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

描述（由申请人提供）：在各种分泌的细胞间信号传导因子中，视黄酸（RA）是独特的，因为它是一种小分子，通过进入靶细胞的细胞核并通过作为核受体的配体与靶基因结合来直接调节基因表达。维生素A（视黄醇）是一种必需的营养素，其通过两步代谢途径作为RA合成的前体，其中视黄醇转化为视黄醇，然后转化为RA。在小鼠中的基因敲除研究已经确定RA信号传导由三种RA受体和三种执行RA合成的最后一步的视黄醇脱氢酶控制。在揭示RA的生理作用方面的主要成功仅在于分析胚胎发育期间的RA功能，因为RA信号传导的消除导致胚胎致死。给予RA或抑制RA合成或受体活性的药物表明，RA还可以控制许多成人功能，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，并且可能无法准确了解出生后或成人RA功能。因此，本研究的目标是建立一个成功的遗传模型，用于分析RA的功能。根据这一目标，我们将开发一种缺乏视黄醇合成的基因敲除小鼠。与不可逆的和组织特异性的视黄醇到RA的代谢相反，视黄醇和视黄醇的相互转化是可逆的，并且在整个生物体中广泛发生。因此，我们建议，缺乏视黄醇合成的模式生物将能够生存出生后，如果维持维生素A补充饮食。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醇醛的酶，即视黄醇脱氢酶-10（RDH 10）和两种醇脱氢酶（ADH 3和ADH 4）。Rdh 10基因敲除的小鼠在妊娠期间由于缺乏RA合成而死亡，而Adh 3或Adh 4基因敲除的小鼠在出生后由于缺乏维生素A而死亡。为了建立成年RA功能的模型，我们建议：（1）建立一种饮食视黄醇处理，使Rdh 10敲除和Rdh 10、缺乏Rdh 10和所有形式ADH的Adh-del复合敲除的大鼠出生后存活;（2）从Rdh 10和Rdh 10中去除视黄醇; Adh-del基因敲除小鼠出生后检测存活率并确定哪些组织具有RA活性的降低或消除;（3）对Rdh 10和Rdh 10进行微阵列研究; Adh-del基因敲除小鼠（retinaldehyde），以确定研究界广泛感兴趣的各种组织中的RA靶基因。

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.