title: Human brain weight is correlated with expression of the 'housekeeping genes' beta-2-microglobulin (β2M) and TATA-binding protein (TBP).
abstract: OBJECTIVE
  Many variables affect mRNA measurements in post mortem human brain tissue. Brain weight has not hitherto been considered to be such a factor. This study examined whether there is any relationship between brain weight and mRNA abundance.
  
  
  METHODS
  We investigated quantitative real-time RT-PCR data for five 'housekeeping genes' using the 104 adult brains of the Stanley Microarray Consortium series. Eleven data sets were analysed, from cerebellum, hippocampus, and anterior cingulate cortex. We used a specified sequence of correlations, partial correlations and multiple regression analyses.
  
  
  RESULTS
  Brain weight correlated with the 'raw' (i.e. non-normalized) data for two mRNAs, β2-microglobulin and TATA-binding protein, measured in cerebellum and hippocampus, respectively. In hippocampus, the geometric mean of three housekeeping gene transcripts also correlated with brain weight. The correlations were significant after adjusting for age, sex and other confounders, and the effect of brain weight was confirmed using multiple regression. No correlations with brain weight were seen in the anterior cingulate cortex, nor for the other mRNAs examined.
  
  
  CONCLUSIONS
  The findings were not anticipated; they need replication in another brain series, and a more systematic survey is indicated. In the interim, we suggest that quantitative gene expression studies in human brain should inspect for a potential influence of brain weight, especially as the affected transcripts are commonly used as reference genes for normalization purposes in studies of neurological and psychiatric disorders. The relationship of brain weight with β2-microglobulin mRNA may reflect the roles of major histocompatibility complex class I genes in synapse formation and plasticity.
authors.affiliation: Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK. paul.harrison@psych.ox.ac.uk
authors.forename: P J
authors.initials: PJ
authors.lastname: Harrison
authors.forename: L M
authors.initials: LM
authors.lastname: Laatikainen
authors.forename: E M
authors.initials: EM
authors.lastname: Tunbridge
authors.forename: S L
authors.initials: SL
authors.lastname: Eastwood
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D035181:TATA-Box Binding Protein / Q000096:biosynthesis* / Q000235:genetics; D001613:beta 2-Microglobulin / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D035181:TATA-Box Binding Protein; D001613:beta 2-Microglobulin