Primate Transcript and Protein Expression Levels Evolve Under Compensatory Selection Pressures

Changes in gene regulation have likely played an important role in the evolution of primates. Differences in messenger RNA (mRNA) expression levels across primates have often been documented; however, it is not yet known to what extent measurements of divergence in mRNA levels reflect divergence in protein expression levels, which are probably more important in determining phenotypic differences. We used high-resolution, quantitative mass spectrometry to collect protein expression measurements from human, chimpanzee, and rhesus macaque lymphoblastoid cell lines and compared them to transcript expression data from the same samples. We found dozens of genes with significant expression differences between species at the mRNA level yet little or no difference in protein expression. Overall, our data suggest that protein expression levels evolve under stronger evolutionary constraint than mRNA levels.Don't Ape Protein Variation
Changes in DNA and messenger RNA (mRNA) expression levels have been used to estimate evolutionary changes between species. However protein expression levels may better reflect selection on divergent and constrained phenotypes. Khan et al. (p. 1100, published online 17 October; see the Perspective by Vogel) measured the differences among and within species between mRNA expression and protein levels in humans, chimpanzees, and rhesus macaques, identifying protein transcripts that seem to be under lineage-specific constraint between humans and chimpanzees.