Project description:Melanoma exhibits numerous transcriptional cell states including neural crest-like cells as well as pigmented melanocytic cells. How these different cell states relate to distinct tumorigenic phenotypes remains unclear. Here, we use a zebrafish melanoma model to identify a transcriptional program linking the melanocytic cell state to a dependence on lipid droplets, the specialized organelle responsible for lipid storage. Single-cell RNA-sequencing of these tumors show a concordance between genes regulating pigmentation and those involved in lipid and oxidative metabolism. This state is conserved across human melanoma cell lines and patient tumors. This melanocytic state demonstrates increased fatty acid uptake, an increased number of lipid droplets, and dependence upon fatty acid oxidative metabolism. Genetic and pharmacologic suppression of lipid droplet production is sufficient to disrupt cell cycle progression and slow melanoma growth in vivo. Because the melanocytic cell state is linked to poor outcomes in patients, these data indicate a metabolic vulnerability in melanoma that depends on the lipid droplet organelle.
Project description:Lipid droplets (LDs) store lipids for metabolic energy and are central to cellular lipid homeostasis. The mechanisms coordinating lipid storage in LDs with cellular metabolism are unclear but relevant to obesity-related diseases. Here we utilized genome-wide screening to identify genes that modulate lipid storage in human macrophages, a cell type relevant to metabolic diseases. Among ~550 genes regulating lipid storage, we identify MLX, a basic helix-loop-helix leucine-zipper transcription factor that regulates multiple metabolic processes. We show that MLX and family members MLXIP/MondoA and MLXIPL/ChREBP bind LDs via C-terminal amphipathic helices. When LDs increase in cells, LD binding of MLX, MLXIP/MondoA, and MLXIPL/ChREBP reduces their transcriptional activity, whereas the absence of LDs results in hyperactivation. Our findings uncover an unexpected component to a lipid storage response, in which binding of MLX transcription factors to the LD surface modulates their activity, adjusting the expression of metabolic genes to lipid storage levels.
Project description:Lipid droplets are fat storage organelles composed of a protein envelope and a lipid rich core. Dynamic regulation of this protein envelope underlies differential lipid droplet formation and function in diverse cell types. In melanoma, the ability to form lipid droplets has been linked to tumor progression and metastasis, but it is not known whether lipid droplet proteins play a role in these phenotypes. To address this, we performed proteomic analysis of the lipid droplet envelope in melanoma. We found that proteins expressed in the lipid droplet were differentially enriched in distinct melanoma states, ranging from melanocytic to neural crest like. DHRS3, which is involved in the conversion of all-trans-retinal to all-trans-retinol, is significantly upregulated in the MITFLO/neural crest-like melanoma cell state, and markedly reduced in the MITFHI/melanocytic state. Increased DHRS3 expression is sufficient to drive the MITFHI/melanocytic cells to a more undifferentiated and invasive state. These changes are due to retinoic acid mediated regulation of melanocytic genes through the retinoid X receptors (RXR). Our data demonstrate that melanoma cell state can be regulated by expression of lipid droplet proteins which affect downstream retinoid signaling.
Project description:Lipid droplets (LDs) store lipids for metabolic eneergy and are central to cellular lipid homeostasis. The mechanisms coordinating lipid storage in LDs with cellular metabolism are unclear but relevant to obesity-related diseases. Here we utilized genome-wide screening to identify genes that modulate lipid storage in human macrophages, a cell type relevant to metabolic diseases. Among ~550 genes regulating lipid storage, we identify MLX, a basic helix-loop-helix leucine-zipper transcription factor that regulates multiple metabolic processes. We show that MLX and family members MLXIP/MondoA and MLXIPL/ChREBP bind LDs via C-terminal amphipathic helices. When LDs increase in cells, LD binding of MLX, MLXIP/MondoA, and MLXIPL/ChREBP reduces their transcriptional activity, whereas the absence of LDs results in hyperactivation. Our findings uncover an unexpected component to a lipid storage response, in which binding of MLX transcription factors to the LD surface modulates their activity, adjusting the expression of metabolic genes to lipid storage levels.
Project description:We tried to find out the contribution of lipid droplets formation-related genes during adipogenesis to osteoblastogenesis through RNA-Seq technique. Among the seventy-nine documented genes, APOB (apolipoprotein B), CES1 (carboxylesterase 1), and CIDEC (cell death inducing DFFA like effector c) were differentially expressed during osteoblastogenesis. We further confirmed gene function of APOB during osteoblastogenesis using lentivirus vector system. This study would provide the vital clues and molecular targets for balance regulation of hMSCs differentiation and new treatment strategy in metabolic bone diseases.
Project description:Liver regeneration is an well orchestrated compensatory process that regulated by multiple factors. We recently reported the importance of chromatin protein, a high-mobility group box 2 (HMGB2) in mouse liver regeneration, however, it’s molecular mechanism is not yet understood. In this study, we aimed to study how HMGB2 regulates hepatocyte proliferation during liver regeneration. Wild-type (WT) and HMGB2-knockout (KO) mice were 70% partial hepatectomized (PHx), and liver tissues were analyzed by microarray, immunohistochemistry, qPCR and western blotting. In vivo experimental findings were confirmed by in vitro experiments using HMGB2 gene knockdown in combination with de novo lipogenesis model. In WT mouse, HMGB2-positive hepatocytes were co-localized with cell proliferation markers, whereas, hepatocyte proliferation was significantly decreased in HMGB2-KO mice. Oil red-O staining detected the transient accumulation of lipid droplets at 12-24 h in WT mouse livers, however, decreased amount of lipid droplets were found in HMGB2-KO mouse livers, and it was prolonged until 36 h. Microarray, immunohistochemistry and qPCR results were demonstrated that lipid metabolism related genes were significantly decreased in HMGB2-KO mouse livers. In vitro experiments demonstrated that decreased lipid droplets in HMGB2-knockdown cells correlated with decreased cell proliferation activity. HMGB2 is involved in the regulation of liver regeneration through transient accumulation of lipid droplets in hepatocytes.
Project description:Lipid droplets (LDs) are multifunctional organelles consisting of a central compartment of non-polar lipids shielded from the cytoplasm by a phospholipid monolayer. The excessive accumulation of lipid droplets in cells is closely related to the development and progression of many diseases in humans and animals, such as liver-related and cardiovascular diseases. Thus, regulating the LDs size and abundance is necessary to maintain metabolic homeostasis. In this study, we found that LPS stimulation reduced the LDs content in the mouse liver. We tried to explain the possible molecular mechanisms at the broad protein and mRNA levels, finding that inhibition of the peroxisome proliferator-activated receptors (PPAR) signalling pathway by LPS may be a critical factor in reducing LDs content.