Jeong-Heon Lee

The intestinal epithelium is exposed to diverse combinations of microbiota-derived compounds; however, the mechanisms by which the host integrates these signals remain poorly defined. Studying two highly abundant microbial metabolites, we identified the purine metabolite hypoxanthine as an effector metabolite that directly drives signaling and the short-chain fatty acid butyrate as a regulatory metabolite that conditions host responsiveness. Specifically, hypoxanthine activates the adenosine A1 receptor–TRPC4 axis in enterochromaffin (EC) cells, triggering calcium influx and serotonin release resulting in accelerated gastrointestinal transit locally and increased platelet activation systemically. In contrast, butyrate epigenetically upregulates specific G protein–coupled receptors and ion channels to enhance response to hypoxanthine and the neurotransmitters norepinephrine and dopamine. These findings define a cooperative signaling framework and highlight the role of EC cells as a distinct epithelial signaling hub that senses and integrates microbial metabolite signals to drive physiological responses. Our findings provide a mechanistic foundation for therapeutic strategies that leverage combinatorial microbial signaling.

Intestinal epithelial cells (IEC) are the primary cell type in direct contact with stimuli from the luminal microbiota, playing a critical role in host-microbe interactions. However, how IECs communicate with underlying immune cells to maintain homeostasis remains poorly understood. In addition, the mechanisms by which IECs sense microbiota-derived stimuli to initiate this crosstalk are not yet fully understood. Here, we demonstrate that oral administration of the gut microbiota metabolite butyrate induces sustained IL-10 production in CD4⁺ T cells, conferring long-lasting protection against intestinal inflammation even after treatment withdrawal. This persistent immunoregulatory effect is also observed in germ-free mice, indicating the establishment of a butyrate-conditioned intestinal environment. By metabolomic profiling, we identify N1-acetylspermidine as a metabolite contributing to the IL-10-inducing activity of butyrate-treated IEC-conditioned medium. Mechanistically, butyrate induces sustained transcriptional and epigenetic activation of the acetylpolyamine biosynthetic enzyme Sat1 in IECs, which catalyzes the acetylation of spermidine to generate N1-acetylspermidine, and this activation persists after butyrate withdrawal. Together, our findings reveal a mechanism by which butyrate sensing establishes persistent crosstalk between IECs and T cells, thereby maintaining intestinal immune tolerance through epigenetic regulation and reprogramming of epithelial metabolism.

Spatial multiomic technologies combined with single-cell profiling offer unprecedented opportunities to elucidate the molecular and cellular architecture of complex tissues. Combining spatial barcoding of nuclei within individual cryosections prepared from tissue blocks embedded in optimal cutting temperature (OCT) freezing medium with single-cell multiomic assays into a simple and efficient workflow can facilitate the annotation and spatially resolved molecular analysis of cells in tissue types. This study reports a spatial cleavage under targets & tagmentation (CUT&Tag) multiome approach that simultaneously profiles histone H3K27ac modification and gene expression in a single frozen brain section. Following spatial barcoding, single nuclei are isolated and subjected to CUT&Tag, combined capture of tagmented DNAs, RNAs, and spatial barcodes, library preparation, and sequencing. The workflow generates spatially annotated epigenomic and transcriptomic profiles from the same nuclei, enabling assignment of the multiomic information to anatomical coordinates. Integrating epigenomic information with spatial transcriptomic data increases the fidelity of cell-type identification and reveals spatially organized regulatory programs and cell-cell interactions within intact tissues.

Immune dysfunction has been increasingly implicated in bipolar disorder, but the underlying mechanisms remain unclear. To address this, we profile 833 genome-wide chromatin immunoprecipitation sequencing datasets spanning five histone marks in peripheral blood immune cells from 88 Type I bipolar disorder patients and 92 controls, integrating them with whole-genome sequencing and clinical data. We identify disease-associated cis -regulatory elements and genetically influenced regulatory elements, revealing immune signatures and pathways involving calcium signaling and endoplasmic reticulum transport. By integrating genetic risk variants, differential and genetically influenced regulatory elements, and regulatory element—gene links, we prioritize 39 driver genes, 28 of which are exclusively supported by blood evidence. We further stratify patients into five epigenomic subtypes with distinct clinical features and genetic risk profiles and identify compounds that reverse disease-associated epigenomic signatures. Here, we combine immune epigenomics with genetics and clinical traits to identify driver genes, patient subtypes, and therapeutic candidates, highlighting immune contributions to type I bipolar disorder pathogenesis.

Obesity is an epidemic with myriad health effects, but little is understood regarding individual obese phenotypes and how they may respond to therapy. Epigenetic changes associated with obesity have been detected in blood, liver, pancreas, and adipose tissues. Previous work using human organoids found that dietary glucose hyperabsorption is a steadfast trait in cultures derived from some obese subjects, but detailed transcriptional or epigenomic features of the intestinal epithelia associated with this persistent phenotype are unknown. This study evaluated differentially expressed genes and relative chromatin accessibility in intestinal organoids established from donors classified as non-obese, obese, or obese hyperabsorptive by body mass index and glucose transport assays. Transcriptomic analysis indicated that obese hyperabsorptive subject organoids have significantly upregulated dietary nutrient absorption transcripts and downregulated type I interferon targets. Chromatin accessibility and transcription factor footprinting predicted that enhanced HNF4G binding may promote the obese hyperabsorption phenotype. Quantitative RT-PCR assessment in organoids representing a larger subject cohort suggested that intestinal epithelial expression of CUBN, GIP, SLC5A11, and SLC2A5 were highly correlated with hyperabsorption. Thus, the obese hyperabsorption phenotype was characterized by transcriptional changes that support increased nutrient uptake by intestinal epithelia, potentially driven by differentially accessible chromatin. Recognizing unique intestinal phenotypes in obesity provides a new perspective in considering therapeutic targets and options with which to manage the disease.

