Loss of Snord116 impacts lateral hypothalamus, sleep, and food-related behaviors

Imprinted genes are highly expressed in the hypothalamus, however whether specific imprinted genes affect hypothalamic neuromodulators and their functions is unknown. It has been suggested that Prader-Willi syndrome (PWS), a neurodevelopmental disorder caused by lack of paternal expression at the chromosome 15q11-q13, characterised with a hypothalamic insufficiency. Here we investigate the role of paternally expressed Snord116 gene within the context of sleep and metabolic abnormalities of PWS, and we report a novel role of this imprinted gene in the function and organisation of the two main neuromodulatory systems of the lateral hypothalamus (LH), namely the orexin (OX) and the melanin concentrating hormone (MCH). We observe that the dynamic between neuronal discharge in the LH and sleep-wake states of mice carrying the paternal deletion of the Snord116 (PWScrm+/p-) is compromised. This abnormal state-dependent neuronal activity is paralleled by a significant reduction of OX neurons in LH of mutants. Therefore, we propose that unbalance between OX- and MCH- expressing neurons in the LH of mutants reflects in a series of deficits manifested in the PWS, such as dysregulation of rapid eye movement (REM) sleep, food intake and temperature control. Investigation of the effect of loss of Snord116 and Sleep Deprivation (SD) on the hypothalamus transcriptome in both normal and PWScrm+/p− mutant mice (paternal Snord116 loss) by performing RNA-sequencing (RNA-seq).  The mice (3-5 per condition) were investigated at the beginning of the light period ZT0 (group 1, G1), six hours later at ZT6 (group 2, G2) and at same ZT6 but following 6-hrs of SD (group 3, G3).印记基因（imprinted genes）在下丘脑（hypothalamus）中呈高表达，但特定印记基因是否会影响下丘脑神经调质及其功能，目前仍不明确。普拉德-威利综合征（Prader-Willi syndrome, PWS）是一种因15号染色体15q11-q13区域父本表达缺失所引发的神经发育障碍，其特征为下丘脑功能不全。本研究针对父本表达的Snord116基因在普拉德-威利综合征睡眠与代谢异常中的作用展开探究，并揭示了该印记基因在外侧下丘脑（lateral hypothalamus, LH）两大主要神经调质系统——即食欲素（orexin, OX）与黑色素浓缩激素（melanin concentrating hormone, MCH）——的功能与组织架构中的全新作用。我们观察到，携带Snord116父本缺失的PWScrm+/p-型小鼠的外侧下丘脑神经元放电与睡眠-觉醒状态之间的动态平衡遭到破坏。这种依赖于状态的异常神经元活动，同时伴随突变小鼠外侧下丘脑中食欲素神经元数量的显著减少。因此，我们提出：突变小鼠外侧下丘脑中表达食欲素与黑色素浓缩激素的神经元失衡，可映射出普拉德-威利综合征所表现出的一系列功能缺陷，例如快速眼动（rapid eye movement, REM）睡眠失调、摄食异常与体温调控障碍。本研究通过RNA测序（RNA-sequencing, RNA-seq）技术，探究了Snord116缺失与睡眠剥夺（Sleep Deprivation, SD）对正常小鼠及父本Snord116缺失的PWScrm+/p-型突变小鼠下丘脑转录组的影响。本研究按实验条件每组设置3-5只小鼠，分别在光照周期开始时的ZT0时刻（第1组，G1）、6小时后的ZT6时刻（第2组，G2），以及在ZT6时刻但经历了6小时睡眠剥夺后的状态下（第3组，G3）对小鼠进行检测分析。