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

描述（由申请人提供）：宫内生长迟缓（IUGR）影响约10%的美国婴儿。这些小于胎龄（SGA）的婴儿面临着增加的即时发病率和死亡率风险，以及长期的神经行为障碍（例如，注意力缺陷多动障碍（ADHD）、成瘾、精神分裂症）。虽然这些婴儿的不良代谢和心血管结局已得到很好的表征，但同时发生的神经行为障碍和特定的中枢神经系统（CNS）异常受到的关注明显较少。IUGR和神经行为障碍之间的联系机制知之甚少，需要进一步研究，因为这些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、神经解剖学和表观遗传学方法来了解IUGR对CNS的长期影响。使用一个特征良好的啮齿动物IUGR模型（低蛋白饮食喂养怀孕的小鼠），我们发现了ADHD的行为组成部分的证据，包括改变奖励处理和多动。这些行为涉及多巴胺（DA），并且在ADHD的动物模型和人类患者中，DA信号的改变已经被记录。我们的IUGR后代改变了控制多巴胺合成和活性的基因表达，这表明多巴胺能功能也因低蛋白饮食而改变，并可能成为观察到的神经行为变化的基础。我们还确定了IUGR动物中CDKN 1c的低甲基化和表达增加，这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，我们观察到甲基化的改变，无论是在全球范围内还是在基因特异性的方式，以及在DNA甲基化中发挥重要作用的基因的表达显着增加，包括DNA甲基转移酶1（DNMT 1）和甲基CpG结合蛋白2（MeCP 2）。该提案将测试中心假设，即母体低蛋白饮食直接影响发育中CNS的DNA甲基化，导致行为变化和多巴胺功能障碍，其方式与ADHD中观察到的相似。在四个目标中，实验将（1）测试IUGR动物表现出与ADHD一致的行为特征的假设（2）检查中脑边缘/中皮层回路中的多巴胺表达和功能（3）确定Cdkn 1c过表达小鼠是否复制IUGR小鼠的行为或基因表达表型和（4）完成IUGR小鼠CNS中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，宫内生长迟缓影响高达10%。这些婴儿可能有神经行为障碍，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，并可能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.