The role of transcription factor Pax6 in glutamatergic versus GABAergic cell fate determination in developing cerebral cortex

转录因子 Pax6 在发育中大脑皮层谷氨酸能细胞与 GABA 能细胞命运决定中的作用

• 批准号: BB/N006542/1
• 负责人: David Price
• 金额: $ 60.07万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FN006542%2F1
• 关键词: role; transcription; factor; Pax6; glutamatergic

The brain contains two major classes of neuron: (1) excitatory neurons, which transmit signals between cells by activating the neurons they connect to; (2) inhibitory neurons, which help keep the excitatory neurons in check by dampening down their activity. Both types are needed in the correct numbers for the brain to work normally. As well as doing different things, excitatory and inhibitory neurons look different and have different chemistries. These differences are created because, early in their existence, each type activates its own distinct set of genes that specify the way in which it develops. We have evidence implicating a protein called Pax6 in the high-level control of this specification process. Pax6 is a transcription factor, meaning that it binds to DNA at specific sites and controls many other genes. We have new data indicating that one of Pax6's most important functions during early embryonic development of the cerebral cortex is to prevent the activation of genes that would turn cells into inhibitory neurons and promote the activation of genes that would turn cells into excitatory neurons. In mouse, 70-80% of neurons in mature cerebral cortex are excitatory. They are generated within the cortex from cells that contain high levels of Pax6. The other 20-30% are inhibitory. In normal development, they are generated outside the cortex by cells that do not express Pax6 and they then migrate into the cortex. That is, the mouse cortex does not normally make its own inhibitory neurons. We have discovered that if Pax6 is removed specifically from cortical cells in the embryo, when they are just starting to make cortical neurons, these cells undergo a highly abnormal, rapid and powerful activation of genes that would be expected to promote the development of inhibitory neurons. In other words, they respond to Pax6 removal by altering their program of gene activation from a pro-excitatory to a pro-inhibitory one.Our finding raises two important questions. (1) What happens to cortical cells that undergo this early reprogramming? Do they go on to form mature inhibitory neurons, or do they later revert to an excitatory type, or do they make cells with a mixture of properties? (2) How does Pax6 normally prevent a pro-inhibitory and promote a pro-excitatory program of gene activation in the embryonic cortex? We aim to provide answers to these questions. To address the first question, we shall remove Pax6 from specifically the cortex in the embryo, using genetic methods, and examine the consequences at progressively older ages through to adulthood. At each age, we shall look at what genes are activated, whether the mutated cells contain proteins associated with inhibitory or excitatory neurons, what the cells look like and what their electrical properties are. To address the second question, we shall test a hypothesis supported by previous evidence suggesting that removal of Pax6 might promoted inhibitory neuron development because it allows abnormal cortical activation of another transcription factor, called Gsx2, that is not normally present in cortex and which can itself activate a pro-inhibitory program. In other words, we suggest that Gsx2 might mediate many of Pax6's actions. To test this hypothesis, we shall simultaneously remove Pax6 and prevent Gsx2 activation and then examine the consequences for inhibitory vs excitatory neuron development in the cortex. We shall assess the effects on neuronal type using methods mentioned above.In summary, we aim to provide new knowledge about the ways in which the cerebral cortex develops a correct balance of inhibitory vs excitatory neurons and also about the capacity of cortical neurons to alter how they develop when perturbed genetically.

