Gene circuits that control morphology in Histoplasma

项目摘要 荚膜组织胞浆菌（Hc）是一种热二型真菌，被认为是最常见的 健康人的真菌呼吸道感染的原因。HC以多细胞菌丝的形式生长在 环境一旦被哺乳动物吸入，HC转化为单细胞酵母形式，定植于巨噬细胞。 温度是一个关键信号，足以触发从土壤到宿主形态的转换（反之亦然）; 在实验室，室温促进菌丝（霉菌）生长，而37ºC促进酵母阶段 增长这项研究的长期目标是确定温度如何调节的分子基础 热二型真菌的形态和毒力。通过阐明Hc细胞如何感知和响应宿主 温度，我们将定义关键的分子标志，促进形态的变化，以及 毒力性状的表达。在以前的工作中，我们鉴定了四种转录因子Ryp 1，2，3和4， 促进酵母形式的生长以响应宿主温度。Ryp蛋白是酵母绝对需要的- 相形态以及绝大多数温度依赖性基因表达程序。超过 在上一个资助期，我们发现了Ryp 1和Ryp 2在转录后受到调控的证据。 此外，为了确定在低温下拮抗Ryp通路的调节机制，我们分离了 酵母锁定突变体，在缺乏正常高表达的情况下不适当地激活Ryp通路。 温度信号我们确定细胞表面信号传导粘蛋白Msb 2是（1）抑制Ryp所必需的， 积累和（2）建立响应低温的菌丝生长。此外，转录 对msb 2突变体的分析使我们能够鉴定出与菌丝生长相关的紧凑基因调节子。 形成或酵母相生长，包括鉴定推定的毒力因子， 与不依赖于温度的酵母形式的生长相关。在这里，我们将（1）调查如何 温度调节组织胞浆菌致病程序，阐明分子机制， 调节Ryp通路;（2）阐明相互对立的Ryp和Msb 2通路如何能够 感测温度;和（3）利用我们的温度定义的毒性基因发现的调控电路。 这些实验将导致对温度如何触发关键细胞命运的详细分子理解 与HC致病能力相关的变化。

Project Summary Histoplasma capsulatum (Hc) is a thermally dimorphic fungus that is thought to be the most common cause of fungal respiratory infections in healthy humans. Hc grows in a multicellular hyphal form in the environment. Once inhaled by mammals, Hc converts to a unicellular yeast form that colonizes macrophages. Temperature is a key signal that is sufficient to trigger the switch from the soil to host form (and vice versa); in the laboratory, room temperature promotes hyphal (mold-form) growth whereas 37ºC promotes yeast-phase growth. The long-term goal of this research is to determine the molecular basis of how temperature regulates morphology and virulence in thermally dimorphic fungi. By elucidating how Hc cells sense and respond to host temperature, we will define critical molecular landmarks that promote changes in morphology as well as the expression of virulence traits. In previous work, we identified four transcription factors, Ryp1, 2, 3, and 4, that promote yeast-form growth in response to host temperature. The Ryp proteins are absolutely required for yeast- phase morphology as well for the vast majority of the temperature-dependent gene expression program. Over the last funding period, we uncovered evidence that Ryp1 and Ryp2 are regulated post-transcriptionally. Additionally, to identify regulatory mechanisms that antagonize the Ryp pathway at low temperature, we isolated yeast-locked mutants that inappropriately activate the Ryp pathway in the absence of the normal high temperature signal. We determined that the cell surface signaling mucin Msb2 is required for (1) inhibition of Ryp accumulation and (2) establishment of hyphal growth in response to low temperature. Additionally, transcriptional profiling of the msb2 mutant allowed us to identify compact gene regulons that are associated with either hyphal formation or yeast-phase growth, including the identification of putative virulence factors whose expression is associated with growth in the yeast form independent of temperature. Here we will (1) investigate how temperature regulates the Histoplasma pathogenic program by elucidating the molecular mechanisms that regulate the Ryp pathway; (2) elucidate how the Ryp and Msb2 pathways, which oppose each other, are able to sense temperature; and (3) utilize our temperature-defined regulatory circuits for virulence gene discovery. These experiments will result in a detailed molecular understanding of how temperature triggers critical cell fate changes that are linked to the ability of Hc to cause disease.