Figure 3.

Gene‐based variance in the mitochondrial DNA (mtDNA) maintenance pathway. Sequence kernel association test (SKAT)‐based gene‐based variance for the mtDNA maintenance pathway in the ParkWest and Parkinson's Progression Markers Initiative datasets for rare, nonsynonymous variation. Variance is a measure of SKAT‐based enrichment (ie, the degree of skewed variant distribution between cases and controls) and is defined as the sum of squared difference in minor allele frequency (MAF) between cases and controls for all variants within each gene, $V={\displaystyle \sum }_{i=0}^N{(MA{F}_{ctr}^i-MA{F}_{PD}^i)}^2$. A high variance score for a gene indicates that variants within that gene show a highly uneven distribution between cases and controls. [Color figure can be viewed at http://wileyonlinelibrary.com]