New Study shows the Human Brain is founded on Fish-like Ancestors

A New Study shows that Genetic events that took place in our fish-like ancestors played a crucial role in the brain biology of our species.In a new study, published in Nature Ecology & Evolution, researchers from the University of Western Australia (UWA) found that non-CpG DNA methylation, an epigenetic control system found abundantly in human brains, first appeared in the first vertebrate animals.

Non-CpG methylation has the ability to turn DNA on and off for genes that control aspects of brain function. The discovery that non-CpG methylation is found in vertebrate animals suggests that it has played a crucial role in enabling the sophisticated cognitive abilities found in human brains and other vertebrates today.

Professor Ryan Lister of the UWA College of Molecular Sciences, who co-led the study, said the researchers analyzed brain samples from animals from across the tree of life.

“We wanted to determine whether non-CpG methylation is restricted to mammalian species, which possess very complex cognitive abilities, or whether it has deeper evolutionary origins,” Professor Lister said in a statement.

The researchers found that non-CpG methylation is seen exclusively in vertebrate animals. This includes lampreys, animals that come from an ancestral jawless fish lineage that share a common ancestor with humans.

This finding suggests that non-CpG methylation arose in the early common ancestors of all vertebrates, organisms that roamed the earth hundreds of millions of years ago.

Co-investigator Dr. Alex de Mendoza said that this result means that non-CpG methylation may have played a crucial role in the development of brain sophistication.

“We looked for non-CpG methylation in the brain of everything we could get, from marsupials, platypuses, birds, frogs, fish, sharks and lampreys, which represents the full range of animals with backbones. We also looked in the brains of various invertebrates like a bee and an octopus,” said de Mendoza.

“We found that non-CpG methylation evolved in vertebrate origin and therefore may have been an important requirement for the brain to develop more complex functions.”

The study also revealed that the evolution of all the genetic tools necessary for cells to use non-CpG methylation took place around the same time.

The gene responsible for writing non-CpG methylation, DNMT3A, and the gene responsible for reading it, MeCP2, were found to originate early in vertebrate evolution.

“This study highlights how events that took place in our fish-like ancestors still play a central role in our own brain biology,” said Professor Lister.