ABSTRACT
Numerous studies have used DNA microarrays to survey gene expression
in cancer and other disease states. Comparatively little is known
about the genes expressed across the gamut of normal human
tissues. Systematic studies of global gene expression patterns, by
linking variation in the expression of specific genes to phenotypic
variation in the cells or tissues in which they are expressed, provide
clues to the molecular organization of diverse cells and to the
potential roles of the genes. Here, we describe a systematic survey
of gene expression in 115 human tissue samples representing 35
different tissue types, using cDNA microarrays representing ~26,000
different human genes. Unsupervised hierarchical cluster analysis of
the gene expression patterns in these tissues identified clusters of
genes with related biological functions and grouped
the tissue
specimens in a pattern that reflected their anatomic locations,
cellular compositions, or physiologic functions. In unsupervised and
supervised analyses, tissue-specific patterns of gene expression were
readily discernable. By comparative hybridization to normal genomic
DNA, we were also able to estimate transcript abundances for expressed
genes. Our dataset provides a baseline for comparison to diseased
tissues, and will aid in the identification of tissue-specific
functions. In addition, our analysis identifies potential molecular
markers for detection of injury to specific organs and tissues, and
provides a foundation for selection of potential targets for selective
anti-cancer therapy.
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