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- Breton, Gwenna, et al.
(författare)
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Deciphering early human history using Approximate Bayesian Computation and 74 whole genomes from Central and Southern Africa
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Human evolutionary history in Africa before and after the out-of-Africa event remains largely unexplored, due to lack of genome sequence data, limited representation of populations and limitations of presently available inference methods. We generated high-coverage genomes from 49 Central African individuals, from five rainforest hunter-gatherer populations and four neighboring populations, and from 25 Khoe-San individuals, from five populations. We analyzed these genomes jointly with 104 comparative genomes from worldwide populations. We showed that rainforest hunter-gatherers and Khoe-San populations define two distinct major axes of genetic variation both at the worldwide and Sub-Saharan scales. This new data provides unprecedented resolution to unravel complex genetic differentiation among rainforest hunter-gatherer populations in particular. Using both deterministic and Approximate Bayesian Computation inferences, we found strong support for gene flow throughout the entire history of Central and Southern Africa, and an early divergence, some 250-370 kya ago, of Khoe-San ancestors from the lineage ancestral to all Central African populations. This event was followed, still in the presence of gene-flow, some 80-240 kya, by the divergence of lineages ancestral to rainforest hunter-gatherers and their neighbors. Finally, divergence between the different Khoe-San populations likely predated that of eastern and western rainforest hunter-gatherers which occurred 16-44 kya. Altogether, our results indicate that a tree-like history of Central Africa incorporating gene-flow among ancient lineages as well as among recent lineages can explain genomic variation observed among populations today.
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- Itzhaki, Ruth F., et al.
(författare)
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Microbes and Alzheimer's Disease
- 2016
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Ingår i: Journal of Alzheimer's Disease. - 1387-2877 .- 1875-8908. ; 51:4, s. 979-984
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We are researchers and clinicians working on Alzheimer’s disease (AD) or related topics, and we write to express our concern that one particular aspect of the disease has been neglected, even though treatment based on it might slow or arrest AD progression. We refer to the many studies, mainly on humans, implicating specific microbes in the elderly brain, notably herpes simplex virus type 1 (HSV1), Chlamydia pneumoniae, and several types of spirochaete, in the etiology of AD [1–4]. Fungal infection of AD brain [5, 6] has also been described, as well as abnormal microbiota in AD patient blood [7]. The first observations of HSV1 in AD brain were reported almost three decades ago [8]. The ever-increasing number of these studies (now about 100 on HSV1 alone) warrants re-evaluation of the infection and AD concept.AD is associated with neuronal loss and progressive synaptic dysfunction, accompanied by the deposition of amyloid-β (Aβ) peptide, a cleavage product of the amyloid-β protein precursor (AβPP), and abnormal forms of tau protein, markers that have been used as diagnostic criteria for the disease [9, 10]. These constitute the hallmarks of AD, but whether they are causes of AD or consequences is unknown. We suggest that these are indicators of an infectious etiology. In the case of AD, it is often not realized that microbes can cause chronic as well as acute diseases; that some microbes can remain latent in the body with the potential for reactivation, the effects of which might occur years after initial infection; and that people can be infected but not necessarily affected, such that ‘controls’, even if infected, are asymptomatic
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