis. Bioinformatic analysis (SIFT, PolyPhen and Grantham) for individual variations and threshold quality scores with a depth of coverage between 100-500X were considered. The potential mutations were further validated by Sanger sequencing (ABI 3130 XL) using BigDye chemistry. Finally, we functionally characterized the mutated gene utilizing a genetic mouse model.

Results : Among the genes that exhibited mutations in PCG, the PRSS56 exhibited 44 variations in patients. Among these, 8 novel heterozygous nonsynonymous variants consisting of 6 missense and 2 frameshifts leading to protein truncation were observed that collectively accounted for 2.47% (95%CI, 1.26%-4.81%) of all PCG cases. Four of the PRSS56 missense variants co-occurred with heterozygous variants in CYP1B1 and LTBP2, indicating a possible digenic inheritance. All these rare variations were highly conserved across different species, absent in the normal controls and 1000G database and were rarely found in the ExAC cohort. Histological analysis of eyes from mice carrying mutant allele of Prss56 showed ocular drainage tissue specific defects that likely contributes to high intraocular pressure.

Conclusions : The present study suggests the involvement of PRSS56 gene in the pathogenesis of PCG. Additionally, our mouse data points to a possible role of PRSS56 in the maintenance and normal functioning of ocular angle structures.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.