The peptide hormone ghrelin is important for both homeostatic and hedonic eating behaviors, and its orexigenic actions occur mainly via binding to the only known ghrelin receptor, the growth hormone secretagogue receptor (GHSR). GHSRs are located in several distinct regions of the central nervous system. This review discusses those central nervous system sites that have been found to play critical roles in the orexigenic actions of ghrelin, including hypothalamic nuclei, the hippocampus, the amygdala, the caudal brain stem, and midbrain dopaminergic neurons. Hopefully, this review can be used as a stepping stone for the reader wanting to gain a clearer understanding of the central nervous system sites of direct ghrelin action on feeding behavior, and as inspiration for future studies to provide an even-more-detailed map of the neurocircuitry controlling eating and body weight.

Recent large-scale genomic studies have classified medulloblastoma into four subtypes: Wnt, Shh, Group 3 and Group 4. Each is characterized by specific mutations and distinct epigenetic states. Previously, we showed that a chromatin regulator SMARCA4/Brg1 is required for Gli-mediated transcription activation in Sonic hedgehog (Shh) signaling. We report here that Brg1 controls a transcriptional program that specifically regulates Shh-type medulloblastoma growth. Using a mouse model of Shh-type medulloblastoma, we deleted Brg1 in precancerous progenitors and primary or transplanted tumors. Brg1 deletion significantly inhibited tumor formation and progression. Genome-wide expression analyses and binding experiments indicate that Brg1 specifically coordinates with key transcription factors including Gli1, Atoh1 and REST to regulate the expression of both oncogenes and tumor suppressors that are required for medulloblastoma identity and proliferation. Shh-type medulloblastoma displays distinct H3K27me3 properties. We demonstrate that Brg1 modulates activities of H3K27me3 modifiers to regulate the expression of medulloblastoma genes. Brg1-regulated pathways are conserved in human Shh-type medulloblastoma, and Brg1 is important for the growth of a human medulloblastoma cell line. Thus, Brg1 coordinates a genetic and epigenetic network that regulates the transcriptional program underlying the Shh-type medulloblastoma development.