Search for a genetic cause of variably protease-sensitive prionopathy

Abstract

Variably protease-sensitive prionopathy (VPSPr) is a rare, atypical subtype of prion disease in which many patients exhibit a family history of dementia. Rare protein-coding variants in PRNP, which are causal for all known forms of genetic prion disease, have been ruled out in all VPSPr cases to date, leading to suspicion that VPSPr could be caused by variants in other genes or by non-coding variation in or near PRNP. We performed exome sequencing and targeted sequencing of PRNP non-coding regions on genomic DNA from autopsy-confirmed VPSPr patients (N=67) in order to search for a possible genetic cause. Our search identified no potentially causal variants for VPSPr. The common polymorphism PRNP M129V was the largest genetic risk factor for VPSPr, with an odds ratio of 7.0. Other variants in and near PRNP exhibited association to VPSPr risk only in proportion to their linkage disequilibrium with M129V, and upstream expression quantitative trait loci showed no evidence of independent association to VPSPr risk. We cannot rule out the possibility of causal variants hiding in regions or classes of genetic variation that our search did not canvas. Nevertheless, our data support the classification of VPSPr as a sporadic prion disease.