Evaluating the causality of novel sequence variants in the prion protein gene by example.

Neurobiol Aging 2018 11 15;71:265.e1-265.e7. Epub 2018 May 15.

MRC Prion Unit, UCL Institute of Prion Diseases, London, UK; National Prion Clinic, National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK. Electronic address:

The estimation of pathogenicity and penetrance of novel prion protein gene (PRNP) variants presents significant challenges, particularly in the absence of family history, which precludes the application of Mendelian segregation. Moreover, the ambiguities of prion disease pathophysiology renders conventional in silico predictions inconclusive. Here, we describe 2 patients with rapid cognitive decline progressing to akinetic mutism and death within 10 weeks of symptom onset, both of whom possessed the novel T201S variant in PRNP. Clinically, both satisfied diagnostic criteria for probable sporadic Creutzfeldt-Jakob disease and in one, the diagnosis was confirmed by neuropathology. While computational analyses predicted that T201S was possibly deleterious, molecular strain typing, prion protein structural considerations, and calculations leveraging large-scale population data (gnomAD) indicate that T201S is at best either of low penetrance or nonpathogenic. Thus, we illustrate the utility of harnessing multiple lines of prion disease-specific evidence in the evaluation of the T201S variant, which may be similarly applied to assess other novel variants in PRNP.

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http://dx.doi.org/10.1016/j.neurobiolaging.2018.05.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6175539PMC
November 2018
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