Whole genome sequencing to elucidate the molecular pathology of Optic Disc Drusen.

Abstract

Purpose : Optic disc drusen (ODD) are acellular deposits in the optic nerve head composed of calcium, amino acids, nucleic acids, and mucopolysaccharides. They are more common in Caucasians and are bilateral in 75% of cases. Pedigree studies suggest that ODD follows an irregular autosomal dominant inheritance pattern with incomplete penetrance, however, the causative genetic loci are yet to be identified. We performed whole genome sequencing (WGS) to identify genetic variants associated with ODD.

Methods : We prospectively recruited ODD patients internationally using approved IRB and performed WGS using the spit DNA samples from 12 ODD families and 14 sporadic cases and compared data with a large population cohort. DNA libraries were prepared by Illumina library preparation kit and sequenced using Novaseq6000 system. 42 samples with missing phenotypes were excluded from analysis. Single nucleotide variants/small insertion-deletion variants (SNVs/INDELs) were identified using GATK4. A population frequency threshold of 0.4% was used to filter out common variants and those shared by all affected members of a family were selected for further analysis. Rvtests software package was used for genetic association studies.

Results : Comparison of affected and unaffected members of two of the largest families with detailed ophthalmic phenotyping revealed 19 genetic variants in family 1 and 101 in family 2 associated with ODD. We performed gene burden test and found 7 genes from family 1 and 34 genes of family 2 to be significantly associated with ODD (p < 0.05). These variants included coding and non-coding mutations, including frameshift & non-frameshift INDELS and SNV, stopgain, stoploss and splicing mutations. A small number of variants were also found in other families or in sporadic cases. Pathways analysis showed that several molecules that play key role in calcium or phosphate transport across endoplasmic reticulum membrane or involved in intra-Golgi or retrograde Golgi-to-ER trafficking. Some genetic variants have known roles in nervous system development or neurodegenerative diseases.

Conclusions : This is the first study to identify ODD risk genotypes through high-throughput whole genome sequencing. We identified a list of promising candidate genes that there are likely multiple genetic variants in different families. Functional characterization of the most likely genetic variants will identify the first genes for ODD.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.