Genetic screen in a large series of patients with primary progressive aphasia
ALZHEIMERS & DEMENTIA
Authors: Ramos, Eliana Marisa; Dokuru, Deepika Reddy; Van Berlo, Victoria; Wojta, Kevin; Wang, Qing; Huang, Alden Y.; Miller, Zachary A.; Karydas, Anna M.; Bigio, Eileen H.; Rogalski, Emily; Weintraub, Sandra; Rader, Benjamin; Miller, Bruce L.; Gorno-Tempini, Maria Luisa; Mesulam, Marek-Marsel; Coppola, Giovanni
Introduction: Primary progressive aphasia (PPA) is a neurological syndrome, associated with both frontotemporal dementia and Alzheimer's disease, in which progressive language impairment emerges as the most salient clinical feature during the initial stages of disease. Methods: We screened the main genes associated with Alzheimer's disease and frontotemporal dementia for pathogenic and risk variants in a cohort of 403 PPA cases. Results: In this case series study, 14 (3.5%) cases carried (likely) pathogenic variants: four C9orf72 expansions, nine GRN, and one TARDBP mutation. Rare risk variants, TREM2 R47H and MAPT A152T, were associated with a three- to seven-fold increase in risk for PPA. Discussion: Our results show that while pathogenic variants within the most common dementia genes were rarely associated with PPA, these were found almost exclusively in GRN and C9orf72, suggesting that PPA is more TDP43- than tau-related in our series. This is consistent with the finding that PPA frequency in dominantly inherited dementias is the highest in kindreds with GRN variants. (C) 2019 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.
Using digital organisms to study the evolutionary consequences of whole genome duplication and polyploidy
Authors: Yao, Yao; Carretero-Paulet, Lorenzo; Van de Peer, Yves
The potential role of whole genome duplication (WGD) in evolution is controversial. Whereas some view WGD mainly as detrimental and an evolutionary 'dead end', there is growing evidence that the long-term establishment of polyploidy might be linked to environmental change, stressful conditions, or periods of extinction. However, despite much research, the mechanistic underpinnings of why and how polyploids might be able to out'-compete non-polyploids at times of environmental upheaval remain indefinable. Here, we improved our recently developed bio-inspired framework, combining an artificial genome with an agent-based system, to form a population of so-called Digital Organisms (DOs), to examine the impact of WGD on evolution under different environmental scenarios mimicking extinction events of varying strength and frequency. We found that, under stable environments, DOs with non-duplicated genomes formed the majority, if not all, of the population, whereas the numbers of DOs with duplicated genomes increased under dramatically challenging environments. After tracking the evolutionary trajectories of individual genomes in terms of sequence and encoded gene regulatory networks (GRNs), we propose that duplicated GRNs might provide polyploids with better chances to acquire the drastic changes necessary to adapt to challenging conditions, thus endowing DOs with increased adaptive potential under extinction events. In contrast, under stable environments, random mutations might easily render the GRN less well adapted to such environments, a phenomenon that is exacerbated in duplicated, more complex GRNs. We believe that our results provide some additional insights into how genome duplication and polyploidy might help organisms to compete for novel niches and survive ecological turmoil, and confirm the usefulness of our computational simulation in studying the role of WGD in evolution and adaptation, helping to overcome some of the traditional limitations of evolution experiments with model organisms.