RESUMO
DNA and histone modifications combine into characteristic patterns that demarcate functional regions of the genome1,2. While many 'readers' of individual modifications have been described3-5, how chromatin states comprising composite modification signatures, histone variants and internucleosomal linker DNA are interpreted is a major open question. Here we use a multidimensional proteomics strategy to systematically examine the interaction of around 2,000 nuclear proteins with over 80 modified dinucleosomes representing promoter, enhancer and heterochromatin states. By deconvoluting complex nucleosome-binding profiles into networks of co-regulated proteins and distinct nucleosomal features driving protein recruitment or exclusion, we show comprehensively how chromatin states are decoded by chromatin readers. We find highly distinctive binding responses to different features, many factors that recognize multiple features, and that nucleosomal modifications and linker DNA operate largely independently in regulating protein binding to chromatin. Our online resource, the Modification Atlas of Regulation by Chromatin States (MARCS), provides in-depth analysis tools to engage with our results and advance the discovery of fundamental principles of genome regulation by chromatin states.
Assuntos
Montagem e Desmontagem da Cromatina , Cromatina , Proteínas Nucleares , Nucleossomos , Proteômica , Humanos , Sítios de Ligação , Cromatina/química , Cromatina/genética , Cromatina/metabolismo , DNA/genética , DNA/metabolismo , Elementos Facilitadores Genéticos , Heterocromatina/genética , Heterocromatina/metabolismo , Histonas/metabolismo , Proteínas Nucleares/análise , Proteínas Nucleares/metabolismo , Nucleossomos/química , Nucleossomos/genética , Nucleossomos/metabolismo , Regiões Promotoras Genéticas , Ligação Proteica , Proteômica/métodosRESUMO
The COVID-19 pandemic is an ongoing global health threat, yet our understanding of the dynamics of early cellular responses to this disease remains limited1. Here in our SARS-CoV-2 human challenge study, we used single-cell multi-omics profiling of nasopharyngeal swabs and blood to temporally resolve abortive, transient and sustained infections in seronegative individuals challenged with pre-Alpha SARS-CoV-2. Our analyses revealed rapid changes in cell-type proportions and dozens of highly dynamic cellular response states in epithelial and immune cells associated with specific time points and infection status. We observed that the interferon response in blood preceded the nasopharyngeal response. Moreover, nasopharyngeal immune infiltration occurred early in samples from individuals with only transient infection and later in samples from individuals with sustained infection. High expression of HLA-DQA2 before inoculation was associated with preventing sustained infection. Ciliated cells showed multiple immune responses and were most permissive for viral replication, whereas nasopharyngeal T cells and macrophages were infected non-productively. We resolved 54 T cell states, including acutely activated T cells that clonally expanded while carrying convergent SARS-CoV-2 motifs. Our new computational pipeline Cell2TCR identifies activated antigen-responding T cells based on a gene expression signature and clusters these into clonotype groups and motifs. Overall, our detailed time series data can serve as a Rosetta stone for epithelial and immune cell responses and reveals early dynamic responses associated with protection against infection.
Assuntos
COVID-19 , Nasofaringe , SARS-CoV-2 , Análise de Célula Única , Linfócitos T , Humanos , COVID-19/imunologia , COVID-19/virologia , SARS-CoV-2/imunologia , SARS-CoV-2/isolamento & purificação , SARS-CoV-2/fisiologia , Nasofaringe/virologia , Nasofaringe/imunologia , Linfócitos T/imunologia , Linfócitos T/virologia , Interferons/imunologia , Interferons/metabolismo , Masculino , Feminino , Macrófagos/imunologia , Macrófagos/virologia , Replicação Viral , Células Epiteliais/virologia , Células Epiteliais/imunologia , Fatores de Tempo , AdultoRESUMO
It is not fully understood why COVID-19 is typically milder in children1-3. Here, to examine the differences between children and adults in their response to SARS-CoV-2 infection, we analysed paediatric and adult patients with COVID-19 as well as healthy control individuals (total n = 93) using single-cell multi-omic profiling of matched nasal, tracheal, bronchial and blood samples. In the airways of healthy paediatric individuals, we observed cells that were already in an interferon-activated state, which after SARS-CoV-2 infection was further induced especially in airway immune cells. We postulate that higher paediatric innate interferon responses restrict viral replication and disease progression. The systemic response in children was characterized by increases in naive lymphocytes and a depletion of natural killer cells, whereas, in adults, cytotoxic T cells and interferon-stimulated subpopulations were significantly increased. We provide evidence that dendritic cells initiate interferon signalling in early infection, and identify epithelial cell states associated with COVID-19 and age. Our matching nasal and blood data show a strong interferon response in the airways with the induction of systemic interferon-stimulated populations, which were substantially reduced in paediatric patients. Together, we provide several mechanisms that explain the milder clinical syndrome observed in children.
