RNA-sequencing analysis of Trichophyton rubrumtranscriptome in response to sublethal doses of acriflavine

Abstract

Background The dermatophyte Trichophyton rubrum is an anthropophilic filamentous fungus that infects keratinized tissues and is the most common etiologic agent isolated in human dermatophytoses. The clinical treatment of these infections is challenging because only few antifungal drugs are commercially available. To understand the mode of action of cytotoxic drugs against fungi, we evaluated the time-dependent effects of acriflavine on T. rubrum transcriptome using high-throughput RNA-sequencing (RNA-seq) technology. Results RNA-seq analysis generated approximately 200 million short reads that were mapped to the Broad Institute's Dermatophyte Comparative Database before differential gene expression analysis was performed. By employing a stringent cut-off threshold of −1.5 and 1.5 log 2 -fold changes in gene expression, a subset of 490 unique genes were found to be modulated in T. rubrum in response to acriflavine exposure. Among the selected genes, 69 genes were modulated at all exposure time points. Functional categorization indicated the putative involvement of these genes in various cellular processes such as oxidation-reduction reaction, transmembrane transport, and metal ion binding. Interestingly, genes putatively involved in the pathogenicity of dermatophytoses were down-regulated suggesting that this drug interferes with the virulence of T. rubrum . Moreover, we identified 159 novel putative transcripts in intergenic regions and two transcripts in intron regions of T. rubrum genome. Conclusion The results provide insights into the molecular events underlying the stress responses of T. rubrum to acriflavine, revealing that this drug interfered with important molecular events involved in the establishment and maintenance of fungal infection in the host. In addition, the identification of novel transcripts will further enable the improvement of gene annotation and open reading frame prediction of T. rubrum and other dermatophyte genomes.

‘Acridines’ as New Horizons in Antifungal Treatment

“…As reported previously, RNA-sequencing analysis of T. rubrum transcriptome in response to the presence of acriflavine (Figure 1) revealed differentially expressed genes involved in transmembrane transport [18]. Most of these genes were downregulated, whereas MDR4 was upregulated.…”

“…Interestingly, genes putatively involved in the pathogenicity of dermatophytosis were downregulated. Results indicated that this drug targets virulence factors of T. rubrum, which are necessary for the establishment and maintenance of fungal infection in the host [18].…”

Major challenges and perspectives in the diagnostics and treatment of dermatophyte infections

“…Additionally, during dermatophyte exposure to drug levels close to those inhibiting growth and multiplication, it was noticed that the expression of genes responsible for cell detoxification was increased (Persinoti et al 2014). On the basis of RNA sequence analysis of a T. rubrum strain exposed to acryflavine, Persinoti et al (2014) showed that genes involved in cell detoxification underwent positive regulation, and in particular genes encoding catalases, which protect the cell from oxidative stress and reactive oxygen. Increased expression of catalase genes can provide a compensatory mechanism to maintain a constant level of this enzyme inside the cell, thus protecting it from the adverse effects of the drug.…”

Heat Shock Proteins in Dermatophytes: Current Advances and Perspectives

“…Several genes were differentially expressed after exposure to acriflavine. Some genes belonging to the hsp70 family were up-regulated and the chaperone dnaK and Hsp90 co-chaperone Cdc37 were down-regulated [ 128 ]. We have shown using another experimental assay that the hsp20 , hspSsc1 , hsp70 , and even the hsf1 and pacC transcripts accumulated after exposure of T. rubrum to acriflavine (Fig.…”