Differential gene expression in the pathogenic dermatophyte Arthroderma benhamiae in vitro versus during infection

Abstract

Although dermatophytes are the most common agents of superficial mycoses in humans and animals, the molecular basis of the pathogenicity of these fungi is largely unknown. In vitro digestion of keratin by dermatophytes is associated with the secretion of multiple proteases, which are assumed to be responsible for their particular specialization to colonize and degrade keratinized host structures during infection. To investigate the role of individual secreted proteases in dermatophytosis, a guinea pig infection model was established for the zoophilic dermatophyte Arthroderma benhamiae, which causes highly inflammatory cutaneous infections in humans and rodents. By use of a cDNA microarray covering approximately 20-25 % of the A. benhamiae genome and containing sequences of at least 23 protease genes, we revealed a distinct in vivo protease gene expression profile in the fungal cells, which was surprisingly different from the pattern elicited during in vitro growth on keratin. Instead of the major in vitroexpressed proteases, others were activated specifically during infection. These enzymes are therefore suggested to fulfil important functions that are not exclusively associated with the degradation of keratin. Most notably, the gene encoding the serine protease subtilisin 6, which is a known major allergen in the related dermatophyte Trichophyton rubrum and putatively linked to host inflammation, was found to be the most strongly upregulated gene during infection. In addition, our approach identified other candidate pathogenicity-related factors in A. benhamiae, such as genes encoding key enzymes of the glyoxylate cycle and an opsin-related protein.Our work provides what we believe to be the first broad-scale gene expression profile in human pathogenic dermatophytes during infection, and points to putative virulence-associated mechanisms that make these micro-organisms the most successful aetiological agents of superficial mycoses.Abbreviations: FDR, false discovery rate; MFS, major facilitator superfamily; PAS, periodic acid Schiff; qRT-PCR, quantitative reverse-transcription PCR.

The dermatophyte species Arthroderma benhamiae: intraspecies variability and mating behaviour

“…Like other dermatophyte species, A. benhamiae is heterothallic and is able to produce cleistothecia (sexual fructifications) containing asci and ascospores when strains from two different mating types, mating type + (mt+) and mating type 2 (mt2), meet. A. benhamiae was selected as an appropriate species for fundamental research on dermatophytes for several practical reasons: (i) the species grows relatively fast in comparison with other dermatophyte species; (ii) it produces abundant microconidia, which are useful for genetic manipulation (Grumbt et al, 2011); and (iii) A. benhamiae causes inflammatory cutaneous infections in guinea pigs, allowing the establishment of an animal infection model (Staib et al, 2010). The genome of an A. benhamiae strain (LAU 23545IHEM 201615CBS 112371), isolated from a patient with highly inflammatory tinea faciei, has recently been sequenced and annotated .…”

The Arthroderma benhamiae Hydrophobin HypA Mediates Hydrophobicity and Influences Recognition by Human Immune Effector Cells

“…In the human host, A. benhamiae infections are characterized by inflammatory progression and are usually quickly eradicated by the host immune system. Besides the putative role of proteases and other enzymes abundantly secreted during infection or under other growth conditions (10,17,34), little is known about the molecular strategies which dermatophytes use to infect mammalian hosts and to counteract the initial immune response. On the host side, infected epithelial tissue reacts to fungal invasion by the secretion of a complex and species-specific cytokine pattern (32).…”

Targeted Gene Deletion and In Vivo Analysis of Putative Virulence Gene Function in the Pathogenic Dermatophyte Arthroderma benhamiae

“…As a consequence, in dermatophyte species only a few genes have to date been analyzed by targeted inactivation, i.e., pacC and MDR2 in Trichophyton rubrum (8, 9), Ku80, areA, and Trim4 in Trichophyton mentagrophytes (Arthroderma vanbreuseghemii) (32), and areA in Microsporum canis (31). Specifically constructed dermatophyte mutants have, to our knowledge, not yet been tested in animal models.In a recent study, we monitored a broad-scale gene expression profile in the human pathogenic dermatophyte Arthroderma benhamiae during keratin degradation and also during cutaneous infection of guinea pigs (25). By this approach, the in vivo activation of genes encoding key enzymes of the glyoxylate cycle, i.e., malate synthase and isocitrate lyase, was detected.…”

“…In a recent study, we monitored a broad-scale gene expression profile in the human pathogenic dermatophyte Arthroderma benhamiae during keratin degradation and also during cutaneous infection of guinea pigs (25). By this approach, the in vivo activation of genes encoding key enzymes of the glyoxylate cycle, i.e., malate synthase and isocitrate lyase, was detected.…”