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PLoS Biol. 2014 Mar 18;12(3):e1001815. doi: 10.1371/journal.pbio.1001815. eCollection 2014 Mar.

A tetraploid intermediate precedes aneuploid formation in yeasts exposed to fluconazole.

Author information

1
Department of Genetics, Cell, and Developmental Biology, University of Minnesota-Twin Cities, Minneapolis, Minnesota, United States of America.
2
Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States of America.
3
Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel.
4
Alexander Grass Center for Bioengineering, The Hebrew University of Jerusalem, Jerusalem, Israel.
5
Department of Pediatrics, University of Rochester Medical Center, Rochester, New York, United States of America.
6
Department of Genetics, Cell, and Developmental Biology, University of Minnesota-Twin Cities, Minneapolis, Minnesota, United States of America; Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel.

Abstract

Candida albicans, the most prevalent human fungal pathogen, is generally diploid. However, 50% of isolates that are resistant to fluconazole (FLC), the most widely used antifungal, are aneuploid and some aneuploidies can confer FLC resistance. To ask if FLC exposure causes or only selects for aneuploidy, we analyzed diploid strains during exposure to FLC using flow cytometry and epifluorescence microscopy. FLC exposure caused a consistent deviation from normal cell cycle regulation: nuclear and spindle cycles initiated prior to bud emergence, leading to "trimeras," three connected cells composed of a mother, daughter, and granddaughter bud. Initially binucleate, trimeras underwent coordinated nuclear division yielding four daughter nuclei, two of which underwent mitotic collapse to form a tetraploid cell with extra spindle components. In subsequent cell cycles, the abnormal number of spindles resulted in unequal DNA segregation and viable aneuploid progeny. The process of aneuploid formation in C. albicans is highly reminiscent of early stages in human tumorigenesis in that aneuploidy arises through a tetraploid intermediate and subsequent unequal DNA segregation driven by multiple spindles coupled with a subsequent selective advantage conferred by at least some aneuploidies during growth under stress. Finally, trimera formation was detected in response to other azole antifungals, in related Candida species, and in an in vivo model for Candida infection, suggesting that aneuploids arise due to azole treatment of several pathogenic yeasts and that this can occur during the infection process.

PMID:
24642609
PMCID:
PMC3958355
DOI:
10.1371/journal.pbio.1001815
[Indexed for MEDLINE]
Free PMC Article

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