GRM5 and early-onset autosomal dominant Alzheimer disease: As a proof of concept, we selected two genes encoding tyrosine hydroxylase (TH)35 and metabotropic glutamate receptor 5 (mGluR5)36, respectively, which are associated with the pathogenesis of neurological disorders including Parkinson’s disease (PD) and Alzheimer’s disease (AD) (Fig. 5a).