Highlights Deterministic barcoding in tissue enables NGS-based spatial multi-omics mapping. DBiT-seq identified spatial patterning of major tissue types in mouse embryos. DBiT-seq revealed fine features such as retinal pigmented epithelium and microvascular endothelium at the cellular level. Direct integration with scRNA-seq data allows for rapid cell type identification.

Spatial omics emerged as a new frontier of biological and biomedical research. Here, we present spatial-CUT&Tag for spatially resolved genome-wide profiling of histone modifications by combining in situ CUT&Tag chemistry, microfluidic deterministic barcoding, and next-generation sequencing. Spatially resolved chromatin states in mouse embryos revealed tissue-type-specific epigenetic regulations in concordance with ENCODE references and provide spatial information at tissue scale. Spatial-CUT&Tag revealed epigenetic control of the cortical layer development and spatial patterning of cell types determined by histone modification in mouse brain. Single-cell epigenomes can be derived in situ by identifying 20-micrometer pixels containing only one nucleus using immunofluorescence imaging. Spatial chromatin modification profiling in tissue may offer new opportunities to study epigenetic regulation, cell function, and fate decision in normal physiology and pathogenesis.

Cellular function in tissue is dependent on the local environment, requiring new methods for spatial mapping of biomolecules and cells in the tissue context1. The emergence of spatial transcriptomics has enabled genome-scale gene expression mapping2–5, but the ability to capture spatial epigenetic information of tissue at the cellular level and genome scale is lacking. Here we describe a method for spatially resolved chromatin accessibility profiling of tissue sections using next-generation sequencing (spatial-ATAC-seq) by combining in situ Tn5 transposition chemistry6 and microfluidic deterministic barcoding5. Profiling mouse embryos using spatial-ATAC-seq delineated tissue-region-specific epigenetic landscapes and identified gene regulators involved in the development of the central nervous system. Mapping the accessible genome in the mouse and human brain revealed the intricate arealization of brain regions. Applying spatial-ATAC-seq to tonsil tissue resolved the spatially distinct organization of immune cell types and states in lymphoid follicles and extrafollicular zones. This technology progresses spatial biology by enabling spatially resolved chromatin accessibility profiling to improve our understanding of cell identity, cell state and cell fate decision in relation to epigenetic underpinnings in development and disease.

Emerging spatial technologies, including spatial transcriptomics and spatial epigenomics, are becoming powerful tools for profiling of cellular states in the tissue context1–5. However, current methods capture only one layer of omics information at a time, precluding the possibility of examining the mechanistic relationship across the central dogma of molecular biology. Here, we present two technologies for spatially resolved, genome-wide, joint profiling of the epigenome and transcriptome by cosequencing chromatin accessibility and gene expression, or histone modifications (H3K27me3, H3K27ac or H3K4me3) and gene expression on the same tissue section at near-single-cell resolution. These were applied to embryonic and juvenile mouse brain, as well as adult human brain, to map how epigenetic mechanisms control transcriptional phenotype and cell dynamics in tissue. Although highly concordant tissue features were identified by either spatial epigenome or spatial transcriptome we also observed distinct patterns, suggesting their differential roles in defining cell states. Linking epigenome to transcriptome pixel by pixel allows the uncovering of new insights in spatial epigenetic priming, differentiation and gene regulation within the tissue architecture. These technologies are of great interest in life science and biomedical research.

In this study, we extended co-indexing of transcriptomes and epitopes (CITE) to the spatial dimension and demonstrated high-plex protein and whole transcriptome co-mapping. We profiled 189 proteins and whole transcriptome in multiple mouse tissue types with spatial CITE sequencing and then further applied the method to measure 273 proteins and transcriptome in human tissues, revealing spatially distinct germinal center reactions in tonsil and early immune activation in skin at the Coronavirus Disease 2019 mRNA vaccine injection site.

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Spatial gene expression heterogeneity plays an essential role in a range of biological, physiological and pathological processes but it remains a scientific challenge to conduct highspatial-resolution, genome-wide, unbiased biomolecular profiling over a large tissue area. Herein, we present a fundamentally new approachmicrofluidic Deterministic Barcoding in Tissue for spatial omics sequencing (DBiT-seq). Parallel microfluidic channels (10μm, 25μm, or 50μm in width) are used to deliver molecular barcodes to the surface of a formaldehyde fixed tissue slide in a spatially confined manner. Crossflow of two sets of barcodes A1-A50 and B1-B50 followed by ligation in situ yields a 2D mosaic of tissue pixels, each containing a unique combination of full barcode AiBj (i=1-50, j=1-50). It permits simultaneous barcoding of mRNAs, proteins, or even other omics on a fixed tissue slide, enabling the construction of a high-spatial-resolution multiomics atlas by NGS sequencing. Applying it to mouse embryo tissues revealed all major tissue types in early organogenesis, distinguished brain microvascular networks, discovered new developmental patterning in forebrain, and demonstrated the ability to detect a single-cell-layer of melanocytes lining an optical vesicle and asymmetric expression of Rorb and Aldh1a1 within it, presumably associated with the onset of retina and lens, respectively. Automated feature identification using spatial differential expression further identified dozens of developmental features. DBiT-seq is a highly versatile technology that may become a universal method for spatial barcoding and sequencing of a range of molecular information at a high resolution and the genome scale. It can be readily adopted by biologists with no experience in microfluidics or advanced imaging, and could be quickly disseminated for broader impacts in a variety of fields including developmental biology, cancer biology, neuroscience, and clinical pathology.

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