While machine learning models offer potential for predicting transcriptomic effects of perturbation, they currently struggle to generalize across cellular contexts. Here, we introduce State, a machine learning model that predicts perturbation effects while accounting for cellular heterogeneity within and across experiments. State is trained using single-cell gene expression data to predict perturbation effects across sets of cells. State improved discrimination of effects on large datasets by more than 30% and identified differentially expressed genes across genetic, signaling, and chemical perturbations with significantly improved accuracy compared with baselines. Its cell embeddings trained on observational data from 167 million cells enable the identification of strong perturbations in cellular contexts where no perturbations were observed during training. We further introduce Cell-Eval, a comprehensive evaluation framework that can be used to evaluate future models. Overall, the performance and flexibility of State set the stage for scaling the development of AI models of cell state.

Abstract CRISPR screens have become the primary discovery engine in modern biology and are widely used to uncover novel targets in immuno-oncology. However, these genetic screens are usually coupled to rather simplistic read-outs such as cell fitness. In contrast, CROP-Seq (or “CRISPR Droplet” Sequencing) screens combine CRISPR perturbation with single-cell transcriptomics, enabling high-content phenotyping at single-cell resolution. Briefly, cells are perturbed with a pooled sgRNA library and transcriptomic profiles of each cell are recorded using conventional single-cell RNA sequencing platforms. Currently, the scale of these screens is limited to the perturbation of a couple of hundred genes, possibly up to 1.000 genes, because of increased costs for single-cell library preparation and next generation sequencing (NGS). At Myllia, we have built a platform allowing high-content CROP-Seq screens in both CRISPR-ready cancer cell lines as well as primary immune cells, e.g., human T cells. Using CRISPR KO, CRISPR interference or CRISPR activation workflows, we can help accelerate the identification of target genes and regulatory networks involved in immuno-oncology. Primary T cells are of great interest in the immunotherapy community as they are key players in autoimmune and inflammatory disease. Engineered T-lymphocytes such as CAR-T cells are currently developed as novel cellular medicines, yet many T cell-intrinsic features involved in CAR-T potency remain elusive. To enable the discovery of novel targets, we have performed multiple customized CROP-Seq CRISPR KO screens in primary human T cells investigating T cell stemness and effector phenotypes as well as CD4+ T helper cell differentiation towards Th1, Th2, or Th17 subsets. Here, we present screens for regulators of functional T cell plasticity and Th2 commitment in which we aimed to identify genes determining critical T cell fate decisions, potentially linking gene (dys)function to either autoimmune/inflammatory disease or functional persistence of cytotoxic T cells for cancer immunotherapy. Overall, the advanced CROP-Seq platform combining large-scale perturbations and targeted sequencing (TA) read-outs will catalyse a paradigm shift for CROP-Seq enabling high-throughput functional genomic screens that support the validation of drug targets in autoimmunity, inflammation and immuno-oncology. Citation Format: Nicole Untermoser, Johanna Irnstorfer, Anatoly Vasilyev, Nikola Vinko, Sumit Pawar, Anke Loregger, Adam Krejci, Henrik Schmidt, Tilmann Bürckstümmer. Single-cell CRISPR screens at scale to understand T cell biology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB289.

CRISPR screens have become the primary discovery engine in modern biology. However, many screening workflows are still performed in cancer cell lines and coupled to simplistic read-outs such as cellular fitness. At Myllia Biotechnology, we combine CRISPR screening with single-cell RNA sequencing, leveraging two transformative technologies to enable genetic screening for complex phenotypes. We utilize the CRISPR screening workflow to map the impact of thousands of genetic perturbations on the global transcriptome at single-cell resolution. Our powerful approach has broad applications in identifying novel drug targets or elucidating unknown mechanisms of actions of drugs. Primary human T cells are currently of great interest in the scientific community. They are not only key players in autoimmunity and other inflammatory diseases, but also represent attractive targets for immunotherapy of cancer. To enable the discovery of novel targets, we built a workflow that utilizes CD4+ T cells from peripheral blood and allows functional genomic screens in these cells. Upon activation, naïve CD4+ T cells proliferate and differentiate into specific T helper cell subsets, such as Th1, Th2, or Th17 cells. Here, we present data of an experiment in which we screened for regulators of T helper cell differentiation and skewed cells towards the Th2 subset. We aimed to identify genes whose knockout boosts or attenuates the ability of primary naïve CD4+ T cells to become Th2 cells. Th2 cells support the humoral immune response, and their dysfunction has been linked to inflammatory diseases, including asthma. In our screen, the different T cell subsets could be captured using curated transcriptomic signatures. Importantly, several gene KOs introduced in a pooled fashion using CRISPR/Cas9 accumulated in distinct subpopulations, suggesting that these genes regulate the differentiation of naïve T cells into the various T helper cell subsets. Overall, our pooled screening approach in primary human T cells allows for novel insights in the plasticity of T cells and identifies genes that could serve as drug targets in autoimmunity, inflammation and immuno-oncology. Citation Format: Anke Loregger, Johanna Irnstorfer, Nicole Untermoser, Nikola Vinko, Adam Krejci, Henrik Schmidt, Tilmann Bürckstümmer. Single-cell CRISPR screens in primary human T cells identify regulators of Th2 cell skewing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB341.

