The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Martin Lascoux - One of the best experts on this subject based on the ideXlab platform.
-
Shift in ecological strategy helps marginal populations of shepherd's purse (Capsella bursa-pastoris) to overcome a high Genetic Load
Proceedings of the Royal Society B: Biological Sciences, 2020Co-Authors: Marion Orsucci, Pascal Milesi, Johanna Hansen, Johanna Girodolle, Sylvain Glémin, Martin LascouxAbstract:The outcome of species range expansion depends on the interplay of demographic, environmental and Genetic factors. Self-fertilizing species usually show a higher invasive ability than outcrossers but selfing and bottlenecks during colonization also lead to an increased Genetic Load. The relationship between genomic and phenotypic characteristics of expanding populations has, hitherto, rarely been tested experimentally. We analysed how accessions of the shepherd's purse, Capsella bursa-pastoris, from the colonization front or from the core of the natural range performed under increasing density of competitors. First, accessions from the front showed a lower fitness than those from the core. Second, for all accessions, competitor density impacted negatively both vegetative growth and fruit production. However, despite their higher Genetic Load and lower absolute performances, accessions from the front were less affected by competition than accessions from the core. This seems to be due to phenotypic trade-offs and a shift in phenology that allow accessions from the front to avoid competition.
-
ecological strategy and Genetic Load in the shepherd s purse capsella bursa pastoris from the core and the limit of its natural range
bioRxiv, 2019Co-Authors: Marion Orsucci, Pascal Milesi, Johanna Hansen, Johanna Girodolle, Sylvain Glémin, Martin LascouxAbstract:Abstract Species range expansion is a complex process whose outcome depends on the interplay of demographic, environmental and Genetic factors. In plants, self-fertilizing species that do not require a mate to reproduce usually show higher invasive ability. However, this comes at a cost as both selfing and bottlenecks occurring during colonization lead to an increase in deleterious mutations accumulation (Genetic Load). Although they are theoretically clearly spelled out, the relationships between genomic and phenotypic characteristics of expanding populations have hitherto rarely been characterized. In the present study we analyzed how different accessions of the shepherd’s purse, C. bursa-pastoris, coming from the front of colonization or from the core of the natural range performed under increasing density of competitors. We first showed that, as expected, accessions from the front of colonization performed the worst for most life history traits compared with accessions from core populations. Second, competitor density had a negative impact on both vegetative growth and reproductive output in term of fruits production for all accessions. However, somewhat unexpectedly given their higher Genetic Load and their lower absolute performance, accessions from the front of colonization were less affected by competition than accessions from the core of the species range. This could be due to phenotypic tradeoffs and a shift in phenology that allow the accessions from the front of colonization to avoid competition. These results are discussed in terms of ecological strategies of expanding populations.
Nikolaos Makris - One of the best experts on this subject based on the ideXlab platform.
-
Genetic Load determines atrophy in hand cortico striatal pathways in presymptomatic huntington s disease
Human Brain Mapping, 2018Co-Authors: Yi Hong, Peter Savadjiev, Fan Zhang, Demian Wassermann, Ofer Pasternak, Jean-paul Vonsattel, Lauren J Odonnell, Hans J Johnson, Jane S Paulsen, Nikolaos MakrisAbstract:Huntington's disease (HD) is an inherited neurodegenerative disorder that causes progressive breakdown of striatal neurons. Standard white matter integrity measures like fractional anisotropy and mean diffusivity derived from diffusion tensor imaging were analyzed in prodromal-HD subjects; however, they studied either a whole brain or specific subcortical white matter structures with connections to cortical motor areas. In this work, we propose a novel analysis of a longitudinal cohort of 243 prodromal-HD individuals and 88 healthy controls who underwent two or more diffusion MRI scans as part of the PREDICT-HD study. We separately trace specific white matter fiber tracts connecting the striatum (caudate and putamen) with four cortical regions corresponding to the hand, face, trunk, and leg motor areas. A multi-tensor tractography algorithm with an isotropic volume fraction compartment allows Hong et al., Genetic Load determines hand atrophy in preHD 2 estimating diffusion of fast-moving extra-cellular water in regions containing crossing fibers and provides quantification of a microstructural property related to tissue atrophy. The tissue atrophy rate is separately analyzed in eight cortico-striatal pathways as a function of CAG-repeats (Genetic Load) by statistically regressing out age effect from our cohort. The results demonstrate a statistically significant increase in isotropic volume fraction (atrophy) bilaterally in hand fiber connections to the putamen with increasing CAG-repeats, which connects the Genetic abnormality (CAG-repeats) to an imaging-based microstructural marker of tissue integrity in specific white matter pathways in HD. Isotropic volume fraction measures in eight cortico-striatal pathways are also correlated significantly with total motor scores and diagnostic confidence levels, providing evidence of their relevance to HD clinical presentation.
