Cellular and genetic changes during and after fluconazole exposure in Cryptococcus neoformans

The validity of genome replication is fundamental to fungal survival, and errors in this process can result in ploidy changes. These changes can have negative effects, such as developmental defects or reduced fitness, or positive effects such as fungal adaptation and resilience. In the fungal pathogen Cryptococcus neoformans, ploidy changes have been consistently observed in clinical populations, and isolates exposed to the antifungal drug fluconazole commonly exhibit chromosome 1 aneuploidy. Chromosomal and putative metabolic function changes due to drug exposure are not well studied and are important for understanding resistance.

This study examined the fluconazole influence on C. neoformans transient aneuploidy and identified any potential genetic pathways that may be implicated.

The study investigated 30 genes predicted to have a role in transient aneuploidy, which are related to chromosome organisation, DNA damage checkpoints and stress signalling. Other factors including ploidy status (haploid, diploid, polyploid) and species were also investigated to observe commonalities for a universal drug treatment strategy.

Fluconazole treatment increased DNA content, cell size and chromosomal changes in the wildtype and mutants. When fluconazole was removed, permanent changes were observed and were highly variable in the wildtypes and the 30 mutants. Additionally, some mutants lacked chromosomal changes such as tel1∆, mrc1∆ and hog1∆, highlighting the potential involvement in the aneuploidy process.

These findings highlight that fluconazole influences the entire genome rather than specific chromosomes, which increases the heterogeneity in permanent changes after fluconazole removal. This heterogeneity may result in long-term consequences, including drug resistance.