The genetic and clinical factors influencing the rate of brain structure change in cognitive decline remain poorly understood. This study aimed to identify genetic variants and risk factors contributi Show more
The genetic and clinical factors influencing the rate of brain structure change in cognitive decline remain poorly understood. This study aimed to identify genetic variants and risk factors contributing to these changes and explore potential causal relationships. We analyzed data from 2036 individuals across three longitudinal cohorts to assess change rates in 17 brain regions associated with cognitive decline. Genome-wide association studies (GWASs) were followed by phenome-wide association studies (PheWASs), Mendelian randomization (MR), and independent replication. We identified loci associated with brain structure change, including known Alzheimer's disease genes (apolipoprotein E, APOC1) and novel signals (BEAN1, SDHC). PheWAS and MR analyses in large biobanks suggested potential causal links between brain atrophy and anemia-related traits as well as type 2 diabetes. Our findings highlight genetic contributors and clinical traits associated with brain structure change in cognitive decline. Larger studies with broader cognitive assessments are needed to validate these findings. Show less
To assess the role of rare copy number variations in Alzheimer's disease (AD), we conducted a case-control study using whole-exome sequencing data from 522 early-onset cases and 584 controls. The most Show more
To assess the role of rare copy number variations in Alzheimer's disease (AD), we conducted a case-control study using whole-exome sequencing data from 522 early-onset cases and 584 controls. The most recurrent rearrangement was a 17q21.31 microduplication, overlapping the CRHR1, MAPT, STH and KANSL1 genes that was found in four cases, including one de novo rearrangement, and was absent in controls. The increased MAPT gene dosage led to a 1.6-1.9-fold expression of the MAPT messenger RNA. Clinical signs, neuroimaging and cerebrospinal fluid biomarker profiles were consistent with an AD diagnosis in MAPT duplication carriers. However, amyloid positon emission tomography (PET) imaging, performed in three patients, was negative. Analysis of an additional case with neuropathological examination confirmed that the MAPT duplication causes a complex tauopathy, including prominent neurofibrillary tangle pathology in the medial temporal lobe without amyloid-β deposits. 17q21.31 duplication is the genetic basis of a novel entity marked by prominent tauopathy, leading to early-onset dementia with an AD clinical phenotype. This entity could account for a proportion of probable AD cases with negative amyloid PET imaging recently identified in large clinical series. Show less