A large-scale proteomic analysis of human embryonic stem cells.
BACKGROUND
Much of our current knowledge of the molecular expression profile of human embryonic stem cells (hESCs) is based on transcriptional approaches. These analyses are only partly predictive of protein expression however, and do not shed light on post-translational regulation, leaving a large gap in our knowledge of the biology of pluripotent stem cells.


RESULTS
Here we describe the use of two large-scale western blot assays to identify over 600 proteins expressed in undifferentiated hESCs, and highlight over 40 examples of multiple gel mobility variants, which are suspected protein isoforms and/or post-translational modifications. Twenty-two phosphorylation events in cell signaling molecules, as well as potential new markers of undifferentiated hESCs were also identified. We confirmed the expression of a subset of the identified proteins by immunofluorescence and correlated the expression of transcript and protein for key molecules in active signaling pathways in hESCs. These analyses also indicated that hESCs exhibit several features of polarized epithelia, including expression of tight junction proteins.


CONCLUSIONS
Our approach complements proteomic and transcriptional analysis to provide unique information on human pluripotent stem cells, and is a framework for the continued analyses of self-renewal.
Schulz
Thomas C
TC
Buck Institute for Age Research, 8001 Redwood Blvd, Novato, CA, USA. tschulz@novocell.com
Swistowska
Anna Maria
AM
Liu
Ying
Y
Swistowski
Andrzej
A
Palmarini
Gail
G
Brimble
Sandii N
SN
Sherrer
Eric
E
Robins
Allan J
AJ
Rao
Mahendra S
MS
Zeng
Xianmin
X
D015153:Blotting, Western; D053595:Embryonic Stem Cells / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D062793:Occludin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D020543:Proteome / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D014158:Transcription, Genetic; D062826:Zonula Occludens-1 Protein
D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; D020033:Protein Isoforms; D020543:Proteome; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D011494:Protein Kinases; D010744:Phosphoric Monoester Hydrolases