Project description:T cells activated by chronic antigen exposure in the setting of viral infections or cancer can adopt an exhausted T cell (TEx) state, characterized by reduced effector function and proliferative capacity, and the upregulation of inhibitory receptors. Here, we generate a single-cell multi-omic atlas of T cell exhaustion in chronic viral infection that redefines the phenotypic diversity and molecular regulation of TEx states. Longitudinal analysis of the T cell response identifies an early effector phenotype that is epigenetically primed for TEx differentiation. However, clonal T cell trajectories defined using paired single-cell RNA and T cell receptor (scRNA/TCR-seq) sequencing reveal divergent differentiation trajectories among clones that recognize shared antigens, resulting in TEx- or effector memory-biased clone behaviors. Multi-organ clonal analysis reveals that T cell clone behaviors are sensitive to the tissue environment, and the liver niche preclude the development of effector memory phenotypes and induce exaggerated exhaustion. Finally, we show that divergent clonal trajectories are driven by differences in TCR affinity, and that high-affinity T cell clones preferentially adopt the divergent fate, while low-affinity clones adopt effector memory fates that are deleted in high antigen niches. These findings reveal heterogeneity in clonal T cell responses to chronic antigen and link TCR signal strength and epigenetic programming to TEx cell fates and persistence, which may be manipulated for cancer immunotherapy.
Project description:T cells activated by chronic antigen exposure in the setting of viral infections or cancer can adopt an exhausted T cell (Tex) state, characterized by reduced effector function and proliferative capacity, and the upregulation of inhibitory receptors. However, whether all antigen-specific T cell clones follow the same molecular and cellular Tex differentiation trajectory remains unclear. Here, we generate a single-cell multi-omic atlas of T cell exhaustion that redefines the phenotypic diversity and molecular regulation of Tex phenotypes. Longitudinal analysis during chronic viral infection identifies an early effector phenotype that is epigenetically primed for Tex differentiation and two late-stage Tex cell states with either a terminal exhaustion or a killer cell lectin-like receptor (KLR)-expressing cytotoxic gene signature. We define clonal trajectories of antigen-specific T cells using paired single-cell RNA and T cell receptor sequencing and reveal distinct differentiation trajectories resulting in terminal Tex-biased, KLR Tex-biased, or divergent clones that differentiate into both phenotypes. Comparison of Tex phenotypes among shared T cell clones that traffic to multiple organs reveals that clonal differentiation trajectories are maintained across tissues. Finally, we show that differences in clonal differentiation trajectory are driven by TCR signaling avidity, whereby high-avidity T cell clones preferentially adopt a terminal Tex fate, while low-avidity clones adopt an effector-like KLR Tex fate. These findings reveal clonal heterogeneity in the T cell response to chronic antigen and genomic programs that underlie Tex fates and persistence.
Project description:Chronic antigen exposure during viral infection or cancer promotes an exhausted T cell (Tex) state with reduced effector function. However, whether all antigen-specific T cell clones follow the same Tex differentiation trajectory remains unclear. Here, we generate a single-cell multiomic atlas of T cell exhaustion in murine chronic viral infection that redefines Tex phenotypic diversity, including two late-stage Tex subsets with either a terminal exhaustion (Texterm) or a killer cell lectin-like receptor-expressing cytotoxic (TexKLR) phenotype. We use paired single-cell RNA and T cell receptor sequencing to uncover clonal differentiation trajectories of Texterm-biased, TexKLR-biased or divergent clones that acquire both phenotypes. We show that high T cell receptor signaling avidity correlates with Texterm, whereas low avidity correlates with effector-like TexKLR fate. Finally, we identify similar clonal differentiation trajectories in human tumor-infiltrating lymphocytes. These findings reveal clonal heterogeneity in the T cell response to chronic antigen that influences Tex fates and persistence.
Project description:To study developmental trajectories in brain organoids, we conducted scRNA-seq and scATAC-seq in parallel on a dense timecourse of early development.
Project description:Understanding complex tissues requires single-cell deconstruction of gene regulation with precision and scale. Here we present a massively parallel droplet-based platform for mapping transposase-accessible chromatin in tens of thousands of single cells per sample (scATAC-seq). We obtain and analyze chromatin profiles of over 200,000 single cells in two primary human systems. In blood, scATAC-seq allows marker-free identification of cell type-specific cis- and trans-regulatory elements, mapping of disease-associated enhancer activity, and reconstruction of trajectories of differentiation from progenitors to diverse and rare immune cell types. In basal cell carcinoma, scATAC-seq reveals regulatory landscapes of malignant, stromal, and immune cell types in the tumor microenvironment. Moreover, scATAC-seq of serial tumor biopsies before and after PD-1 blockade allows identification of chromatin regulators and differentiation trajectories of therapy-responsive intratumoral T cell subsets, revealing a shared regulatory program driving CD8+ T cell exhaustion and CD4+ T follicular helper cell development in association with clinical response. We anticipate that droplet-based single-cell chromatin accessibility will provide a broadly applicable means of identifying regulatory factors and elements that underlie cell type and function.
Project description:The mammalian cerebral cortex contains an extraordinary diversity of cell types that emerge through the implementation of different developmental programs. Delineating when and how cellular diversification occurs is particularly challenging for cortical inhibitory neurons, as they represent a relatively small proportion of all cortical cells, migrate tangentially from their embryonic origin to the cerebral cortex, and have a protracted development. Here we combine single-cell RNA sequencing and spatial transcriptomics to characterize the emergence of neuronal diversity among somatostatin-expressing (SST+) cells, the most diverse subclass of inhibitory neurons in the mouse cerebral cortex. We found that SST+ inhibitory neurons segregate during embryonic stages into long-range projection (LRP) neurons and two types of interneurons, Martinotti cells and non-Martinotti cells, following distinct developmental trajectories. Two main subtypes of LRP neurons and several subtypes of interneurons are readily distinguishable in the embryo, although interneuron diversity is further refined during early postanal life. Our results suggest that the timing for cellular diversification is unique for different subtypes of SST+ neurons and particularly divergent for LRP neurons and interneurons. Thus, the diversification of SST+ inhibitory neurons involves a temporal cascade of unique molecular programs driving their divergent developmental trajectories.