Henrik Wernérus

Towards a knowledge-based Human Protein Atlas

1. Anonymous. Nat. Biotechnol. 28, 987 (2010). 2. Plosila, W.H. Econ. Dev. Q. 18, 113–126 (2004). 3. Stayn, S. BNA Med. Law Pol. Rep. 5, 718–725 (2006). 4. Lomax, G. & Stayn, S. BNA Med. Law Pol. Rep. 7, 695–698 (2008). 5. Levine, A.D. Public Adm. Rev. 68, 681–694 (2008). 6. Levine, A.D. Nat. Biotechnol. 24, 865–866 (2006). 7. McCormick, J.B., Owen-Smith, J. & Scott, C.T. Cell Stem Cell 4, 107–110 (2009). 8. Fossett, J.W., Ouellette, A.R., Philpott, S., Magnus, D. & Mcgee, G. Hastings Cent. Rep. 37, 24–35 (2007). 9. Mintrom, M. Publius 39, 606–631 (2009). 10. Scott, C.T., McCormick, J.B. & Owen-Smith, J. Nat. Biotechnol. 27, 696–697 (2009). 11. Takahashi, K. & Yamanaka, S. Cell 126, 663–676 (2006). Foundation and the Georgia Research Alliance, and Georgia Tech. They thank J. Walsh at Georgia Tech for helpful comments on an earlier version of this manuscript. They also appreciate the assistance they received with data collection from officials in various state stem cell agencies. A.D.L. would also like to thank A. Jakimo, whose comment at a meeting of the Interstate Alliance on Stem Cell Research inspired collection of these data. stem cell programs, as well as similar state programs supporting other areas of science, is uncertain. The analysis here suggests that state stem cell funding programs are sufficiently large and established that simply ending the programs, at least in the absence of substantial investment in the field by other funding sources, could have deleterious effects. Such action would fail to capitalize on the initial efforts of scientists who have been drawn to the field of stem cell research by state programs and leave many stem cell scientists suddenly searching for funding to continue their research. Large-scale state funding for basic research is a relatively new phenomenon, and many questions remain about the impact of these programs on the development of scientific fields and the careers of scientists. The influence of state funding programs on the distribution of research publications, the acquisition of future external funding, the creation of new companies and the translation of basic research into medical practice, for instance, are important unanswered questions. Similarly, comparing state funding programs with federal funding programs as well as foundations could offer new insight into the relative priorities of different funding bodies and the extent to which their funding portfolios overlap or are distinct. We hope the analysis presented here and the public release of the underlying database will inspire additional analysis of state science funding programs generally and state-funded stem cell science in particular.

A Human Protein Atlas for Normal and Cancer Tissues Based on Antibody Proteomics

Antibody-based proteomics provides a powerful approach for the functional study of the human proteome involving the systematic generation of protein-specific affinity reagents. We used this strategy to construct a comprehensive, antibody-based protein atlas for expression and localization profiles in 48 normal human tissues and 20 different cancers. Here we report a new publicly available database containing, in the first version, ∼400,000 high resolution images corresponding to more than 700 antibodies toward human proteins. Each image has been annotated by a certified pathologist to provide a knowledge base for functional studies and to allow queries about protein profiles in normal and disease tissues. Our results suggest it should be possible to extend this analysis to the majority of all human proteins thus providing a valuable tool for medical and biological research.

