Why human beings are the most intelligent animals on the planet? Researchers at the University of Toronto gave an answer to it these days. This owes to a key molecular events. Studies have shown that a small change of PTBP1 protein controls the generation of neurons, helping mammals to evolve larger and more complicated brains.

The size and complexity of the brain of vertebrates has significant difference. For example, humans and frogs have independently evolved over 350 million years, and the functions of their brain are quite different. So how is the huge gap formed? Scientists have found that the gene used by human and frog is quite similar, and the difference is mainly from alternative splicing (AS).

Alternative splicing can generate multiple proteins from a single gene, and therefore the type of proteins is much more than genes in the cells. Benjamin Blencowe, a professor from University of Toronto noted that the regulation of cellular protein diversity reflected the potential of the cells to assume different functions. His previous work has shown that the high complexity of the vertebrates would lead to more alternative splicing events. For this reason, despite the use of genes are similar in vertebrate, the diversity of protein in mammals was significantly higher than those in birds and frogs. The brain is the most popular location for alternative splicing.

PTBP1 protein in mammals is different from the one in other vertebrates. Due to alternative splicing, PTBP1 protein in mammals is relatively short. The researchers pointed out that PTBP1 is not only the target of the AS but also the primary regulator. Full-length PTBP1 will delay other alternative splicing events, so the cells can not become neurons. While the short PTBP1 in mammals will liberate a series of alternative splicing events, and change the balance of intracellular proteins, so cells eventually develop into neurons.

Researchers modified the chicken cells, making it produce short PTBP1 that is similar to mammals’. As a result, they found that this transformation can make chicken cells to have similar AS as mammalian cells.

“Different types of PTBP1 may affect the timing of embryonic generating neurons, the complexity and size of brain is thus produced,” Blencowe commented.