In utero programming of the dopamine system: behavior, neuroanatomy & epigenetics

描述(由申请人提供)：胎儿宫内发育迟缓(IUGR)影响大约10%的美国婴儿。这些小于胎龄(SGA)的婴儿面临着立即发病率和死亡率以及长期神经行为残疾(例如注意力缺陷多动障碍(ADHD)、成瘾、精神分裂症)的风险增加。虽然这些婴儿的不良代谢和心血管结局有很好的特点，但同时发生的神经行为障碍和特定的中枢神经系统(CNS)异常却明显较少受到关注。IUGR和神经行为障碍之间的联系机制还不清楚，值得进一步研究，因为这种知识对于早期诊断和干预至关重要。为了阐明这些问题，我们建议整合行为学、神经解剖学和表观遗传学的方法来了解IUGR对中枢神经系统的长期影响。使用一个具有良好特征的啮齿动物IUGR模型(喂养怀孕小鼠的低蛋白饮食)，我们发现了ADHD的行为成分的证据，包括改变的奖励处理和多动。这些行为涉及多巴胺(DA)，在ADHD的动物模型和人类患者中，DA信号的变化都已被记录在案。我们的IUGR后代改变了控制多巴胺合成和活动的基因的表达，这表明低蛋白饮食也改变了多巴胺能功能，可能是观察到的神经行为变化的基础。我们还在IUGR动物中发现了CDKN1c的低甲基化和高表达，CDKN1c是多巴胺能细胞分化的关键基因，可能会改变多巴胺能神经元的发育轨迹。此外，我们观察到全球和基因特有的甲基化改变，以及在DNA甲基化中起重要作用的基因表达的显著增加，包括DNA甲基转移酶1(DNMT1)和甲基CpG结合蛋白2(MeCP2)。这项提议将检验核心假设，即母亲的低蛋白饮食直接影响发育中的中枢神经系统的DNA甲基化，导致行为变化和多巴胺功能障碍，与ADHD的观察方式类似。实验将有四个目标：(1)检验IUGR动物表现出与ADHD一致的行为特征的假设；(2)检测中脑边缘/中皮质回路中的多巴胺表达和功能；(3)确定过表达CDKN1c的小鼠是否复制了IUGR小鼠的行为或基因表达表型；(4)完成对IUGR小鼠中枢神经系统差异甲基化基因的全基因组筛选。 公共卫生相关性： 在美国出生的所有婴儿中，胎儿宫内发育迟缓的比例高达10%。这些婴儿可能会有神经行为障碍，包括注意力缺陷多动障碍(ADHD)的风险增加。本申请中提出的实验将使用动物模型来探索这些大脑和行为变化的潜在机制，并潜在地确定可能的干预途径。

DESCRIPTION (provided by applicant): Intrauterine growth retardation (IUGR) affects approximately 10% of all US infants. These small-for- gestational age (SGA) babies face increased risk for immediate morbidity and mortality, as well as long-term neurobehavioral disabilities (e.g., attention deficit hyperactivity disorder (ADHD), addiction, schizophrenia). While adverse metabolic and cardiovascular outcomes have been well characterized in these infants, the coincident neurobehavioral disabilities and specific central nervous system (CNS) abnormalities have received significantly less attention. The mechanisms linking IUGR and neurobehavioral disabilities are poorly understood and warrant further investigation, as this knowledge is critical for early diagnosis and intervention. To shed light on these issues, we propose the integration of behavioral, neuroanatomical, and epigenetic approaches to understand the long-term CNS impact of IUGR. Using a well-characterized rodent IUGR model (low protein diet fed to pregnant mice), we have found evidence for behavioral components of ADHD, including altered reward processing and hyperactivity. These behaviors involve dopamine (DA), and in both animal models of and human patients with ADHD, alterations in DA signaling have been documented. Our IUGR offspring have altered expression of genes that control dopamine synthesis and activity, suggesting that dopaminergic function is also altered as a result of the low protein diet and may underlie the observed neurobehavioral changes. We have also identified hypomethylation and increased expression of CDKN1c in IUGR animals, a gene critical for dopaminergic cell differentiation, which may alter the developmental trajectory of dopaminergic neurons. Additionally, we observe altered methylation, both globally and in a gene-specific manner, as well as significant increases in the expression of genes that play an important role in DNA methylation, including DNA methyltransferase 1 (DNMT1) and methyl CpG binding protein 2 (MeCP2). This proposal will test the central hypothesis that maternal low protein diet directly affects DNA methylation in the developing CNS, leading to behavioral changes and dopamine dysfunction, in a manner similar to what is observed in ADHD. In four aims, experiments will (1) test the hypothesis that IUGR animals demonstrate a behavioral profile consistent with ADHD (2) examine dopamine expression and function within the mesolimbic/ mesocortical circuitry (3) determine whether Cdkn1c overexpressing mice replicate the behavioral or gene expression phenotype of the IUGR mice and (4) complete a genome-wide screen of differentially methylated genes in the CNS of IUGR mice. PUBLIC HEALTH RELEVANCE: Intrauterine growth retardation affects up to 10% of all babies born in the US. These babies can have neurobehavioral disabilities, including an increased risk for attention deficit hyperactivity disorder (ADHD). Experiments proposed in this application will use an animal model to explore the underlying mechanisms for these brain and behavior changes and potentially identify possible avenues of intervention.