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• Time of issue:2018-09-28
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(Summary description)
Survival of the fittest and survival of the fittest are the most misunderstood terms in biology. Recently, in a study published in the international journal PNAS, researchers from the University of California showed that for humans, natural selection may be more inclined By giving grandparents genetic protection against dementia, maintaining better cognition and memory in old age may encourage older adults to spread their wisdom and care for their children and grandchildren, while older adults with dementia are less likely to take care of themselves. .

This grandmother hypothesis is more in line with the rules of kin selection (blood elimination), that is, individuals can carry on their genes, not only through offspring, but also by enabling offspring who share genetic mutations to survive easily through This may seem altruistic, such as why an ant builds a bridge while its relatives can cross an obstacle, or why a squirrel warns by screaming; for humans, grandparents do this by teaching offspring Certain survival techniques are used to increase the likelihood of future child survival.

Humans and toothed whales are the only remaining mammals that lived in past breeding eras. Killer whales can survive post-menopause, possibly because they can use the environment to teach young calves how to snatch food to survive; and humans also experience followed the same evolutionary path until the advent of Alzheimer's, a disease that impairs cognitive abilities in older adults. In the article, the researchers searched for novel genetic mutations that could neutralize the tendency of dementia, and eventually they first discovered a gene called CD33, which encodes a receptor that maintains inflammatory and immune responses. This "C" etc. The allele is associated with early dementia, but the "A" allele protects cognition by promoting the uptake of excess beta-amyloid by microglia.

In this study, researchers identified 10 mutated genes that protect the body against vascular forms of dementia: APOE, AGT, SCG2, CAPN10, TCF7L2, EBF1, COX-2, CYP3A5, PPARG, and PON1. Vascular dementia tends to block blood flow, and these 10 genes protect the body against high blood pressure, type 2 diabetes and cardiovascular disease. The researchers also found these derivatives in modern Africans protective alleles, suggesting that these genes have been around for at least 100,000 years.

Finally, researcher Ganeux said, our study does not prove that these factors are involved in the selective screening process of CD33, APOE and other gene protective mutants, but it can help speculate the possibility of this phenomenon after all; after all, across generations The care and transfer of information between individuals are important factors in the survival of young offspring in a family, and are critical to broad social networks and tribes. Later researchers are also more than happy to develop new genetic panels to help detect new genes that could ward off dementia. (Qjbio www.qjbio.com.cn)

doi:10.1073/pnas.1517951112

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Human-specific derived alleles of CD33 and other genes protect against postreproductive cognitive decline

Flavio Schwarza,b,c,d,1, Stevan A. Springera,b,d,1, Tasha K. Altheidea,b,c,d, Nissi M. Varkia,b,e, Pascal Gagneuxa,b,e,2 , and Ajit Varkia,b,c,d,2

The individuals of most vertebrate species die when they can no longer reproduce. Humans are a rare exception, having evolved a prolonged postreproductive lifespan. Elders contribute to cooperative offspring care, assist in foraging, and communicate important ecological and cultural knowledge, increasing the survival of Younger individuals. Age-related deterioration of cognitive capacity in humans compromises these benefits and also burdens the group with socially costly members. We investigated the contribution of the immunoregulatory receptor CD33 to a uniquely human postreproductive disease, Alzheimer's dementia. Surprisingly, even though selection at advanced age is expected to be weak, a CD33 allele protective against Alzheimer's disease is derived and unique to humans and favors a functional molecular state of CD33 resembling that of the chimpanzee. Thus, derived alleles may be compensatory and restore interactions altered as a consequence of human-specific brain evolution. We found several other examples of derived alleles at other human loci that protect against age-related cognitive deterioration arising from neurodegenerative disease or cerebrovascular insufficiency. Selection by inclusive fitness may be strong enough to favor alleles protecting specifically against cognitive decline in postreproductive humans. Such selection would operate by maximizing the contributions of postreproductive individuals to the fitness of younger kin.