question: What is Snord116?
answer: SNORD116 is a small nucleolar (sno) RNA gene cluster (HBII-85) implicated as a major contributor the Prader-Willi phenotype. 
  SNORD116 genes appears to be responsible for the major features of PWS. 
  SNORD116 is a paternally expressed box C/D snoRNA gene cluster.
  The mouse C/D box snoRNA MBII-85 (SNORD116) is processed into at least five shorter RNAs using processing sites near known functional elements of C/D box snoRNAs.
  Snord116 expression in the medial hypothalamus, particularly within nuclei that are part of feeding circuitry. High expression of Snord116 was evident in the paraventricular (PVN) and ventromedial (VMH) nuclei, but particularly prevalent in the arcuate nucleus (ARC) according to in situ hybridization. Snord116 expression level in ventral hypothalamic dissections including ARC was significantly greater (by 2-fold) than that in cortex; and its expression level in dorsal hypothalamic dissections including PVN was double that in cortex. The enhanced expression pattern of Snord116 in hypothalamic nuclei was observed at weaning and young adult stages, but less obvious neonatally when expression was significantly more widespread. Therefore the expression of Snord116 likely is regulated developmentally.
  Snord116del mice with paternally derived deletion lack expression of this snoRNA. They have early-onset postnatal growth deficiency, but normal fertility and lifespan. While pituitary structure and somatotrophs are normal, liver Igf1 mRNA is decreased. In cognitive and behavior tests, Snord116del mice are deficient in motor learning and have increased anxiety. Around three months of age, they develop hyperphagia, but stay lean on regular and high-fat diet. On reduced caloric intake, Snord116del mice maintain their weight better than wild-type littermates, excluding increased energy requirement as a cause of hyperphagia. Normal compensatory feeding after fasting, and ability to maintain body temperature in the cold indicate normal energy homeostasis regulation. Metabolic chamber studies reveal that Snord116del mice maintain energy homeostasis by altered fuel usage. Prolonged mealtime and increased circulating ghrelin indicate a defect in meal termination mechanism. Snord116del mice, the first snoRNA deletion animal model, reveal a novel role for a non-coding RNA in growth and feeding regulation.