CROP-seq/Perturb-seq screens combine CRISPR perturbation with single-cell RNA sequencing. In brief, cells are perturbed with a pooled sgRNA library and transcriptomic profiles of each cell are recorded using conventional single-cell RNA sequencing platforms. Currently, the scale of these screens is limited to the perturbation of a couple of hundred genes, possibly up to 1.000 genes, because costs for single-cell library preparation and next generation sequencing are high. Here, we aimed to conduct a genome-scale CRISPR screen within a reasonable budget. We chose Jurkat T cells for this experiment and focused on T cell activation because signaling pathways in these cells are well understood and we could utilize the published knowledge to benchmark the performance of our platform. To accomplish this, we utilized a CRISPR interference setup in which multiple sgRNAs can be delivered to the same cell, thus “squeezing” more perturbations into one cell. We targeted 18.595 human genes with four sgRNAs per gene and delivered this genome-scale library to Jurkat cells harboring dCas9-KRAB. Cells were stimulated with anti-TCR and anti-CD28 antibodies for 24 hours to activate T cell signaling. Following that, we processed 1.000.000 cells in one go, using the Chromium X platform that has recently been launched by 10X Genomics. Following single-cell library preparation, we amplified a selected set of 374 transcripts and submitted the corresponding library for NGS on one NovaSeq S4 flowcell. First, we confirmed that the perturbation of 374 marker genes by CRISPR interference led to the downregulation of the cognate targets, suggesting that the CRISPR perturbation workflow is functional. Then, we assessed whether T cell activation could be recapitulated from the chosen markers and found that activated Jurkat T cells can be distinguished from their unactivated counterparts using the signature in question. Finally, we assessed the phenotypes of gene knockouts introduced at genome-scale. Of the 18.595 genes perturbed, a set of 70 genes affected T cell activation, partitioning to 55 activators (whose knockout led to diminished signaling) and 15 inhibitors (whose knockout led to enhanced signaling). Of note, our screen recovered key signaling nodes that are proximal to the TCR and have been well described in the literature, including LAT, LCK, ZAP70, CD3E, ITK, RASGRP1 and VAV1. Overall, the screen presented here will catalyse a paradigm shift for CROP-seq/Perturb-seq type CRISPR screens towards genome scale. Citation Format: Anke Loregger, Nicole Untermoser, Anatoly Vasilyev, Adam Krejci, Henrik Schmidt, Tilmann Bürckstümmer. A genome-scale CROP-seq screen reveals mediators of T cell signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB249.

