Gene expression in peripheral blood mononuclear cells from patients with chronic fatigue syndrome

Abstract

Background: Chronic fatigue syndrome (CFS) is a multisystem disease, the pathogenesis of which remains undetermined.

Aims: To test the hypothesis that there are reproducible abnormalities of gene expression in patients with CFS compared with normal healthy persons.

Methods: To gain further insight into the pathogenesis of this disease, gene expression was analysed in peripheral blood mononuclear cells from 25 patients with CFS diagnosed according to the Centers for Disease Control criteria and 25 normal blood donors matched for age, sex, and geographical location, using a single colour microarray representing 9522 human genes. After normalisation, average difference values for each gene were compared between test and control groups using a cutoff fold difference of expression > or = 1.5 and a p value of 0.001. Genes showing differential expression were further analysed using Taqman real time polymerase chain reaction (PCR) in fresh samples.

Results: Analysis of microarray data revealed differential expression of 35 genes. Real time PCR confirmed differential expression in the same direction as array results for 16 of these genes, 15 of which were upregulated (ABCD4, PRKCL1, MRPL23, CD2BP2, GSN, NTE, POLR2G, PEX16, EIF2B4, EIF4G1, ANAPC11, PDCD2, KHSRP, BRMS1, and GABARAPL1) and one of which was downregulated (IL-10RA). This profile suggests T cell activation and perturbation of neuronal and mitochondrial function. Upregulation of neuropathy target esterase and eukaryotic translation initiation factor 4G1 may suggest links with organophosphate exposure and virus infection, respectively.

Conclusion: These results suggest that patients with CFS have reproducible alterations in gene regulation.

Figure 1

Hierarchical clustering experiment of differentially expressed gene profiles among patients with chronic fatigue syndrome (CFS; n  =  25) and normal persons (n  =  25) identified by analysis in BRB Array Tools. The figure was generated using Genepilot software. Each column represents the expression profile for each of the 35 genes. Each row represents a single gene, with its GenBank accession number to the right hand side of the figure. Coloured pixels represent the magnitude of the response for any gene. Shades of red and green represent induction and repression, respectively, relative to the mean value for each respective gene among the normal persons. This figure shows a cluster of 18 subjects (from P29–P9) consisting of predominantly patients with CFS (n  =  17) and one normal person, who have a similar profile of expression of these 35 genes. P, patients; C, controls.

Figure 2

(A) Bar chart showing the fold difference in gene expression between test and control groups by microarray (shaded) and real time polymerase chain reaction (solid black) for 16 genes that are differentially expressed in chronic fatigue syndrome (CFS). (B) Bar chart showing the mean relative quantity of mRNA transcripts in test (shaded) and control (solid black) groups for 16 genes that are differentially expressed in CFS. Error bars indicate the standard deviation from the mean in each case. All values for the mean relative quantity mRNA transcript are shown on the left y axis, except those for NTE and EIF4G1, which are shown on the right y axis.