Data_Sheet_1_Down-Regulation of miRNA-708 Promotes Aberrant Calcium Signaling by Targeting Neuronatin in a Mouse Model of Angelman Syndrome.PDF

The expression of ubiquitin ligase UBE3A is paternally imprinted in neurons and loss of function of maternally inherited UBE3A causes Angelman syndrome (AS), a neurodevelopmental disorder characterized by severe intellectual disability and motor disturbances. Over activation of UBE3A is also linked with autism. Mice deficient for maternal Ube3a (AS mice) exhibit various behavioral features of AS including cognitive and motor deficits although the underlying molecular mechanism is poorly understood. Here, we investigated possible involvement of miRNA in AS pathogenesis and identified miR-708 as one of the down-regulated miRNA in the brain of AS mice. This miR-708 targets endoplasmic reticulum resident protein neuronatin (a developmentally regulated protein in the brain) leading to decrease in intracellular Ca2+. Suppression of miR-708 or ectopic expression of neuronatin increased the level of intracellular Ca2+ and phosphorylation of CaMKIIα at Thr286. Neuronatin level was significantly increased in various brain regions of AS mice during embryonic and early postnatal days as well as in parvalbumin-positive GABAergic neurons during adulthood with respect to age-matched wild type controls. Differentiated cultured primary cortical neurons obtained from AS mice brain also exhibited higher expression of neuronatin, increased intracellular basal Ca2+ along with augmented phosphorylation of CaMKIIα at Thr286. These results indicate that miR-708/neuronatin mediated aberrant calcium signaling might be implicated in AS pathogenesis.

泛素连接酶（ubiquitin ligase）UBE3A在神经元中呈父本印记表达，母本遗传的UBE3A功能丧失会导致安格曼综合征（Angelman syndrome，AS）——一种以重度智力障碍和运动障碍为特征的神经发育障碍。UBE3A的过度激活也与自闭症相关。母本Ube3a缺陷型小鼠（AS小鼠）表现出安格曼综合征的多种行为表型，包括认知与运动缺陷，但其潜在分子机制尚不清楚。本研究探究了微小RNA（microRNA，miRNA）在安格曼综合征发病机制中的潜在作用，并鉴定出miR-708是AS小鼠脑组织中下调的微小RNA之一。该miR-708可靶向内质网驻留蛋白神经调节素（neuronatin，一种脑内发育调控蛋白），进而导致细胞内钙离子（Ca²+）水平降低。抑制miR-708或异位表达神经调节素均可提升细胞内钙离子水平，以及钙/钙调蛋白依赖性蛋白激酶Ⅱα（CaMKIIα）在Thr286位点的磷酸化水平。与同龄野生型对照相比，AS小鼠胚胎期及出生早期的多个脑区，以及成年小鼠的小白蛋白阳性γ-氨基丁酸能神经元（parvalbumin-positive GABAergic neurons）中的神经调节素水平均显著升高。从AS小鼠脑组织中分离的分化原代皮层神经元（primary cortical neurons）同样表现出神经调节素表达升高、细胞内基础钙离子水平上升，以及CaMKIIα在Thr286位点的磷酸化水平增强。上述结果表明，miR-708/神经调节素介导的异常钙信号通路可能参与安格曼综合征的发病过程。