Rheb activation in subventricular zone progenitors leads to heterotopia, ectopic neuronal differentiation, and rapamycin-sensitive olfactory micronodules and dendrite hypertrophy of newborn neurons.
Rheb activation in subventricular zone progenitors leads to heterotopia, ectopic neuronal differentiation, and rapamycin-sensitive olfactory micronodules and dendrite hypertrophy of newborn neurons.
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DOI：
10.1523/jneurosci.1840-12.2013
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发表时间：
2013-02-06
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影响因子：
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通讯作者：
Bordey A
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作者：
Lafourcade CA;Lin TV;Feliciano DM;Zhang L;Hsieh LS;Bordey A
Tsc 1杂合子小鼠围产期神经祖细胞（NPC）中的mTOR过度活跃导致异位和异常神经元形态发生，如在结节性硬化症患者中所见。考虑到病理性高活性mTOR也发生在不携带基因突变的个体中，我们检查了野生型小鼠新生NPC中mTOR活性的增加是否会重演上述表型。将编码组成型活性Rheb（RhebCA）的质粒电穿孔到室管膜下区NPC中增加了新生细胞中的mTOR活性。在电穿孔（dpe）后19天，观察到异位和异位细胞的神经元形态沿着迁移路径（RMS）和嗅球（OB）。这些异位细胞表现出动作电位，并接受突触输入，将其识别为突触整合神经元。RMS异位包含星形胶质细胞、神经元和包埋的神经母细胞。在3 dpe的免疫染色显示Mash1+ Olig2−细胞在迁移路线中的存在，伴随着异位神经元分化，并在7 dpe改变了成神经细胞迁移的方向和速度，这表明非细胞自主的迁移中断。在>19 dpe时，新生的RhebCA表达神经元显示分布改变，并在OB中形成微结节。此外，它们表现出树突复杂性增加沿着膜生物物理学改变和GABA能突触输入频率增加。雷帕霉素治疗可显著预防OB异位、微结节和树突肥大，表明其具有mTOR依赖性。总的来说，这些数据表明，野生型小鼠的新生NPC中mTOR活性的增加概括了在Tsc 1突变小鼠中观察到的病理学。此外，在没有已知突变的个体中增加mTOR活性可能会显著影响神经发生和回路形成。
mTOR hyperactivity in perinatal neural progenitor cells (NPCs) of Tsc1-heterozygote mice leads to heterotopia and abnormal neuronal morphogenesis as seen in patients with tuberous sclerosis. Considering that pathological hyperactive mTOR also occurs in individuals carrying no genetic mutations, we examined whether increasing mTOR activity in neonatal NPCs of wild-type mice would recapitulate the above phenotypes. Electroporation of a plasmid encoding constitutively active Rheb (RhebCA) into subventricular zone NPCs increased mTOR activity in newborn cells. At 19 days post-electroporation (dpe), heterotopia and ectopic cells with a neuronal morphology were observed along the migratory path (RMS) and in the olfactory bulb (OB). These ectopic cells displayed action potentials and received synaptic inputs identifying them as synaptically integrated neurons. RMS heterotopias contained astrocytes, neurons, and entrapped neuroblasts. Immunostaining at 3 dpe revealed the presence of Mash1+ Olig2− cells in the migratory route accompanied by ectopic neuronal differentiation and altered direction and speed of neuroblast migration at 7 dpe, suggesting a non-cell autonomous disruption of migration. At >19 dpe, newborn RhebCA-expressing neurons displayed altered distribution and formed micronodules in the OB. In addition, they displayed increased dendritic complexity along with altered membrane biophysics and increased frequency of GABAergic synaptic inputs. OB heterotopia, micronodules and dendrite hypertrophy were notably prevented by rapamycin treatment, suggesting their mTOR-dependence. Collectively, these data show that increasing mTOR activity in neonatal NPCs of wild-type mice recapitulate the pathologies observed in Tsc1 mutant mice. In addition, increased mTOR activity in individuals without known mutations could significantly impact neurogenesis and circuit formation.