Assuntos
COVID-19/sangue , COVID-19/imunologia , Células Dendríticas/imunologia , Interferons/imunologia , Células Matadoras Naturais/imunologia , SARS-CoV-2/imunologia , Linfócitos T Citotóxicos/imunologia , Adulto , Brônquios/imunologia , Brônquios/virologia , COVID-19/patologia , Chicago , Estudos de Coortes , Progressão da Doença , Células Epiteliais/citologia , Células Epiteliais/imunologia , Células Epiteliais/virologia , Feminino , Humanos , Imunidade Inata , Londres , Masculino , Mucosa Nasal/imunologia , Mucosa Nasal/virologia , SARS-CoV-2/crescimento & desenvolvimento , Análise de Célula Única , Traqueia/virologia , Adulto JovemRESUMO
Nonsense-mediated decay (NMD) is a surveillance system that degrades mRNAs containing a premature termination codon (PTC) and plays important roles in protein homeostasis and disease. The efficiency of NMD is variable, impacting the clinical outcome of genetic mutations. However, limited resolution of bulk analyses has hampered the study of NMD efficiency. Here, we develop an assay to visualize NMD of individual mRNA molecules in real time. We find that NMD occurs with equal probability during each round of translation of an mRNA molecule. However, this probability is variable and depends on the exon sequence downstream of the PTC, the PTC-to-intron distance, and the number of introns both upstream and downstream of the PTC. Additionally, a subpopulation of mRNAs can escape NMD, further contributing to variation in NMD efficiency. Our study uncovers real-time dynamics of NMD, reveals key mechanisms that influence NMD efficiency, and provides a powerful method to study NMD.
Assuntos
Códon sem Sentido/genética , Degradação do RNAm Mediada por Códon sem Sentido/genética , RNA Mensageiro/genética , Códon sem Sentido/química , Éxons/genética , Humanos , Íntrons/genética , Mutação/genética , Estabilidade de RNA/genética , RNA Mensageiro/química , Imagem Individual de MoléculaRESUMO
Comprehensively characterizing the cellular composition and organization of tissues has been a long-term scientific challenge that has limited our ability to study fundamental and clinical aspects of human physiology. The Human Cell Atlas (HCA) is a global collaborative effort to create a reference map of all human cells as a basis for both understanding human health and diagnosing, monitoring, and treating disease. Many aspects of the HCA are analogous to the Human Genome Project (HGP), whose completion presents a major milestone in modern biology. To commemorate the HGP's 20-year anniversary of completion, we discuss the launch of the HCA in light of the HGP, and highlight recent progress by the HCA consortium.
Assuntos
Linhagem da Célula/genética , Fenômenos Fisiológicos Celulares/genética , Células/classificação , Genoma Humano/genética , Projeto Genoma Humano , HumanosRESUMO
The nonsense-mediated mRNA decay (NMD) pathway degrades some but not all mRNAs bearing premature termination codons (PTCs). Decades of work have elucidated the molecular mechanisms of NMD. More recently, statistical analyses of large genomic datasets have allowed the importance of known and novel 'rules of NMD' to be tested and combined into methods that accurately predict whether PTC-containing mRNAs are degraded or not. We discuss these genomic approaches and how they can be applied to identify diseases and individuals that may benefit from inhibition or activation of NMD. We also discuss the importance of NMD for gene editing and tumor evolution, and how inhibiting NMD may be an effective strategy to increase the efficacy of cancer immunotherapy.
