Whole‐exome sequencing of a Portuguese cohort of early‐onset Alzheimer’s disease implicates X‐linked lysosomal gene GLA

Abstract

AbstractBackgroundCerebrovascular disease is a common comorbidity in patients with Alzheimer’s disease (AD) and other dementias. Accumulating evidence indicates that dysfunction of the cerebral vasculature and AD neuropathology interact in multiple ways. In fact, some studies have associated common variants in COL4A1 and rare variants in HTRA1, NOTCH3, COL4A1, and CST3 with AD pathogenesis.We aimed to identify rare genetic variants in genes associated with monogenic small vessel disease in in a cohort of Portuguese early‐onset AD patients.MethodWe performed whole‐exome sequencing in a cohort of 104 thoroughly studied patients with early‐onset AD, without known pathogenic variants in the genes associated with AD or frontotemporal dementia. In these patients, we searched for rare (MAF<0.001) non‐synonymous variants in genes associated with small vessel disease: NOTCH3, HTRA1, COL4A1, COL4A2, CSTA, GLA and TREX1.ResultIn total, we found 12 rare variants in 18 patients. We found 3 male AD patients with a pathogenic GLA variant. We found other rare variants in NOTCH3, COL4A2 and HTRA1. Of the 3 patients carrying a GLA variant, one had a neuropathological study confirming the diagnosis of AD . This individual also revealed Fabry disease pathology in the hippocampal formation (CA1 to CA4 and subiculum).ConclusionWe found several rare variants on the genes of interest in our cohort. We provide evidence supporting the pathogenicity of the GLA variant. We show that 3 carriers of this variant, without other probable genetic cause responsible for the disease, developed early‐onset AD. One of those cases had post‐mortem confirmation of the diagnosis. We further show the localization of Fabry pathology in several areas that are vulnerable in AD. This poses the question of the variant’s possible role in AD pathogenesis.