Role of histone ubiquitination in neurodevelopment and disease

在皮质发育过程中，神经前体细胞产生成熟的神经元亚型。 时间顺序。鼻咽癌多能性的限制决定了六层皮质神经元的组成 大脑皮层，并受鼻咽癌染色质变化的控制。皮质子代的异常产生是导致 以自闭症为特征的神经发育障碍的病理学。染色质重塑基因通常是 因此，在自闭症谱系障碍(ASD)中发现的神经元表观遗传机制可能是 对皮质醇生成来说是必不可少的。染色质景观中组蛋白修饰的发育重塑 允许对转录电路进行空间和时间调节，从而限制NPC的多能性。一个染色质 修饰是组蛋白H_2A赖氨酸119单泛素化(H_2AUb1)，这是一种进化保守的抑制物 组蛋白修饰的聚梳基(PcG)蛋白。我们最近发现人类从头开始占优势 PcG蛋白ASXL3(附加性梳状3)的致病变异是该病的遗传基础 具有自闭症和智力残疾症状的神经发育障碍。ASXL3显然发挥了作用 在哺乳动物的大脑功能中起着核心作用。我们建议用实验来描述ASXL3的机制 皮质醇生成的调控。我们已经证明ASXL3是多梳抑制基因的一个组成部分 脱泛素酶复合体(PR-DUB)，用于脱泛量化H_2AUb1。致病性人类ASXL3变异体改变 全基因组的H_2AUb1水平并影响患者来源细胞的转录调控。我们已经确认 并将这一发现扩展到老鼠和人类的神经前体细胞(NPC)中。尽管对H2AUb1进行了描述 三十多年前，它在转录调控和表观遗传抑制中的功能还不是很好。 比其他组蛋白修饰更容易理解。我们假设ASXL3依赖的去泛素化活性 在指定NPC转录程序方面发挥关键作用，这些程序有助于神经元的多样性 大脑皮层，最终，更高的大脑功能。我们将定义受调节的皮质发育机制 ASXL3和H2AUb1通过：(目标1)使用现有的Asx13突变小鼠，(目标2)确定全基因组 过量的H_2AUb1在鼻咽癌中的分布及其与皮质生的表观基因组学机制 转基因小鼠，以及(目标3)测试ASXL3病理和PR-DUB在人类中的保守性 神经发育的大脑器官模型。我们的实验策略将建立表观遗传学 皮质发育的基础，确定鼻咽癌中皮质神经发生的范例，并最终揭开 导致ASD病理的调节失调的机制。

During cortical development, neural progenitor cells (NPCs) produce mature neuronal subtypes in a defined temporal order. Restriction of NPC multipotency determines the cortical neuron composition of the six-layer cortex and is governed by changes to NPC chromatin. Abnormal production of cortical progeny underlies the pathology of neurodevelopmental disorders with features of autism. Chromatin remodeling genes are often identified in autism spectrum disorder (ASD), therefore, neuronal epigenetic mechanisms are likely to be essential for corticogenesis. Developmental remodeling of histone modifications across the chromatin landscape permits spatial and temporal regulation of transcription circuitry that restricts NPC multipotency. One chromatin modification is histone H2A lysine 119 mono-ubiquitination (H2AUb1), an evolutionarily conserved repressive histone modification of the Polycomb group (PcG) proteins. We recently identified human de novo dominant pathogenic variants in the PcG protein ASXL3 (Additional sex comb-like 3) as the genetic basis of neurodevelopmental disorders with syndromic features of autism and intellectual disability. ASXL3 clearly plays a central role in mammalian brain function. We propose experiments to delineate mechanisms of ASXL3 regulation in corticogenesis. We have shown that ASXL3 is a component of the Polycomb repressive deubiquitinase complex (PR-DUB), which deubiqutinates H2AUb1. Pathogenic human ASXL3 variants alter the genome-wide H2AUb1 levels and affect transcriptional regulation in patient-derived cells. We have confirmed and extended this finding in mouse and human neural progenitor cells (NPCs). Although H2AUb1 was described more than three decades ago, its functions in transcriptional regulation and epigenetic repression are less well understood than other histone modifications. We hypothesize that ASXL3-dependent deubiquitination activity plays a critical role in specifying NPC transcriptional programs that contribute to the neuronal diversity of the cortex, and, ultimately, higher brain function. We will define the cortical developmental mechanisms regulated by ASXL3 and H2AUb1 by: (Aim 1) using an existing Asxl3 mutant mice, (Aim 2) determining the genome-wide distribution of excess H2AUb1 in NPCs and the epigenomic mechanisms of corticogenesis using genetically- engineered mice, and (Aim 3) testing the conservation of ASXL3 pathology and PR-DUB activity in human cerebral organoid models of neural development. Our experimental strategy will establish the epigenetic foundation of cortical development, identify paradigms for cortical neurogenesis in NPCs, and, ultimately, unveil the mechanisms of dysregulation that leads to ASD pathology.