miRNAs and epidermal langerhans cell development and function

描述（由申请人提供）： 树突状细胞（Dendritic cells，DCs）是来源于骨髓造血干细胞（hematopoietic stem cells，HSCs）的一种异质性细胞群，是专职的抗原提呈细胞，在免疫和耐受诱导之间的平衡中起着关键作用。朗格汉斯细胞（LC）是皮肤驻留的DC，其表达C型凝集素Langerin并且具有不同于许多其他类型的DC的生命周期。尽管LC在100多年前首次被描述，但它们的发育和免疫功能仍然是个谜。MicroRNA（miRNAs）是一类长度为21-25 nt的单链非编码小RNA，通过抑制mRNA的翻译而成为基因表达的重要调控因子。核糖核酸酶III酶Dicer是加工成熟和功能性miRNA所必需的。使用Cre-loxP组织特异性Dicer缺失，我们的实验室和其他人已经报道了HSC中miRNA的缺失显著影响不同免疫细胞的发育和功能。然而，miRNAs在LC发育中的作用目前仍不清楚。为了测试miRNA在LC发育中的作用，我们使用Langerin-Cre产生了具有LC中Dicer的组织特异性破坏的新小鼠品系。令人惊讶的是，在LC中具有miRNA缺陷的小鼠具有显著减少的表皮LC数量，并且在miRNA缺陷的LC中Langerin的表达显著降低。此外，与其他免疫细胞相比，LC具有特定的miRNA基因表达谱。因此，我们的中心假设是，miRNA是控制LC发育和功能的分子电路的非常重要的组成部分。我们将通过以下三个具体目标来验证我们的假设：1）确定LC成熟过程中miRNAs的表达模式; 2）研究miRNAs在LC发育和功能中的作用; 3）鉴定参与LC发育的miRNAs的靶基因。我们的研究将大大提高我们对LC发展和功能的分子机制的认识，也可能促进癌症，感染性和自身免疫性疾病的新干预策略的发展。 公共卫生相关性： 朗格汉斯细胞（LC）是皮肤居民的DC，维持皮肤的稳态，但详细的分子途径调节LC的发展和功能仍然在很大程度上未知。microRNAs（miRNAs）是近年来发现的一类进化上保守的小分子非编码RNA，负调控蛋白质编码基因的表达。该提案的总体目标是在开发过程中鉴定LC特异性miRNA表达谱，并确定其功能和直接靶点。上述开创性研究的结果不仅可以阐明LC发展的新的免疫学和分子机制，而且还可以促进基于LC细胞治疗的相关自身免疫性疾病，感染和癌症的新干预策略的发展。

DESCRIPTION (provided by applicant): Dendritic cells (DCs), a heterogeneous population originating from hematopoietic stem cells (HSCs) in the bone marrow (BM), are professional antigen-presenting cells that play key roles in determining the balance between immunity and tolerance induction. Langerhans cells (LCs) are skin-resident DCs that express the C-type lectin Langerin and have a life cycle distinct from many other types of DCs. Even though LCs were first described more than 100 years ago, their development and immunological functions still remain enigmatic. MicroRNAs (miRNAs), a class of 21-25 nt single-stranded non-coding small RNAs, are increasingly being recognized as important regulators of gene expression through the inhibition of effective mRNA translation. The ribonuclease III enzyme Dicer is required for the processing of mature and functional miRNAs. Using Cre-loxP tissue-specific Dicer deletion, our laboratory and others have reported that deletion of miRNAs in HSCs significantly affects the development and function of different immune cells. However, the role of miRNAs in the development of LCs is still currently unknown. To test the roles of miRNAs in the development of LCs, we generated a new mouse strain with tissue- specific disruption of Dicer in LCs using Langerin-Cre. Surprisingly, mice with miRNAs-deficiency in LCs had significantly reduced number of epidermal LCs and the expression of Langerin was significantly reduced in miRNA-deficient LCs. Furthermore, LCs have a specific miRNA gene expression profile compared to other immune cells. Thus, our central hypothesis is that miRNAs are very important components of the molecular circuitry that controls LC development and function. We will test our hypothesis by pursuing the following three Specific Aims: 1) To determine the expression patterns of miRNAs during LC maturation; 2) To investigate the role of miRNAs in LC development and function; 3) To identify the target genes of miRNAs involved in LC development. Our study will dramatically advance our knowledge on the molecular mechanisms underlying LC development and function, and may also facilitate the development of new intervention strategies for cancer, infectious and autoimmune diseases. PUBLIC HEALTH RELEVANCE: Langerhans cells (LCs) are skin-resident DCs that maintain skin homeostasis, but the detailed molecular pathways regulating LC development and function remain largely unknown. MicroRNAs (miRNAs) are a recently discovered class of evolutionarily conserved small non-coding RNAs that negatively regulate the expression of protein-coding genes. The overall goal of this proposal is to identify the LC-specific miRNA expression profile during development and define their function and direct targets. The results from the above pioneering studies may not only illuminate the new immunological and molecular mechanisms underlying LC development, but may also facilitate the development of new intervention strategies for related autoimmune diseases, infection, and cancer based on the LC cell therapy.