Chimp ‘mini-brains’ help decode how humans got big brains

A group of researchers in the US have created organoids, a replica of chimpanzees’ brain --- our closest genus relative --- in the laboratory using stem cells of chimps and humans, to understand how human brains develop and organise the neurons. The finding, which inspired this interesting research and development, says that at some point during evolution of human species, certain genetic changes triggered a dramatic threefold expansion of the neocortex region of the human brain. The neocortex is the wrinkly outermost layer of the brain tissue that’s responsible for everything from language and self-awareness to abstract thought. The researchers were curious to find out what caused this evolutionary shift as this turning point in the story of human evolution is fundamental for understanding what exactly makes us human.

The team of researchers was led by Aparna Bhaduri, a postdoctoral researcher from India at UCSF. Under her leadership, the research team deconstructed human and chimpanzee organoids at different stages of development and observed the differences in the gene activity. Bhaduri identified several hundred genetic changes unique to the human lineage that explained the evolutionary origins of the distinguished human brain.

One of the findings said that neural precursor cells, also known as Outer Radial Glia (oRG) showed heightened activity of crucial network which indicates growth. The network is known as the mTOR pathway in human organoids. “It was exciting to discover a molecular pathway in the neural precursor cells; the molecular pathway appears to have been specifically targeted during the periods of evolution and the data stored in the pathway may help explain their specialised role in forming the advanced human cortex,” Bhaduri said. On the other hand, challenges faced at the regions of mTOR signalling have also been linked to autism and other unique neuro-developmental disorders in humans, raising new questions, one of them being — Do these pathways involved in the relatively recent evolution of our unusually large brains play an important role in these disorders?   - IANS