  For much of biology, the manner in which genotype maps to phenotype remains a
fundamental mystery. The few maps that are known tend to show modular
pleiotropy: sets of phenotypes are determined by distinct sets of genes. One
key map that has evaded discovery is that of the human brain's network
architecture. Here, we determine the form of this map for gene coexpression and
single nucleotide polymorphisms. We discover that mostly non-overlapping sets
of genes encode the connectivity of brain network modules (or so-called
communities), suggesting that brain network communities demarcate genetic
transitions. We find that these clean boundaries break down at connector hubs,
whose integrative connectivity is encoded by pleiotropic genes from mostly
non-overlapping sets. Broadly, this study opens fundamentally new directions in
the study of genetic encoding of brain development, evolution, and disease.