Assuntos
Processamento Alternativo/genética , Doenças Genéticas Inatas/genética , Neoplasias/genética , Degradação do RNAm Mediada por Códon sem Sentido/genética , Códon sem Sentido/genética , Humanos , RNA Mensageiro/genéticaRESUMO
Rationale: Obesity affects 40% of U.S. adults, is associated with a proinflammatory state, and presents a significant risk factor for the development of severe coronavirus disease (COVID-19). To date, there is limited information on how obesity might affect immune cell responses in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Objectives: To determine the impact of obesity on respiratory tract immunity in COVID-19 across the human lifespan. Methods: We analyzed single-cell transcriptomes from BAL in three ventilated adult cohorts with (n = 24) or without (n = 9) COVID-19 from nasal immune cells in children with (n = 14) or without (n = 19) COVID-19, and from peripheral blood mononuclear cells in an independent adult COVID-19 cohort (n = 42), comparing obese and nonobese subjects. Measurements and Main Results: Surprisingly, we found that obese adult subjects had attenuated lung immune or inflammatory responses in SARS-CoV-2 infection, with decreased expression of IFN-α, IFN-γ, and TNF-α (tumor necrosis factor α) response gene signatures in almost all lung epithelial and immune cell subsets, and lower expression of IFNG and TNF in specific lung immune cells. Peripheral blood immune cells in an independent adult cohort showed a similar but less marked reduction in type-I IFN and IFNγ response genes, as well as decreased serum IFNα, in obese patients with SARS-CoV-2. Nasal immune cells from obese children with COVID-19 also showed reduced enrichment of IFN-α and IFN-γ response genes. Conclusions: These findings show blunted tissue immune responses in obese patients with COVID-19, with implications for treatment stratification, supporting the specific application of inhaled recombinant type-I IFNs in this vulnerable subset.
Assuntos
COVID-19 , Interferon Tipo I , Obesidade Infantil , Adulto , Humanos , Criança , SARS-CoV-2 , Leucócitos Mononucleares , Pulmão/patologiaRESUMO
Recent work from others and us revealed interactions between the Sin3/HDAC complex, the H3K4me3 demethylase KDM5A, GATAD1, and EMSY. Here, we characterize the EMSY/KDM5A/SIN3B complex in detail by quantitative interaction proteomics and ChIP-sequencing. We identify a novel substoichiometric interactor of the complex, transcription factor ZNF131, which recruits EMSY to a large number of active, H3K4me3 marked promoters. Interestingly, using an EMSY knock-out line and subsequent rescue experiments, we show that EMSY is in most cases positively correlated with transcriptional activity of its target genes and stimulates cell proliferation. Finally, by immunohistochemical staining of primary breast tissue microarrays we find that EMSY/KDM5A/SIN3B complex subunits are frequently overexpressed in primary breast cancer cases in a correlative manner. Taken together, these data open venues for exploring the possibility that sporadic breast cancer patients with EMSY amplification might benefit from epigenetic combination therapy targeting both the KDM5A demethylase and histone deacetylases.
Assuntos
Neoplasias da Mama/metabolismo , Proteínas de Ligação a DNA/metabolismo , Histonas/metabolismo , Complexos Multiproteicos/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Proteínas de Ligação a DNA/genética , Feminino , Técnicas de Inativação de Genes , Células HeLa , Histonas/genética , Humanos , Complexos Multiproteicos/genética , Proteínas de Neoplasias/genética , Proteínas Nucleares/genética , Proteínas Repressoras/genética , Proteína 2 de Ligação ao Retinoblastoma/genética , Proteína 2 de Ligação ao Retinoblastoma/metabolismo , Fatores de Transcrição/genéticaRESUMO
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.
