title: Systematic analysis of gene expression in human brains before and after death.
abstract: BACKGROUND
  Numerous studies have employed microarray techniques to study changes in gene expression in connection with human disease, aging and evolution. The vast majority of human samples available for research are obtained from deceased individuals. This raises questions about how well gene expression patterns in such samples reflect those of living individuals.
  
  
  RESULTS
  Here, we compare gene expression patterns in two human brain regions in postmortem samples and in material collected during surgical intervention. We find that death induces significant expression changes in more than 10% of all expressed genes. These changes are non-randomly distributed with respect to their function. Moreover, we observe similar expression changes due to death in two distinct brain regions. Consequently, the pattern of gene expression differences between the two brain regions is largely unaffected by death, although the magnitude of differences is reduced by 50% in postmortem samples. Furthermore, death-induced changes do not contribute significantly to gene expression variation among postmortem human brain samples.
  
  
  CONCLUSIONS
  We conclude that postmortem human brain samples are suitable for investigating gene expression patterns in humans, but that caution is warranted in interpreting results for individual genes.
authors.affiliation: Max-Planck-Institute for Evolutionary Anthropology, Deutscher Platz, D-04103 Leipzig, Germany.
authors.forename: Henriette
authors.initials: H
authors.lastname: Franz
authors.forename: Claudia
authors.initials: C
authors.lastname: Ullmann
authors.forename: Albert
authors.initials: A
authors.lastname: Becker
authors.forename: Margaret
authors.initials: M
authors.lastname: Ryan
authors.forename: Sabine
authors.initials: S
authors.lastname: Bahn
authors.forename: Thomas
authors.initials: T
authors.lastname: Arendt
authors.forename: Matthias
authors.initials: M
authors.lastname: Simon
authors.forename: Svante
authors.initials: S
authors.lastname: Pääbo
authors.forename: Philipp
authors.initials: P
authors.lastname: Khaitovich
mesh_terms: D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001344:Autopsy; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D002648:Child; D003643:Death; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged