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Variations in the transcriptome of Alzheimer's disease reveal molecular networks involved in cardiovascular diseases

Monika Ray1, Jianhua Ruan2 and Weixiong Zhang13*

Author Affiliations

1 Washington University School of Engineering, Department of Computer Science and Engineering, 1 Brookings Drive, Saint Louis, Missouri 63130, USA

2 University of Texas at San Antonio, Department of Computer Science, One UTSA Circle, San Antonio, Texas 78249, USA

3 Washington University School of Medicine, Department of Genetics, 660 S. Euclid Ave, Saint Louis, Missouri 63110, USA

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Genome Biology 2008, 9:R148  doi:10.1186/gb-2008-9-10-r148

Published: 8 October 2008

Abstract

Background

Because of its polygenic nature, Alzheimer's disease is believed to be caused not by defects in single genes, but rather by variations in a large number of genes and their complex interactions. A systems biology approach, such as the generation of a network of co-expressed genes and the identification of functional modules and cis-regulatory elements, to extract insights and knowledge from microarray data will lead to a better understanding of complex diseases such as Alzheimer's disease. In this study, we perform a series of analyses using co-expression networks, cis-regulatory elements, and functions of co-expressed gene modules to analyze single-cell gene expression data from normal and Alzheimer's disease-affected subjects.

Results

We identified six co-expressed gene modules, each of which represented a biological process perturbed in Alzheimer's disease. Alzheimer's disease-related genes, such as APOE, A2M, PON2 and MAP4, and cardiovascular disease-associated genes, including COMT, CBS and WNK1, all congregated in a single module. Some of the disease-related genes were hub genes while many of them were directly connected to one or more hub genes. Further investigation of this disease-associated module revealed cis-regulatory elements that match to the binding sites of transcription factors involved in Alzheimer's disease and cardiovascular disease.

Conclusion

Our results show the extensive links between Alzheimer's disease and cardiovascular disease at the co-expression and co-regulation levels, providing further evidence for the hypothesis that cardiovascular disease and Alzheimer's disease are linked. Our results support the notion that diseases in which the same set of biochemical pathways are affected may tend to co-occur with each other.