MicroRNAs as T cell sensitivity Rheostats

描述（由申请人提供）：T细胞对抗原的敏感性在淋巴细胞发育和成熟过程中受到内在调节，以确保免疫和耐受性的适当发展，但这是如何完成的尚不清楚。MicroRNAs （miRNAs）是一类丰富的约22个核苷酸（nt）的小非编码rna，在动物发育、癌症发病和免疫反应中发挥着重要作用。其中miR-181a在淋巴细胞发育过程中优先表达，在T细胞和B细胞发育中起重要作用。在成熟T细胞中增加miR-181a表达增加了对肽抗原的敏感性，而在未成熟T细胞中抑制miR-181a表达则降低了敏感性，并损害了阳性和阴性选择。有趣的是，miR-181a对T细胞敏感性的定量调节使成熟T细胞能够识别拮抗剂——抑制性肽抗原——作为激动剂，这表明抗原敏感性的定量调节可能导致T细胞激活阈值的改变。支持miR-181a可能在T细胞发育过程中作为内在抗原敏感性“变阻器”的观点是，在各种T细胞群体中，更高的miR-181a表达似乎与更高的T细胞敏感性相关。拟开展的研究计划将检测mir-181家族基因在淋巴细胞发育、选择和功能过程中调控T细胞对抗原敏感性的功能，并进一步测试调节miRNA表达对耐受性发展的影响。具体而言，我们将使用功能丧失方法，包括药理学（antagomir敲除）和遗传学（小鼠靶向缺失）方法，减少或消除DP细胞中mir-181家族基因的表达，以确定这些miRNA基因在控制DP胸腺细胞中TCR信号强度和影响阳性和阴性选择中的作用（Specific Aim 1）。我们还将描述mir-181家族基因在外周血T细胞受体库以及幼稚T细胞和记忆T细胞发育中的作用（Specific Aim 2）。最后，我们将通过控制前tcr和Notch信号通路来研究mir-181家族基因在胸腺早期T细胞发育中的功能（Specific Aim 3）。公共卫生相关性：拟议的研究将为miRNA异常表达如何促进自身免疫性疾病（如系统性红斑狼疮、类风湿性关节炎、多发性硬化症和1型自身免疫性糖尿病）的发病机制提供基本见解。

DESCRIPTION (provided by applicant): T cell sensitivity to antigens is intrinsically regulated during lymphocyte development and maturation to ensure proper development of immunity and tolerance, but how this is accomplished remains elusive. MicroRNAs (miRNAs), an abundant class of ~22-nucleotide (nt) small noncoding RNAs, have emerged as important players in animal development, the pathogenesis of cancers, and immune responses. Among them, miR-181a is preferentially expressed during lymphocyte development and plays important roles in T and B cell development. Increasing miR-181a expression in mature T cells augments the sensitivity to peptide antigens, whereas inhibiting miR-181a expression in immature T cells reduces sensitivity and impairs both positive and negative selection. Interestingly, quantitative regulation of T cell sensitivity by miR-181a enables mature T cells to recognize antagonists--the inhibitory peptide antigens--as agonists, suggesting that quantitative regulation of antigen sensitivity could result in a shift in the activation threshold in T cells. Supporting the idea that miR-181a may function as an intrinsic antigen-sensitivity `rheostat' during T cell development is that higher miR-181a expression seems to correlate with greater T cell sensitivity in various T cell populations. The proposed research plan will examine the function of the mir-181 family genes in regulating T cell sensitivity to antigens during lymphocyte development, selection, and function, and will further test the effects of tuning miRNA expression on the development of tolerance. Specifically, we will use loss-of-function approaches, including pharmacological (antagomir knock-down) and genetic (targeted deletions in mice) approaches, to reduce or abrogate the expression of the mir-181 family genes in DP cells, in order to determine the roles these miRNA genes play in controlling TCR signaling strength in DP thymocytes and in influencing positive and negative selection (Specific Aim 1). We will also characterize the roles of the mir-181 family genes in the development of the peripheral T cell receptor repertoire as well as naive and memory T cells (Specific Aim 2). Finally, we will investigate the functions of the mir-181 family genes in early T cell development in the thymus by controlling the pre-TCR and Notch signaling pathways (Specific Aim 3). PUBLIC HEALTH RELEVANCE: The proposed study will provide fundamental insight as to how aberrant miRNA expression may contribute to the pathogeneses of autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, and type-1 autoimmune diabetes.