C Becomes G: The Tiny Event That Changed Human History
What distinguishes humans from monkeys and apes? The gene ARHGAP11B is probably among the things that make humans special: This gene is only present in humans and contributes to the amplification of brain stem cells. Researchers at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden have now made a spectacular finding: It is a single base pair substitution in the ARHGAP11B gene that ultimately is responsible for the ability of the ARHGAP11B protein to amplify brain stem cells, a process thought to underlie the expansion of the neocortex in modern humans.
The substitution of a single letter (red) in the code of the ARHGAP11B gene results in more brain stem cells being developed in modern humans than in earlier forms of humans.
During evolution, the human genome has undergone subtle changes that underlie the expansion of a particular region of the brain called the neocortex. This part of the brain is responsible for cognitive functions like speaking and thinking. Wieland Huttner, research group leader and director at the Max Planck Institute in Dresden, and his team have recently shown that the gene ARHGAP11B is key to the regulation of brain size.
The human-specific gene ARHGAP11B arose through a partial duplication of the ubiquitous gene ARHGAP11A approximately five million years ago along the evolutionary lineage leading to Neanderthals, Denisovans, and present-day humans, and after this lineage had segregated from that leading to the chimpanzee. However, the big leap in neocortex expansion began later, about two million years ago. How, then, could ARHGAP11B possibly be a key player in increasing neocortex size, researchers wondered.
There is more to ARHGAP11B that makes it unique: Not only is the gene as such human-specific, but the protein encoded by the gene contains a sequence of 47 amino acids that is only found in humans and that is due to a shift in the reading frame caused by the absence of 55 nucleotides in the ARHGAP11B messenger RNA.
Wieland Huttner and Marta Florio, PhD student in Huttner’s group, first thought that the absence of these 55 nucleotides would go back to when ARHGAP11B arose by partial gene duplication five million years ago. This is when they got lost, the researchers assumed. But then they realized, to their astonishment, that the stretch of 55 nucleotides is indeed present in the ARHGAP11B DNA and only disappears when the messenger RNA of ARHGAP11B is produced – they are spliced out. This is triggered by a single C-to-G base substitution in the ARHGAP11B gene.
The C-to-G base substitution in ARHGAP11B probably happened much later than when this gene arose around five million years ago, anytime between 1.5 million and 500,000 years ago. The Dresden researchers wanted to cross-check the significance of this base substitution for the function of the ARHGAP11B protein, and therefore reconstructed an ancestral version of the ARHGAP11B gene as it likely arose five million years ago – without the single base pair substitution. Remarkably, when expressed in mice, the ancestral ARHGAP11B protein did not lead to an increase in the abundance of basal progenitors.
The finding that a mere single point mutation may have causally contributed to the expansion of the neocortex is remarkable. Huttner says: “This change is tiny on a genomic scale but substantial in its functional and evolutionary consequences – it’s a single base substitution that likely drove brain size evolution and that may have set the stage for what makes humans special.” Point mutations are not rare, but in the case of ARHGAP11B its advantages seem to have immediately influenced human evolution.
Contacts and sources:
Prof. Dr. Wieland B. Huttner
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden
Source: http://www.ineffableisland.com/2016/12/c-becomes-g-tiny-event-that-changed.html
Anyone can join.
Anyone can contribute.
Anyone can become informed about their world.
"United We Stand" Click Here To Create Your Personal Citizen Journalist Account Today, Be Sure To Invite Your Friends.
Please Help Support BeforeitsNews by trying our Natural Health Products below!
Order by Phone at 888-809-8385 or online at https://mitocopper.com M - F 9am to 5pm EST
Order by Phone at 866-388-7003 or online at https://www.herbanomic.com M - F 9am to 5pm EST
Order by Phone at 866-388-7003 or online at https://www.herbanomics.com M - F 9am to 5pm EST
Humic & Fulvic Trace Minerals Complex - Nature's most important supplement! Vivid Dreams again!
HNEX HydroNano EXtracellular Water - Improve immune system health and reduce inflammation.
Ultimate Clinical Potency Curcumin - Natural pain relief, reduce inflammation and so much more.
MitoCopper - Bioavailable Copper destroys pathogens and gives you more energy. (See Blood Video)
Oxy Powder - Natural Colon Cleanser! Cleans out toxic buildup with oxygen!
Nascent Iodine - Promotes detoxification, mental focus and thyroid health.
Smart Meter Cover - Reduces Smart Meter radiation by 96%! (See Video).
Reading the article, I thought this would be an article about music, I am disappointed.
*Reading the article title, I thought this would be an article about music, I am disappointed.