Large-scale MRI and genetic datasets are helping us understand the common variants of the genes that help build the human cerebral cortex
To map regions of the brain to specific genes, researchers at the University of California – San Diego did genome-wide association studies (GWAS) of the regional cortical surface area and thickness of 39,898 adults and 9,136 children. That is, they scanned complete sets of DNA (genomes), looking for genetic variations. They were especially interested in variations that might be associated with a problem like autism, epilepsy, or dementia.
By and large, construction of the human brain is determined by heredity, though factors like environmental exposures also play a role, particularly during sensitive periods of neurodevelopment during childhood. Large-scale MRI and genetic datasets have increasingly illuminated the common genetic variants that help build the human cerebral cortex — the outer, layered sheet of wrinkled tissue associated with humans’ highest mental capabilities, such as language, memory, perception, awareness and consciousness.
But what about variations, especially the ones that cause problems? Describing their work, the researchers, led by Carolina Makowski, noted that the use of genetically defined atlases of the brain allowed them to uncover 440 genome-wide significant loci in the study group and 800 in a combined meta-analysis later — “the largest number of genetic variants to date associated with the size and thickness of the cortex.”
Intriguingly, many of the genes that these loci map to are also associated with neurodevelopmental disorders, such as autism, epilepsy and intellectual disability, and dementia,” said [radiologist Chi-Hua] Chen.
Chen, who led the work, also offered,
”To some extent, the molecular machinery for normal brain development and disorders overlaps, which could reflect a continuous spectrum of genetic effects on normal brain structural variation to aberrant neurodevelopment. One possible mechanism is that certain genetic compositions cause abnormal brain development, which leads to neurodevelopmental disorders. The loci we discovered can be used by researchers for further mechanistic studies of how genes impact the brain and diseases.”
The more we know about exactly how some difficult disorders originate, the more opportunities we have to head them off.