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The X chromosome overstep from mom to offspring may accelerate brain aging , a newfangled animal sketch suggests .
The inquiry highlight a potential fundamental difference in how Male ' and females ' brains age . The research was conducted in black eye , but if the finding read to human race , they could point to sex - specific drivers of cognitive fall and , eventually , ways to forestall or treat them .
Scientists have uncovered a potential sex difference in how the brain ages, linked to the X chromosome.
" Females show resilience in many measures of aging , " said aged discipline authorDr . Dena Dubal , a professor of neurology and the David A. Coulter endue chair in aging and neurodegenerative disease at the University of California , San Francisco ( UCSF ) . For instance , theytend to go longer than malesand have lower rates ofvarious manakin of dementia . One exception isAlzheimer ’s disease , which impress female at higher rates , but even so , some studies suggest thatfemales survive longer with Alzheimer’sthan males do .
Dubal and colleague wonder if the sex chromosomes , X and Y , could help explain these differences . There ’s grounds of genes on the X chromosome that assist guard against dementia , while others contribute to the risk of cognitive decline , saidRachel Buckley , an associate prof of neurology at Harvard Medical School who was not involved in the new survey .
The new study , put out Jan. 22 in the journalNature , uncovers a potential factor that shapes the X chromosome ’s influence .
Related : Is there really a dispute between male and female brains ? Emerging science is unwrap the result .
The origin of the X matters
Typically , females carry two Xchromosomesin each cell — one from their mom and one from their pa . But a cellphone needs only one X to be dynamic , so the other is " hush . " This ensue in females extend a arial mosaic of cells that have silenced either their paternal or enate decade chromosome . Meanwhile , males — who typically carry one X and one Y — only ever inherit their X from their female parent , and it ’s active in every cell .
" That make us enquire about distaff resiliency and whether that diversity of the hug drug chromosome , birth Mom ’s and Dad ’s , might bestow to resilience , " Dubal said .
To explore this idea , Dubal;Samira Abdulai - Saiku , a postdoctoral fellow at UCSF ; and colleagues did experimentation with distaff lab computer mouse of different eld . Some experimentation involved using a genetic thaumaturgy to silence all of the paternal cristal chromosome in certain mice , leave only the mother ’s X active . These mice were compared with others that had a commixture of maternal and agnate ex ’s flip on .
" I actually really liked that glide path , " Buckley enjoin . Comparing females to males would have introduced additional sexual activity - touch on factors , like hormonal differences , Buckley told Live Science .
The team also ascertain that the X chromosomes from each parent were genetically identical , Dubal noted . So any differences that emerge would be concern to which parent passed them along , not to differences in the genes themselves , she explained . This also enabled the team to nail differences inepigenetics — chemical tag that attach to DNA and control which genes can be switched on .
Young " Mom - go " mice were cognitively interchangeable to other untested black eye , performing about the same in maze - based tests . But at older ages , they show starker cognitive decline , especially in their spacial computer memory andworking memory . " The assay showed a fairly outstanding effect , " Dubal say .
The team wondered if these declines were interrelate to changes in thehippocampus , a primal store pith in the brain . To see , they search at epigenetic markers on DNA from the hippocampi of young and older computer mouse . Epigenetic tags switch across the lifespan , with certain patternscorrelating with " higher " biological ages — in other words , a more advanced stage of senescence . At older chronological age , the Mom - X mice showed a greater level of biological aging in the genus Hippocampus than did mouse with both ecstasy ’s .
The scientists then sorted neurons from the genus Hippocampus based on whether the mom ’s or dad ’s X was active , so they could count at which genes were switched on .
Three gene were silenced on the parental X — Sash3 , Tlr7 and Cysltr1 — but were very participating on the agnate X. Using thegene - editing tool CRISPR , they enquire what would happen if they switch these genes back on in the brains of old black eye with only enatic X ’s . In tests , these mouse showed improvements in spacial scholarship and memory .
What does it mean for humans?
Interestingly , in human , these three genes areinvolved inimmuneprotection , but their exact part in nerve cell are n’t full sympathize , Dubal said . next work could further investigate what the genes do in neurons and in other types of psyche cells . It ’s also unreadable how or why the tenner chromosomes from unlike parents undergo different epigenetic changes , she add .
The team also wants to enquire what these findings might mean for males , who carry only enate X chromosome — and could , in hypothesis , then have greater rates of mind aging . " One can imagine " that , the more active maternal X ’s a person carries , the more enunciate the impact on brain aging , Dubal speculated . But that remains to be confirm .
— 1st - ever ancient case of Turner syndrome , with just 1 XTC chromosome alternatively of 2 , see in ancient DNA
— Women have 4 time men ’s rate of autoimmune disease . The X chromosome may be to blame .
— The mystery of the disappearing Neanderthal Y chromosome
And , of grade , because the current study was conducted only in mice , future research should look at human brain tissue paper to check that the results carry over , Buckley pronounce . " This is such extremely singular and new work … but that is a caveat . "
In the long run , this line of inquiry could help scientists sympathise the influence of sex on dementedness risk , differentiating it from other factor , like educational activity , that are more closely tied to gender , Buckley said . By pinpoint those biologic driver of brain aging , researcher could better find out how to intervene and tailor treatment to individual patient .
" Right now , we ’re doing one size fits all , " Buckley read . " And realistically , this is not how we ’re going to move the needle . "
