Animal Model to Study Retinoic Acid Function in Postnatal and Adult Tissues

描述（由申请人提供）：在多种分泌的细胞间信号因子中，视黄酸（retinoic acid， RA）的独特之处在于它是一种小分子，通过进入靶细胞的细胞核，作为核受体的配体与靶基因结合，直接调节基因表达。维生素A（视黄醇）是一种必需的营养素，作为RA合成的前体，通过两步代谢途径，视黄醇转化为视黄醛，然后转化为RA。小鼠基因敲除研究已经确定，RA信号是由三种RA受体和三种视黄醛脱氢酶控制的，这些酶执行RA合成的最后一步。由于RA信号的消除会导致胚胎死亡，因此在揭示RA生理作用方面取得的重大成功仅来自于对胚胎发育过程中RA功能的分析。给予类风湿性关节炎或抑制类风湿性关节炎合成或受体活性的药物表明，类风湿性关节炎也可能控制许多成人功能，包括海马神经发生、免疫功能、精子发生、干细胞功能、皮肤和毛囊再生以及预防癌症。然而，与基因敲除方法相比，这些方法更容易产生伪影和误解，并且可能无法准确显示出生后或成人RA功能。因此，本项目的目标是建立一个成功的遗传模型来分析RA的产后功能。根据这一目标，我们将开发缺乏视黄醛合成的敲除小鼠。视黄醇和视黄醛的相互转化是可逆的，并且在整个机体中广泛发生，而视黄醇和视黄醛的相互转化是可逆的。因此，我们提出，缺乏视黄醛合成的模式生物如果维持在补充视黄醛的饮食中，将能够在出生后存活。基因敲除研究支持存在三种将视黄醇转化为RA合成和存活所需的视黄醛的酶，即视黄醇脱氢酶-10 （RDH10）和两种醇脱氢酶（ADH3和ADH4）。Rdh10基因敲除小鼠由于缺乏RA合成而在妊娠期间死亡，而Adh3或Adh4基因敲除小鼠在出生后被放置在缺乏维生素a的饮食中死亡。为了建立成人RA功能模型，我们建议：(1)建立膳食视黄醛治疗，使Rdh10基因敲除者和Rdh10能够在出生后存活；缺乏RDH10和所有形式ADH的ADH -del化合物敲除；(2)从Rdh10和Rdh10中提取视黄醛；Adh-del敲除小鼠在出生后检查存活率并确定哪些组织降低或消除了RA活性；(3)对Rdh10和Rdh10进行芯片研究；Adh-del敲除小鼠（视黄醛）来鉴定各种组织中的RA靶基因是研究界广泛关注的问题。

DESCRIPTION (provided by applicant): Among the various secreted intercellular signaling factors, retinoic acid (RA) is unique in that it is a small molecule that directly regulates gene expression by entering the nucleus of target cells and binding to target genes by acting as a ligand for nuclear receptors. Vitamin A (retinol) is an essential nutrient that serves as a precursor for RA synthesis through a two step metabolic pathway in which retinol is converted to retinaldehyde which is then converted to RA. Gene knockout studies in mice have determined that RA signaling is controlled by three RA receptors and three retinaldehyde dehydrogenases that perform the last step of RA synthesis. Major success in unraveling the physiological roles of RA has come only for analysis of RA function during embryonic development since elimination of RA signaling leads to embryonic lethality. Administration of RA or drugs that inhibit RA synthesis or receptor activity suggests that RA may also control many adult functions including hippocampal neurogenesis, immune function, spermatogenesis, stem cell function, skin and hair follicle regeneration, and prevention of cancer. However, these approaches are more prone to artifacts and misinterpretation compared with gene knockout approaches, and may not reveal an accurate view of postnatal or adult RA function. Thus, the goal of this project is to develop a successful genetic model for analysis of RA function postnatally. Pursuant to this goal, we will develop a knockout mouse lacking retinaldehyde synthesis. In contrast to metabolism of retinaldehyde to RA, which is irreversible and tissue-specific, interconversion of retinol and retinaldehyde is reversible and occurs widely throughout the organism. Therefore, we propose that a model organism lacking retinaldehyde synthesis will be able to survive postnatally if maintained on a retinaldehyde-supplemented diet. Gene knockout studies support the existence of three enzymes that convert retinol to retinaldehyde needed for RA synthesis and survival, i.e. retinol dehydrogenase-10 (RDH10) and two alcohol dehydrogenases (ADH3 and ADH4). Rdh10 knockout mice die during gestation due to lack of RA synthesis, and Adh3 or Adh4 knockout mice die postnatally when placed on a vitamin A deficient diet. In order to generate a model for adult RA function, we propose to: (1) Establish a dietary retinaldehyde treatment that will allow postnatal survival of Rdh10 knockouts and Rdh10;Adh-del compound knockouts lacking RDH10 and all forms of ADH; (2) Withdraw retinaldehyde from Rdh10 and Rdh10;Adh-del knockout mice postnatally to examine survival and determine what tissues have a reduction or elimination of RA activity; (3) Perform microarray studies on Rdh10 and Rdh10;Adh-del knockout mice ( retinaldehyde) to identify RA target genes in a variety of tissues that are of broad interest to the research community.