An Lmx1b-miR135a2 regulatory circuit modulates Wnt1/Wnt signaling and determines the size of the midbrain dopaminergic progenitor pool.
An Lmx1b-miR135a2 regulatory circuit modulates Wnt1/Wnt signaling and determines the size of the midbrain dopaminergic progenitor pool.
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DOI：
10.1371/journal.pgen.1003973
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发表时间：
2013
期刊：
影响因子：
4.5
通讯作者：
Awatramani R
中科院分区：
文献类型：
--
作者：
Anderegg A;Lin HP;Chen JA;Caronia-Brown G;Cherepanova N;Yun B;Joksimovic M;Rock J;Harfe BD;Johnson R;Awatramani R
microRNA在不同的生理情况下调节基因表达。它们在形态发生相关信号通路的控制中的作用研究较少，特别是在胚胎中枢神经系统（CNS）发育的背景下。在这里，我们揭示了microRNA在限制形态发生蛋白表达和功能的时空范围中的作用。Wnt 1是胚胎中脑中的关键形态原，并指导增殖、存活、图案化和神经发生。我们揭示了转录因子Lmx1b和新表征的microRNA miR135a2之间的自动调节负反馈环，miR135a2调节Wnt 1/Wnt信号传导的程度和多巴胺祖域的大小。条件性功能增益研究表明，Lmx1b促进Wnt 1/Wnt信号传导，从而增加中脑大小和多巴胺祖细胞分配。有条件地去除Lmx1b具有相反的效果，因为多巴胺前体结构域的扩增严重受损。接下来，我们提供的证据表明，microRNA参与限制多巴胺祖细胞分配。胚胎干细胞（ESC）中Dicer 1的条件性缺失导致扩增的Lmx 1a/B+祖细胞。相比之下，在体内早期窗口期间miR135a2的强制升高表型模仿Lmx1b条件性敲除。当En1：：Cre而不是Shh：：Cre或内斯：：Cre用于重组时，Lmx 1a/B+祖细胞的扩增被选择性地减少。生物信息学和荧光素酶分析数据表明，miR135a2靶向Lmx1b和Wnt信号通路中的许多基因，包括Ccnd1，Gsk3b和Tcf7l2。与此一致，我们证明该突变体显示Lmx1b/Wnt 1结构域的大小和典型Wnt信号传导范围的减少。我们认为，microRNA对早期中脑/峡部Lmx1b/Wnt轴的调节可以决定中脑的大小和多巴胺祖细胞的分配。由于经典的Wnt活性最近被认为是体外将ESC向多巴胺能命运编程的关键成分，因此这些研究可能会影响此类方案的合理设计。为了实现极其复杂的行为，哺乳动物的中枢神经系统由许多类型的神经元组成，每种神经元都有不同的功能。这些不同的神经元类型是在胚胎发育期间由神经祖细胞产生的。胚胎神经祖细胞如何被编程以产生不同的神经元类型，在正确的位置和数量，是发育神经科学的中心问题。我们专注于研究胚胎产生的一个关键神经元类型，中脑多巴胺神经元（mDA），这是特别脆弱的帕金森病（PD）。我们实验室和其他人以前的工作表明，Wnt信号对多巴胺神经元的产生至关重要。在这里，我们提供了一个机制，如何启动Wnt信号，然后下调。启动这一过程的关键是转录因子Lmx1b，而对下调过程很重要的是新表征的microRNA miR135a2。这些因素的数量平衡决定了胚胎发育过程中产生多少多巴胺神经元。这些研究将对从干细胞中有效编程多巴胺神经元产生直接影响，这是PD再生方法的关键目标。
MicroRNAs regulate gene expression in diverse physiological scenarios. Their role in the control of morphogen related signaling pathways has been less studied, particularly in the context of embryonic Central Nervous System (CNS) development. Here, we uncover a role for microRNAs in limiting the spatiotemporal range of morphogen expression and function. Wnt1 is a key morphogen in the embryonic midbrain, and directs proliferation, survival, patterning and neurogenesis. We reveal an autoregulatory negative feedback loop between the transcription factor Lmx1b and a newly characterized microRNA, miR135a2, which modulates the extent of Wnt1/Wnt signaling and the size of the dopamine progenitor domain. Conditional gain of function studies reveal that Lmx1b promotes Wnt1/Wnt signaling, and thereby increases midbrain size and dopamine progenitor allocation. Conditional removal of Lmx1b has the opposite effect, in that expansion of the dopamine progenitor domain is severely compromised. Next, we provide evidence that microRNAs are involved in restricting dopamine progenitor allocation. Conditional loss of Dicer1 in embryonic stem cells (ESCs) results in expanded Lmx1a/b+ progenitors. In contrast, forced elevation of miR135a2 during an early window in vivo phenocopies the Lmx1b conditional knockout. When En1::Cre, but not Shh::Cre or Nes::Cre, is used for recombination, the expansion of Lmx1a/b+ progenitors is selectively reduced. Bioinformatics and luciferase assay data suggests that miR135a2 targets Lmx1b and many genes in the Wnt signaling pathway, including Ccnd1, Gsk3b, and Tcf7l2. Consistent with this, we demonstrate that this mutant displays reductions in the size of the Lmx1b/Wnt1 domain and range of canonical Wnt signaling. We posit that microRNA modulation of the Lmx1b/Wnt axis in the early midbrain/isthmus could determine midbrain size and allocation of dopamine progenitors. Since canonical Wnt activity has recently been recognized as a key ingredient for programming ESCs towards a dopaminergic fate in vitro, these studies could impact the rational design of such protocols. To achieve exquisitely complex behavior, the mammalian CNS is comprised of numerous neuron types, each with different functions. These distinct neuron types are produced from neural progenitors during embryonic development. How the embryonic neural progenitors are programmed to produce distinct neuron types, in the correct position and number, is a central question in developmental neuroscience. We focused on studying the embryonic production of a key neuron type, the midbrain dopamine neuron (mDA), which is particularly vulnerable in Parkinson's disease (PD). Previous works from our lab and others have shown that Wnt signaling is critical for dopamine neuron production. Here we provide a mechanism for how Wnt signaling is initiated, and then downregulated. Key to initiating this process is a transcription factor, Lmx1b, whereas important to the downregulation process is a newly characterized microRNA, miR135a2. The quantitative balance of these factors determines how many dopamine neurons are produced during embryonic development. These studies will have direct implications for efficiently programming dopamine neurons from stem cells, a key goal of regenerative approaches for PD.
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影响因子：
10.5
作者：
DAVIS, CA;JOYNER, AL
通讯作者：
JOYNER, AL
影响因子：
5.2
作者：
Cajanek, Lukas;Ribeiro, Diogo;Arenas, Ernest
通讯作者：
Arenas, Ernest
影响因子：
4.6
作者：
Agarwala, S;Ragsdale, CW
通讯作者：
Ragsdale, CW
DOI：
10.1177/1073858410392382
发表时间：
2012-02
期刊：
The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry
影响因子：
--
作者：
He X;Yu Y;Awatramani R;Lu QR
通讯作者：
Lu QR
影响因子：
3.9
作者：
Gromak, Natalia
通讯作者：
Gromak, Natalia