Activity-dependent transcription influences neuronal connectivity, but the roles and mechanisms of inactivation of activity-dependent genes have remained poorly understood. Genome-wide analyses in the mouse cerebellum revealed that the nucleosome remodeling and deacetylase (NuRD) complex deposits the histone variant H2A.z at promoters of activity-dependent genes, thereby triggering their inactivation. Purification of translating mRNAs from synchronously developing granule neurons (Sync-TRAP) showed that conditional knockout of the core NuRD subunit Chd4 impairs inactivation of activity-dependent genes when neurons undergo dendrite pruning. Chd4 knockout or expression of NuRD-regulated activity genes impairs dendrite pruning. Imaging of behaving mice revealed hyperresponsivity of granule neurons to sensorimotor stimuli upon Chd4 knockout. Our findings define an epigenetic mechanism that inactivates activity-dependent transcription and regulates dendrite patterning and sensorimotor encoding in the brain.
Heart muscle is metabolically versatile, converting energy stored in fatty acids, glucose, lactate, amino acids, and ketone bodies. Here, we use mouse models in ketotic nutritional states (24 h of fasting and a very low carbohydrate ketogenic diet) to demonstrate that heart muscle engages a metabolic response that limits ketone body utilization. Pathway reconstruction from microarray data sets, gene expression analysis, protein immunoblotting, and immunohistochemical analysis of myocardial tissue from nutritionally modified mouse models reveal that ketotic states promote transcriptional suppression of the key ketolytic enzyme, succinyl-CoA:3-oxoacid CoA transferase (SCOT; encoded by Oxct1), as well as peroxisome proliferatoractivated receptor ␣-dependent induction of the key ketogenic enzyme HMGCS2. Consistent with reduction of SCOT, NMR profiling demonstrates that maintenance on a ketogenic diet causes a 25% reduction of myocardial 13 C enrichment of glutamate when 13 C-labeled ketone bodies are delivered in vivo or ex vivo, indicating reduced procession of ketones through oxidative metabolism. Accordingly, unmetabolized substrate concentrations are higher within the hearts of ketogenic diet-fed mice challenged with ketones compared with those of chow-fed controls. Furthermore, reduced ketone body oxidation correlates with failure of ketone bodies to inhibit fatty acid oxidation. These results indicate that ketotic nutrient environments engage mechanisms that curtail ketolytic capacity, controlling the utilization of ketone bodies in ketotic states.The mammalian heart must maintain constant levels of ATP to perform its mechanical and electrical functions. A variety of experimental approaches have established that cardiomyopathy is associated with changes in cardiac energy metabolism and that altered energy metabolism can cause cardiomyopathy (1-5). In the normal adult heart, mitochondrial oxidative phosphorylation provides more than 95% of the ATP generated. Substrate utilization is dynamic, and metabolic flexibility under differing physiological conditions is an important adaptive property of myocardium (6 -8). Adaptations over time are
NH dialysis provides a means for dialysing our most ill and debilitated patients in the convenience and comfort of the NH setting. The success of this programme is demonstrated by the fact that almost 40% of patients are successfully rehabilitated and discharged home. Nonetheless, healthcare providers and families must recognize that patients entering an NH HD programme are a high risk population with significant morbidity and mortality. Compared with established dialysis patients, patients entering the NH programme who are new to dialysis represent a particularly high risk group. However, it is likely that the poor survival seen in the NH programme may represent end of life care, as the overall survival from initiation of chronic dialysis in this population is consistent with that of patients entering the ESRD programme at a similar age.
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