Background: Adoptive transfer of tumor-infiltrating lymphocytes (TIL) fails to consistently elicit tumor rejection. Manipulation of intrinsic fac-tors that inhibit T cell effector function and neoantigen recognition may therefore improve TIL therapy outcomes. We previously identified the cytokine-induced SH2 protein (CISH) as a key regulator of T cell functional avidity in mice. Here, we investigate the mechanistic role of CISH in regulating human T cell effector function in solid tumors and demonstrate that CRISPR/Cas9 disruption of CISH enhances TIL neoan-tigen recognition and response to checkpoint blockade.Methods: Single-cell gene expression profiling was used to identify a negative correlation between high CISH expression and TIL activation in patient-derived TIL. A GMP-compliant CRISPR/Cas9 gene editing process was developed to assess the impact of CISH disruption on the molecular and functional phenotype of human peripheral blood T cells and TIL. Tumor-specific T cells with disrupted Cish function were adoptively transferred into tumor-bearing mice and evaluated for efficacy with or without checkpoint blockade.Findings: CISH expression was associated with T cell dysfunction. CISH deletion using CRISPR/Cas9 resulted in hyper-activation and improved functional avidity against tumor-derived neoantigens without perturb-ing T cell maturation. Cish knockout resulted in increased susceptibility to checkpoint blockade in vivo.Conclusions: CISH negatively regulates human T cell effector function, and its genetic disruption offers a novel avenue to improve the thera-peutic efficacy of adoptive TIL therapy.Funding: This study was funded by Intima Bioscience, U.S. and in part through the Intramural program CCR at the National Cancer Institute.

ABSTRACT Argonautes are nucleases that can be programmed by short oligonucleotides to cleave complementary sequences. Here, we performed an unbiased bioinformatic search to mine bacterial genomes for prokaryotic Argonautes (pAgos) harboring a PIWI domain. Our search identified 3,033 pAgos in total, of which 1,464 portend to the subgroup of long pAgos with more than 600 amino acids. We purified a subset of 49 pAgos which were found in proximity to helicases and tested their nuclease activity in vitro . Ten of these were active towards single-stranded DNA substrates and this activity could be programmed by exogenous guide DNAs or RNAs. Cleavage of double-stranded plasmid DNA was much less readily observed and was fostered by elevated temperatures or exogenous addition of a DNA single-strand binding protein (ET-SSB). The efficiency of pAgo-mediated plasmid cleavage was dependent on the DNA target sequence as well as the surrounding sequence, suggesting that unwinding of the DNA double helix was a limiting factor. Intriguingly, we identified a cluster of pAgos from the Clostridial clade which was active at 37°C and activity was enhanced by exogenous ET-SSB. This suggests that Clostridial pAgos may be particularly suited to catalyze DNA double-strand cleavage and implies that such pAgos may be repurposed as gene editing tools in future.

ABSTRACTAdeno-associated viruses (AAV) have attracted significant attention in the field of gene and cell therapy due to highly effective delivery of therapeutic genes into human cells. The ability to generate recombinant AAV vectors compromised of unique or substituted protein sequences has led to the development of capsid variants with improved therapeutic properties. Seeking a novel AAV capable of enhanced transduction of human T cells for applications in immunotherapy, we have developed a unique capsid variant termed AAVX-Vivo(AAV-XV) that is a chimera of AAV12 VP1/2 sequences and the VP3 sequence of AAV6. This AAV chimera showed enhanced infection of human primary T cells and hematopoietic stem cells, and superiority over wildtype AAV6 for the genomic integration of DNA sequences either by AAV alone or in combination with CRISPR gene editing. AAV-XV demonstrated transduction efficiency equivalent to AAV6 at multiplicities of infection 2 logs lower, enabling T cell engineering at low AAV doses. Analyzing the protein coding sequence of AAV-XV revealed disruptions within the assembly-activating protein (AAP) which likely accounted for observed lower virus yield. A series of genome alterations reverting the AAP sequence back to wildtype had a negative impact on the enhanced transduction seen with AAV-VX, indicating overlapping functions within this sequence for both viral assembly and effective T cell transduction. Our findings show that AAV-XV is highly efficient at T cell engineering at low AAV dose and demonstrates the importance of AAP coding region in both viral particle assembly and cell infection.IMPORTANCEA major hurdle to the therapeutic potential of AAV in gene therapy lies in achieving clinically meaningful AAV doses, and secondarily, ability to manufacture commercially viable titers of AAV to support this. By virtue of neutralizing antibodies against AAV that impede patient repeat-dosing, the dose of AAV forin vivogene delivery has been high, which has resulted in unfortunate recent safety concerns and deaths in patients given higher-dose AAV gene therapy. We have generated a new AAV variant possessing a unique combination of capsid proteins for ex-vivo application termed AAV-XV, which delivers high levels of cell transduction and gene delivery at a lower MOI. Furthermore, we demonstrate a novel finding, and an important consideration for recombinant AAV design, that a region of the AAV genome encoding the capsid protein and AAP gene is critical for both virus yield and the enhancement of infection/transduction.

