Analysis of human transcriptomes

Abstract

How many human genes are expressed ubiquitously, in all human tissues, and how many are expressed in tissue-specific patterns? To answer these fundamental questions in molecular biology, we have analysed 3.5-million transcripts from 19 normal and diseased tissue types. We found that as many as 43,500 genes can be expressed in a single cell type. Only a small fraction of transcripts were exclusively expressed in any individual tissue, whereas nearly 1,000 genes were expressed in all cell types examined. We found 40 genes to be expressed at elevated levels in all cancer tissues but not in normal cells. Serial analysis of gene expression (SAGE) studies1, 2 of 84 libraries derived from 19 different sources identified 134,135 transcripts from approximately 84,000 different genes (Table 1; data and analysis available at http://genetics. nature. com/supplementary_info/). Expression levels for these genes ranged …