Cryptococcus neoformans Overcomes Stress of Azole Drugs by Formation of Disomy in Specific Multiple Chromosomes

Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, United States of America.
PLoS Pathogens (Impact Factor: 7.56). 04/2010; 6(4):e1000848. DOI: 10.1371/journal.ppat.1000848
Source: PubMed


Cryptococcus neoformans is a haploid environmental organism and the major cause of fungal meningoencephalitis in AIDS patients. Fluconazole (FLC), a triazole, is widely used for the maintenance therapy of cryptococcosis. Heteroresistance to FLC, an adaptive mode of azole resistance, was associated with FLC therapy failure cases but the mechanism underlying the resistance was unknown. We used comparative genome hybridization and quantitative real-time PCR in order to show that C. neoformans adapts to high concentrations of FLC by duplication of multiple chromosomes. Formation of disomic chromosomes in response to FLC stress was observed in both serotype A and D strains. Strains that adapted to FLC concentrations higher than their minimal inhibitory concentration (MIC) contained disomies of chromosome 1 and stepwise exposure to even higher drug concentrations induced additional duplications of several other specific chromosomes. The number of disomic chromosomes in each resistant strain directly correlated with the concentration of FLC tolerated by each strain. Upon removal of the drug pressure, strains that had adapted to high concentrations of FLC returned to their original level of susceptibility by initially losing the extra copy of chromosome 1 followed by loss of the extra copies of the remaining disomic chromosomes. The duplication of chromosome 1 was closely associated with two of its resident genes: ERG11, the target of FLC and AFR1, the major transporter of azoles in C. neoformans. This adaptive mechanism in C. neoformans may play an important role in FLC therapy failure of cryptococcosis leading to relapse during azole maintenance therapy.

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Available from: Kyung J Kwon-Chung, Feb 17, 2015
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    • "Twelve of the 34 lines were aneuploid, and each of these 12 lines contained either chrVIII aneuploidy (5 lines) or chrII aneuploidy (8 lines). Chromosomal aneuploidy seems to be a common route to adaptation for fungal species reproducing asexually in a diverse array of environmental stressors such as drug resistance (Selmecki et al. 2009; Sionov et al. 2010), high temperature (Yona et al. 2012), and salt (Dhar et al. 2011). Aneuploidy is an intriguing beneficial mutation, as it has the potential to affect many genes simultaneously , yet has a much higher reversion rate than other types of mutations. "
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    • "Treatment of haploid C. neoformans cells with fluconazole resulted in disomy of up to four chromosomes (Chrs 1, 4, 10, and 14) (Sionov et al. 2009, 2010). Chr1 disomy was common to all resistant isolates and included the genes encoding Erg11 and the major azole transporter, Afr1 (Sionov et al. 2010). Genes on Chr4 also were linked to drug resistance. "
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