Chromosome loss in the fungal pathogen C. albicans

描述（由申请方提供）：白色念珠菌是最常见的真菌病原体，可引起粘膜和全身感染，尤其是在免疫功能低下的人群中。直到最近，这种机会致病菌被认为是无性的，仅作为二倍体生物存在。然而，一个交配型样（MTL）基因座被确定，并通过遗传操作导致了实验室构建的交配能力菌株的C。白色念珠菌交配的产物是四倍体品系，如果要实现完整的性周期，则必须经历减数分裂以返回二倍体状态。In C.在白色念珠菌中，这种减数分裂（从四倍体到二倍体）可以通过涉及协同染色体丢失的非减数分裂机制发生。由此产生的二倍体本身具有交配能力，从而在该生物体中完成准性周期。 本研究的目的是确定协同染色体丢失的机制，在C。白念珠菌，并了解它在生物体的生命周期中所起的作用，特别强调它在感染过程中可能发挥的作用。四倍体菌株的染色体丢失模式将通过染色体丢失的中间体并将其DNA与念珠菌微阵列杂交来绘制。这将揭示某些染色体是否优先丢失，以及它们是否以规定的顺序丢失。还将通过显微镜直接观察发生染色体丢失的细胞来检查染色体丢失。如果发生染色体不分离，则可以观察到有丝分裂器的缺陷。还将比较二倍体和四倍体菌株的转录谱。特别强调将放在了解四倍体菌株在染色体丢失的转录程序。这些研究的一个主要目标是检查四倍体和染色体丢失在感染中的作用。因此，四倍体菌株的毒力较低。将白色念珠菌与二倍体菌株进行比较，并在感染模型中跟踪染色体丢失。最后，这些研究将直接解决是否念珠菌含有隐性致死等位基因在其二倍体基因组的等位基因芯片的建设。这也将允许在C.白色念珠菌待鉴定。

DESCRIPTION (provided by applicant): Candida albicans is the most common fungal pathogen, causing both mucosal and systemic infections, particularly in immunocompromised people. Until recently, this opportunistic pathogen was thought to be asexual, existing only as a diploid organism. However, a mating-type-like (MTL) locus was identified and genetic manipulation of it led to the laboratory construction of mating-competent strains of C. albicans. The products of mating are tetraploid strains that must undergo a reductional division to return to the diploid state if a complete sexual cycle is to be achieved. In C. albicans, this reductional division (from tetraploid to diploid) can occur by a non-meiotic mechanism involving concerted chromosome loss. The resultant diploids are themselves mating-competent, thereby completing a parasexual cycle in this organism. The goal of this study is to determine the mechanism of concerted chromosome loss in C. albicans, and to understand the role it plays in the life-cycle of the organism, with special emphasis on its possible role during infection. The pattern of chromosome loss from tetraploid strains will be mapped by taking intermediates in chromosome loss and hybridizing their DNA to Candida microarrays. This will reveal if certain chromosomes are lost preferentially, and whether they are lost in a prescribed order. Chromosome loss will also be examined by directly visualizing cells undergoing chromosome loss by microscopy. If chromosome non-disjunction is occurring then defects in the mitotic apparatus may be observed. The transcriptional profiles of diploid and tetraploid strains will also be compared. Particular emphasis will be placed on understanding the transcriptional program of tetraploid strains during chromosome loss. A major goal of these studies is to examine the role of the tetraploid and chromosome loss in infection. Therefore, the virulence of the tetraploid strain of C. albicans will be compared to that of diploid strains, and chromosome loss will be followed in models of infection. Finally, these studies will directly address whether Candida contains recessive lethal alleles in its diploid genome by construction of an allelic microarray. This will also allow recombination events that take place during the parasexual cycle of C. albicans to be identified.