Determining Genetic and Molecular Mechanisms that Specify C. albicans Morphology

简介（申请人提供）：白色念珠菌是口腔念珠菌病的主要病原。患这种粘膜感染的风险最大的个体是那些免疫系统受损或有其他易感因素的人。口腔念珠菌病的症状可能很严重，导致这些患者的生活质量很差。耐药的白色念珠菌菌株也正在出现，使这种口腔真菌病原体更难治疗。允许白色念珠菌引起疾病的基本毒力特性之一是它能够从出芽酵母细胞可逆地转换形态为假菌丝和菌丝。我们的长期研究目标是更好地了解白色念珠菌的毒力特性和形态转换，以便开发新的抗真菌疗法来治疗口腔真菌感染。目前认为假菌丝和菌丝形态是由不同的基因集决定的，但缺乏直接证据。控制菌丝生长的分子机制尚不明确。我们现在已经产生了一种菌株，使我们能够探索这些问题。最近，我们的实验室发现了一种新的丝特异性转录调节因子Ume6，它对菌丝延伸和丝特异性基因表达很重要。我们发现当UME6在高组成水平表达时，白色念珠菌生长为一个几乎完整的菌丝群体。在感染过程中，我们观察到高水平的组成型UME6表达足以促进毒力。有趣的是，我们观察到低水平的UME6表达导致大多数假菌丝群体。我们发现UME6水平对几种已知纤维特异性基因的表达有差异调节。我们的假设是，UME6水平通过上调丝特异性基因重叠子集，包括正确菌丝形成所需的基因，以剂量依赖的方式决定白色念珠菌的形态。为了验证这一假设，我们将开展旨在实现以下目标的实验：1)确定白色假丝酵母菌生长的基因表达谱和由UME6表达水平指定的菌丝形态；2)确定UME6在指定适当菌丝生长的分子机制中的调节作用。

DESCRIPTION (provided by applicant): Candida albicans is the main etiologic agent of oral candidiasis. Individuals most at risk for developing this mucosal infection are those with compromised immune systems or people with other predisposing factors. Symptoms of oral candidiasis can be severe, leading to a poor quality of life for these patients. Drug resistant strains of C. albicans are also emerging, making this oral fungal pathogen even more difficult to treat. One of the essential virulence properties that allows C. albicans to cause disease is its ability to reversibly switch morphology from budding yeast cells to pseudohyphal and hyphal filaments. The long term goal of our research is to gain a better understanding of the C. albicans virulence property, morphological switching, in order to develop new antifungal therapies to treat oral fungal infections. Currently, it is thought that the pseudohyphal and hyphal morphologies are determined by distinetgene sets, however direct evidence is lacking. The molecular mechanisms that control hyphal growth are not well defined. We have now generated a strain that allows us to explore these questions. Recently, our lab identified a novel filament-specific transcriptional regulator, Ume6, which is important for hyphal extension and filament-specific gene expression. We found that when UME6 is expressed at high constitutive levels, C. albicans grows as a nearly complete hyphal population. During an infection, we observed that high-level constitutive UME6 expression is sufficient to promote virulence. Interestingly, we observed that lower levels of UME6 expression resulted in a majority pseudohyphal population. We found that UME6 levels differentially regulated the expression of several known filament-specific genes. Our hypothesis is that UME6 levels determine C. albicans morphology in a dosage-dependent manner by up-regulating overlapping subset of filament-specific genes, including genes required for proper hyphal formation. In order to test this hypothesis, we will carry out experiments designed to accomplish the following aims: 1) determine the gene expression profile of C. albicans growing as pseudohyphal and hyphal morphologies specified by UME6 expression levels, 2) determine the role of UME6 in the regulation of the molecular mechanisms that specify proper hyphal growth. Public Health Relevance: At the completion of our studies, we expect to have a more in-depth knowledge of C. albicans morphological switching, which may lead to the development of more effective antifungal therapies to treat oral disease. Candida albicans causes severe oral disease, leading to a poor quality of life. The proposed study will increase our understanding of a property that is essential to the ability of C. albicans to cause disease.