Origin of Cryptococcus neoformans var. neoformans diploid strains
Origin of Cryptococcus neoformans var. neoformans diploid strains
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DOI：
10.1128/jcm.39.11.3889-3894.2001
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发表时间：
2001-11-01
影响因子：
9.4
通讯作者：
Viviani, MA
中科院分区：
文献类型：
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作者：
Cogliati, M;Esposito, MC;Viviani, MA
担子菌酵母新型隐球菌是一种重要的人类真菌病原体。已经鉴定出两个品种，新形式C. var. neoformans和新形式C. var. gattii。它们都是异thallic，有两种交配类型，MATa和MAT α。一些罕见的分离株是自育的，偶尔被认为是二倍体或非整倍体菌株。在本研究中，研究了133株分离株，主要来自意大利患者，以检测米兰Igiene大学培养收集的二倍体菌株的存在。用不同的方法对所有的二倍体分离株进行了进一步的研究，以阐明它们的起源。流式细胞术鉴定出49株二倍体菌株。利用（GACA）(4)引物进行PCR指纹图谱鉴定，二倍体状态与VN3和VN4两种特异性基因型相关。在VS汁培养基上的配种方式测定证实，大多数菌株是无菌的。以MFa和MF α两个信息素基因为探针，采用PCR和点印迹法鉴定出49株二倍体分离株中有36株为MATa/ α。信息素基因测序结果显示，A、d两种血清型均存在两个等位基因MFa基因，且MFa基因序列在两种血清型中均保守。血清型特异性STE20等位基因扩增结果表明，该二倍体菌株含有一个遗传自血清型a亲本的交配位点和一个遗传自血清型D亲本的交配位点。目前的研究结果表明，二倍体分离株可能在新生弓形虫种群中很常见，在意大利和其他欧洲国家，血清型A和D种群不是遗传分离的，而是能够通过有性繁殖重组的。
The basidiomycetous yeast Cryptococcus neoformans is an important human fungal pathogen. Two varieties, C. neoformans var. neoformans and C. neoformans var. gattii, have been identified. Both are heterothallic with two mating types, MATa and MAT alpha Some rare isolates are self-fertile and are considered occasional diploid or aneuploid strains. In the present study, 133 isolates, mostly from Italian patients, were investigated to detect the presence of diploid strains in the Igiene University Milano culture collection. All of the diploid isolates were further investigated by different methods to elucidate their origins. Forty-nine diploid strains were identified by flow cytometry. PCR fingerprinting using the (GACA)(4) primer showed that the diploid state was associated with two specific genotypes identified as VN3 and VN4. Determination of mating type on VS juice medium confirmed that the majority of the strains were sterile. PCR and dot blotting using the two pheromone genes (MFa and MF alpha) as probes identified 36 of the 49 diploid isolates as MATa/alpha. The results of pheromone gene sequencing showed that two allelic MFa genes exist and are distinct for serotypes A and D. In contrast, the MFa gene sequence was conserved in both serotype alleles. Amplification of serotype-specific STE20 alleles demonstrated that the diploid strains contained one mating locus inherited from a serotype A parent and one inherited from a serotype D parent. The present results suggest that diploid isolates may be common among the C. neoformans population and that in Italy and other European countries serotype A and D populations are not genetically isolated but are able to recombine by sexual reproduction.