Researchers have discovered that a small change in a protein in our cells could hold the key to how we evolved to become the smartest animal on the planet.
The change in a protein called PTBP1 that can spur the creation of neurons - cells that make the brain - could have fuelled the evolution of mammalian brains to become the largest and most complex among vertebrates, the findings showed.
A cell's ability to regulate protein diversity at any given time reflects its ability to take on different roles in the body.
The researchers earlier found that prevalence of alternative splicing (AS), whereby gene products are assembled into proteins, which are the building blocks of life, increases with vertebrate complexity.
So although the genes that make bodies of vertebrates might be similar, the proteins they give rise to are far more diverse in animals such as mammals, than in birds and frogs.
And nowhere is AS more widespread than in the brain.
"We wanted to see if AS could drive form and structural differences in the brains of different vertebrate species," said lead author of the study Serge Gueroussov, a graduate student in the lab of Benjamin Blencowe, professor at the University of Toronto in Canada.
Gueroussov previously helped identify PTBP1 as a protein that takes on another form in mammals, in addition to the one common to all vertebrates.
PTBP1's job in a cell is to stop it from becoming a neuron by holding off AS of hundreds of other gene products.
The researchers showed that in mammalian cells, the presence of a second, shorter version of PTBP1 unleashes a cascade of AS events, tipping the scales of protein balance so that a cell becomes a neuron.
What is more, when the researchers engineered chicken cells to make the shorter, mammalian-like, PTBP1, this triggered AS events that are found in mammals.
The study was published in the journal Science.