Congenic strains of serotype A Cryptococcus neoformans

描述（由申请方提供）：新型隐球菌是一种重要的人类真菌病原体，可导致危及生命的感染。感染本质上是机会性的，通常发生在免疫功能低下的患者中，艾滋病患者的风险最大。隐球菌病通常表现为脑膜炎，艾滋病患者通常被视为无法治愈，需要终身抗真菌治疗。感染是世界性的，大约90 - 95%的感染是由血清型A菌株引起的。这种真菌作为病原体的重要性导致了基因组测序项目的征集和资助。然而，所选择的菌株是血清型D菌株，其引起的所有感染不到10%。选择该菌株是因为存在性相容菌株（指定为MAT α和MAT a），而由于缺乏可育MAT a菌株，因此无法获得相容的血清型A菌株。C.交配的另一个重要性。与新生儿感染相比，几乎所有的感染都是由一种交配类型（MAT α）引起的。 我们最近鉴定了一种血清型A MATa菌株，该菌株具有生育能力，并与血清型A MATalpha菌株（包括菌株H99，该血清型的标准实验室菌株）有效杂交。该菌株的存在为研究C.因为它将使传统的遗传学研究能够在血清型A菌株中进行。这项建议包括三个目标。第一个目标是制备两个仅在交配型上不同的同源对菌株。遗传标记将被插入这些菌株，使它们成为未来遗传和分子研究的有用工具。第二个目标是测试交配型在毒力中的作用。通过在这些实验中使用同源菌株，交配型基因座的信息在毒力中的作用可以独立于非交配型信息进行测试。在最后一个目标中，将克隆和定位血清型A MATa交配型基因座以确定其大小。目前，C.新形变种新生儿（包括血清型A和D）处于不同的表征阶段。血清型A MATa基因座的分离将完成本研究，这是重要的，因为交配型在毒力中起作用。

DESCRIPTION (provided by applicant): Cryptococcus neoformans is an important human fungal pathogen that can cause life-threatening infections. Infections are opportunistic in nature and typically occur in immunocompromised patients, with AIDS patients being at greatest risk. Cryptococcosis is usually manifested as meningitis, which is often treated as incurable in AIDS patients and can require life-long antifungal therapy. Infections are worldwide with approximately 90- 95% of all infections being caused by serotype A strains. The importance of this fungus as a pathogen resulted in the solicitation and funding of a genome-sequencing project. The strain that was chosen, however, was a serotype D strain, which causes less than 10% of all infections. This strain was chosen because sexually compatible strains (designated MATalpha and MATa) exist, whereas compatible serotype A strains are not available due to the absence of a fertile MATa strain. An added significance of mating in C. neoformans is that virtually all infections are caused by one mating type (MATalpha). We have recently identified a serotype A MATa strain that is fertile and crosses efficiently with serotype A MATalpha strains, including strain H99, the standard laboratory strain for this serotype. The existence of this strain provides a powerful tool for studying C. neoformans because it will enable traditional genetic studies to be performed in serotype A strains. This proposal consists of three aims. The first aim will prepare two congenic pairs of strains that differ only in mating type. Genetic markers will be inserted into these strains to make them useful tools for future genetic and molecular studies. The second aim will test the role of mating type in virulence. By using congenic strains in these experiments, the role of information at the mating type locus in virulence can be tested independent of non mating-type information. In the last aim, the serotype A MATa mating type locus will be cloned and mapped to determine its size. Presently three out of the four mating type loci of C. neoformans var. neoformans (comprised of serotype A and D) are in various stages of characterization. Isolation of the serotype A MATa locus will complete this study, which is significant because of the role that mating type plays in virulence.