GABAergic neurogenesis in humans and the effect of prematurity

描述(由申请人提供)：大约50%的早产儿会出现注意力不集中、多动症、自闭症、情绪障碍、社交能力低下、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。早产和相关的并发症--缺氧、低血压和败血症--会影响GABA能中间神经元的产生，并扰乱神经元电路。因此，我们询问中间神经元在妊娠后半期是如何发育的，以及早产是如何扰乱它们的生成、密度和分布的。回答这些问题将确定早产儿认知和行为障碍的基础。释放GABA的中间神经元构成了皮质抑制神经元的主要群体，并根据它们产生的神经肽进行分类。它们在人类的背侧室下区(SVZ)和腹侧SVZ(神经节隆起，GE)中都有产生，而在啮齿类动物中只在GE中产生。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，早产剥夺了婴儿缺氧的宫内环境以及胎盘激素和母体营养。尽管如此，中间神经元在怀孕后半期的发育还没有被研究过，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)随着胎龄的增加，中间神经元及其前体在密度、增殖和分布方面经历了明显的发育变化；b)早产儿干扰了它们的发生和分布。我们的方法是a)使用人类组织来研究妊娠晚期中间神经元的发育，以及b)使用人类样本和兔模型来评估早产对GABA能神经发生的影响。人类研究势在必行，因为人类的大脑皮层是独一无二的，比动物更复杂。目的1：晚生中间神经元的产生(20-40周)：观察胎儿和早产儿(20-40周)背侧SVZ和GE中GABA+、小白蛋白+、Calretinin+、生长抑素+亚型及其前体Nkx2.1+、Dlx1/2+、Mash1+和b)转录因子Nkx2.1、Dlx1/2、Lhx6、Mash1基因表达的变化。目的#2：早产对GABA能神经发生的影响：A)人：比较a)亚型中间神经元的密度和增殖；b)两组早产儿之间GE和背侧SVZ中它们的祖细胞(Dlx1/2+、Nkx2.1+和Mash1+)的密度和增殖情况：出生后长存活(24周+2周=26周)与短存活(26周++lt；3d=26周)--同等月经后年龄(胎龄+出生后)的早产(E29，3 d)和足月(E32，&lt；2小时大)与人类实验相同的绝经后年龄的幼崽。

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.