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Browsing by Author "Roh, Hyun Cheol"
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Item Adipocytes fail to maintain cellular identity during obesity due to reduced PPARγ activity and elevated TGFβ-SMAD signaling(Elsevier, 2020-09-28) Roh, Hyun Cheol; Kumari, Manju; Taleb, Solaema; Tenen, Danielle; Jacobs, Christopher; Lyubetskaya, Anna; Tsai, Linus T. -Y.; Rosen, Evan D.; Biochemistry and Molecular Biology, School of MedicineObjective Obesity due to overnutrition causes adipose tissue dysfunction, which is a critical pathological step on the road to type 2 diabetes (T2D) and other metabolic disorders. In this study, we conducted an unbiased investigation into the fundamental molecular mechanisms by which adipocytes transition to an unhealthy state during obesity. Methods We used nuclear tagging and translating ribosome affinity purification (NuTRAP) reporter mice crossed with Adipoq-Cre mice to determine adipocyte-specific 1) transcriptional profiles (RNA-seq), 2) promoter and enhancer activity (H3K27ac ChIP-seq), 3) and PPARγ cistrome (ChIP-seq) profiles in mice fed chow or a high-fat diet (HFD) for 10 weeks. We also assessed the impact of the PPARγ agonist rosiglitazone (Rosi) on gene expression and cellular state of adipocytes from the HFD-fed mice. We integrated these data to determine the transcription factors underlying adipocyte responses to HFD and conducted functional studies using shRNA-mediated loss-of-function approaches in 3T3-L1 adipocytes. Results Adipocytes from the HFD-fed mice exhibited reduced expression of adipocyte markers and metabolic genes and enhanced expression of myofibroblast marker genes involved in cytoskeletal organization, accompanied by the formation of actin filament structures within the cell. PPARγ binding was globally reduced in adipocytes after HFD feeding, and Rosi restored the molecular and cellular phenotypes of adipocytes associated with HFD feeding. We identified the TGFβ1 effector protein SMAD to be enriched at HFD-induced promoters and enhancers and associated with myofibroblast signature genes. TGFβ1 treatment of mature 3T3-L1 adipocytes induced gene expression and cellular changes similar to those seen after HFD in vivo, and knockdown of Smad3 blunted the effects of TGFβ1. Conclusions Our data demonstrate that adipocytes fail to maintain cellular identity after HFD feeding, acquiring characteristics of a myofibroblast-like cell type through reduced PPARγ activity and elevated TGFβ-SMAD signaling. This cellular identity crisis may be a fundamental mechanism that drives functional decline of adipose tissues during obesity.Item Chronic cAMP activation induces adipocyte browning through discordant biphasic remodeling of transcriptome and chromatin accessibility(Elsevier, 2022) So, Jisun; Taleb, Solaema; Wann, Jamie; Strobel, Olivia; Kim, Kyungchan; Roh, Hyun Cheol; Biochemistry and Molecular Biology, School of MedicineObjective: Adipose tissue thermogenesis has been suggested as a new therapeutic target to promote energy metabolism for obesity and metabolic disease. Cold-inducible thermogenic adipocytes, called beige adipocytes, have attracted significant attention for their potent anti-obesity activity in adult humans. In this study, we identified the mechanisms underlying beige adipocyte recruitment, so-called adipocyte browning, by different stimuli. Methods: We generated a new adipocyte cell line with enhanced browning potentials and determined its transcriptomic and epigenomic responses following cAMP (forskolin, FSK) versus PPARγ activation (rosiglitazone). We performed time-course RNA-seq and compared the treatments and in vivo adipocyte browning. We also developed an improved protocol for Assay for Transposase Accessible Chromatin-sequencing (ATAC-seq) and defined changes in chromatin accessibility in a time course. The RNA-seq and ATAC-seq data were integrated to determine the kinetics of their coordinated regulation and to identify a transcription factor that drives these processes. We conducted functional studies using pharmacological and genetic approaches with specific inhibitors and shRNA-mediated knockdown, respectively. Results: FSK, not rosiglitazone, resulted in a biphasic transcriptomic response, resembling the kinetics of in vivo cold-induced browning. FSK promoted tissue remodeling first and subsequently shifted energy metabolism, concluding with a transcriptomic profile similar to that induced by rosiglitazone. The thermogenic effects of FSK were abolished by PPARγ antagonists, indicating PPARγ as a converging point. ATAC-seq uncovered that FSK leads to a significant chromatin remodeling that precedes or persists beyond transcriptomic changes, whereas rosiglitazone induces minimal changes. Motif analysis identified nuclear factor, interleukin 3 regulated (NFIL3) as a transcriptional regulator connecting the biphasic response of FSK-induced browning, as indicated by disrupted thermogenesis with NFIL3 knockdown. Conclusions: Our findings elucidated unique dynamics of the transcriptomic and epigenomic remodeling in adipocyte browning, providing new mechanistic insights into adipose thermogenesis and molecular targets for obesity treatment.Item Endoplasmic Reticulum Calcium in the Pathogenesis of Type 1 Diabetes(2023-12) Weaver, Staci Anne; Evans-Molina, Carmella; Roh, Hyun Cheol; Sims, Emily K.; Wek, Ronald C.Type 1 diabetes (T1D) accounts for 5-10% of all diabetes cases and results from immune-mediated destruction of pancreatic β-cells. Individuals with Darier Disease, which is caused by loss of function germline mutation(s) in the sarcoendoplasmic reticulum Ca2+-ATPase pump (SERCA2) gene, have an elevated risk of being diagnosed with T1D (risk ratio, 1.74; 95% CI, 1.13-2.69), suggesting a potential mechanistic relationship between SERCA2 and T1D pathogenesis. To determine the impact of reduced SERCA2 