Assuntos
Desenvolvimento Embrionário , Regulação da Expressão Gênica no Desenvolvimento , Proteoma/metabolismo , Proteínas de Xenopus/metabolismo , Animais , Desenvolvimento Embrionário/genética , Óvulo/metabolismo , Proteoma/genética , RNA Mensageiro/metabolismo , Análise de Célula Única , Transcriptoma , Proteínas de Xenopus/genética , Xenopus laevisRESUMO
Transcription factors (TFs) bind specific DNA sequences to regulate transcription. Apart from DNA sequences, local factors such as DNA accessibility and chromatin structure determine the affinity of a TF for any given locus. Including these factors when measuring TF-DNA affinities has proven difficult. To address this challenge, we recently developed a method called binding affinities in native chromatin by sequencing (BANC-seq). In BANC-seq, intact mammalian nuclei are incubated with a concentration range of epitope-tagged TF, followed by either chromatin immunoprecipitation or cleavage under target and release using nuclease with spike-in DNA. This allows determination of apparent dissociation constant (KdApp) values, defined by the concentration of TF at which half-maximum binding occurs, across the genome. Here we present a detailed stepwise protocol for BANC-seq, including downstream data analysis. In principle, any molecular biologist should be able to perform a BANC-seq experiment in as little as 1.5 d (excluding analysis). However, preprocessing and analysis of the sequencing data does require some experience in command-line shell and R programming.
RESUMO
Recent advances in single-cell immune profiling have enabled the simultaneous measurement of transcriptome and T cell receptor (TCR) sequences, offering great potential for studying immune responses at the cellular level. However, integrating these diverse modalities across datasets is challenging due to their unique data characteristics and technical variations. Here, to address this, we develop the multimodal generative model mvTCR to fuse modality-specific information across transcriptome and TCR into a shared representation. Our analysis demonstrates the added value of multimodal over unimodal approaches to capture antigen specificity. Notably, we use mvTCR to distinguish T cell subpopulations binding to SARS-CoV-2 antigens from bystander cells. Furthermore, when combined with reference mapping approaches, mvTCR can map newly generated datasets to extensive T cell references, facilitating knowledge transfer. In summary, we envision mvTCR to enable a scalable analysis of multimodal immune profiling data and advance our understanding of immune responses.
Assuntos
COVID-19 , Receptores de Antígenos de Linfócitos T , SARS-CoV-2 , Análise de Célula Única , Transcriptoma , Receptores de Antígenos de Linfócitos T/metabolismo , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Análise de Célula Única/métodos , Humanos , SARS-CoV-2/imunologia , SARS-CoV-2/genética , COVID-19/imunologia , COVID-19/virologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Perfilação da Expressão Gênica/métodos , Antígenos Virais/imunologia , Antígenos Virais/genéticaRESUMO
Assessment of single-cell gene expression (single-cell RNA sequencing) and adaptive immune receptor (AIR) sequencing (scVDJ-seq) has been invaluable in studying lymphocyte biology. Here we introduce Dandelion, a computational pipeline for scVDJ-seq analysis. It enables the application of standard V(D)J analysis workflows to single-cell datasets, delivering improved V(D)J contig annotation and the identification of nonproductive and partially spliced contigs. We devised a strategy to create an AIR feature space that can be used for both differential V(D)J usage analysis and pseudotime trajectory inference. The application of Dandelion improved the alignment of human thymic development trajectories of double-positive T cells to mature single-positive CD4/CD8 T cells, generating predictions of factors regulating lineage commitment. Dandelion analysis of other cell compartments provided insights into the origins of human B1 cells and ILC/NK cell development, illustrating the power of our approach. Dandelion is available at https://www.github.com/zktuong/dandelion .
