Enabling temporal and spatial restriction of MYT1L to identify molecular and postnatal circuit-level druggable targets

项目摘要 推测MTY1L基因功能丧失突变导致新定义的智力和发育 然而，这种关系背后的神经生物学机制仍不清楚。Myt1综合征 其特点是全球发育迟缓(特别是在运动和语言发育方面)、智力 残疾、高度渗透性肥胖和低眼压，以及自闭症谱系障碍和/或 注意力缺陷/多动障碍。可变外显的其他症状包括癫痫，小头畸形， 白质变薄和神经内分泌紊乱。到目前为止，已经描述了大约100名患者 临床和患病率估计为~1：2000。然而，Myt1l的功能研究才刚刚开始， 因此，我们目前对Myt1功能突变如何导致疾病知之甚少。我们最近 开发了第一个Myt11单倍体缺陷小鼠模型，成功地概括了许多患者 表型，包括多动症、交流行为的变化、社交行为挑战、肌肉 低眼压、小头畸形和肥胖。我们还发现了基因表达受阻，早熟神经元 分化是小头畸形的一种机制，成人的转录和染色质成熟失败。 因此，利用该模型，我们加深了对Myt1l功能的理解，并建立了临床前模型 Myt1l综合征。然而，它在发育过程中的什么时候，以及在大脑的什么地方受到干扰尚不清楚 Myt1蛋白的突变导致了每一种特定的临床相关表型。这是因为我们没有能力 明确定义Myt1l的相关分子和电路水平的靶标，识别这些靶标将使 潜在的抢救疗法的研究。为了开始解决这些漏洞，我们最近生成了一个Myt1l 与我们的结构性单倍体模型针对相同外显子的条件模型不足以支持空间和 Myt1l损失的时间限制。该项目的目标是验证该工具在时间和空间上的有效性 应用，并确定出生后Myt1l功能对表型的影响程度 在成人中观察，并确定出生后大脑中受Myt1l调控的基因。这些洞察力将有助于 帮助定义可用药的分子和电路靶点，以及Myt1l的治疗时间窗口 综合症。在目标1中，我们将验证我们的新工具，用于在时间和空间控制的 用于研究潜在的治疗作用的分子靶点。一个根本问题 如果Myt1l丢失中断，我们必须为这种罕见的疾病制定治疗策略 神经发育(即，在胚胎中)或神经维持(即，出生后和成人)。为了解决这个问题 这个问题，在目标2中，我们将利用我们新的条件模型和可诱导的Cre-重组酶遗传工具 在早期神经发育完成后，诱导出生后大脑中Myt1l的丢失，并确定 表型与Myt1l的出生后功能有关。最终，这一工具将指导未来的研究 Myt1l综合征的靶向治疗，以及潜在的其他相关IDDS。

Project Summary Putative loss of function mutations in the MTY1L gene lead to a newly defined intellectual and developmental syndrome, yet the neurobiological mechanisms underlying this relationship remain unknown. MYT1L Syndrome is characterized by global developmental delay (particularly in motor and language development), intellectual disability, highly penetrant obesity and hypotonia, and a significant subset with autism spectrum disorder and/or attention-deficit/hyperactivity disorder. Other symptoms of variable penetrance include epilepsy, microcephaly, white-matter thinning, and neuroendocrine disruptions. Thus far, about 100 patients have been described clinically and prevalence estimates are ~1:2000. However, the function of MYT1L has just begun to be studied, therefore, we currently know very little about how MYT1L loss of function mutations result in disease. We recently developed the first MYT1L haploinsufficient mouse model, which successfully recapitulated many of the patient phenotypes, including hyperactivity, changes in communicative behavior, social behavior challenges, muscle hypotonia, microcephaly, and obesity. We also identified disrupted gene expression, precocious neuronal differentiation as a mechanism for microcephaly, and failure of transcriptional and chromatin maturation in adults. Thus, with this model, we enhanced the understanding of MYT1L function and established a preclinical model of MYT1L Syndrome. However, it is unknown when during development, and where in the brain the disruption of MYT1L protein leads to each specific clinically-relevant phenotype. This is because we lack the ability to clearly define the relevant molecular and circuit-level targets of MYT1L, identification of which would enable studies of potential rescue therapies. To begin to address these holes, we recently generated a MYT1L conditional model targeting the same exon as our constitutive haploinsufficient model to allow for spatial and temporal restriction of MYT1L loss. The goal of this project is to validate this tool for temporal and spatial applications, and to determine the extent to which postnatal MYT1L function is responsible for the phenotypes observed in adults and identify the genes regulated by MYT1L in the postnatal brain. Such insights will serve to help define druggable molecular and circuit targets, as well as therapeutic temporal windows for MYT1L syndrome. In Aim 1, we will validate our new tool for inducing MYT1L loss in a temporally and spatially controlled manner and for enabling studies of molecular targets for potential therapeutic action. A fundamental question we must answer to develop therapeutic strategies for this rare disease is if MYT1L loss disrupts neurodevelopment (i.e, in the embryo) or neuromaintenance (i.e., postnatally, and in adults). In order to address this question, in Aim 2, we will leverage our new conditional model and inducible Cre-recombinase genetic tools to induce loss of MYT1L in the postnatal brain, after completion of early neurodevelopment, and determine which phenotypes are due to the postnatal functions of MYT1L. Ultimately, this tool will guide future studies into targeted therapies for MYT1L Syndrome, and potentially other related IDDs.