C9orf72, AAO and ancestry help discriminating behavioural from language variants in FTLD cohorts
Publication: Neurology
Beatrice Costa, Claudia Manzoni, Manuel Bernal-Quiros, Demis A Kia, Miquel Aguilar, Ignacio Alvarez, Victoria Alvarez, Ole Andreassen, Maria Anfossi, Silvia Bagnoli, Luisa Benussi, Livia Bernardi, Giuliano Binetti, Daniel Blackburn, Mercè Boada, Barbara Borroni, Lucy Bowns, Geir Bråthen, Amalia C Bruni, Huei-Hsin Chiang, James B Rowe et al
17 September 2020
The researchers sought to characterise C9orf72 expansions in relation to genetic ancestry and age at onset (AAO), and to use these parameters to discriminate the behavioural from the language variant syndrome, in a large pan-European cohort of frontotemporal lobar degeneration (FTLD) cases.
They found C9orf72 pathogenic expansions in 4% of all cases (56/1396). Expansion carriers differently distributed across syndromes: 12/101 FTLD-MNDs (11.9%), 40/800 bvFTDs (5%) and 4/495 of PPAs (0.8%). While addressing population-substructure through principal component analysis (PCA), we defined 2 patients groups with Central/Northern (n=873) and Southern European (n=523) ancestry. The proportion of expansion carriers was significantly higher in bvFTDs compared to PPAs (5% vs. 0.8% [p=2.17×10-5; OR=6.4; CI:2.31-24.99]), as well as in individuals with Central/Northern European compared to Southern European ancestry (4.4% vs. 1.8% [p=1.1×10-2; OR=2.5; CI:1.17-5.99]). Pathogenic expansions and Central/Northern European ancestry independently and inversely correlated with AAO. Their prediction model (based on expansions status, genetic ancestry and AAO) predicted a diagnosis of bvFTD with 64% accuracy.
The results indicate correlation between pathogenic C9orf72 expansions, AAO, PCA-based Central/Northern European ancestry and a diagnosis of bvFTD, implying to complex genetic risk-architectures differently underpinning the behavioural and language variant syndromes.