Pare che il Neanderthal sia stato generoso con noi: scopriamo sempre nuovi lasciti.
Il più recente sembra essere collegato al metabolismo dei lipidi. Si sa che l'Uomo anatomicamente moderno si è in qualche modo incrociato con Neanderthal, fuori dall'Africa. Ed infatti, questi 'lasciti' riguardano solamente Europei ed Asiatici, in genere, seppure in modo differente. In particolare, gli europei avrebbero ereditato una quantità di geni che agiscono sul metabolismo lipidico almeno tre volte superiore a quella degli Asiatici (studio su 11 popolazioni differenti, pubblicato on line su Nature Communications e di libera consultazione). Si tratta di geni che scindono i grassi, producendo energia. Inoltre, si è visto che la concentrazione di acidi grassi dei tessuti cerebrali presenta enormi differenze negli Europei, rispetto sia agli Asiatici sia agli scimpanzé: questo significa che si tratta di mutamenti causati da evoluzione recente. Gli europei mostrano anche differenze nel funzionamento degli enzimi noti per avere una funzione riguardante il metabolismo dei grassi encefalici. L'equipe sta cercando di stabilire quale sia esattamente il significato di queste differenze e se possa in qualche modo avere effetto sulle funzioni cerebrali stesse. Si ritiene che qualche azione debba esserci - altrimenti non si osserverebbe questa differente concentrazione di acidi grassi encefalici - e che possa essere servita per dare all'Uomo anatomicamente moderno qualche vantaggio.
Neandertals gave Europeans lipid catabolism genes
In the latest study, published online today in Nature Communications, Khaitovich and his international team analyzed the distribution of Neandertal gene variants in the genomes of 11 populations from Africa, Asia, and Europe.
They found that Europeans inherited three times as many genes involved in lipid catabolism, the breakdown of fats to release energy, from Neandertals as did Asians. (As expected, Africans did not carry any of these Neandertal variants.) The difference in the number of Neandertal genes involved with lipid processing was “huge,” Khaitovich says. The study also offers another example of the lingering genetic legacy left in some people today by the extinct Neandertals.
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The team found that Europeans had differences in the concentration of various fatty acids in the brain that were not found in Asians or chimpanzees, which suggests they had evolved recently. The Europeans also showed differences in the function of enzymes that are known to be involved with the metabolism of fat in the brain.
Now the team is trying to figure out what the fatty acids do in the brain and how differences in their concentration might affect function. “We think it’s a very strong effect with very profound physiological changes,” Khaitovich says. “Otherwise, we wouldn’t see it in the brain tissue.”The article itself is open access.
Nature Communications 5, Article number: 3584 doi:10.1038/ncomms4584
Neanderthal ancestry drives evolution of lipid catabolism in contemporary Europeans
Ekaterina E. Khrameeva et al.
Although Neanderthals are extinct, fragments of their genomes persist in contemporary humans. Here we show that while the genome-wide frequency of Neanderthal-like sites is approximately constant across all contemporary out-of-Africa populations, genes involved in lipid catabolism contain more than threefold excess of such sites in contemporary humans of European descent. Evolutionally, these genes show significant association with signatures of recent positive selection in the contemporary European, but not Asian or African populations. Functionally, the excess of Neanderthal-like sites in lipid catabolism genes can be linked with a greater divergence of lipid concentrations and enzyme expression levels within this pathway, seen in contemporary Europeans, but not in the other populations. We conclude that sequence variants that evolved in Neanderthals may have given a selective advantage to anatomically modern humans that settled in the same geographical areas.
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