A Genecentric Human Protein Atlas for Expression Profiles Based on Antibodies

An attractive path forward in proteomics is to experimentally annotate the human protein complement of the genome in a genecentric manner. Using antibodies, it might be possible to design protein-specific probes for a representative protein from every protein-coding gene and to subsequently use the antibodies for systematical analysis of cellular distribution and subcellular localization of proteins in normal and disease tissues. A new version (4.0) of the Human Protein Atlas has been developed in a genecentric manner with the inclusion of all human genes and splice variants predicted from genome efforts together with a visualization of each protein with characteristics such as predicted membrane regions, signal peptide, and protein domains and new plots showing the uniqueness (sequence similarity) of every fraction of each protein toward all other human proteins. The new version is based on tissue profiles generated from 6120 antibodies with more than five million immunohistochemistry-based images covering 5067 human genes, corresponding to ∼25% of the human genome. Version 4.0 includes a putative list of members in various protein classes, both functional classes, such as kinases, transcription factors, G-protein-coupled receptors, etc., and project-related classes, such as candidate genes for cancer or cardiovascular diseases. The exact antigen sequence for the internally generated antibodies has also been released together with a visualization of the application-specific validation performed for each antibody, including a protein array assay, Western blot analysis, immunohistochemistry, and, for a large fraction, immunofluorescence-based confocal microscopy. New search functionalities have been added to allow complex queries regarding protein expression profiles, protein classes, and chromosome location. The new version of the protein atlas thus is a resource for many areas of biomedical research, including protein science and biomarker discovery.

A global view of protein expression in human cells, tissues, and organs

Defining the protein profiles of tissues and organs is critical to understanding the unique characteristics of the various cell types in the human body. In this study, we report on an anatomically comprehensive analysis of 4842 protein profiles in 48 human tissues and 45 human cell lines. A detailed analysis of over 2 million manually annotated, high‐resolution, immunohistochemistry‐based images showed a high fraction (>65%) of expressed proteins in most cells and tissues, with very few proteins (<2%) detected in any single cell type. Similarly, confocal microscopy in three human cell lines detected expression of more than 70% of the analyzed proteins. Despite this ubiquitous expression, hierarchical clustering analysis, based on global protein expression patterns, shows that the analyzed cells can be still subdivided into groups according to the current concepts of histology and cellular differentiation. This study suggests that tissue specificity is achieved by precise regulation of protein levels in space and time, and that different tissues in the body acquire their unique characteristics by controlling not which proteins are expressed but how much of each is produced.

Biotechnological applications for surface-engineered bacteria.

Display of heterologous proteins on the surface of micro‐organisms, enabled by means of recombinant DNA technology, has become an increasingly popular strategy in microbiology, biotechnology and vaccinology. Both Gram‐negative and Gram‐positive bacteria have been investigated for potential applications. The present review will describe the most commonly used systems for bacterial display, with a focus on the biotechnology applications. Live bacterial vaccine‐delivery vehicles have long been investigated through the surface display of foreign antigens and, recently, ‘second‐generation’ vaccine‐delivery vehicles have been generated by the addition of mucosal targeting signals, as a means to increase immune responses. Engineered bacteria have also the potential to act as novel microbial biocatalysts with heterologous enzymes immobilized as surface exposed on the bacterial cell surface. They provide the potential for new types of whole‐cell diagnostic devices, since single‐chain antibodies and other type of tailor‐made binding proteins can be displayed on bacteria. Bacteria with increased binding capacity for certain metal ions can be created, and potential environmental or biosensor applications for such recombinant bacteria as biosorbents are being explored. Certain bacteria have also been employed to display various polypeptide libraries for use as devices in in vitro selection applications. Part of the present review has been devoted to a more in‐depth description of a promising Gram‐positive display system, i.e. Staphylococcus carnosus, and its applications. The review describes the basic principles of the different bacterial display systems and discusses current uses and possible future trends of these emerging technologies.

Optimization of electroporation-mediated transformation : Staphylococcus carnosus as model organism

Aims:  The study was conducted with an aim to optimize the transformation efficiency of the Gram‐positive bacterium Staphylococcus carnosus to a level that would enable the creation of cell surface displayed combinatorial protein libraries.

