Ziegemeier, Ellen

Abstract The cortical asymmetry index evaluates the cortical thickness asymmetry between hemispheres. We investigated cortical asymmetry index in asymptomatic and symptomatic mutation carriers of autosomal dominant Alzheimer’s disease to explore the brain asymmetry within the Alzheimer’s disease continuum. Sixty baseline T1-weighted MRI scans were obtained from the Clinic Barcelona cohort. Baseline and longitudinal MRI data from 564 participants within the dominantly inherited Alzheimer network observational study were used as an independent, confirmatory cohort. Cerebrospinal fluid and plasma neurofilament light chain levels were included when available. Cortical thickness was calculated using Freesurfer and cortical asymmetry index was calculated via an open-source pipeline. Cross-sectional analyses examined cortical asymmetry index differences based on clinical classification and APOE ε4 status, adjusting for age, sex and estimated years from onset, while correlations were assessed with age, estimated years from onset, mini-mental state examination scores, and neurofilament light. Longitudinal cortical asymmetry index evolution was modelled using generalized additive models in the dominantly inherited Alzheimer network observational study cohort, incorporating age, sex, and the interaction between group and estimated years from onset. The cortical asymmetry index successfully distinguished asymptomatic mutation carrier and symptomatic mutation carriers from healthy controls in the Clinic Barcelona cohort and symptomatic mutation carriers from controls in dominantly inherited Alzheimer network observational study. Higher cortical asymmetry index in mutation carriers (asymptomatic mutation carrier and symptomatic mutation carriers combined) and in symptomatic mutation carriers were associated with higher plasma neurofilament light levels, a closer proximity to symptom onset, and lower mini-mental state examination in the Clinic Barcelona cohort. In the dominantly inherited Alzheimer network observational study cohort, mutation carriers exhibited increased cortical asymmetry index compared to controls and correlated with elevated neurofilament light (plasma and Cerebrospinal fluid), lower mini-mental state examination, and a closer proximity to symptom onset. APOE3/3 carriers showed greater asymmetry than other APOE genotypes and significant cortical asymmetry index differences between asymptomatic mutation carrier and symptomatic mutation carriers. Longitudinally, cortical asymmetry index increased over time significantly in symptomatic mutation carriers. These findings underscore brain asymmetry as a potential biomarker for early Alzheimer’s disease progression in autosomal dominant Alzheimer’s disease, with implications for detection and monitoring tracking disease-related neuroanatomical changes.

Abstract We present a comprehensive global analysis of genetic variants associated with autosomal-dominant Alzheimer’s disease (ADAD). A total of 550 variants in the APP, PSEN1 and PSEN2 genes were identified, of which 279 were classified as pathogenic or likely pathogenic based on American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria, utilizing data from the Dominantly Inherited Alzheimer Network (DIAN), literature and public databases. Symptomatic age at onset (AAO) data were estimated for 227 of these variants, allowing detailed characterization of their frequency, pathogenicity and AAO. Importantly, 226 variants met eligibility criteria for inclusion in disease-modifying clinical trials. Furthermore, we demonstrated the predictive value of mean variant AAO and parental AAO in predicting symptomatic AAO, validated against converters who became symptomatic during follow-up in the DIAN Observational Study. This dataset provides critical insights into the global landscape of ADAD and reveals the genetic and AAO heterogeneity of ADAD variants while refining variant trial eligibility criteria.

AbstractBackgroundMore than 300 variants in the presenilin 1 (PSEN1), presenilin 2 (PSEN2), or amyloid precursor protein (APP) genes have been reported to cause Dominantly Inherited Alzheimer Disease (DIAD). However, most of these reports come from non‐Hispanic whites and the full extent of DIAD remains understudied in Latin American (LatAm) countries. Here we describe five AD affected families from LatAm carrying novel DIAD variants.MethodsFive novel variants in the presenilin1 (PSEN1) gene were identified in Brazilian (p.Val103_Ser104delinsGly, p.Lys395Ile, p.Pro264Se and p.Ala275Thr) and Mexican families (p.Ile414Thr). To assign the likelihood of pathogenicity among these variants of unknown significance, we report pedigree information, frequency in control populations, in silico predictions, and cell‐based models.ResultThe mean age at onset in newly identified families was 43.5 years (range 36‐54). The novel variants were absent from gnomAD genome and exome databases. Two PSEN1 variants (p.Val103_Ser104delinsGly and p.Lys395Ile) showed segregation with the disease status; segregation studies were not possible in the other three families. Additionally, PSEN1 p.Val103_Ser104delinsGly, p.Lys395Ile, p.Pro264Se, p.Ala275Thr produced Aβ profiles consistent with known AD pathogenic mutations (i.e. increased extracellular Aβ42/40); thus, we consider them as likely pathogenic. PSEN1 p.Ile414Thr did not alter Aβ in a manner consistent with a known pathogenic mutation; therefore, PSEN1 p.Ile414Thr likely represents an AD risk factor or benign polymorphism.ConclusionOur study provides further insights into the genetics of AD in LatAm by identifying novel DIAD pathogenic variants in Brazil and Mexico, two countries with distinct genetic admixtures. Expanding the families eligible to participate in observational and clinical trials of DIAD enhances the generalizability of diagnosis and treatment approaches.