Human Proteome Remapped

Independent teams announced in 2014 two draft maps of the human proteome determined using mass spectrometry methods. Swedish researchers have now acquired a more detailed map of the human proteome, this time using antibody-based analysis and RNA sequencing to achieve spatial mapping at the single-cell level (Science 2015, DOI: 10.1126/science.1260419). Mathias Uhlén of the Royal Institute of Technology and coworkers used 24,028 antibodies to map tissue-specific protein expression in 44 major tissues and organs. The team sequenced the transcribed RNA of 20,344 genes in 32 of the tissue types. Approximately 9,000 genes—the so-called housekeeping proteins—are expressed in all tissues, the team reports. In most tissues, only about 10% of the transcripts encode proteins that are elevated in that tissue relative to other tissues. Exceptions are the liver and the pancreas, in which 35% and 70% of transcripts, respectively, encode tissue-elevated proteins. The researchers analyzed subsets of the proteome, including secreted and membrane proteins. Only 677 putative protein-coding genes still have no experimental evidence, they note. These “missing genes” may turn out to not be protein-coding after all, the scientists say. Their data are available online in an interactive database at www.proteinatlas.org.