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, 41 (12), 2744-9

Distinctive RNA Expression Profiles in Blood Associated With White Matter Hyperintensities in Brain

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Distinctive RNA Expression Profiles in Blood Associated With White Matter Hyperintensities in Brain

Huichun Xu et al. Stroke.

Abstract

Background and purpose: White matter hyperintensities (WMH) are areas of high signal detected by T2 and fluid-attenuated inversion recovery sequences on brain MRI. Although associated with aging, cerebrovascular risk factors, and cognitive impairment, the pathogenesis of WMH remains unclear. Thus, RNA expression was assessed in the blood of individuals with and without extensive WMH to search for evidence of oxidative stress, inflammation, and other abnormalities described in WMH lesions in brain.

Methods: Subjects included 20 with extensive WMH (WMH+), 45% of whom had Alzheimer disease, and 18 with minimal WMH (WMH-), 44% of whom had Alzheimer disease. All subjects were clinically evaluated and underwent quantitative MRI. Total RNA from whole blood was processed on human whole genome Affymetrix HU133 Plus 2.0 microarrays. RNA expression was analyzed using an analysis of covariance.

Results: Two hundred forty-one genes were differentially regulated at ± 1.2-fold difference (P < 0.005) in subjects with WMH+ as compared to WMH-, regardless of cognitive status and 50 genes were differentially regulated with ± 1.5-fold difference (P < 0.005). Cluster and principal components analyses showed that the expression profiles for these genes distinguished WMH+ from WMH- subjects. Function analyses suggested that WMH-specific genes were associated with oxidative stress, inflammation, detoxification, and hormone signaling, and included genes associated with oligodendrocyte proliferation, axon repair, long-term potentiation, and neurotransmission.

Conclusions: The unique RNA expression profile in blood associated with WMH is consistent with roles of systemic oxidative stress and inflammation, as well as other potential processes in the pathogenesis or consequences of WMH.

Conflict of interest statement

Disclosure The authors report no conflicts of interest.

Figures

Figure 1
Figure 1. Principal Components Analysis (PCA)
The 241 genes that were differentially expressed in extensive WMH subjects (WMH+) versus minimal WMH subjects (WMH-) (p<0.005 and fold change >1.2) were used for a PCA. The top three principal components were represented on the X, Y and Z axes. Each symbol represents one subject with red being subjects with extensive WMH+ (n=20) and green being subjects with WMH- (n=18). The distance between samples in the 3-D space shows their differences based on the expression pattern. Each of the two ellipsoids represents a two-standard deviation space from the mean of each group of samples.
Figure 2
Figure 2. Cluster Analysis of WMH-associated genes for all subjects
The 241 genes that were differentially expressed in extensive WMH subjects (WMH+) versus minimal WMH subjects (WMH-) (p<0.005 and fold change >1.2) were used for an unsupervised Pearson cluster analysis. Individual genes (n=241) are shown on the x-axis and individual subjects (n=38) are shown on the y-axis. Genes showing high expression are in red and genes with low expression are in blue. Note that all of the subjects with WMH+ are clustered separately from low WMH subjects (WMH-) and that there is a specific gene expression profile for each with little evidence for subgroups based upon these genes.

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