-
Genetic Load determines atrophy in hand cortico-striatal pathways in presymptomatic Huntington’s disease
Human Brain Mapping, 2018Co-Authors: Yi Hong, Lauren O'donnell, Peter Savadjiev, Fan Zhang, Demian Wassermann, Ofer Pasternak, Hans Johnson, Jane Paulsen, Jean-paul Vonsattel, Nikolaos MakrisAbstract:Huntington's disease (HD) is an inherited neurodegenerative disorder that causes progressive breakdown of striatal neurons. Standard white matter integrity measures like fractional anisotropy and mean diffusivity derived from diffusion tensor imaging were analyzed in prodromal-HD subjects; however, they studied either a whole brain or specific subcortical white matter structures with connections to cortical motor areas. In this work, we propose a novel analysis of a longitudinal cohort of 243 prodromal-HD individuals and 88 healthy controls who underwent two or more diffusion MRI scans as part of the PREDICT-HD study. We separately trace specific white matter fiber tracts connecting the striatum (caudate and putamen) with four cortical regions corresponding to the hand, face, trunk, and leg motor areas. A multi-tensor tractography algorithm with an isotropic volume fraction compartment allows Hong et al., Genetic Load determines hand atrophy in preHD 2 estimating diffusion of fast-moving extra-cellular water in regions containing crossing fibers and provides quantification of a microstructural property related to tissue atrophy. The tissue atrophy rate is separately analyzed in eight cortico-striatal pathways as a function of CAG-repeats (Genetic Load) by statistically regressing out age effect from our cohort. The results demonstrate a statistically significant increase in isotropic volume fraction (atrophy) bilaterally in hand fiber connections to the putamen with increasing CAG-repeats, which connects the Genetic abnormality (CAG-repeats) to an imaging-based microstructural marker of tissue integrity in specific white matter pathways in HD. Isotropic volume fraction measures in eight cortico-striatal pathways are also correlated significantly with total motor scores and diagnostic confidence levels, providing evidence of their relevance to HD clinical presentation.
Denis Bourguet - One of the best experts on this subject based on the ideXlab platform.
-
FACTORS AFFECTING THE Genetic Load IN DROSOPHILA: SYNERGISTIC EPISTASIS AND CORRELATIONS AMONG FITNESS COMPONENTS
Evolution - International Journal of Organic Evolution, 2000Co-Authors: Michael Whitlock, Denis BourguetAbstract:Two factors that can affect Genetic Load, synergistic epistasis and sexual selection, were investigated in Drosophila melanogaster. A set of five chromosomal regions containing visible recessive mutations were put together in all combinations to create a full set of 32 homozygous lines fixed for different numbers of known mutations. Two measures of fitness were made for each line: productivity (a combined measure of fecundity and egg-to-adult survi-vorship) and competitive male mating success. Productivity, but not male mating success, showed a pattern of strong average synergistic epistasis, such that the log fitness declined nonlinearly with increasing numbers of mutations. Synergistic epistasis is known to reduce the mutation Load. Both fitness components show some positive and some negative interactions between specific sets of mutations. Furthermore, alleles with deleterious effects on productivity tend to also diminish male mating success. Given that male mating success can affect relative fitness without changing the mean productivity of a population, these additional effects would lead to lower frequencies and lower fixation rates of deleterious alleles without higher costs to the mean fitness of the population. The concept of Genetic Load has had a long history in evolutionary biology, dating back to Haldane's discussions of the fitness consequences of recurrent deleterious mutations and the costs of substituting one allele for a more favorable allele. Today the deleterious effects of mutations are known to be important to a variety of interesting evolutionary processes , including the evolution of sex and recombination
-
factors affecting the Genetic Load in drosophila synergistic epistasis and correlations among fitness components
Evolution, 2000Co-Authors: Michael C Whitlock, Denis BourguetAbstract:Two factors that can affect Genetic Load, synergistic epistasis and sexual selection, were investigated in Drosophila melanogaster. A set of five chromosomal regions containing visible recessive mutations were put together in all combinations to create a full set of 32 homozygous lines fixed for different numbers of known mutations. Two measures of fitness were made for each line: productivity (a combined measure of fecundity and egg-to-adult survivorship) and competitive male mating success. Productivity, but not male mating success, showed a pattern of strong average synergistic epistasis, such that the log fitness declined nonlinearly with increasing numbers of mutations. Synergistic epistasis is known to reduce the mutation Load. Both fitness components show some positive and some negative interactions between specific sets of mutations. Furthermore, alleles with deleterious effects on productivity tend to also diminish male mating success. Given that male mating success can affect relative fitness without changing the mean productivity of a population, these additional effects would lead to lower frequencies and lower fixation rates of deleterious alleles without higher costs to the mean fitness of the population.
