Excessive astrocyte-derived neurotrophin-3 contributes to the abnormal neuronal dendritic development in a mouse model of fragile X syndrome.
Excessive astrocyte-derived neurotrophin-3 contributes to the abnormal neuronal dendritic development in a mouse model of fragile X syndrome.
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DOI：
10.1371/journal.pgen.1003172
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发表时间：
2012
期刊：
影响因子：
4.5
通讯作者：
Zhao MG
中科院分区：
文献类型：
--
作者：
Yang Q;Feng B;Zhang K;Guo YY;Liu SB;Wu YM;Li XQ;Zhao MG
脆性X综合征（FXS）是人类遗传性智力低下的一种形式，由Fmr 1基因中CGG重复序列的扩增引起。最近的研究表明星形胶质细胞在神经元发育中的作用。然而，参与FXS对星形胶质细胞的调控过程的机制仍不清楚。在这项研究中，我们发现，星形胶质细胞来源于脆性X模型，Fmr 1敲除（KO）小鼠，缺乏FMRP表达，抑制适当的阐述神经元的树突状过程在体外。此外，星形胶质细胞条件培养基（ACM）从KO星形胶质细胞抑制适当的树突状生长的野生型（WT）和KO神经元。通过转染KO星形胶质细胞中的FMRP载体诱导FMRP的表达，恢复了树突状形态和突触蛋白的水平。进一步的实验揭示了在KO ACM和Fmr 1 KO小鼠的前额叶皮层中神经营养因子-3（NT-3）的水平升高。然而，神经生长因子（NGF）、脑源性神经营养因子（BDNF）、胶质细胞源性神经营养因子（GDNF）和睫状神经营养因子（CNTF）的水平均正常。FMRP具有多个RNA结合基序，并参与翻译调控。RNA结合蛋白免疫沉淀（RIP）显示WT星形胶质细胞中NT-3 mRNA与FMRP相互作用。向培养基中添加高浓度的外源性NT-3降低了神经元树突和突触蛋白水平，而这些措施通过中和NT-3抗体或通过短发夹RNA（shRNA）敲低KO星形胶质细胞中的NT-3表达来改善。前额叶皮层显微注射WT星形胶质细胞或NT-3 shRNA感染的KO星形胶质细胞可挽救KO小鼠的微量恐惧记忆缺陷，同时降低前额叶皮层中NT-3水平。本研究表明，星形胶质细胞中过量的NT-3有助于神经元树突发育异常，星形胶质细胞可能是FXS的潜在治疗靶点。脆性X综合征是人类遗传性智力低下的一种形式，由Fmr 1基因中CGG重复序列的扩增引起。最近的研究表明，星形胶质细胞在神经元生长中发挥作用。在这项研究中，我们发现，星形胶质细胞来自脆性X模型，Fmr 1基因敲除（KO）小鼠，抑制体外神经元的树突状过程的适当阐述。过量的神经营养因子-3（NT-3）在来自Fmr 1 KO小鼠的星形胶质细胞中释放。在Fmr 1 KO星形胶质细胞中，通过中和抗体阻断NT-3和通过使用短发夹RNA（shRNAs）敲低NT-3可以拯救神经元树突发育。体内实验表明，前额叶皮层显微注射WT星形胶质细胞或NT-3 shRNA感染的KO星形胶质细胞挽救了KO小鼠的痕量恐惧记忆缺陷。这项研究提供的证据表明，缺乏FMRP导致NT-3的过度表达，从而减少神经元中的树突生长。
Fragile X syndrome (FXS) is a form of inherited mental retardation in humans that results from expansion of a CGG repeat in the Fmr1 gene. Recent studies suggest a role of astrocytes in neuronal development. However, the mechanisms involved in the regulation process of astrocytes from FXS remain unclear. In this study, we found that astrocytes derived from a Fragile X model, the Fmr1 knockout (KO) mouse which lacks FMRP expression, inhibited the proper elaboration of dendritic processes of neurons in vitro. Furthermore, astrocytic conditioned medium (ACM) from KO astrocytes inhibited proper dendritic growth of both wild-type (WT) and KO neurons. Inducing expression of FMRP by transfection of FMRP vectors in KO astrocytes restored dendritic morphology and levels of synaptic proteins. Further experiments revealed elevated levels of the neurotrophin-3 (NT-3) in KO ACM and the prefrontal cortex of Fmr1 KO mice. However, the levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), and ciliary neurotrophic factor (CNTF) were normal. FMRP has multiple RNA–binding motifs and is involved in translational regulation. RNA–binding protein immunoprecipitation (RIP) showed the NT-3 mRNA interacted with FMRP in WT astrocytes. Addition of high concentrations of exogenous NT-3 to culture medium reduced the dendrites of neurons and synaptic protein levels, whereas these measures were ameliorated by neutralizing antibody to NT-3 or knockdown of NT-3 expression in KO astrocytes through short hairpin RNAs (shRNAs). Prefrontal cortex microinjection of WT astrocytes or NT-3 shRNA infected KO astrocytes rescued the deficit of trace fear memory in KO mice, concomitantly decreased the NT-3 levels in the prefrontal cortex. This study indicates that excessive NT-3 from astrocytes contributes to the abnormal neuronal dendritic development and that astrocytes could be a potential therapeutic target for FXS. Fragile X syndrome is a form of inherited mental retardation in humans that results from expansion of a CGG repeat in the Fmr1 gene. Recent studies suggest that astrocytes play a role in neuronal growth. In this study, we find that astrocytes derived from a Fragile X model, the Fmr1 knockout (KO) mouse, inhibit the proper elaboration of dendritic processes of neurons in vitro. Excessive neurotrophin-3 (NT-3) is released in the astrocytes from Fmr1 KO mice. Blockage of NT-3 by neutralizing antibodies and knockdown of NT-3 by using short hairpin RNAs (shRNAs) in Fmr1 KO astrocytes can rescue the neuronal dendritic development. In vivo experiments show that prefrontal cortex microinjection of WT astrocytes or NT-3 shRNA–infected KO astrocytes rescues the deficit of trace fear memory in KO mice. This study provides the evidence that a lack of FMRP leads to an overexpression of NT-3, which reduces dendritic growth in neurons.
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DOI：
10.1083/jcb.85.3.890
发表时间：
1980-06
期刊：
The Journal of cell biology
影响因子：
--
作者：
McCarthy KD;de Vellis J
通讯作者：
de Vellis J
影响因子：
25
作者：
Ballas, Nurit;Lioy, Daniel T.;Grunseich, Christopher;Mandel, Gail
通讯作者：
Mandel, Gail
影响因子：
5.3
作者：
Haber, Michael;Zhou, Lei;Murai, Keith K.
通讯作者：
Murai, Keith K.
影响因子：
30.8
作者：
DEVYS, D;LUTZ, Y;MANDEL, JL
通讯作者：
MANDEL, JL
影响因子：
4.8
作者：
Fernandes, Brisa Simoes;Gama, Clarissa Severino;Kapczinski, Flavio
通讯作者：
Kapczinski, Flavio