Genome wide imaging genetics on the Betula cognition sample

Inter-individual variations in the human healthy brain functions and morphology can be captured with brain imaging. It has been shown, that a large proportion of these inter-individual variance can be attributed to genetic variations. Understanding which genes influence these variations is essential to understand how the brain functions and is shaped, in the normal functioning. Consequently this knowledge will shed light on the dysfunctioning of the brain in mental health disorders such as psychiatric disorders or neurodegenerative disorders. In order to identify these genetic variants it is necessary to obtain brain imaging and genetics information from large population of individuals. Together with our colleagues from the University of Umeå, who collected cognitive information and imaging information from a large sample (the BETULA sample), we collected genome wide genetic information from a sample of 360 individuals. Using these genetic information, we were able to identify genes that are associated with changes in the white fibre tracts measure by Diffusion Tension Imaging. This study was replicated in a Norwegian sample with comparable information. In the last 2-3 years, there has been large progress in understanding how genetic variations influence different brain structures. It has become evident that these genetic effects are very small and require the collection of large samples. Collecting samples big enough can only be achieved by large multi-centre studies. In brain imaging, the major consortium that performs these studies is the ENIGMA consortium. Since we had relevant samples, we were invited to participate in the ENIGMA latest study, which led to the identification of genetic variants associated with the volume of the hippocampus, the putamen and the caudate. We were also invited to participate in a study that identified genes associated with general cognition in the elderly population, led by the CHARGE consortium. In this study, several genetic variants were associated with cognitive ageing , including the involvement of a gene associated with increased risk to develop Alzheimer disease. The results obtained in this project have participated in our general understanding of which genes are implicated in several brain imaging functions: inter-individual variation in white finer tracts properties, inter-individual variation in the volume of several brain structures and inter-individual variation of cognition in the elderly. For the association with fibre tracts we identified the implication of a gene that has been associated with schizophrenia and a gene implicated tin the cortico-thalamic development. These results will hep understanding how these genes can influence the functioning of the healthy brain and also how these genetic variation relate with brain dysfunction. Notably, how the genes that relate to cognitive aging are related with genes implicated in Alzheimer disease. Additional studies are also now being carried as part of the ENIGMA consortium to investigate if the genes that are associated with brain volumes have an effect in several mental health related traits. Similarly, we are also participating now in further studies to identify more genes implicated in the inter-individual variability in white finer tracts.