Mini human brains develop slower than other primates

New Age. BBC | Published: 13:02, Oct 18,2019

 
 

Four lab-grown chimpanzee "mini-brains". Each one is about the size of a small pea. — BBC photo

Human ‘mini-brains’ develop more slowly than those of other primates, shows a recent Swiss research. ‘Mini-brains’ are miniature collections of cells that allow scientists to study how the brain develops.

The Swiss team has grown artificial human, chimp and macaque versions in their lab from stem cells.

In a study published in Nature journal, the team produced an ‘atlas’ of the genes involved in each stage of the three types of brain development, reports BBC.

They say that the work will help them to answer the basic question of what makes us human. Stem cells are the body’s master cells, which can then grow into more specialised tissues.

The recent emergence of the technology to grow brain tissue from stem cells has enabled researchers to directly compare brain development in different primates. The ‘mini-brains’ are grown for four months and are about the size of a pea.

Known formally as ‘cerebral organoids’, they are simple structures consisting of different types of brain cells and are not capable of any functions.

The researchers noted that the three types of brain developed at the same speed to begin with, but once the cells began to specialise into different types of neurons, the macaque’s developed the fastest, followed by the chimpanzee, with the human brain being the slowest.

Co-author professor Barbara Treutlein of Basel University, Switzerland, said the slow development might be required to develop the larger and more complex human brain.

‘It seems that we take more time to develop our brains but the end state that we reach is more complex. Maybe it takes this additional time to get the greater number of connections between neurons and reach the higher cognitive functions we have. But we don’t really know yet why this might be the case,’ she told BBC News.

All cells develop by following instructions contained in DNA. But the genetic information of humans and chimps has comparatively few differences yet their brains are very different. Treutlein believes that the resolution of this this apparent dichotomy is that the timing and sequence of how brain-building instructions are read from the genes are different. To assess this, her team took thousands of snapshots of what the genes were doing at each stage of brain development of the three types of mini-brains.

Put together the snapshots give what the researchers call an ‘atlas’ of brain development for each primate brain. These atlases give researchers a resource with which to examine the roles of collections of genes in brain development.

According to Dr Grayson Camp, also at Basel University, the differences between the human and chimp brains should give an indication why our brains are more complex.

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