SWITCHING IN THE ORAL COMMENSAL CANDIDA GLABRATA

描述（由申请人提供）：光秃念珠菌的出现是老年人口腔中的主要共生体，也是第二常见的酵母菌血流感染，这是一个可怕的问题。由于光秃念珠菌具有天然的耐药性，它使老年人和免疫功能低下的人处于危险之中，并导致难以治疗的慢性感染。然而，这种病原体的成功令人困惑，因为与白色念珠菌不同，它似乎既不经历高频表型转换，也不经历二态性，这两种发育程序为发病机制的快速适应提供了机制。因此，我们寻找并发现了这两个发育程序。C. glabrata在四种“核心”表型（白色（Wh）、浅棕色（LB）、深棕色（DB）和深棕色（vDB））之间自发、可逆和高频切换，此外还可以在两种“相关”开关表型(不稳定白色（unWh）和不规则皱纹（IWr）之间切换。核心开关的独特之处在于，所有被测试的表型特征和开关调节基因的表达都按照Wh小于LB小于DB小于vDB或Wh大于LB大于DB大于vDB的等级进行分级。基于这一独特的分级开关系统的发现，以及最近对慢性阴道炎患者口腔和阴道核心开关表型解剖专门化的建议，提出以下具体目标：1)完成开关的表征，明确相关开关表型与核心开关系统的关系；2)通过差异杂交筛选和使用酿酒酵母dna阵列鉴定和表征其他开关调节基因；3)利用REMI诱变技术，鉴定和表征参与转换过程的基因；4)对参与分级表达的顺式作用序列和反式作用因子进行功能表征；5)区分与unWh和IWr表型相关的基因以及与假菌丝和芽生长形式相关的基因；6)在动物模型中测试开关是否影响药物敏感性、其他毒力性状和毒力，并证实核心开关表型具有解剖专一性。

DESCRIPTION (provided by applicant): The emergence of Candida glabrata as a major commensal in the oral cavity of the elderly, and as the second most common yeast blood stream infection is a matter of dire concern. Because Candida glabrata is naturally drug-resistant, it puts at risk the elderly and immunocompromised, and causes chronic infections that an difficult to treat. The success of this pathogen, however, was puzzling since, unlike Candida albicans, it appeared to undergo neither high frequency phenotypic switching nor dimorphism, two developmental programs that provide mechanism for rapid adaptation in pathogenesis. We, therefore, searched for and discovered both developmental programs in C. glabrata. C. glabrata switches spontaneously, reversibly and at high frequency between four "core" phenotypes distinguishable on CuSO4-containing agar, white (Wh), light brown (LB), dark brown (DB) and very dark brown (vDB), and in addition switch to and from two "associated" switch phenotypes, unstable white (unWh) and irregular wrinkle (IWr). Core switching is unique in that all tested phenotypic characteristics and the expression of switching-regulated genes are graded in the hierarchies Wh less than LB less than DB less than vDB or Wh greater than LB greater than DB greater than vDB. Based upon the discovery of this uniquely graded switching system, and the recent suggestion of anatomical specialization of core switch phenotypes in the oral cavity and vagina of a chronic vaginitis patient, the following specific aims are proposed: 1) complete the characterization of switching and define the relationship of the associated switch phenotypes and the core switching system; 2) identify and characterize additional switching-regulated genes by differential hybridization screens and the use of S. cerevisiae cDNA-based arrays; 3) using REMI mutagenesis, identify and characterize genes involved in the switching process; 4) functionally characterize the cis-acting sequences and trans-acting factors involved in the graded expression; 5) discriminate between genes involved in the unWh and IWr phenotypes and genes involved in the pseudohypha and bud growth forms and 6) test whether switching affects drug susceptibility, other virulence traits and virulence in animal models, and confirm that the core switch phenotypes exhibit anatomical specialization.