Nucleic Acid Research 2014
On November 1, 2014, Matteo Perino, Gert Jan Veenstra and Michiel Vermeulen (Radboud University, Nijmegen, The Netherlands) published a paper in Nucleic Acid Research.
Smits AH, Lindeboom RG, Perino M, van Heeringen SJ, Veenstra GJ, Vermeulen M. Global absolute quantification reveals tight regulation of protein expression in single Xenopus eggs. Nucleic Acids Res. 2014 Sep;42(15):9880-91. doi: 10.1093/nar/gku661.
While recent developments in genomic sequencing technology have enabled comprehensive transcriptome analyses of single cells, single cell proteomics has thus far been restricted to targeted studies. Here, we perform global absolute protein quantification of fertilized Xenopus laevis eggs using mass spectrometry-based proteomics, quantifying over 5800 proteins in the largest single cell proteome characterized to date. Absolute protein amounts in single eggs are highly consistent, thus indicating a tight regulation of global protein abundance. Protein copy numbers in single eggs range from tens of thousands to ten trillion copies per cell. Comparison between the single-cell proteome and transcriptome reveal poor expression correlation. Finally, we identify 439 proteins that significantly change in abundance during early embryogenesis. Downregulated proteins include ribosomal proteins and upregulated proteins include basal transcription factors, among others. Many of these proteins do not show regulation at the transcript level. Altogether, our data reveal that the transcriptome is a poor indicator of the proteome and that protein levels are tightly controlled in X. laevis eggs.