Development of the brain is dependent on environmental and genetic factors during fetal development and early childhood. A massive international study using data from nearly 300 researchers from 193 institutions has revealed variants of genes that affect the volume of certain brain structures, while confirming three others. This could have large implications for disorders regarding memory and behavior, as well as a suite of neurodegenerative diseases including Alzheimer’s and Huntington's. Derrek Hibar of the University of Southern California, Los Angeles, was lead author of the paper published in Nature.
“This study is the triumph of international collaboration, with data contributed by over 200 investigators that brought together 50 cohorts from all over the world,” co-author Perminder Sachdev said in a press release. “It represents the next phase of medical research in which biomedical scientists, much like physicists, work collaboratively on problems too large to be solved by individual researchers."
The study used genetic data and MRI scans of over 30,000 patients, searching for connections between the loci of genetic variants and the size of certain brain structures. A total of six connections were verified, with another eight suggested. Some of the variants were inside the protein-coding portion of the gene, while others were nearby in regulatory regions. These variations were linked to a 1.5% reduction in the volume of brain tissue.
Three loci associated with the volume of the putamen were identified and another four suggested, while one locus was suggested to be connected with caudate volume. The putamen and caudate are at the base of the forebrain in the basal ganglia, where they play a large role in learned behavior, voluntary muscle movement, eye movement, and emotion. These structures have been linked to a variety of motor disorders including Tourette’s, Parkinson’s, and Huntingon’s, along with certain psychiatric disorders.
Two loci are suspected to influence volume of the amygdala. Amygdalae are located in the temporal lobes and influence emotion, decision-making, and emotions. Disorders connected to the amygdala include aggression, anxiety, and alcoholism.
The study also confirmed three loci of previously discovered variants believed to regulate volume of the hippocampus. There are two hippocampi in the brain, one in each hemisphere in the medial temporal lobe. This structure is responsible for spatial orientation and the creation and storage of memories. The hippocampus is also associated with psychiatric disorders like Alzheimer’s, schizophrenia, epilepsy, and depression.
One locus was identified to play a role in overall intracranial volume, which has implications in Alzheimer’s, dementia, and cognitive impairment.
Moving forward, the researchers would like to establish which genetic variations are connected to particular neurological disorders, as this could possibly reveal predisposition and allow proactive treatment.