Project description:The nervous system has a tremendous capacity for experience-dependent plasticity. In response to changes in activity induced by environmental cues, many types of neurons undergo a process known as homeostatic plasticity, which serves to maintain overall network function in the face of mounting experience-dependent changes in synaptic strengths. Homeostatic plasticity involves both changes in synaptic scaling and regulation of intrinsic excitability. Increases in spontaneous firing and excitability of sensory neurons are evident in some forms of chronic pain in both animal models and in human patients. However, it is not known whether homeostatic plasticity is engaged in sensory neurons under normal conditions or whether dysfunction in these homeostatic mechanisms might contribute to the pathophysiology of chronic pain. To address these questions, we tested the impact of sustained depolarization on various measures of excitability in mouse and human sensory neurons. Depolarization induced by 30mM KCl induces a compensatory decrease in the excitability of both mouse and human sensory neurons. Moreover, we also find that voltage-gated sodium currents are robustly inhibited in mouse sensory neurons after chronic depolarization, thus contributing to the overall decrease in neuronal excitability and serving as a potential regulatory mechanism to drive intrinsic neuronal homeostatic control. Our results indicate that mouse and human sensory neurons undergo homeostatic regulation of intrinsic excitability in response to sustained depolarization. Decreased efficacy of these homeostatic mechanisms could potentially contribute to the development of pathological conditions, including chronic pain.
Project description:Dietary nutrients interact with the gene networks to orchestrate adaptive responses during metabolic stress. Tissue metabolic reprogramming is frequently linked to induction of pathways with pathophysiological consequences. Here we identified Baf60a as a diet-sensitive subunit of the SWI/SNF chromatin-remodeling complexes in the liver that links the consumption of fat- and cholesterol-rich diet to elevated plasma cholesterol levels. The expression of Baf60a in the liver was elevated following western diet feeding. Hepatocyte-specific inactivation of Baf60a reduced bile acid production and intestinal cholesterol absorption, and attenuated diet-induced hypercholesterolemia and atherosclerosis in mice. At the mechanistic level, Baf60a stimulates the expression of hepatic genes involved in bile acid synthesis, modification, and transport through a CAR/Baf60a feedforward regulatory loop. Baf60a is required for the recruitment of the SWI/SNF chromatin-remodeling complexes to facilitate an activating epigenetic switch on the CAR target genes. These studies elucidate an unexpected regulatory pathway that mediates the hyperlipidemic and atherogenic effects of western diet consumption. We used microarrays to elucidate the role of hepatic Baf60a in the regulation of lipid metabolism.
Project description:Although KMT2D, also known as MLL2, is known to play an essential role in development, differentiation, and tumor suppression, its role in pancreatic cancer development is not well understood. Here, we discovered a novel signaling axis mediated by KMT2D, which links TGF-β to the activin A pathway. We found that TGF-β upregulates a microRNA, miR-147b, which in turn leads to post-transcriptional silencing of KMT2D. Loss of KMT2D induces the expression and secretion of activin A, which activates a non-canonical p38 MAPK-mediated pathway to modulate cancer cell plasticity, promote a mesenchymal phenotype, and enhance tumor invasion and metastasis in mice. We observed a decreased KMT2D expression in human primary and metastatic pancreatic cancer. Furthermore, inhibition or knockdown of activin A reversed the pro-tumoral role of KMT2D loss. These findings support a tumor-suppressive role of KMT2D in pancreatic cancer and identify miR-147b and activin A as novel therapeutic targets.