It is known that brain structure is under strong genetic control, and while researchers understand that genes strongly underpin brain development, it is still unclear which specific genes are implicated or how they contribute to different brain structures. Now, a study from researchers at University of New South Wales identifies the inheritable neurogenetics of brain grey matter structures in older adult twins. The team state that their study unlocks important clues about how genes influence the development of key grey matter structures, paving the way for a genetic blueprint of the human brain. The opensource study is published in the journal Scientific Reports.
Previous studies show that the patterning of the cerebral cortex, known as arealization, has been systematically studied in animals. Work on transcription factors, morphogens and signalling molecules in the rodent has shown how the regional identity of cortical areas develop. Genetic influence on the human cortex has been investigated; however, whether and how the genetic influence on cortical and subcortical structures, which are responsible for functions ranging from memory and visual processing, to motor control, is shared is an intriguing question which to date has not been examined. The current study uses the twin design to to examine genetic correlations between all the brain’s structures.
The current study analyses the MRI scans of 322 individuals from the Older Australian Twins Study to map the genetic relatedness, or heritability, of cortical and subcortical structures in their brains. MRI scans of 93 sets of identical twins and 68 sets of fraternal twins were analysed where all participants were caucasian men and women without dementia, with an average age of 70. The participant’s brain structure volume was measured and the heritability, or the extent to which genes contribute to phenotypic, or physical, differences, for each determined.
Results show that the volume of cortical and subcortical brain structures have moderate to strong genetic contributions of between 40 and 80%, with the subcortical hippocampus, which play a key role in memory processes, exhibiting a genetic contribution greater than 70% in older people. Data findings show that cortical structures, including the frontal lobe, contributing to movement, memory and motivation, and occipital lobe, which is used mainly in visual processing, have genetic contributions greater than 70%.
The researchers state that there is symmetry in the brain with corresponding structures in the left and right hemispheres influenced by the same genetic factors. They go on to add their data suggests that there are three genetically correlated clusters within the brain. They explain that these are regions where the same sets of genes seem to be influencing multiple structures. Results show that one cluster involves the 4 cortical lobe structures, while the other two involve clusters of subcortical structures.
The team surmise that their study provides a blueprint for forming a new model of the brain, subdivided into genetically-linked structures. For the future, the researchers state that now the global medical community can understand the genetic basis for variability in human brains, they can begin to understand the mechanisms which cause these differences and underpin development of neurological-based diseases.
Source: University of New South Wales
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