Staphylococcal Surface Display of Metal-Binding Polyhistidyl Peptides

ABSTRACT Recombinant Staphylococcus xylosus andStaphylococcus carnosus strains were generated with surface-exposed chimeric proteins containing polyhistidyl peptides designed for binding to divalent metal ions. Surface accessibility of the chimeric surface proteins was demonstrated and the chimeric surface proteins were found to be functional in terms of metal binding, since the recombinant staphylococcal cells were shown to have gained Ni2+- and Cd2+-binding capacity, suggesting that such bacteria could find use in bioremediation of heavy metals. This is, to our knowledge, the first time that recombinant, surface-exposed metal-binding peptides have been expressed on gram-positive bacteria. Potential environmental or biosensor applications for such recombinant staphylococci as biosorbents are discussed.

A novel affinity protein selection system based on staphylococcal cell surface display and flow cytometry

Here we describe the first reported use of a Gram-positive bacterial system for the selection of affinity proteins from large combinatorial libraries displayed on the surface of Staphylococcus carnosus. An affibody library of 3 x 10(9) variants, based on a 58 residue domain from staphylococcal protein A, was pre-enriched for binding to human tumor necrosis factor-alpha (TNF-alpha) using one cycle of phage display and thereafter transferred to the staphylococcal host ( approximately 10(6) variants). The staphylococcal-displayed library was subjected to three rounds of flow-cytometric sorting, and the selected clones were screened and ranked by on-cell analysis for binding to TNF-alpha and further characterized using biosensor analysis and circular dichroism spectroscopy. The successful sorting yielded three different high-affinity binders (ranging from 95 pM to 2.2 nM) and constitutes the first selection of a novel affinity protein using Gram-positive bacterial display. The method combines the simplicity of working with a bacterial host with the advantages of displaying recombinant proteins on robust Gram-positive bacteria as well as using powerful flow cytometry in the selection and characterization process.

Generation of Metal-Binding Staphylococci through Surface Display of Combinatorially Engineered Cellulose-Binding Domains

ABSTRACT Ni2+-binding staphylococci were generated through surface display of combinatorially engineered variants of a fungal cellulose-binding domain (CBD) from Trichoderma reeseicellulase Cel7A. Novel CBD variants were generated by combinatorial protein engineering through the randomization of 11 amino acid positions, and eight potentially Ni2+-binding CBDs were selected by phage display technology. These new variants were subsequently genetically introduced into chimeric surface proteins for surface display on Staphylococcus carnosus cells. The expressed chimeric proteins were shown to be properly targeted to the cell wall of S. carnosus cells, since full-length proteins could be extracted and affinity purified. Surface accessibility for the chimeric proteins was demonstrated, and furthermore, the engineered CBDs, now devoid of cellulose-binding capacity, were shown to be functional with regard to metal binding, since the recombinant staphylococci had gained Ni2+-binding capacity. Potential environmental applications for such tailor-made metal-binding bacteria as bioadsorbents in biofilters or biosensors are discussed.

Evaluation of Staphylococcal Cell Surface Display and Flow Cytometry for Postselectional Characterization of Affinity Proteins in Combinatorial Protein Engineering Applications

ABSTRACT For efficient generation of high-affinity protein-based binding molecules, fast and reliable downstream characterization platforms are needed. In this work, we have explored the use of staphylococcal cell surface display together with flow cytometry for affinity characterization of candidate affibody molecules directly on the cell surface. A model system comprising three closely related affibody molecules with different affinities for immunoglobulin G and an albumin binding domain with affinity for human serum albumin was used to investigate advantages and differences compared to biosensor technology in a side-by-side manner. Equilibrium dissociation constant (KD) determinations as well as dissociation rate analysis were performed using both methods, and the results show that the on-cell determinations give both KD and dissociation rate values in a very fast and reproducible manner and that the relative affinities are very similar to the biosensor results. Interestingly, the results also show that there are differences between the absolute affinities determined with the two different technologies, and possible explanations for this are discussed. This work demonstrates the advantages of cell surface display for directed evolution of affinity proteins in terms of fast postselectional, on-cell characterization of candidate clones without the need for subcloning and subsequent protein expression and purification but also demonstrates that it is important to be aware that absolute affinities determined using different methods often vary substantially and that such comparisons therefore could be difficult.