RESUMEN
Animals adapt to varying environmental conditions by modifying the function of their internal organs, including the brain. To be adaptive, alterations in behavior must be coordinated with the functional state of organs throughout the body. Here we find that thyroid hormone- a prominent regulator of metabolism in many peripheral organs- activates cell-type specific transcriptional programs in anterior regions of cortex of adult mice via direct activation of thyroid hormone receptors. These programs are enriched for axon-guidance genes in glutamatergic projection neurons, synaptic regulators across both astrocytes and neurons, and pro-myelination factors in oligodendrocytes, suggesting widespread remodeling of cortical circuits. Indeed, whole-cell electrophysiology recordings revealed that thyroid hormone induces local transcriptional programs that rewire cortical neural circuits via pre-synaptic mechanisms, resulting in increased excitatory drive with a concomitant sensitization of recruited inhibition. We find that thyroid hormone bidirectionally regulates innate exploratory behaviors and that the transcriptionally mediated circuit changes in anterior cortex causally promote exploratory decision-making. Thus, thyroid hormone acts directly on adult cerebral cortex to coordinate exploratory behaviors with whole-body metabolic state.
RESUMEN
Targeted activation of endogenous genes is an important approach for cell engineering. Here, we report that the nuclease-deactivated dCas9 fused to a transcriptional activator (VPR) and an epigenetic effector (the catalytic domain of histone acetyltransferase p300core) simultaneously, sequentially, or as a single quadripartite effector can lead to enhanced activation of target genes. The composite activator, VPRP, behaves more efficiently than individual activators across a set of genes in different cell types. We characterize off-target effects for host chromatin acetylation and transcriptome using the effectors. Our work demonstrates that transcriptional and epigenetic effectors can be used together to enhance gene activation and suggests the need for further optimization of epigenetic effectors to reduce off-targets.