Biology subjects

Sung, M.-H.

Publications and source records attributed to Sung, M.-H..

3 recordsLinked to original sources

bioRxiv2026

A novel multicellular model of the adult mouse sinoatrial node retains spontaneous electrical activity and enables live investigation of the S100B-associated cell population

Approximately half of the adult sinoatrial node (SAN) consists of non-myocyte populations, indicating that cardiac pacemaking depends on interactions within a multicellular tissue rather than on pacemaker cardiomyocytes alone. Among these, an S100B-associated cell population has been implicated in pacemaker function, yet its identity and physiological roles remain poorly understood. These cells are rare and dispersed throughout the small, structurally complex SAN, making them difficult to observe repeatedly while preserving the native multicellular environment. Here, we established a dissociated multicellular culture of adult mouse SAN tissue on soft collagen-gelatin hydrogels that retains spontaneous electrical activity and permits longitudinal live imaging of S100B-associated cells. Using an S100B-EGFP+ reporter, we identified at least six reproducible morphological and behavioral phenotypes, including migration, proliferation, phagocytic behavior, and spontaneous self-organization into three-dimensional clusters. Cultures remained spontaneously electrically active for more than 10 days in vitro, with peak activity around day 10. This multicellular culture model bridges the gap between intact SAN preparations and isolated-cell cultures, allowing repeated observation of rare S100B-associated cells within a spontaneously active multicellular environment. HighlightsO_LIThe platform enables longitudinal live imaging of rare S100B-associated cells within an diverse multicellular SAN culture. C_LIO_LILive imaging reveals at least six reproducible morphological and behavioral phenotypes of S100B-associated cells. C_LIO_LIDissociated multicellular SAN cultures remain spontaneously electrically active for more than 10 days in vitro. C_LI

cell biology↗

bioRxiv2020

Hedgehog dysregulation contributes to tissue-specific inflammaging of resident macrophages

Age-associated low-grade sterile inflammation, commonly referred to as inflammaging, is a recognized hallmark of aging, which contributes to many age-related diseases. While tissue-resident macrophages are innate immune cells that secrete many types of inflammatory cytokines in response to various stimuli, it is not clear whether they have a role in driving inflammaging. Here we characterized the transcriptional changes associated with physiological aging in mouse resident macrophage populations across different tissues and sexes. Although the age-related transcriptomic signatures of resident macrophages were strikingly tissue-specific, the differentially expressed genes were collectively enriched for those with important innate immune functions such as antigen presentation, cytokine production, and cell adhesion. The brain-resident microglia had the most wide-ranging age-related alterations, with compromised expression of tissue-specific genes and relatively exaggerated responses to endotoxin stimulation. Despite the tissue-specific patterns of aging transcriptomes, components of the hedgehog (Hh) signaling pathway were decreased in aged macrophages across multiple tissues. In vivo suppression of Hh signaling in young animals increased the expression of pro-inflammatory cytokines, while in vitro activation of Hh signaling in old macrophages, in turn, suppressed the expression of these inflammatory cytokines. This suggests that hedgehog signaling could be a potential intervention axis for mitigating age-associated inflammation and related diseases. Overall, our data represent a resourceful catalog of tissue-specific and sex-specific transcriptomic changes in resident macrophages of peritoneum, liver, and brain, during physiological aging.

immunology↗

bioRxiv2019

Gene Activation and repression by the glucocorticoid receptor are mediated by sequestering Ep300 and two modes of chromatin binding

The transcription factor glucocorticoid receptor (GR) is a key mediator of stress response and a broad range of physiological processes. How can GR rapidly activate the expression of some genes while repress others, remains an open question due to the challenge to associate GR binding sites (GBSs) to their distant gene targets. Mapping the full 3D scope of GR-responsive promoters using high-resolution 4C-seq unravelled spatial separation between chromatin interaction networks of GR-activated and repressed genes. Analysing GR binding sites and other regulatory loci in their functional 3D context revealed that GR sequesters the co-activator Ep300 from active non-GBS enhancers in both activated and repressed gene compartments. While this is sufficient for rapid gene repression, gene activation is countered by productive recruitment of Ep300 to GBS. Importantly, in GR-activated compartments Klf4 binding at non-GBS regulatory elements cluster in 3D with GBS and antagonizes GR activation. In addition, we revealed ROR and Rev-erb transcription factors as novel co-regulators for GR-mediated gene expression.

molecular biology↗