DNMT3A and TET2 are epigenetic regulator genes commonly mutated in age-related clonal hematopoiesis (CH). Despite having opposed epigenetic functions, these mutations are associated with increased all-cause mortality and a low risk for progression to hematologic neoplasms. Although individual impacts on the epigenome have been described using different model systems, the phenotypic complexity in humans remains to be elucidated. Here, we make use of a natural inflammatory response occurring during coronavirus disease 2019 (COVID-19), to understand the association of these mutations with inflammatory morbidity (acute respiratory distress syndrome [ARDS]) and mortality. We demonstrate the age-independent, negative impact of DNMT3A mutant (DNMT3Amt) CH on COVID-19–related ARDS and mortality. Using single-cell proteogenomics we show that DNMT3A mutations involve myeloid and lymphoid lineage cells. Using single-cell multiomics sequencing, we identify cell-specific gene expression changes associated with DNMT3A mutations, along with significant epigenomic deregulation affecting enhancer accessibility, resulting in overexpression of interleukin-32 (IL-32), a proinflammatory cytokine that can result in inflammasome activation in monocytes and macrophages. Finally, we show with single-cell resolution that the loss of function of DNMT3A is directly associated with increased chromatin accessibility in mutant cells. Hence, we demonstrate the negative prognostic impact of DNMT3Amt CH on COVID-19–related ARDS and mortality. DNMT3Amt CH in the context of COVID-19, was associated with inflammatory transcriptional priming, resulting in overexpression of IL32. This overexpression was secondary to increased chromatic accessibility, specific to DNMT3Amt CH cells. DNMT3Amt CH can thus serve as a potential biomarker for adverse outcomes in COVID-19.

The snATAC + snRNA platform allows epigenomic profiling of open chromatin and gene expression with single-cell resolution. The most critical assay step is to isolate high-quality nuclei to proceed with droplet-base single nuclei isolation and barcoding. With the increasing popularity of multiomic profiling in various fields, there is a need for optimized and reliable nuclei isolation methods, mainly for human tissue samples. Herein we compared different nuclei isolation methods for cell suspensions, such as peripheral blood mononuclear cells (PBMC, n = 18) and a solid tumor type, ovarian cancer (OC, n = 18), derived from debulking surgery. Nuclei morphology and sequencing output parameters were used to evaluate the quality of preparation. Our results show that NP-40 detergent-based nuclei isolation yields better sequencing results than collagenase tissue dissociation for OC, significantly impacting cell type identification and analysis. Given the utility of applying such techniques to frozen samples, we also tested frozen preparation and digestion (n = 6). A paired comparison between frozen and fresh samples validated the quality of both specimens. Finally, we demonstrate the reproducibility of scRNA and snATAC + snRNA platform, by comparing the gene expression profiling of PBMC. Our results highlight how the choice of nuclei isolation methods is critical for obtaining quality data in multiomic assays. It also shows that the measurement of expression between scRNA and snRNA is comparable and effective for cell type identification.

The snATAC + snRNA platform allows epigenomic profiling of open chromatin and gene expression with single-cell resolution. The most critical assay step is to isolate high-quality nuclei to proceed with droplet-base single nuclei isolation and barcoding. With the increasing popularity of multiomic profiling in various fields, there is a need for optimized and reliable nuclei isolation methods, mainly for human tissue samples. Herein we compared different nuclei isolation methods for cell suspensions, such as peripheral blood mononuclear cells (PBMC, n=18) and a solid tumor type, ovarian cancer (OC) (n=18), derived from debulking surgery. Nuclei morphology and sequencing output parameters were used to evaluate the quality of preparation. Our results show that NP-40 detergent-based nuclei isolation yields better sequencing results than collagenase tissue dissociation for OC, significantly impacting cell identification and analysis. Given the utility of applying such techniques to frozen samples, we also tested frozen preparation and digestion (n=6). A paired comparison between frozen and fresh samples validated the quality of both specimens. Finally, we demonstrate the reproducibility of scRNA and snATAC + snRNA platform, by comparing the gene expression profiling of PBMC. Our results highlight how the choice of nuclei isolation methods is critical for obtaining quality data in multiomic assays. It also shows that the measurement of expression between scRNA and snRNA is comparable and effective for cell type identification.

Chromatin immunoprecipitation (ChIP) is an antibody-based approach that is frequently utilized in chromatin biology and epigenetics. The challenge in experimental variability by unpredictable nature of usable input amounts from samples and undefined antibody titer in ChIP reaction still remains to be addressed. Here, we introduce a simple and quick method to quantify chromatin inputs and demonstrate its utility for normalizing antibody amounts to the optimal titer in individual ChIP reactions. For a proof of concept, we utilized ChIP-seq validated antibodies against the key enhancer mark, acetylation of histone H3 on lysine 27 (H3K27ac), in the experiments. The results indicate that the titration-based normalization of antibody amounts improves assay outcomes including the consistency among samples both within and across experiments for a broad range of input amounts.