A central goal of neuroscience is to advance knowledge of the molecular basis of human brain function. Most molecular studies of the human brain have been performed using tissue from postmortem brain donors rather than living people. The assumption underlying this practice - which had never been rigorously tested prior to this report - is that the postmortem human brain is an appropriate proxy for the living human brain at the molecular level. Here, this assumption is thoroughly challenged for the first time by comparing human prefrontal cortex gene expression between 275 living samples and 243 postmortem samples. Vast differences in gene expression were found between the living and postmortem human brain. Expression levels differed significantly for nearly 80% of genes, and this finding was not a consequence of any potential technical or biological confounders of the gene expression data. Postmortem brain gene expression signatures of Alzheimer's disease, schizophrenia, Parkinson's disease, bipolar disorder, and autism spectrum disorder were shown to be inaccurate representations of disease processes occurring in the living brain. In light of these findings, the use of postmortem tissue as a proxy for living tissue in human brain research should be reconsidered. To advance knowledge of the molecular basis of human brain function, the study of tissue from living people should be prioritized.

Schizophrenia (SCZ) is a chronic mental illness and among the most debilitating conditions encountered in medical practice. A recent landmark SCZ study of the protein-coding regions of the genome identified a causal role for ten genes and a concentration of rare variant signals in evolutionarily constrained genes1. This recent study—and most other large-scale human genetics studies—was mainly composed of individuals of European (EUR) ancestry, and the generalizability of the findings in non-EUR populations remains unclear. To address this gap, we designed a custom sequencing panel of 161 genes selected based on the current knowledge of SCZ genetics and sequenced a new cohort of 11,580 SCZ cases and 10,555 controls of diverse ancestries. Replicating earlier work, we found that cases carried a significantly higher burden of rare protein-truncating variants (PTVs) among evolutionarily constrained genes (odds ratio = 1.48; P = 5.4 × 10−6). In meta-analyses with existing datasets totaling up to 35,828 cases and 107,877 controls, this excess burden was largely consistent across five ancestral populations. Two genes (SRRM2 and AKAP11) were newly implicated as SCZ risk genes, and one gene (PCLO) was identified as shared by individuals with SCZ and those with autism. Overall, our results lend robust support to the rare allelic spectrum of the genetic architecture of SCZ being conserved across diverse human populations.

Schizophrenia is a chronic mental illness that is amongst the most debilitating conditions encountered in medical practice. A recent landmark schizophrenia study of the protein-coding regions of the genome identified a causal role for ten genes and a concentration of rare variant signals in evolutionarily constrained genes1. This study -- and most other large-scale human genetic studies -- was mainly composed of individuals of European ancestry, and the generalizability of the findings in non-European populations is unclear. To address this gap in knowledge, we designed a custom sequencing panel based on current knowledge of the genetic architecture of schizophrenia and applied it to a new cohort of 22,135 individuals of diverse ancestries. Replicating earlier work, cases carried a significantly higher burden of rare protein-truncating variants among constrained genes (OR=1.48, p-value = 5.4 x 10-6). In meta-analyses with existing schizophrenia datasets totaling up to 35,828 cases and 107,877 controls, this excess burden was largely consistent across five continental populations. Two genes (SRRM2 and AKAP11) were newly implicated as schizophrenia risk genes, and one gene (PCLO) was identified as a shared risk gene for schizophrenia and autism. Overall, our results lend robust support to the rare allelic spectrum of the genetic architecture of schizophrenia being conserved across diverse human populations.