A novel method for transient and repeatable axonal tracing in developing marmosets

项目总结 临床前神经发育障碍(NDDS)动物模型，包括自闭症谱系障碍(ASDS) 以及那些智力残疾的人，已经对候选遗传病因有了洞察力，但电路水平 行为改变(尤其是社会障碍)背后的假设仍然难以捉摸。一个 开发生物标记物和诊断工具的重大挑战一直是技术上的-因为规范 神经束追踪技术需要死后组织的组织学，电路的纵向评估 发展很少，相距甚远。为了解决这一关键的未得到满足的需求，我们提议开发一部小说， 一种暂时的、可重复的方法，它完全避开了侵入性组织化学，并允许纵向 恒河猴发育过程中轴突水平的追踪。常见的绒猴(Callithrix Jacchus)是理想的 用于研究与异常社会发展相关的回路轨迹的临床前建模物种。我们最近 发现绒猴和人类一样，在额叶皮质具有社会选择性的面部处理斑块。 因此，绒猴可以概括形成诊断标准的灵长类特有的社会行为。 对于许多NDD来说。在目标1中，我们将优化我们的方法，它使用经颅聚焦超声(FUS)来 将MnCl2，一种磁共振成像(MRI)可见的轴突示踪剂输送到大脑的任何指定区域。 在目标2中，我们试图证明FUS-MEMRI技术是一种可靠的发育筛查工具。 具有重测可靠性的电路级像差。我们将利用我们遗传多样性的繁育群体 绒猴研究自然产生的社会面孔加工差异的结构基础 很小的时候。从成年两个月开始，我们将使用fus-meri方法追踪轴突。 我们先前发现的社交选择性脸部斑块在内侧额叶皮质的连通性。这种迂回是 表面上参与了给面孔分配社交显着性，这是自闭症的典型特征缺陷。通过使用我们的 已经建立的fmri范式--这是被动的，可以用于非常年轻的绒猴--我们将把轴突 面孔社会加工中功能变异性的发展。此外，我们将使用训练有素的机器- 将凝视模式与相关面部特征分离的学习算法，提供人脸的行为指数 正在处理。通过这种非侵入性的多模式方法，我们将建立健康的可变性参数 在我们的绒猴种群中的电路，为遗传和药物模型奠定了基础 由我们的实验室和其他公司共同开发。这项工作将导致建立一种新的无创 纵向轴突追踪的方法是瞬时的、有针对性的和可重复的。这项技术将具有广泛的应用前景 在翻译研究中的应用，特别是在神经发育应用中，提供了一种非 侵袭性地追踪神经病理出现的电路功能障碍从年轻的时候。作为纵向的 技术，FUS-MEMRI方法也非常适合于追踪旨在确定 新陈代谢综合征早期治疗策略的疗效。

PROJECT SUMMARY Preclinical animal models of neurodevelopmental disorders (NDDs), including autism spectrum disorders (ASDs) and those of intellectual disabilities, have yielded insight into candidate genetic etiologies, but circuit-level hypotheses underlying behavioral alterations (particularly social impairments) have remained elusive. A significant challenge for developing biomarkers and diagnostic tools has been technological – because canonical neuronal tract-tracing techniques require histology of post-mortem tissue, longitudinal assessments of circuit development are few and far between. To address this critical unmet need, we propose to develop a novel, transient, and repeatable method that circumvents invasive histochemistry altogether and allows for longitudinal axonal-level tracing in developing marmoset monkeys. The common marmoset (Callithrix jacchus) is an ideal preclinical modeling species for studying circuit trajectories related to aberrant social development. We recently discovered that marmosets, like humans, possess socially selective face processing patches in frontal cortex. As such, marmosets can recapitulate primate-specific aspects of social behaviors that form the diagnostic criteria for many NDDs. In Aim 1, we will optimize our approach, which uses transcranial focused ultrasound (FUS) to deliver MnCl2, a magnetic resonance imaging (MRI)-visible axonal tracer to any prescribed region of the brain. In Aim 2, we seek to demonstrate that the FUS-MEMRI technique is a reliable screening tool for developmental circuit-level aberrations with test-retest reliability. We will leverage our genetically diverse breeding colony of marmosets to study the structural underpinnings of naturally occurring differences in social face processing from an early age. From two months into adulthood, we will employ the FUS-MEMRI method to track the axonal connectivity of our previously identified socially selective face patch in medial frontal cortex. This circuity is ostensibly involved in assigning social salience to faces, a classic hallmark deficit in ASDs. By employing our established fMRI paradigm – which is passive and can be used with very young marmosets – we will link axonal development to functional variability in social processing of faces. Further, we will employ trained machine- learning algorithms to isolate gaze patterns to relevant facial features, providing a behavioral index of face processing. With this noninvasive multimodal approach, we will establish parameters of healthy variability of this circuitry in our marmoset population, laying the groundwork for genetic and pharmacological models currently in development by our laboratory and others. This work will lead to the establishment of a novel noninvasive approach for longitudinal axonal tracing that is transient, targeted, and repeatable. This technique will have broad application in translational research, especially for neurodevelopmental applications, providing a means to non- invasively track the neuropathological emergence of circuit dysfunction from a young age. As a longitudinal technique, the FUS-MEMRI method is also well suited to track therapeutic outcomes aimed at determining the efficacy of early treatment strategies for NDDs.