NMNAT2 and early-onset autosomal dominant Alzheimer disease: This is supported by the wide range of NMNAT2 levels in humans which are non-pathogenic in the absence of other neurodegenerative insults (e.g. NMNAT2 expression is highly variable in aged postmortem human brains, and further decreased in brains with Alzheimer’s disease ( ~ 75–100% of controls levels)10).