Polygenic architecture of human neuroanatomical diversity

We analysed the genomic architecture of neuroanatomical diversity using magnetic resonance imagingand single nucleotide polymorphism (SNP) data from >26,000 individuals from the UK Biobank projectand 5 other projects that had previously participated in the ENIGMA consortium. Our results confirm thepolygenic architecture of neuroanatomical diversity, with SNPs capturing from 40% to 54% of regionalbrain volume variance. Chromosomal length correlated with the amount of phenotypic variance captured,r~0.64 on average, suggesting that at a global scale causal variants are homogeneously distributedacross the genome. At a local scale, SNPs within genes (~51%) captured ~1.5 times more geneticvariance than the rest; and SNPs with low minor allele frequency (MAF) captured less variance than therest: the 40% of SNPs with MAF<5% captured <1/4th of the genetic variance. We also observedextensive pleiotropy across regions, with an average genetic correlation of rG ~0.45. Genetic correlationswere similar to phenotypic and environmental correlations, however, genetic correlations were oftenlarger than phenotypic correlations for the left/right volumes of the same region. The heritability ofdifferences in left/right volumes was generally not statistically significant, suggesting an importantinfluence of environmental causes in the variability of brain asymmetry. Our code is available athttps://github.com/neuroanatomy/genomic-architecture.