大脑包含两大类神经元：(1)兴奋性神经元，通过激活细胞连接的神经元在细胞之间传递信号；(2)抑制性神经元，通过抑制兴奋性神经元的活动来帮助抑制兴奋性神经元的活动。这两种类型都需要正确的数字，大脑才能正常工作。除了做不同的事情外，兴奋性神经元和抑制性神经元看起来不同，化学成分也不同。之所以产生这些差异，是因为在它们存在的早期，每种类型都激活了自己独特的一组基因，这些基因指定了它们的发育方式。我们有证据表明，一种名为Pax6的蛋白质参与了这一特定过程的高级控制。Pax6是一种转录因子，这意味着它在特定的位置与DNA结合，并控制许多其他基因。我们有新的数据表明，Pax6‘S在大脑皮层早期胚胎发育过程中最重要的功能之一是阻止将细胞转变为抑制性神经元的基因的激活，以及促进将细胞转变为兴奋性神经元的基因的激活。在小鼠大脑皮质中，70-80%的成熟神经元是兴奋性的。它们是在皮质内由含有高水平Pax6的细胞产生的。其他20%-30%的人是抑制性的。在正常发育过程中，它们由不表达Pax6的细胞在皮质外产生，然后迁移到皮质。也就是说，小鼠的大脑皮质通常不会产生自己的抑制性神经元。我们已经发现，如果专门从胚胎的皮质细胞中移除Pax6，当它们刚刚开始制造皮质神经元时，这些细胞会经历一种高度异常、快速和强大的基因激活，这些基因有望促进抑制性神经元的发育。换句话说，他们对Pax6移除的反应是通过将他们的基因激活程序从支持兴奋的程序改变为支持抑制的程序。我们的发现提出了两个重要的问题。(1)经历这种早期重新编程的皮质细胞会发生什么？它们是继续形成成熟的抑制性神经元，还是后来恢复到兴奋型，或者它们使细胞具有多种特性？(2)Pax6通常如何阻止胚胎皮质中的前抑制和促进基因激活的前兴奋程序？我们的目标是为这些问题提供答案。为了解决第一个问题，我们将使用遗传方法，从胚胎的皮质中专门移除Pax6，并研究从逐渐增大的年龄到成年的后果。在每一个年龄段，我们将观察哪些基因被激活，突变的细胞是否含有与抑制性或兴奋性神经元相关的蛋白质，细胞是什么样子，以及它们的电学特性是什么。为了回答第二个问题，我们将测试一个假说，该假说得到了之前证据的支持，该假说表明，移除Pax6可能会促进抑制性神经元的发育，因为它允许另一种名为Gsx2的转录因子在大脑皮层异常激活，而Gsx2通常不存在于皮质中，它本身可以激活亲抑制程序。换句话说，我们认为Gsx2可能介导了Pax6‘S的许多动作。为了验证这一假设，我们将同时移除Pax6和阻止Gsx2激活，然后检查大脑皮质中抑制性和兴奋性神经元发育的后果。我们将使用上述方法评估对神经元类型的影响。综上所述，我们的目标是提供关于大脑皮层如何发展抑制性神经元和兴奋性神经元的正确平衡的新知识，以及皮质神经元在受到基因干扰时改变其发育方式的能力。

项目成果

Loss of Pax6 Causes Regional Changes in Dll1 Expression in Developing Cerebral Cortex.

Pax6 的缺失会导致发育中的大脑皮层中 Dll1 表达的区域变化。

• DOI: 10.3389/fncel.2019.00078
• 发表时间: 2019
• 期刊: Frontiers in cellular neuroscience
• 影响因子: 5.3
• 作者: Dorà E

Pax6 limits the competence of developing cerebral cortical cells to respond to inductive intercellular signals.

• DOI: 10.1371/journal.pbio.3001563
• 发表时间: 2022-09
• 期刊: PLoS biology
• 影响因子: 9.8

Pax6 Lengthens G1 Phase and Decreases Oscillating Cdk6 Levels in Murine Embryonic Cortical Progenitors.

• DOI: 10.3389/fncel.2018.00419
• 发表时间: 2018
• 期刊: Frontiers in cellular neuroscience
• 影响因子: 5.3
• 作者: Mi D;Manuel M;Huang YT;Mason JO;Price DJ
• 通讯作者: Price DJ

Lateral cortical Cdca7 expression levels are regulated by Pax6 and influence the production of intermediate progenitors.

• DOI: 10.1186/s12868-017-0365-0
• 发表时间: 2017-06-05
• 期刊: BMC neuroscience
• 影响因子: 2.4
• 作者: Huang YT;Mason JO;Price DJ
• 通讯作者: Price DJ

Expression of Barhl2 and its relationship with Pax6 expression in the forebrain of the mouse embryo.

• DOI: 10.1186/s12868-016-0311-6
• 发表时间: 2016-11-25
• 期刊: BMC neuroscience
• 影响因子: 2.4
• 作者: Parish EV;Mason JO;Price DJ
• 通讯作者: Price DJ