Gene Circuits that Control Morphology in Histoplasma

描述（由申请人提供）：真菌感染是一种日益严重的医学威胁，特别是对免疫功能低下的个体。从分子水平上了解真菌病原体是如何感知和应对环境的，将增强我们识别这些生物体的致命弱点以达到治疗目的的能力。该研究项目的长期目标是确定环境信号如何调节真菌病原体荚膜组织胞浆菌的形态和毒力。H. capsulatum在土壤中以丝状霉菌（菌丝体）形式生长，在宿主中以芽殖酵母形式生长。从菌丝体形式到酵母形式的转变被认为是毒力所必需的。虽然温度是触发两种形式的H之间转换的关键信号。capsulatum，很少有人知道温度如何调节形态的分子机制。 我们假设H. capsulatum使用会聚在主转录因子上的保守信号转导途径来响应于温度调节形态。该提案的目的是利用遗传学和功能基因组学来确定这一过程所需的关键分子。我们的具体目标是（1）使用高通量菌落形态学分析进行遗传筛选，以鉴定响应于温度的正常形态所需的基因;（2）使用基因表达谱作为灵敏的分析来表征形态调节剂的功能;和（3）使用分子遗传学实验如基因失活，异位表达和亚细胞定位。这些研究将有助于理解H. capsulatum根据环境信号改变其生长程序。此外，本研究还将阐明H. capsulatum响应温度调节毒力特性。

DESCRIPTION (provided by the applicant): Fungal infections are a growing medical threat, particularly for immunocompromised individuals. A molecular understanding of how fungal pathogens sense and respond to their environment will strengthen our ability to identify the Achilles' heel of these organisms for therapeutic purposes. The long-term goal of this research project is to determine how environmental signals regulate morphology and virulence in the fungal pathogen Histoplasma capsulatum. H. capsulatum grows in a filamentous mold (mycelial) form in the soil and a budding yeast form in the host. The transition from the mycelial form to the yeast form is thought to be essential for virulence. Although temperature is known to be a key signal that triggers the conversion between the two forms of H. capsulatum, little is known about the molecular mechanism of how temperature regulates morphology. We hypothesize that H. capsulatum uses conserved signal transduction pathways converging on master transcription factors to regulate morphology in response to temperature. The objective of this proposal is to use genetics and functional genomics to identify key molecules that are required for this process. Our specific aims are (1) to perform a genetic screen using a high throughput colony morphology assay to identify genes required for normal morphology in response to temperature; (2) to use gene expression profiling as a sensitive assay to characterize the function of regulators of morphology; and (3) to further characterize the function of putative regulators of morphology using molecular genetic experiments such as gene inactivation, ectopic expression, and subcellular localization. These studies will generate an understanding of the regulatory circuits used by H. capsulatum to shift its growth program in response to environmental signals. Moreover, the proposed research will elucidate the mechanism of how H. capsulatum regulates virulence properties in response to temperature.