Pathogenic environmental regulation of miRNA biogenesis and function

描述（由申请人提供）：人类暴露于环境毒物是众所周知的疾病原因，低慢性暴露可能会显著增加慢性疾病的纵向风险。许多环境毒物的致病机制仍然不明确，这限制了有效干预措施的发展，以防止环境衍生的慢性病。低剂量接触饮用水中的三价砷（III）是一个重大的公共卫生问题，会导致包括心血管和代谢疾病在内的许多疾病和病理。虽然在了解导致砷诱导疾病的致病信号事件方面取得了进展，但许多相关机制尚未阐明。控制miRNA的表达和作用为了解砷暴露的下游效应提供了一种有希望的新手段；然而，关于砷如何调节miRNA的表达并影响其功能的报道很少。因此，拟议的研究将使用砷作为理想的致病性环境毒物来检查对miRNA调节的表型程序的影响。为了使研究更加集中，我们将研究砷对miR-29家族（包括miR-29a、29b-1、29b-2和29c）生物发生和致病作用的影响。该miRNA家族是根据几项研究选择的，这些研究表明miR-29成员在心血管和代谢性疾病的病因中增加。我们的初步数据显示，砷暴露（100 mg/L饮用水中2周）小鼠分离的白色和棕色脂肪组织以及人类脂肪源性间充质干细胞（hMSC）中，miR-29的诱导作用是砷抑制脂肪细胞分化。干细胞或祖细胞分化能力的降低被认为是疾病进展的基本手段，我们将使用hMSCs分化为脂肪细胞和心肌细胞作为模型来研究砷对致病性miRNA调控程序的影响。研究的主要假设是，砷诱导mirna的转录表达，并影响其在抑制调节hMSC分化的基因程序中的功能，从而损害心脏或代谢组织的再生能力和适应性修复。研究这一假说的具体目的如下：1 .砷诱导miR-29家族成员表达的调控机制及其功能影响。砷刺激miR-29生物发生的机制将在hMSC中进行研究，重点关注受损的hMSC、脂肪细胞和肌细胞分化。限速步骤的分子敲低将确定砷如何诱导miR-29家族成员的表达及其致病作用。2。验证细胞背景和环境因素影响相关miRNA功能活性的假设。重点将是研究砷如何调节miR-29家族成员对其mRNA靶标的差异活性。我们将研究mRNA结合蛋白的表达和能力，以及它们增强或减少miRNA介导的翻译抑制的能力。

DESCRIPTION (provided by applicant): Human exposure to environmental toxicants is a well known cause of disease and low chronic exposure may contribute significantly to longitudinal risk of chronic diseases. Pathogenic mechanisms for many environmental toxicants remain poorly defined which limits development of effective interventions to protect against environmentally-derived chronic diseases. Low dose exposure to trivalent arsenic As(III) in drinking water is a major public health concern that contributes to a number of diseases and pathologies, including cardiovascular and metabolic diseases. While progress has been made in the understanding of the pathogenic signaling events contributing to arsenic-induced disease, many responsible mechanisms have not been elucidated. Control of miRNA expression and action presents a promising new means for understanding downstream effects of arsenic exposure; however, there are few reports of how arsenic regulates expression of miRNA and impacts their function. Thus the proposed studies will use arsenic as an ideal pathogenic environmental toxicant to examine impact on miRNA regulated phenotypic programs. To focus the studies, impact of arsenic on miR-29 family (including miR-29a, 29b-1, 29b-2 and 29c) biogenesis and pathogenic actions will be investigated. This miRNA family was selected based on several studies implicating increased miR-29 members in the etiology cardiovascular and metabolic diseases. Our preliminary data show induction of miR-29 in white and brown adipose tissue isolated from arsenic exposed (100 mg/L in drinking water for 2 wk) mice and in human adipose-derived mesenchymal stem cells (hMSC) as arsenic inhibited adipocyte differentiaton. Reduced stem or progenitor cell differentiation capacity is believed to be a fundamental means for disease progression and we will use the differentiation of hMSCs into adipocytes and cardiomyoctes as a model to examine arsenic effects on pathogenic miRNA regulatory programs. The overarching hypothesis investigated is that arsenic induces transcriptional expression of miRNAs and impacts their function in repressing gene programs that regulate hMSC differentiation thereby impairing regenerative capacity and adaptive repair of cardiac or metabolic tissues. This hypothesis will be studied by the following specific aims: I. Identificatio of the mechanisms regulating arsenic-induced miR-29 family member expression and its functional impact. Mechanisms of arsenic-stimulated miR-29 biogenesis will be studied in hMSC with focus on impaired hMSC, adipocyte and myocyte differentiation. Molecular knockdown of rate limiting steps will identify how arsenic induces the expression and pathogenic role of the miR-29 family members. II. To test the hypothesis that cell context and environmental factors impact the functional activity of relevant miRNA. Focus will be on investigating how arsenic regulates differential activity of miR-29 family members on their mRNA targets. The expression and ability of mRNA binding proteins will be studied in relation to their ability to enhance or reduce miRNA mediated translational inhibition.