Rdh10 and retinoic acid effects on differentiation

视黄醇脱氢酶10（Rdh 10）催化全反式维甲酸（atRA）合成的第一步和限速步骤 通过生成视黄醛，由视黄醇进行生物合成，所述视黄醛酶将所述视黄醛酶转化成atRA。最Rdh 10 研究集中在视觉周期或胚胎发育上。在产后方面所做的工作有限， Rdh 10功能。然而，atRA控制间充质干细胞（MSC）分化为脂肪细胞的命运， 成骨细胞在成人调节肥胖和骨骼健康。atRA在指导MSC中的作用机制 分化和atRA生物合成的调控仍不清楚。文献中包含了矛盾的 报道了由atRA和其他分化刺激物调节的主要靶基因。大多数关于atRA的研究 脂肪细胞与成骨细胞之间平衡的调节已经在细胞系中完成，并且已经集中在 单个基因控制一个干细胞的命运，通常在分化后期。使用细胞系（例如3 T3 - 3 T4）， L1，F442 A，C2 C12，MC 3 T3-E1）很可能导致了相互矛盾的结论，因为细胞系确实 没有忠实地模拟原代细胞，彼此不同，甚至细胞系具有相同的标称名称 由于长期的文化差异，该提案通过以下方式解决了atRA在指导MSC命运中的功能： 建议研究atRA不足的体内模型，这将伴随着产生原发性 小鼠胚胎成纤维细胞产生全面的机制，以确定脂肪细胞与 成骨细胞命运。体内模型依赖于杂合子消融的Rdh 10（Rdh 10 +/-），其具有表型 在生命早期，骨髓中的肥胖和脂肪细胞增殖增加， 成骨细胞Rdh 10 +/-模型（纯合子是胚胎致死的）提供了一致的减毒 维生素A在体内通过可再现地减少atRA发挥作用。这是一个创新的模式，将提供新的 关于atRA调节脂肪细胞与成骨细胞分化功能的见解，以及新的见解 Rdh 10功能和atRA生物合成。了解Rdh 10和atRA在肥胖症中的作用， 脂肪生成有望直接应用于人类健康。这一期望得到了26国集团的支持。 与体重指数和体重增加相关的基因间性状，其图谱接近人类Rdh 10。目标1将 确定降低Rdh 10表达和atRA浓度的表型和代谢后果 在体内（Rdh 10 +/-小鼠），侧重于脂肪细胞和成骨细胞分化。这一目标将检验这一假设 Rdh 10是控制atRA稳态以调节脂肪细胞中类维生素A功能主要酶， 成骨细胞分化目的2将确定Rdh 10 +/-小鼠表型的机制， 细胞命运的决定。该目的将使用两组MEF：1）来自Rdh 10 +/-小鼠; 2）永生化的 用Rdh 10的完全敲除的MEF来检验由Rdh 10产生的atRA指导 MSC通过调控基因表达很早就决定了细胞命运，并将识别出应答基因。

Retinol dehydrogenase 10 (Rdh10) catalyzes the first and rate-limiting step in all-trans-retinoic acid (atRA) biosynthesis from retinol by generating retinal, which retinal dehydrogenases convert into atRA. Most Rdh10 research has focused on the visual cycle or embryonic development. Limited work has been done on postnatal Rdh10 function. Yet, atRA controls the fate of mesenchymal stem cell (MSC) differentiation into adipocytes vs osteoblasts in the adult to regulate adiposity and bone health. Mechanisms of atRA action in directing MSC differentiation remain unclear as does regulation of atRA biosynthesis. The literature contains conflicting reports as to the primary target genes regulated by atRA and other differentiation stimuli. Most studies of atRA regulation of the balance between adipocytes vs osteoblasts has been done in cell lines, and has focused on single genes controlling in one stem cell fate, often later during differentiation. The use of cell lines (e.g. 3T3- L1, F442A, C2C12, MC3T3-E1) most likely has contributed to the conflicting conclusions, because cell lines do not faithfully model primary cells, differ from each other, and even cell lines with the same nominal designation often differ as a result of long-term culture. This proposal addresses atRA function in directing MSC fate by proposing study of an in vivo model of atRA insufficiency, which will be accompanied by generating primary mouse embryonic fibroblasts to produce comprehensive mechanistic insight into determining adipocyte vs. osteoblast cell fates. The in vivo model relies on heterozygote ablated Rdh10 (Rdh10+/-) that has a phenotype of increased adiposity and adipocyte proliferation in bone marrow early in life, with decreased calcification of osteoblasts. The Rdh10+/- model (the homozygote is embryonic lethal) provides for consistently attenuated vitamin A function in vivo through reproducibly reduced atRA. This is an innovative model that will provide new insight into atRA function concerning regulating differentiation of adipocytes vs osteoblasts, and new insight into Rdh10 function and atRA biogenesis. Understanding the roles of Rdh10 and atRA in obesity and adipogenesis promises direct human health applications. This expectation is supported by the twenty-six intergenic traits related to body mass index and weight gain that map close to human Rdh10. Aim 1 will determine the phenotype and metabolic consequences of reducing Rdh10 expression and atRA concentrations in vivo (Rdh10+/- mice), focusing on adipocyte and osteoblast differentiation. This aim will test the hypothesis that Rdh10 is a major enzyme that controls atRA homeostasis to regulate retinoid function in adipocyte and osteoblast differentiation. Aim 2 will determine mechanism(s) that underlie the phenotype of Rdh10+/- mice with respect to cell fate determination. This aim will use two sets of MEF: 1) from Rdh10+/- mice; 2) immortalized MEF with a total knockout of Rdh10 to test the hypothesis that atRA generated by Rdh10 directs maturation of MSC by regulating gene expression very early in cell fate determination, and will identify the responsive genes.