expression on T1D pathogenesis, we generated SERCA2 haploinsufficient mice by backcrossing C57BL6/J-S2+/- mice onto the non-obese diabetic (NOD) background (NOD-S2+/- mice). Female NOD-S2+/- mice showed accelerated T1D onset (14wks vs. 18wks, p<0.0001), elevated circulating anti-insulin antibodies, and increased immune cell infiltration into the islets compared to NOD-WT mice. Single-cell RNA sequencing (scRNA-seq) on islets and spatial proteomics on pancreatic lymph node (PLN) and spleen at 6 wks of age revealed increased immune cell presence in islets and enhanced B and T cell activation in PLN and spleen of NOD-S2+/- mice. Furthermore, scRNA-seq on isolated islets revealed temporal alterations in pathways related to mitochondria function in β cells, and mechanistic studies revealed decreased glucose-stimulated ATP production, reduced mitochondrial membrane potential, decreased islet expression of ATP synthase/mitochondrial complex III, increased mitochondrial Ca2+, and altered mitochondrial ultrastructure in NOD-S2+/- islets at 10 wks of age. In co-culture experiments, NOD-S2+/- B cells showed increased activation and NOD-S2+/- T cells showed increased proliferation and activation when cultured with NOD-WT islets. Interestingly, NOD-S2+/- islets induced B and T cell proliferation and T cell activation when cultured with NOD-WT immune cells. Lastly, administration of a small molecule SERCA activator in NOD-S2+/- mice decreased immune cell infiltration into the islet and delayed T1D onset. In summary, our results demonstrate a novel pathway whereby modulation of SERCA2 impacts islet mitochondrial function, islet immunogenicity, and immune cell proliferation and activation which fuel progression to T1D.Item Sex-dependent differential chromatin state changes in adipocytes across different fat depots during obesity(2023-08) Chaisakhon, Natthamon; Roh, Hyun Cheol; Mosley, Amber L.; Cornett, Evan M.Adipose tissue exhibits a high degree of plasticity and undergoes significant cellular remodeling in response to nutritional availability. While adipose tissue remodeling displays sexual dimorphism, its underlying molecular mechanisms remain poorly understood. In this study, we investigate the role of epigenetic modifications and gene expression in sexual dimorphism of adipose tissue in mice during obesity. We perform CUT&Tag (Cleavage Under Targets and Tagmentation) technique in conjunction with RNA-sequencing with female adipocytes from different fat depots and compare them to male mice. We find significant changes in H3K27ac, H3K27me3, H3K9me3 and RNA-seq after high fat diet (HFD) feeding. The changes are functionally characterized by a reduction in cellular metabolism and an elevation in cytoskeletal organization. Interestingly, these changes commonly occur in both visceral and subcutaneous fat depots with minor differences in females, which distinguishes them from males that exhibit differential responses between depots. Surprisingly, the chromatin states and expression profiles of female subcutaneous fat depots closely resemble those of male visceral adipose tissues during obesity. These results suggest that distinct responses across fat depots in male and females may contribute to different susceptibilities to metabolic diseases between the sexes. These findings enhance our understanding of the molecular mechanisms underlying adipocyte dysfunction during obesity and highlights the interplay between sex, adipose tissue depots, and metabolic responses.Item Uncoupling protein 1-driven Cre (Ucp1-Cre) is expressed in the epithelial cells of mammary glands and various non-adipose tissues(bioRxiv, 2023-10-22) Kim, Kyungchan; Wann, Jamie; Kim, Hyeong-Geug; So, Jisun; Rosen, Evan D.; Roh, Hyun Cheol; Biochemistry and Molecular Biology, School of MedicineObjective: Uncoupling protein 1 (UCP1), a mitochondrial protein responsible for nonshivering thermogenesis in adipose tissue, serves as a distinct marker for thermogenic brown and beige adipocytes. Ucp1-Cre mice are thus widely used to genetically manipulate these thermogenic adipocytes. However, evidence suggests that UCP1 may also be expressed in non-adipocyte cell types. In this study, we investigated the presence of UCP1 expression in different mouse tissues that have not been previously reported. Methods: We employed Ucp1-Cre mice crossed with Cre-inducible transgenic reporter Nuclear tagging and Translating Ribosome Affinity Purification (NuTRAP) mice, to investigate Ucp1-Cre expression in various tissues of adult female mice and developing embryos. Tamoxifen-inducible Ucp1-CreERT2 mice crossed with NuTRAP mice were used to assess active UCP1 expression. Immunostaining, RNA analysis, and single-cell/nucleus RNA-seq (sc/snRNA-seq) data analysis were performed to determine the expression of endogenous UCP1 and Ucp1-Cre-driven reporter expression. We also investigated the impact of UCP1 deficiency on mammary gland development and function using Ucp1-knockout (KO) mice. Results: Ucp1-Cre expression was observed in the mammary glands within the inguinal white adipose tissue of female Ucp1-Cre; NuTRAP mice. However, endogenous Ucp1 was not actively expressed as Ucp1-CreERT2 failed to induce the reporter expression in the mammary glands. Ucp1-Cre was activated during embryonic development in various tissues, including mammary glands, as well as in the brain, kidneys, eyes, and ears, specifically in epithelial cells in these organs. While sc/snRNA-seq data suggest potential expression of UCP1 in mammary epithelial cells in adult mice and humans, Ucp1-KO female mice displayed normal mammary gland development and function. Conclusions: Our findings reveal widespread Ucp1-Cre expression in various non-adipose tissue types, starting during early development. These results highlight the importance of exercising caution when interpreting data and devising experiments involving Ucp1-Cre mice.