Background Neoantigen-specific T cells isolated from tumors have shown promise clinically but fail to consistently elicit durable tumor regression. Expression of the intracellular checkpoint CISH is elevated in human tumor infiltrating lymphocytes (TIL) and has been shown to inhibit neoantigen reactivity in murine TIL. Methods To explore CISH function in human T cells we developed a CRISPR/Cas9-based strategy to knockout (KO) CISH in human T cells with high-efficiency (>90%) and without detectable off-target editing. Results CISH KO in peripheral blood T cells enhanced proliferation, cytokine polyfunctionality, and cytotoxicity in vitro. To determine if CISH KO similarly enhances TIL function, we developed a clinical-scale, GMP-compliant manufacturing process for CISH disruption in primary human TIL. In process validation runs we achieved CISH KO efficiencies >90% without detectable off-target editing while maintaining high viability and expansion. Compared to WT controls, CISH KO in patient-derived TIL demonstrated increased proliferation, T cell receptor (TCR) avidity, neoantigen recognition, and unmasked reactivity to common p53 mutations. Hyperactivation in CISH KO TIL did not increase differentiation, suggesting that CISH KO may uncouple activation and differentiation pathways. Single cell profiling identifies a pattern of CISH expression inverse to key regulators of activation, and CISH KO in human TIL increases PD1 expression. Adoptive transfer of Cish KO T cells synergistically combines with PD1 inhibition resulting in durable tumor regression in mice, highlighting orthogonal dual cell surface and intracellular checkpoint inhibition as a novel combinatorial approach for T cell immunotherapy. Conclusions These pre-clinical data offer new insight into neoantigen recognition and serve as the basis for a recently initiated human clinical trial at the University of Minnesota (NCT04426669) evaluating inhibition of the novel intracellular immune checkpoint CISH in a CRISPR-engineered, neoantigen-specific T cell therapy for solid tumors. Updates from the clinical trial will be highlighted. Trial Registration NCT04426669

Gene knock outs (KOs) are efficiently engineered through CRISPR-Cas9-induced frameshift mutations. While the efficiency of DNA editing is readily verified by DNA sequencing, a systematic understanding of the efficiency of protein elimination has been lacking. Here we devised an experimental strategy combining RNA sequencing and triple-stage mass spectrometry to characterize 193 genetically verified deletions targeting 136 distinct genes generated by CRISPR-induced frameshifts in HAP1 cells. We observed residual protein expression for about one third of the quantified targets, at variable levels from low to original, and identified two causal mechanisms, translation reinitiation leading to N-terminally truncated target proteins or skipping of the edited exon leading to protein isoforms with internal sequence deletions. Detailed analysis of three truncated targets, BRD4, DNMT1 and NGLY1, revealed partial preservation of protein function. Our results imply that systematic characterization of residual protein expression or function in CRISPR-Cas9-generated KO lines is necessary for phenotype interpretation.

The availability of CRISPR/Cas9 technology has enabled the rapid establishment of gene knockouts in many cell types and even whole organisms. However, conditional inactivation of essential genes remains a challenge. We devised an approach named DECAI ( DEgradation based on Cre-regulatedArtificial Intron). It utilizes a small cassette of just 201 nucleotides that is inserted into the coding exon of a target gene using CRISPR/Cas9 technology and homology-directed repair. As its sequence is derived from an artificial intron, the cassette is removed by the splicing machinery and thus leaves no trace in the "off-state". Upon activation with Cre recombinase ("on-state"), the intron is crippled and the target gene is disrupted by a series of stop codons. We exemplify the utility of this approach on several nonessential and essential human genes. Clones bearing the conditional knockout cassette are recovered at frequencies above 5% and cassette function can be traced at the genomic DNA and the mRNA level. Importantly, cassette activation leads to loss of gene expression as judged by flow cytometry, Western blot or immunofluorescence. Altogether, this highlights the broad utility of the approach for conditional gene inactivation and suggests that this tool could be used to study the loss-of-function phenotypes of essential genes.

