Differences and similarities between human and chimpanzee neural progenitors during cerebral cortex development

What is it about?

We have analysed brain stem cells from human, chimpanzee and orangutan cells. The experiments showed that the human and other great ape cells were remarkably similar in many ways, including in the mix of cell types and in how these cells were arranged. Nevertheless, progenitor cells that form the human cerebral cortex spend around 50% more time in a stage of the cell division process called metaphase compared to the same cells from chimpanzees or orangutans. Metaphase is the part of the division process when the cell makes sure that structures called chromosomes, which carry the cell’s DNA, can be separated and distributed equally between the two daughter cells.

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Why is it important?

The human brain is about three times as big as the brain of our closest living relative, the chimpanzee. Moreover, a part of the brain called the cerebral cortex – which plays a key role in memory, attention, awareness and thought – contains twice as many cells in humans as the same region in chimpanzees. Networks of brain cells in the cerebral cortex also behave differently in the two species. How these species differences arise is not clear, but it likely occurs in the earliest phases of development when brain stem and progenitor cells divide and give rise to cerebral cortex cells in the growing brain. Our work suggests that a longer metaphase may be a characteristic feature of human brain stem cells and how they proliferate and differentiate. This may be involved in generating the differences that make the human brain unique.

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