Understanding the neurodevelopmental role and mechanism of histone demethylase JMJD3

JMJD3（KDM6B）是一种染色质调节剂，其作用对正常发育以及广泛的免疫调节具有重要意义。 人类疾病，包括癌症和人类神经障碍。例如，JMJD3中的突变是 家族性智力残疾的常染色体隐性遗传，新发JMJD3突变与 自闭症谱系障碍（ASD）。了解复杂疾病遗传原因的重要下一步 是在小鼠模型中研究疾病相关基因。虽然JMJD3对某些人来说很重要， 神经细胞发育方面，JMJD3缺乏是否真的会导致认知功能障碍， 不为人知。初步研究表明，JMJD 3对小鼠的发育至关重要 海马齿状回（DG）。在DG中，颗粒神经元在整个生命过程中从群体中产生， 神经干细胞（NSC）缺陷的DG神经发生损害许多海马依赖性行为， 与认知缺陷有关，包括智力残疾和ASD。如果没有Jmjd3， 成体DG中神经干细胞不能形成，颗粒神经元的产生严重减少 不正常在这些小鼠中，依赖于海马的学习是有缺陷的。杂合性缺失 Jmjd3也导致了DG的异常发育，表明这一过程对基因敏感， 剂量.目的1：研究Jmjd3在DG神经发生中的作用。体内实验将测试 假设Jmjd3调节DG NSC群体的出生后扩增和建立，以及 即使减少Jmjd3基因剂量也会导致认知功能障碍。单细胞RNA测序分析将 为观察到的表型提供分子见解，并帮助指导Aim 2的机制研究。目标二是 以确定JMJD3调节基因表达的机制。JMJD3具有脱甲基酶活性， 组蛋白3赖氨酸27三甲基化（H3K27me3），这是一种染色质修饰， 转录抑制研究脱甲基酶依赖性和潜在的脱甲基酶非依赖性 为了研究JMJD3的活性，我们开发了基于CRISPR的创新技术来招募JMJD3蛋白， 基因组通过开发一种新的，易于使用的方法来映射层相关域（LAD）-a 抑制性核区室-我们还发现NSC中的JMJD3在基因组LAD处富集 "边界"是富含转录调控元件的基因组区域。因此，我们建议 研究JMJD3在调节高级染色质结构方面的作用。拟议 神经发育和行为分析与机制研究相结合，预计将提供一个 科学框架，其中开始了解人类JMJD 3突变如何导致疾病。的 JMJD3机制的研究也有望对基于染色质的更广泛领域具有重要意义。 表观遗传学以及核室相关的基因组组织-一个新兴的研究领域。

JMJD3 (KDM6B) is a chromatin regulator with roles central to normal development as well as a wide range of human diseases including cancer and human neurological disorders. For instance, mutations in JMJD3 are autosomal recessive for familial intellectual disability, and de novo JMJD3 mutations are associated with autism spectrum disorder (ASD). An important next step to understanding genetic causes of complex diseases is to study disease-associated genes in mouse models. While it is known that JMJD3 is important to certain aspects of neural cell development, whether JMJD3 deficiency can actually cause cognitive dysfunction has not been known. Preliminary Studies indicate that JMJD3 is critical for the development of the mouse hippocampal dentate gyrus (DG). In the DG, granule neurons are generated throughout life from a population of neural stem cells (NSCs). Defective DG neurogenesis impairs many hippocampal-dependent behaviors and has been associated with cognitive deficits including that of intellectual disability and ASD. Without Jmjd3, NSCs failed to become established in the adult DG, and granule neuron production was severely decreased and abnormal. In these mice, hippocampal-dependent learning was defective. Heterozygous deletion of Jmjd3 also resulted in abnormal postnatal DG development, indicating that this process is sensitive to gene dosage. Aim 1 is to determine the role of Jmjd3 in DG neurogenesis. In vivo experiments will test the hypothesis that Jmjd3 regulates the postnatal expansion and establishment of the DG NSC population, and that even reduced Jmjd3 gene dosage causes cognitive dysfunction. Single cell RNA sequencing analysis will provide molecular insights into the observed phenotype and help guide mechanistic studies of Aim 2. Aim 2 is to determine the mechanisms by which JMJD3 regulates gene expression. JMJD3 has demethylase activity for histone 3 lysine 27 trimethylation (H3K27me3), which is a chromatin modification associated with transcriptional repression. To investigate demethylase-dependent and potential demethylase-independent activities of JMJD3, we have developed innovative CRISPR-based technologies to recruit JMJD3 proteins to the genome. By developing a novel, easy-to-use method for mapping lamina-associated domains (LADs) – a repressive nuclear compartment – we have also found that JMJD3 in NSCs is enriched at the genomic LAD “borders,” which are genomic regions enriched for transcriptional regulatory elements. Thus, we propose investigating the role of JMJD3 in regulating this aspect of higher-order chromatin structure. The proposed neurodevelopmental and behavioral analyses combined with mechanistic studies is expected to provide a scientific framework in which to begin understanding how human JMJD3 mutations can cause disease. The studies of JMJD3 mechanism is also expected to be important to the broader field of chromatin-based epigenetics as well as nuclear compartment-associated genome organization – an emerging area of research.