CHRNA7 and CHRFAM7A mRNAs: co-localized and their expression levels altered in the postmortem dorsolateral prefrontal cortex in major psychiatric disorders

Am J Psychiatry. 2015 Nov 1;172(11):1122-30. doi: 10.1176/appi.ajp.2015.14080978. Epub 2015 Jul 24.

Abstract

Objective: CHRNA7, coding α-7 nicotinic acetylcholine receptor (α7 nAChR), is involved in cognition through interneuron modulation of dopamine and glutamate signaling. CHRNA7 and its partially duplicated chimeric gene CHRFAM7A have been implicated in schizophrenia through linkage and association studies.

Method: Expression of CHRNA7 and CHRFAM7A mRNA was measured in the postmortem prefrontal cortex in more than 700 subjects, including patients with schizophrenia, bipolar disorder, major depression, and normal comparison subjects. The effects of antipsychotics and nicotine, as well as associations of CHRNA7 SNPs with gene expression, were explored. Fluorescent in-situ hybridization was used to examine coexpression of both transcripts in the human cortex.

Results: CHRFAM7A expression and CHRFAM7A/CHRNA7 ratios were higher in fetal compared with postnatal life, whereas CHRNA7 expression was relatively stable. CHRFAM7A expression was significantly elevated in all diagnostic groups, while CHRNA7 expression was reduced in the schizophrenia group and increased in the major depression group compared with the comparison group. CHRFAM7A/CHRNA7 ratios were significantly increased in the schizophrenia and bipolar disorder groups compared with the comparison group. There was no effect of nicotine or antipsychotics and no association of SNPs in CHRNA7 with expression. CHRNA7 and CHRFAM7A mRNAs were expressed in the same neuronal nuclei of the human neocortex.

Conclusions: These data show preferential fetal CHRFAM7A expression in the human prefrontal cortex and suggest abnormalities in the CHRFAM7A/CHRNA7 ratios in schizophrenia and bipolar disorder, due mainly to overexpression of CHRFAM7A. Given that these transcripts are coexpressed in a subset of human cortical neurons and can interact to alter function of nAChRs, these results support the concept of aberrant function of nAChRs in mental illness.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bipolar Disorder / genetics*
  • Bipolar Disorder / metabolism
  • Case-Control Studies
  • Depressive Disorder, Major / genetics*
  • Depressive Disorder, Major / metabolism
  • Female
  • Fetus / metabolism*
  • Gene Expression
  • Humans
  • In Situ Hybridization, Fluorescence
  • Male
  • Middle Aged
  • Prefrontal Cortex / metabolism*
  • RNA, Messenger / metabolism*
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Schizophrenia / genetics*
  • Schizophrenia / metabolism
  • Young Adult
  • alpha7 Nicotinic Acetylcholine Receptor / genetics*

Substances

  • Chrna7 protein, human
  • RNA, Messenger
  • alpha7 Nicotinic Acetylcholine Receptor