GABAergic neurogenesis in humans and the effect of prematurity

描述（由申请人提供）：约50%的早产儿存在注意力不集中、多动、自闭症、情绪障碍、社交能力不足、癫痫和智力低下。这些疾病归因于神经元回路中抑制性gaba能和兴奋性谷氨酸能传递之间的不平衡。早产及其相关并发症——缺氧、低血压和败血症——可影响gaba能中间神经元的生成并破坏神经回路。因此，我们想知道中间神经元在怀孕的后半段是如何发育的，以及早产是如何破坏它们的产生、密度和分布的。回答这些问题将决定早产儿童认知和行为障碍的基础。释放GABA的中间神经元构成皮层抑制性神经元的主要群体，并根据它们产生的神经肽进行分类。它们在人类中产生于背脑室下区（SVZ）和腹侧脑室下区（神经节隆起，GE），而在啮齿动物中仅产生于GE。它们的形成受转录因子Nkx2.1、Dlx1/2、Lhx6和Mash1的调控。早产会影响中间神经元的发育。这是因为氧气水平调节神经发生，早产剥夺了婴儿的低氧宫内环境以及胎盘激素和母体营养物质。尽管如此，中间神经元的发育尚未在怀孕后半期进行研究，也没有关于早产如何影响中间神经元的信息。因此，我们假设a)中间神经元及其前体随着胎龄的增加在密度、增殖和分布方面发生了明显的发育变化，b)早产破坏了它们的产生和分布。我们的方法是：a)使用人体组织研究妊娠后期中间神经元的发育；b)使用人类样本和兔子模型来评估早产对gaba能神经发生的影响。人类的研究是必要的，因为人类皮层是独特的，比动物更复杂。目的1：后期出生的中间神经元的产生（20-40周）：评估a)中间神经元亚型gaba +、parvalbumin+、calretinin+、somatostatin+及其前体Nkx2.1+、Dlx1/2+、Mash1+的增殖和密度，以及b)调节gaba能神经发生的转录因子Nkx2.1、Dlx1/2、Lhx6、Mash1的基因表达，在人类胎儿和早产儿（20-40周）的SVZ背和GE中。目的#2：早产对gaba能神经发生的影响：A)人类：比较两组早产儿之间的密度和增殖A)中间神经元亚型，和b)它们的祖细胞（Dlx1/2+, Nkx2.1+和Mash1+）在GE和SVZ背侧的密度和增殖-长产后生存（24周孕龄+ 2周大=26周）vs短产后生存（26周孕龄+ <3周大=26周）-等效月经后年龄（胎龄+出生后年龄）b) RABBIT模型：比较同等经后年龄的早产儿（E29, 3天大）和足月幼崽（E32,<2小时天大）在人体实验中的参数。

DESCRIPTION (provided by applicant): Inattention, hyperactivity, autism, emotional disturbance, social incompetence, epilepsy, and lower intellectual abilities are found in about 50% of preterm-born children. These disorders are attributed to an imbalance between inhibitory GABAergic and excitatory glutamatergic transmission in neuronal circuits. Premature birth and associated complications---hypoxia, hypotension, and sepsis--can affect the generation of GABAergic interneurons and disrupt neuronal circuitry. Therefore, we ask how interneurons develop in the second half of pregnancy, and how prematurity disrupts their generation, density, and distribution. Answering these questions will determine the bases of cognitive and behavioral disorders in preterm-born children. Interneurons releasing GABA constitute the major population of cortical inhibitory neurons and are classified based on the neuropeptides they produce. They are generated into both dorsal subventricular zone (SVZ) and ventral SVZ (ganglionic eminence, GE) in humans and only in GE in rodents. Their formation is regulated by transcription factors including, Nkx2.1, Dlx1/2, Lhx6, and Mash1. Prematurity can impact the development of interneurons. This is because oxygen level regulates neurogenesis and preterm birth deprives the infants of the hypoxic intrauterine environment along with the placental hormones and maternal nutrients. Despite this, the development of interneurons has not been studied in the second half of pregnancy and there is no information on how premature birth affects interneurons. Therefore, we hypothesize that a) interneurons and their precursors undergo distinct developmental changes in their density, proliferation, and distribution with advance in gestational age and that b) prematurity disrupts their generation and distribution. Our approach is to a) use human tissues for studying interneuron development in late pregnancy and b) employ both human samples and a rabbit model to assess the effect of prematurity on GABAergic neurogenesis. Human studies are imperative as the human cortex is unique and more complex than animals. Aim #1: Generation of late-born interneurons (20-40 weeks): Evaluate a) the proliferation and density of subtypes of interneurons-GABA+, parvalbumin+, calretinin+, somatostatin+-and their precursors-Nkx2.1+, Dlx1/2+, Mash1+, and b) gene expression of transcription factors regulating GABAergic neurogenesis, Nkx2.1, Dlx1/2, Lhx6, Mash1, in the dorsal SVZ and GE of human fetuses & preterm infants (20-40 weeks). Aim #2: Effect of prematurity on GABAergic neurogenesis: A) HUMAN: Compare the density and proliferation of a) subtypes of interneurons, and b) their progenitors (Dlx1/2+, Nkx2.1+, and Mash1+) in the GE and dorsal SVZ between two sets of premature infants- long postnatal survival (24 week gestational age + 2 week old=26 weeks) vs. short postnatal survival (26 wk gestation + <3d old=26 weeks)--of equivalent postmenstrual age (gestational age + postnatal age) B) RABBIT model: To compare preterm (E29, 3 d old) and term (E32,<2 h old) pups of an equivalent postmenstrual age for parameters as in human experiments.