Development of neuronal subtypes and local circuits in the hippocampus

项目摘要/摘要 在大脑发育期间，神经元必须适当地分化成不同的亚型，才能健康地组装起来 电路。因此，这一过程的中断可能会影响神经结构和连接，并导致紊乱 如自闭症、精神分裂症和癫痫。海马体是一种大脑结构，对学习和 记忆，它的功能在这些障碍中受到损害。CA1区兴奋性锥体细胞为 海马区计算的主要输出到其他脑区。这些单元格可以根据它们的 CA1内的物理位置为“深”或“浅”。深部和浅部海马区锥体细胞 不同类型的神经元，表现出不同的分子特征，电生理特性， 传入输入的来源，以及与局部抑制性中间神经元的电路连接。确定 它们分化的机制对于理解海马的发育和功能至关重要。 无论是健康还是疾病。CA1区浅层锥体细胞优先表达转录因子 调节因子Satb2，通过改变染色质结构来控制基因表达。在人类中，基因突变 Satb2会导致发育迟缓、智力残疾、癫痫和自闭症行为。我们的初步数据 表明在小鼠早期发育过程中敲除Satb2基因会干扰浅表性神经细胞的分化 CA1区锥体细胞。此外，还有非细胞自主的变化，以迁移和生存 与对照组相比，突变小鼠中间神经元的不同亚型。在本提案中，有三个具体的 AIMS将验证关于早期表达Satb2对海马锥体细胞是必要的假设 CA1的分化和电路发育，而后期的表达是必要的，以促进经验- 依赖突触可塑性。这些实验将在小鼠身上使用分子遗传学工具来有条件地 在发育的早期和晚期，敲除锥体细胞中的Satb2。AIM 1将使用 电生理学和电刺激研究不同传入来源的强度和可塑性 急性脑片向深、浅层CA1区锥体细胞投射。这一目标将检验这一假设，即早期 Satb2的表达是建立传入输入强度差异所必需的，而后者的表达是 对于这些输入的活动驱动的突触可塑性是必要的。Aim 2将使用成对的全细胞录音 锥体细胞(深层和浅层)和已识别的中间神经元亚型之间的关系，以映射电路和 研究它们突触生理的细节。这一目标将检验早期Satb2表达是 在局部抑制性中间神经元和浅层锥体细胞之间建立回路模体是必要的，而 后来的表达是必要的，以招募新的抑制性突触，以响应环境的丰富。目标 3将使用单细胞RNA-seq和atac-seq来确定Satb2基因敲除如何改变基因表达和 CA1在多个发育时间点的染色质可及性。这一目标将提供分子洞察力 Satb2如何通过发育控制CA1的基因表达，以及它的功能如何随着时间的推移而变化。

PROJECT SUMMARY/ABSTRACT During brain development, neurons must properly differentiate into distinct subtypes to assemble healthy circuits. Thus, disruption of this process can impact neural architecture and wiring, and contribute to disorders such as autism, schizophrenia, and epilepsy. The hippocampus is a brain structure crucial for learning and memory, and its function is compromised in these disorders. Excitatory pyramidal cells in area CA1 provide a major output of hippocampal computations to other brain regions. These cells can be parsed based on their physical position within CA1 as “deep” or “superficial.” Deep and superficial hippocampal pyramidal cells are distinct classes of neurons that exhibit differential molecular signatures, electrophysiological properties, sources of afferent input, and circuit connectivity with local inhibitory interneurons. Determining the mechanisms underlying their differentiation is crucial for understanding hippocampal development and function in both health and disease. Superficial pyramidal cells in CA1 preferentially express the transcriptional regulator Satb2, which controls gene expression by modifying chromatin structure. In humans, mutations of Satb2 cause developmental delay, intellectual disability, epilepsy, and autistic behaviors. Our preliminary data show that knocking out Satb2 during early development in mice disrupts the differentiation of superficial pyramidal cells in CA1. Furthermore, there are non-cell-autonomous changes to the migration and survival of distinct subtypes of interneurons in mutant mice relative to controls. In the present proposal, three specific aims will test the hypothesis that early expression of Satb2 is necessary for hippocampal pyramidal cell differentiation and circuit development in CA1, while later expression is necessary to promote experience- dependent synaptic plasticity. These experiments will use molecular genetic tools in mice to conditionally knock out Satb2 from pyramidal cells during both early and late developmental stages. Aim 1 will use electrophysiology and electrical stimulation to study the strength and plasticity of different sources of afferent input to deep and superficial CA1 pyramidal cells in acute slices. This aim will test the hypothesis that early Satb2 expression is necessary to establish differences in afferent input strength, while later expression is necessary for activity-driven synaptic plasticity of these inputs. Aim 2 will use paired whole-cell recordings between pyramidal cells (deep and superficial) and identified subtypes of interneurons to map circuits and study details of their synaptic physiology. This aim will test the hypothesis that early Satb2 expression is necessary to establish circuit motifs between local inhibitory interneurons and superficial pyramidal cells, while later expression is necessary to recruit new inhibitory synapses in response to environmental enrichment. Aim 3 will use single-cell RNA-seq and ATAC-seq to determine how Satb2 knockout alters gene expression and chromatin accessibility in CA1 at multiple developmental timepoints. This aim will provide molecular insight into how Satb2 controls gene expression in CA1 through development, and how its function may change over time.