YALE (US) — A tiny variation of a single gene determines the formation of convolutions in the brain—the basis for rational and abstract thought.
A genetic analysis of a Turkish patient whose brain lacks the characteristic convolutions in part of his cerebral cortex revealed that the deformity was caused by the deletion of two genetic letters from 3 billion in the human genetic alphabet. Similar variations of the same gene, called laminin gamma3 (LAMC3), were discovered in two other patients with similar abnormalities.
“The demonstration of the fundamental role of this gene in human brain development affords us a step closer to solve the mystery of the crown jewel of creation, the cerebral cortex,” says Murat Gunel, professor of neurosurgery at Yale University.
The folding of the brain, seen only in mammals with larger brains, such as dolphins and apes, and most pronounced in humans, expand the surface area of the cerebral cortex and allow for complex thought and reasoning without taking up more space in the skull.
Such foldings aren’t seen in rodents or other animals. Despite their importance, no one has yet been able to explain how the brain creates them. The LAMC3 gene—involved in cell adhesion that plays a key role in embryonic development—may be crucial to the process.
The research is published in the journal Nature Genetics.
An analysis of the gene shows that it is expressed during the embryonic period that is vital to the formation of dendrites, which form synapses or connections between brain cells, Gunel says.
“Although the same gene is present in lower organisms with smooth brains such as mice, somehow over time, it has evolved to gain novel functions that are fundamental for human occipital cortex formation and its mutation leads to the loss of surface convolutions, a hallmark of the human brain.”
Researchers from several institutions in Turkey contributed to the research that was funded in part by the National Institute of Neurological Disorders and Stroke.
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