Exon microarray analysis of human dorsolateral prefrontal cortex in alcoholism

Abstract

Background: Alcohol abuse is associated with cellular and biochemical disturbances that impact upon protein and nucleic acid synthesis, brain development, function, and behavioral responses. To further characterize the genetic influences in alcoholism and the effects of alcohol consumption on gene expression, we used a highly sensitive exon microarray to examine mRNA expression in human frontal cortex of alcoholics and control males.

Methods: Messenger RNA was isolated from the dorsolateral prefrontal cortex (dlPFC; Brodmann area 9) of 7 adult alcoholic (6 males, 1 female, mean age 49 years) and 7 matched controls. Affymetrix Human Exon 1.0 ST array was performed according to standard procedures and the results analyzed at the gene level. Microarray findings were validated using quantitative reverse transcription polymerase chain reaction, and the ontology of disturbed genes characterized using Ingenuity Pathway Analysis (IPA).

Results: Decreased mRNA expression was observed for genes involved in cellular adhesion (e.g., CTNNA3, ITGA2), transport (e.g., TF, ABCA8), nervous system development (e.g., LRP2, UGT8, GLDN), and signaling (e.g., RASGRP3, LGR5) with influence over lipid and myelin synthesis (e.g., ASPA, ENPP2, KLK6). IPA identified disturbances in network functions associated with neurological disease and development including cellular assembly and organization impacting on psychological disorders.

Conclusions: Our data in alcoholism support a reduction in expression of dlPFC mRNA for genes involved with neuronal growth, differentiation, and signaling that targets white matter of the brain.

Keywords: Affymetrix; Alcoholism; Exon Microarray; Frontal Cortex; Myelin.

Figure 1

Heatmap of mRNAs clustered and based upon significant disturbances in the frontal cortex of alcoholics and control subjects (red or dark gray represents increased expression and green or light gray represents decreased expression).

Figure 2

qRT-PCR amplification of brain mRNA of selected disturbed genes in alcoholism relative to control gene (GAPDH) expression for A. UDP glycosyltransferase 8 (UGT8) B. Transferrin (TF) and C. Low density lipoprotein receptor-related protein 2 (LRP2). GAPDH: Black= control subjects (N=7), Blue= alcohol dependent subjects (N=7); Selected disturbed genes: Red= control subjects (N=7), Yellow= alcohol dependent subjects (N=7)