Assuntos
Taraxacum , Humanos , Linfócitos T , Análise de Célula ÚnicaRESUMO
Children infected with SARS-CoV-2 rarely progress to respiratory failure. However, the risk of mortality in infected people over 85 years of age remains high. Here we investigate differences in the cellular landscape and function of paediatric (<12 years), adult (30-50 years) and older adult (>70 years) ex vivo cultured nasal epithelial cells in response to infection with SARS-CoV-2. We show that cell tropism of SARS-CoV-2, and expression of ACE2 and TMPRSS2 in nasal epithelial cell subtypes, differ between age groups. While ciliated cells are viral replication centres across all age groups, a distinct goblet inflammatory subtype emerges in infected paediatric cultures and shows high expression of interferon-stimulated genes and incomplete viral replication. In contrast, older adult cultures infected with SARS-CoV-2 show a proportional increase in basaloid-like cells, which facilitate viral spread and are associated with altered epithelial repair pathways. We confirm age-specific induction of these cell types by integrating data from in vivo COVID-19 studies and validate that our in vitro model recapitulates early epithelial responses to SARS-CoV-2 infection.
Assuntos
Enzima de Conversão de Angiotensina 2 , COVID-19 , Células Epiteliais , Mucosa Nasal , SARS-CoV-2 , Serina Endopeptidases , Humanos , COVID-19/virologia , SARS-CoV-2/fisiologia , SARS-CoV-2/patogenicidade , SARS-CoV-2/genética , Enzima de Conversão de Angiotensina 2/metabolismo , Enzima de Conversão de Angiotensina 2/genética , Adulto , Pessoa de Meia-Idade , Idoso , Células Epiteliais/virologia , Serina Endopeptidases/metabolismo , Serina Endopeptidases/genética , Mucosa Nasal/virologia , Criança , Fatores Etários , Replicação Viral , Pré-Escolar , Tropismo Viral , Masculino , Feminino , Idoso de 80 Anos ou mais , Células Cultivadas , Adolescente , LactenteRESUMO
Transcription factor binding across the genome is regulated by DNA sequence and chromatin features. However, it is not yet possible to quantify the impact of chromatin context on transcription factor binding affinities. Here, we report a method called binding affinities to native chromatin by sequencing (BANC-seq) to determine absolute apparent binding affinities of transcription factors to native DNA across the genome. In BANC-seq, a concentration range of a tagged transcription factor is added to isolated nuclei. Concentration-dependent binding is then measured per sample to quantify apparent binding affinities across the genome. BANC-seq adds a quantitative dimension to transcription factor biology, which enables stratification of genomic targets based on transcription factor concentration and prediction of transcription factor binding sites under non-physiological conditions, such as disease-associated overexpression of (onco)genes. Notably, whereas consensus DNA binding motifs for transcription factors are important to establish high-affinity binding sites, these motifs are not always strictly required to generate nanomolar-affinity interactions in the genome.
Assuntos
Cromatina , Fatores de Transcrição , Cromatina/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Ligação Proteica , DNA/genética , DNA/metabolismo , Regulação da Expressão Gênica , Sítios de Ligação/genética , Análise de Sequência de DNARESUMO
Single-cell transcriptomics has allowed unprecedented resolution of cell types/states in the human lung, but their spatial context is less well defined. To (re)define tissue architecture of lung and airways, we profiled five proximal-to-distal locations of healthy human lungs in depth using multi-omic single cell/nuclei and spatial transcriptomics (queryable at lungcellatlas.org ). Using computational data integration and analysis, we extend beyond the suspension cell paradigm and discover macro and micro-anatomical tissue compartments including previously unannotated cell types in the epithelial, vascular, stromal and nerve bundle micro-environments. We identify and implicate peribronchial fibroblasts in lung disease. Importantly, we discover and validate a survival niche for IgA plasma cells in the airway submucosal glands (SMG). We show that gland epithelial cells recruit B cells and IgA plasma cells, and promote longevity and antibody secretion locally through expression of CCL28, APRIL and IL-6. This new 'gland-associated immune niche' has implications for respiratory health.
