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）的婴儿面临着立即发病和死亡的风险增加，以及长期的神经行为障碍（例如，注意缺陷多动障碍（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经很好地表征，但同时发生的神经行为障碍和特异性中枢神经系统（CNS）异常却很少受到关注。IUGR和神经行为障碍之间的联系机制尚不清楚，需要进一步研究，因为这些知识对早期诊断和干预至关重要。为了阐明这些问题，我们提出综合行为学、神经解剖学和表观遗传学的方法来理解IUGR对中枢神经系统的长期影响。利用一种具有良好特征的啮齿动物IUGR模型（给怀孕小鼠喂食低蛋白饮食），我们发现了ADHD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信号的改变已经被记录下来。我们的IUGR后代已经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，这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的低甲基化和表达增加，这是一个对多巴胺能细胞分化至关重要的基因，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以基因特异性的方式，以及在DNA甲基化中起重要作用的基因的表达显著增加，包括DNA甲基转移酶1 （DNMT1）和甲基CpG结合蛋白2 （MeCP2）。这一提议将验证母体低蛋白饮食直接影响发育中的中枢神经系统DNA甲基化的中心假设，从而导致行为改变和多巴胺功能障碍，其方式类似于在多动症中观察到的。在四个目标中，实验将(1)验证IUGR动物表现出与ADHD一致的行为特征的假设(2)检测多巴胺在中脑边缘/中脑皮层回路中的表达和功能(3)确定Cdkn1c过表达小鼠是否复制IUGR小鼠的行为或基因表达表型(4)完成IUGR小鼠中枢神经系统中差异甲基化基因的全基因组筛选。

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.