DEFINING CANDIDATE PARKINSON’S DISEASE GENES THROUGH THE ANALYSIS OF GENOME-WIDE HOMOZYGOSITY

ABSTRACT Early-onset Parkinson’s disease (EOPD) can be caused by biallelic mutations in PRKN, DJ1 and PINK1 . However, while the identification of novel genes is becoming increasingly challenging, new insights into EOPD genetics have important relevance for understanding the pathways driving disease pathogenesis. Here, using extended runs of homozygosity (ROH) >8Mb as a marker for possible autosomal recessive inheritance, we identified 90 EOPD patients with extended ROH. Investigating rare, damaging homozygous variants to identify candidate genes for EOPD, 81 genes were prioritised. Through the assessment of biallelic (homozygous and compound heterozygous) variant frequencies in cases and controls from three independent cohorts totalling 3,381 PD patients and 2,463 controls, we identified two biallelic MIEF1 variant carriers among EOPD patients. We further investigated the role of disease-associated variants in MIEF1 which encodes for MID51, an outer mitochondrial membrane protein, and found that putative EOPD-associated variants in MID51 preferentially disrupted its oligomerization state. These findings provide further support for the role of mitochondrial dysfunction in the development of PD. Together, we have used genome-wide homozygosity mapping to identify potential EOPD genes, and future studies incorporating expanded datasets and further functional analyses will help to determine their roles in disease aetiology.