BACKGROUND:Chromosomal translocations are a hallmark of cancer cells and give rise to fusion oncogenes. To gain insight into the mechanisms governing tumorigenesis, adequate model cell lines are required.RESULTS:We employ the versatile CRISPR/Cas system to engineer cell lines in which chromosomal translocations are either generated de novo (CD74-ROS1) or existing translocations are reverted back to the original configuration (BCR-ABL1). To this end, we co-apply two guide RNAs to artificially generate two breakpoints and screen for spontaneous fusion events by PCR.CONCLUSIONS:The approach we use is efficient and delivers clones bearing translocationsin a predictable fashion. Detailed analysis suggests that the clones display no additional undesired alterations, implying that the approach is robust and precise.

Abstract Reverse genetic screens have driven gene annotation and target discovery in model organisms. However, many disease‐relevant genotypes and phenotypes cannot be studied in lower organisms. It is therefore essential to overcome technical hurdles associated with large‐scale reverse genetics in human cells. Here, we establish a reverse genetic approach based on highly robust and sensitive multiplexed RNA sequencing of mutant human cells. We conduct 10 parallel screens using a collection of engineered haploid isogenic cell lines with knockouts covering tyrosine kinases and identify known and unexpected effects on signaling pathways. Our study provides proof of concept for a scalable approach to link genotype to phenotype in human cells, which has broad applications. In particular, it clears the way for systematic phenotyping of still poorly characterized human genes and for systematic study of uncharacterized genomic features associated with human disease.

Genome engineering has been greatly enhanced by the availability of Cas9 endonuclease that can be targeted to almost any genomic locus using so called guide RNAs (gRNAs). However, the introduction of foreign DNA sequences to tag an endogenous gene is still cumbersome as it requires the synthesis or cloning of homology templates. Here we present a strategy that enables the tagging of endogenous loci using one generic donor plasmid. It contains the tag of interest flanked by two gRNA recognition sites that allow excision of the tag from the plasmid. Co-transfection of cells with Cas9, a gRNA specifying the genomic locus of interest, the donor plasmid and a cassette-specific gRNA triggers the insertion of the tag by a homology-independent mechanism. The strategy is efficient and delivers clones that display a predictable integration pattern. As showcases we generated NanoLuc luciferase- and TurboGFP-tagged reporter cell lines.

A collection of single-gene-mutant human cells is described. This growing resource is based on gene-trap mutagenesis of a near-haploid human cell line and covers almost 3,500 human genes. Knockout collections are invaluable tools for studying model organisms such as yeast. However, there are no large-scale knockout collections of human cells. Using gene-trap mutagenesis in near-haploid human cells, we established a platform to generate and isolate individual 'gene-trapped cells' and used it to prepare a collection of human cell lines carrying single gene-trap insertions. In most cases, the insertion can be reversed. This growing library covers 3,396 genes, one-third of the expressed genome, is DNA-barcoded and allows systematic screens for a wide variety of cellular phenotypes. We examined cellular responses to TNF-α, TGF-β, IFN-γ and TNF-related apoptosis-inducing ligand (TRAIL), to illustrate the value of this unique collection of isogenic human cell lines.

BACKGROUND:The interactions between proteins and nucleic acids have a fundamental function in many biological processes, including gene transcription, RNA homeostasis, protein translation and pathogen sensing for innate immunity. While our knowledge of the ensemble of proteins that bind individual mRNAs in mammalian cells has been greatly augmented by recent surveys, no systematic study on the non-sequence-specific engagement of native human proteins with various types of nucleic acids has been reported.RESULTS:We designed an experimental approach to achieve broad coverage of the non-sequence-specific RNA and DNA binding space, including methylated cytosine, and tested for interaction potential with the human proteome. We used 25 rationally designed nucleic acid probes in an affinity purification mass spectrometry and bioinformatics workflow to identify proteins from whole cell extracts of three different human cell lines. The proteins were profiled for their binding preferences to the different general types of nucleic acids. The study identified 746 high-confidence direct binders, 139 of which were novel and 237 devoid of previous experimental evidence. We could assign specific affinities for sub-types of nucleic acid probes to 219 distinct proteins and individual domains. The evolutionarily conserved protein YB-1, previously associated with cancer and drug resistance, was shown to bind methylated cytosine preferentially, potentially conferring upon YB-1 an epigenetics-related function.CONCLUSIONS:The dataset described here represents a rich resource of experimentally determined nucleic acid-binding proteins, and our methodology has great potential for further exploration of the interface between the protein and nucleic acid realms.

