Fibrillogenic propensity of Olfactomedin1 as a causal relationship for retinal ganglion cell death in glaucoma

Abstract

Purpose : Olfactomedin (OLFM) domain-containing proteins including MYOCILIN (MYOC) and OLFM1/2/3 are of great importance in the pathophysiology of glaucoma and other eye diseases. While MYOC is expressed in angle tissues, OLFM1/2/3 are actively expressed in retinal ganglion cells (RGCs) and are constituents of the functional AMPA receptor complex. Changes in the composition and properties of this complex may lead to RGCs death. Most of the glaucoma-causing mutations in the MYOC gene are located in the third exon encoding the OLFM domain. Since OLFM domains are conserved in those proteins, here, we explored the impact of reported MYOC mutations in the OLFM domain of OLFM1 to reveal their functional consequences in RGC insult and the possible mechanism of AMPA receptor mediated RGCs death in glaucoma.

Methods : Glaucoma-causing missense mutations of MYOC from ClinVar database was mapped to the OLFM1 variations from Ensembl database to identify their conserved homologous site mutations. Mutational impact was predicted by different computational tools: SAAMBE-3D, SIFT, PolyPhen, Mutation Assessor, MetaLR, CADD, and REVEL. Aggregation propensity was determined by identifying sequence homology of MYOC and OLFM1 with Aβ₄₂, Tau, and α-Synuclein. Structural mapping was performed using PyMol and ChimeraX to elucidate the structure-function relationships of OLFM1 mutations in protein-protein interactions.

Results : Among 182 glaucoma-causing MYOC mutations, only 27 (14.8%) were pathogenic with majority 136 mutation (74.7%) having uncertain clinical significance. We identified 7 spatially conserved glaucoma-causing MYOC mutations in OLFM1 at their homologous sites. Three of these MYOC mutations D380N, E385K, and Q424H predicted as deleterious, while G246R and G434S to be likely deleterious in OLFM1. Interestingly, these conserved mutations were reported at or in close vicinity of Aβ₄₂ (D380N, E385K, G434S), Tau (Q424H, G434S), and α-Synuclein (G246R, Q424H) fibrillogenic sites. Further, structural mapping revealed the presence of these spatially conserved mutations and aggregation prone residues mostly on the surface that may affect OLFM1 interaction with other proteins.

Conclusions : The glaucoma causing spatially conserved MYOC mutations in OLFM1 may have deleterious impact on the fibrillogenic propensity of its OLFM domain that may prevent its interaction with AMPA receptors.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.