Developmental Regulation of Drug Processing Genes

描述（由申请人提供）：尽管最近在了解药物加工基因（即成人药物代谢酶和转运蛋白）的表达模式和调节机制方面取得了快速进展，但对儿科时期的这些却知之甚少。长期目标是了解药物加工基因的个体调控机制，以便在儿童中实现有效、安全的药物治疗。已知有几个因素对于正常发育至关重要，包括肝细胞核因子 11 (HNF11)、法尼醇 X 受体 (FXR)、生长激素 (GH) 信号传导和表观遗传影响。 HNF11 是早期肝脏发育的主要调节因子，调节大量药物加工基因的肝脏表达。主要通过 FXR 介导的胆汁酸信号通路的启动是围产期肝脏发育的标志。 GH 对于出生后肝基因表达和成熟至关重要。转录因子对靶基因的可及性很大程度上取决于组蛋白和 DNA 序列的甲基化/乙酰化状态。初步研究表明，在发育中的小鼠肝脏中，药物加工基因和转录因子以不同的动态模式表达，并与表观遗传特征相关。该提案的目的是阐明小鼠药物加工基因个体表达的调节机制。该提案的基本原理是，其成功完成将产生基础知识，为进一步了解人类儿科药理学奠定基础。中心假设是：药物加工基因的发育调节是由激素调节的连续事件，激素激活转录因子以修改表观遗传特征并调节基因表达。该假设将在两个目标中进行检验。目标 1 将确定药物加工基因的个体表达模式以及与转录因子和表观遗传特征的相关性。将检查雄性小鼠肝脏与肠道和肾脏中主要 I/II 相酶和药物转运蛋白的相对 mRNA 表达，并将其与转录因子和染色体修饰（全基因组 DNA 甲基化和组蛋白修饰）的表达相关联。目标 2 将使用相同的工作策略阐明转录因子和 GH 在确定 HNF11 缺失、FXR 缺失和 GH 缺陷 (lit/lit) 小鼠中药物加工基因的个体肝脏表达中的作用。这项研究是新颖的，因为它将使用全基因组方法来阐明激素和转录因子的改变如何调节药物加工基因的表观遗传特征和肝脏个体发育表达。这项研究意义重大，因为人们对儿科阶段肝脏药物处理基因的调控知之甚少。本研究的结果将：1）提供关于肝脏、肾脏和肠道中药物加工基因和核受体的个体表达模式的基础知识； 2) 帮助了解围产期激素和核受体的变化如何通过调节表观遗传特征影响药物加工基因的阶段特异性和长期表达。 公共健康相关性：拟议的研究对于治疗药物的吸收、分布、代谢和排泄中重要的基因的发育表达模式的调节机制具有重要意义，并且是一个尚未得到充分研究的领域。因此，这些发现有望适用于提高儿科药理学的疗效和安全性。

DESCRIPTION (provided by applicant): Despite recent rapid progress in understanding the expression patterns and regulatory mechanisms of drug processing genes, namely drug metabolizing enzymes and transporters in adults, little is known about these in the pediatric period. The long-term goal is to understand mechanisms of ontogenic regulation of drug processing genes, so that efficacious and safe drug treatments can be achieved in children. Several factors are known to be essential for normal development, including hepatocyte nuclear factor 11 (HNF11), farnesoid X receptor (FXR), growth hormone (GH) signaling, and epigenetic influences. HNF11, a master regulator of early liver development, regulates hepatic expression of a large battery of drug processing genes. Initiation of bile-acid signaling pathways, mediated largely via the FXR, is a hallmark of perinatal liver development. GH is essential for postnatal hepatic gene expression and maturation. The accessibility of transcription factors to the target genes is largely determined by the methylation/acetylation status of histones and DNA sequences. Preliminary studies illustrate that in developing mouse livers, drug processing genes and transcription factors are expressed in distinct dynamic patterns and correlate with epigenetic signatures. The objective of this proposal is to elucidate the regulatory mechanisms of ontogenic expression of drug processing genes in mice. The rationale of this proposal is that its successful completion will generate basic knowledge that will serve as the foundation for further understanding pediatric pharmacology in humans. The central hypothesis is: developmental regulation of drug processing genes is a sequential event regulated by hormones, which activate transcription factors to modify epigenetic signatures and regulate gene expression. This hypothesis will be tested in 2 aims. Aim 1 will determine the ontogenic expression patterns of drug processing genes and the correlation with transcription factors and epigenetic signatures. The relative mRNA expression of major phase I/II enzymes and drug transporters in male mouse livers versus intestine and kidney will be examined, and correlated with expression of transcription factors and chromosome modifications (genome-wide DNA methylation and histone modifications). Aim 2 will elucidate roles of transcription factors and GH in determining ontogenic hepatic expression of drug processing genes in HNF11-null, FXR-null, and GH deficiency (lit/lit) mice using the same working strategy. This study is novel, because it will use a genome-wide approach to elucidate how alterations of hormones and transcription factors modulate epigenetic signatures and hepatic ontogenic expression of drug processing genes. This study is significant, because little is known about the regulation of hepatic drug processing genes in pediatric stages. Results from this study will: 1) provide basic knowledge on the ontogenic expression patterns of drug processing genes and nuclear receptors in liver, kidney, and intestine; and 2) help to understand how perinatal alterations in hormones and nuclear receptors, via modulating epigenetic signatures, affect stage-specific and long-term expression of drug processing genes. PUBLIC HEALTH RELEVANCE: The proposed studies are of importance and an under-investigated area of regulatory mechanisms of the developmental expression patterns of genes important in the absorption, distribution, metabolism, and excretion of therapeutic drugs. Thus, the findings are expected to be applicable to the improvement of efficacy and safety of pediatric pharmacology.