A systems approach provides a global perspective of the different strategies that viruses use to modulate the cellular innate immune response; this may be useful in the design of future viral intervention strategies. Andreas Pichlmair et al. take a systems approach to obtain a global perspective of the different strategies that viruses use to modulate the cellular innate immune response. The results demonstrate that viruses have evolved to exploit a variety of cellular mechanisms, and suggest that the host cell relies on homeostatic regulation across these diverse cellular processes to defend itself against pathogen interference. A central goal of this work is to identify common targets and general network properties in the host antiviral defence system that may be useful in the design of future viral-intervention strategies. Viruses must enter host cells to replicate, assemble and propagate. Because of the restricted size of their genomes, viruses have had to evolve efficient ways of exploiting host cell processes to promote their own life cycles and also to escape host immune defence mechanisms1,2. Many viral open reading frames (viORFs) with immune-modulating functions essential for productive viral growth have been identified across a range of viral classes3,4. However, there has been no comprehensive study to identify the host factors with which these viORFs interact for a global perspective of viral perturbation strategies5,6,7,8,9,10,11. Here we show that different viral perturbation patterns of the host molecular defence network can be deduced from a mass-spectrometry-based host-factor survey in a defined human cellular system by using 70 innate immune-modulating viORFs from 30 viral species. The 579 host proteins targeted by the viORFs mapped to an unexpectedly large number of signalling pathways and cellular processes, suggesting yet unknown mechanisms of antiviral immunity. We further experimentally verified the targets heterogeneous nuclear ribonucleoprotein U, phosphatidylinositol-3-OH kinase, the WNK (with-no-lysine) kinase family and USP19 (ubiquitin-specific peptidase 19) as vulnerable nodes in the host cellular defence system. Evaluation of the impact of viral immune modulators on the host molecular network revealed perturbation strategies used by individual viruses and by viral classes. Our data are also valuable for the design of broad and specific antiviral therapies.

Aicardi-Goutières syndrome (AGS) is a rare inherited autoimmune disease caused by mutations in genes encoding the RNase H2 subunits A, B, and C; the DNase three prime repair exonuclease 1 (TREX1); and sterile alpha motif (SAM) domain and HD domain-containing protein 1 (SAMHD1). Using unbiased affinity purification coupled to protein mass spectrometry, we identify SAMHD1 as a nucleic-acid-binding protein displaying a preference for RNA over DNA. In contrast to TREX1 and the RNase H2 complex, SAMHD1 has no obvious nuclease activity. In addition, interrogating truncation mutants of SAMHD1 observed in AGS patients, we map the nucleic-acid-binding domain to residues 164-442, thus overlapping with the HD domain. Furthermore, we show that although wild-type SAMHD1 displays almost exclusive nuclear localization, 11 of 12 SAMHD1 mutants show at least partial mislocalization to the cytosol. Overall, these data suggest that SAMHD1 has a role in the nucleus that, if disrupted by mutation, leads to cytosolic accumulation of SAMHD1 and autoimmune disease.

BACKGROUND:On the basis of large proteomics datasets measured from seven human cell lines we consider their intersection as an approximation of the human central proteome, which is the set of proteins ubiquitously expressed in all human cells. Composition and properties of the central proteome are investigated through bioinformatics analyses.RESULTS:We experimentally identify a central proteome comprising 1,124 proteins that are ubiquitously and abundantly expressed in human cells using state of the art mass spectrometry and protein identification bioinformatics. The main represented functions are proteostasis, primary metabolism and proliferation. We further characterize the central proteome considering gene structures, conservation, interaction networks, pathways, drug targets, and coordination of biological processes. Among other new findings, we show that the central proteome is encoded by exon-rich genes, indicating an increased regulatory flexibility through alternative splicing to adapt to multiple environments, and that the protein interaction network linking the central proteome is very efficient for synchronizing translation with other biological processes. Surprisingly, at least 10% of the central proteome has no or very limited functional annotation.CONCLUSIONS:Our data and analysis provide a new and deeper description of the human central proteome compared to previous results thereby extending and complementing our knowledge of commonly expressed human proteins. All the data are made publicly available to help other researchers who, for instance, need to compare or link focused datasets to a common background.