Jun Cai - One of the best experts on this subject based on the ideXlab platform.
-
Genetic Load and potential mutational meltdown in cancer cell populations
Molecular Biology and Evolution, 2019Co-Authors: Yi Zhang, Tianqi Zhu, Yong Tao, Xu Shen, Dapeng Wang, Jialin Liu, Jue Ruan, Jun CaiAbstract:Large genomes with elevated mutation rates are prone to accumulating deleterious mutations more rapidly than natural selection can purge (Muller's ratchet). As a consequence, it may lead to the extinction of small populations. Relative to most unicellular organisms, cancer cells, with large and nonrecombining genome and high mutation rate, could be particularly susceptible to such "mutational meltdown." However, the most common type of mutation in organismal evolution, namely, deleterious mutation, has received relatively little attention in the cancer biology literature. Here, by monitoring single-cell clones from HeLa cell lines, we characterize deleterious mutations that retard the rate of cell proliferation. The main mutation events are copy number variations (CNVs), which, estimated from fitness data, happen at a rate of 0.29 event per cell division on average. The mean fitness reduction, estimated reaching 18% per mutation, is very high. HeLa cell populations therefore have very substantial Genetic Load and, at this level, natural population would likely face mutational meltdown. We suspect that HeLa cell populations may avoid extinction only after the population size becomes large enough. Because CNVs are common in most cell lines and tumor tissues, the observations hint at cancer cells' vulnerability, which could be exploited by therapeutic strategies.
Marion Orsucci - One of the best experts on this subject based on the ideXlab platform.
-
Shift in ecological strategy helps marginal populations of shepherd's purse (Capsella bursa-pastoris) to overcome a high Genetic Load
Proceedings of the Royal Society B: Biological Sciences, 2020Co-Authors: Marion Orsucci, Pascal Milesi, Johanna Hansen, Johanna Girodolle, Sylvain Glémin, Martin LascouxAbstract:The outcome of species range expansion depends on the interplay of demographic, environmental and Genetic factors. Self-fertilizing species usually show a higher invasive ability than outcrossers but selfing and bottlenecks during colonization also lead to an increased Genetic Load. The relationship between genomic and phenotypic characteristics of expanding populations has, hitherto, rarely been tested experimentally. We analysed how accessions of the shepherd's purse, Capsella bursa-pastoris, from the colonization front or from the core of the natural range performed under increasing density of competitors. First, accessions from the front showed a lower fitness than those from the core. Second, for all accessions, competitor density impacted negatively both vegetative growth and fruit production. However, despite their higher Genetic Load and lower absolute performances, accessions from the front were less affected by competition than accessions from the core. This seems to be due to phenotypic trade-offs and a shift in phenology that allow accessions from the front to avoid competition.
-
ecological strategy and Genetic Load in the shepherd s purse capsella bursa pastoris from the core and the limit of its natural range
bioRxiv, 2019Co-Authors: Marion Orsucci, Pascal Milesi, Johanna Hansen, Johanna Girodolle, Sylvain Glémin, Martin LascouxAbstract:Abstract Species range expansion is a complex process whose outcome depends on the interplay of demographic, environmental and Genetic factors. In plants, self-fertilizing species that do not require a mate to reproduce usually show higher invasive ability. However, this comes at a cost as both selfing and bottlenecks occurring during colonization lead to an increase in deleterious mutations accumulation (Genetic Load). Although they are theoretically clearly spelled out, the relationships between genomic and phenotypic characteristics of expanding populations have hitherto rarely been characterized. In the present study we analyzed how different accessions of the shepherd’s purse, C. bursa-pastoris, coming from the front of colonization or from the core of the natural range performed under increasing density of competitors. We first showed that, as expected, accessions from the front of colonization performed the worst for most life history traits compared with accessions from core populations. Second, competitor density had a negative impact on both vegetative growth and reproductive output in term of fruits production for all accessions. However, somewhat unexpectedly given their higher Genetic Load and their lower absolute performance, accessions from the front of colonization were less affected by competition than accessions from the core of the species range. This could be due to phenotypic tradeoffs and a shift in phenology that allow the accessions from the front of colonization to avoid competition. These results are discussed in terms of ecological strategies of expanding populations.