Spatiotemporal Regulation of Intestinal Gene Expression

描述(申请人提供)：乳糖酶不持久(成人型乳汁过长)导致消化系统对乳糖的吸收不良，乳糖是牛奶中存在的碳水化合物大量营养素。最近发现了与肠道乳糖酶持久性和非持久性相关的人类DNA序列变体。这项研究的重点是描述人类肠道乳糖酶持久性的遗传决定因素。我们以前已经在细胞培养和活体动物中描述了调控大鼠乳糖酶基因肠道特异性表达的分子机制。我们现在将把注意力集中在人类乳糖酶基因持续和非持续的分子机制以及啮齿类动物乳糖酶的暂时下降上。初步研究表明，乳糖酶基因多态区域的DNA序列可以结合核蛋白，增强乳糖酶启动子的活性。我们假设，与乳糖酶持久性相关的DNA多态通过与特定核蛋白转录因子的差异相互作用来调节成人肠上皮细胞乳糖酶基因的转录。因此，研究目标旨在确定人类乳糖酶持久性的遗传决定因素的机制作用。在目标1中，我们将描述与人类乳糖酶基因转录持续相关的DNA多态的功能作用。乳糖酶基因多态的功能特征将在细胞培养和转基因小鼠体内进行研究。在目标2中，我们将定义调控人乳糖酶持久性基因转录的分子机制。这一目标的目的是鉴定和鉴定与乳糖酶持久性相关的乳糖酶基因多态区域中能够与DNA序列相互作用的核蛋白，并表征核蛋白是否具有调节乳糖酶转录的功能。在目标3中，为了补充我们对人类乳糖酶持久性机制的研究，我们将进一步阐明啮齿类动物乳糖酶暂时下降的机制。对人类乳糖酶基因表达调控机制的了解可能为未来导致上皮细胞消化功能丧失或不适当获得的胃肠道疾病提供新的诊断、治疗或预后策略。我们的体外和体内实验方法的结合将阐明与乳糖酶持久性和非持久性相关的遗传决定因素的作用。与公共卫生相关：成人型乳汁过少，乳糖酶不持久，使世界上许多成人人口无法忍受过量食用牛奶和其他乳制品。然而，在一些成年人中，高水平的乳糖酶活性可能由于遗传了阻止乳糖酶表达正常成熟下降的基因突变而持续到成年。了解消化乳糖酶基因的表达调控机制可能为促进消化酶在肠道疾病中的表达提供新的策略，并将对了解其他基因随年龄增长的调控具有广泛的意义。

DESCRIPTION (provided by applicant): Lactase non-persistence (adult-type hypolactasia) results in digestive system malabsorption of lactose, the carbohydrate macronutrient present in milk. Human DNA sequence variants associated with intestinal lactase persistence and non-persistence have recently been identified. This research project focuses on characterization of the genetic determinants of intestinal lactase persistence in humans. We have previously characterized molecular mechanisms regulating intestine-specific expression of the rat lactase gene in cell culture and in living animals. We will now direct attention to characterization of the molecular mechanisms mediating human lactase gene persistence and non- persistence and the temporal decline of lactase in rodents. Preliminary studies have shown that DNA sequences in the region of lactase gene polymorphisms can bind nuclear proteins and enhance lactase promoter activity. We hypothesize that DNA polymorphisms associated with lactase persistence function to regulate lactase gene transcription in adult human enterocytes via differential interaction with specific nuclear protein transcription factors. Research objectives are therefore aimed at defining the mechanistic roles of genetic determinants of human lactase persistence. In Aim 1, we will characterize a functional role for DNA polymorphisms associated with persistence of lactase gene transcription in humans. Functional characterization of lactase gene polymorphisms will be investigated in cell culture and in vivo in transgenic mice. In Aim 2, we will define the molecular mechanisms regulating human lactase persistence gene transcription. The goals of this aim will be to identify and characterize nuclear proteins capable of interacting with DNA sequences in the region of lactase gene polymorphisms associated with lactase persistence and to characterize whether the nuclear proteins function to regulate lactase transcription. In Aim 3, to complement our investigation of the mechanism of lactase persistence in humans, we will further elucidate mechanisms regulating the temporal decline of lactase in rodents. Knowledge of mechanisms regulating human lactase gene expression may provide future novel diagnostic, therapeutic or prognostic strategies for gastrointestinal disorders that result in loss or inappropriate gain of epithelial cell digestive function. Our combination of in vitro and in vivo experimental approaches will elucidate roles for the genetic determinants associated with lactase persistence and non-persistence. PUBLIC HEALTH RELEVANCE: Adult-onset hypolactasia, lactase non-persistence, renders much of the world's adult human population intolerant of excessive consumption of milk and other dairy products. In some adults, however, high levels of lactase enzyme activity persist in adulthood presumably due to inheritance of a genetic mutation that prevents the normal maturational decline in lactase expression. Knowledge of mechanisms regulating expression of the digestive lactase gene may provide novel strategies for enhancing expression of digestive enzymes in intestinal diseases and will have broad implications for understanding regulation of other genes with aging.