Assuntos
Pulmão , Mucosa Respiratória , Humanos , Mucosa Respiratória/metabolismo , Células Epiteliais/metabolismo , Linfócitos B , Imunoglobulina A/metabolismoRESUMO
Innate immune memory, also called "trained immunity," is a functional state of myeloid cells enabling enhanced immune responses. This phenomenon is important for host defense, but also plays a role in various immune-mediated conditions. We show that exogenously administered sphingolipids and inhibition of sphingolipid metabolizing enzymes modulate trained immunity. In particular, we reveal that acid ceramidase, an enzyme that converts ceramide to sphingosine, is a potent regulator of trained immunity. We show that acid ceramidase regulates the transcription of histone-modifying enzymes, resulting in profound changes in histone 3 lysine 27 acetylation and histone 3 lysine 4 trimethylation. We confirm our findings by identifying single-nucleotide polymorphisms in the region of ASAH1, the gene encoding acid ceramidase, that are associated with the trained immunity cytokine response. Our findings reveal an immunomodulatory effect of sphingolipids and identify acid ceramidase as a relevant therapeutic target to modulate trained immunity responses in innate immune-driven disorders.
Assuntos
Ceramidase Ácida , Imunidade Treinada , Ceramidase Ácida/genética , Ceramidase Ácida/metabolismo , Histonas , Lisina , Esfingolipídeos/genética , Imunidade InataRESUMO
Studies of human lung development have focused on epithelial and mesenchymal cell types and function, but much less is known about the developing lung immune cells, even though the airways are a major site of mucosal immunity after birth. An unanswered question is whether tissue-resident immune cells play a role in shaping the tissue as it develops in utero. Here, we profiled human embryonic and fetal lung immune cells using scRNA-seq, smFISH, and immunohistochemistry. At the embryonic stage, we observed an early wave of innate immune cells, including innate lymphoid cells, natural killer cells, myeloid cells, and lineage progenitors. By the canalicular stage, we detected naive T lymphocytes expressing high levels of cytotoxicity genes and the presence of mature B lymphocytes, including B-1 cells. Our analysis suggests that fetal lungs provide a niche for full B cell maturation. Given the presence and diversity of immune cells during development, we also investigated their possible effect on epithelial maturation. We found that IL-1ß drives epithelial progenitor exit from self-renewal and differentiation to basal cells in vitro. In vivo, IL-1ß-producing myeloid cells were found throughout the lung and adjacent to epithelial tips, suggesting that immune cells may direct human lung epithelial development.
Assuntos
Imunidade Inata , Pulmão , Humanos , Diferenciação Celular , Células Matadoras Naturais , Células EpiteliaisRESUMO
Micrometastases of colorectal cancer can remain dormant for years prior to the formation of actively growing, clinically detectable lesions (i.e., colonization). A better understanding of this step in the metastatic cascade could help improve metastasis prevention and treatment. Here we analyzed liver specimens of patients with colorectal cancer and monitored real-time metastasis formation in mouse livers using intravital microscopy to reveal that micrometastatic lesions are devoid of cancer stem cells (CSC). However, lesions that grow into overt metastases demonstrated appearance of de novo CSCs through cellular plasticity at a multicellular stage. Clonal outgrowth of patient-derived colorectal cancer organoids phenocopied the cellular and transcriptomic changes observed during in vivo metastasis formation. First, formation of mature CSCs occurred at a multicellular stage and promoted growth. Conversely, failure of immature CSCs to generate more differentiated cells arrested growth, implying that cellular heterogeneity is required for continuous growth. Second, early-stage YAP activity was required for the survival of organoid-forming cells. However, subsequent attenuation of early-stage YAP activity was essential to allow for the formation of cell type heterogeneity, while persistent YAP signaling locked micro-organoids in a cellularly homogenous and growth-stalled state. Analysis of metastasis formation in mouse livers using single-cell RNA sequencing confirmed the transient presence of early-stage YAP activity, followed by emergence of CSC and non-CSC phenotypes, irrespective of the initial phenotype of the metastatic cell of origin. Thus, establishment of cellular heterogeneity after an initial YAP-controlled outgrowth phase marks the transition to continuously growing macrometastases. SIGNIFICANCE: Characterization of the cell type dynamics, composition, and transcriptome of early colorectal cancer liver metastases reveals that failure to establish cellular heterogeneity through YAP-controlled epithelial self-organization prohibits the outgrowth of micrometastases. See related commentary by LeBleu, p. 1870.