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Aspergillus fumigatus adhesion factors in dormant conidia revealed through comparative phenotypic and transcriptomic
Azusa Takahashi-Nakaguchi1, Kanae Sakai1, Hiroki Takahashi1
1Medical Mycology Research Center, Chiba University, Chiba, Japan.
Abstract:
Aspergillus fumigatus is an important fungal pathogen of humans. Inhaled conidia of A. fumigatus adhere to pulmonary epithelial cells, causing opportunistic infection. However, little is known about the molecular mechanism of the adherence of resting conidia. Fungal molecules adhesive to host cells are presumed to be displayed on the conidial surface during conidial formation as a result of changes in gene expression. Therefore, we exhaustively searched for adhesion molecules by comparing the phenotypes and the gene expression profiles of A. fumigatus strains that have conidia showing either high or low adherence to human pulmonary A549 cells. Morphological observation suggested that strains that produce conidia of reduced size, hydrophobicity, or number show decreased adherence to A549 cells. K-means cluster analyses of gene expression revealed 31 genes that were differentially expressed in the high-adherence strains during conidial formation. We knocked out three of these genes and showed that the conidia of AFUA_4G01030 (encoding a hypothetical protein) and AFUA_4G08805 (encoding a haemolysin-like protein) knockout strains had significantly reduced adherence to host cells. Furthermore, the conidia of these knockout strains had lower hydrophobicity and fewer surface spikes compared to the control strain. We suggest that the selectively expressed gene products, including those we identified experimentally, have composite synergistic roles in the adhesion of conidia to pulmonary epithelial cells.
Insights
This study identifies key genes in Aspergillus fumigatus responsible for fungal conidia adherence to lung cells. Understanding these fungal adhesion mechanisms is crucial for treating opportunistic infections.
Area of Science:
- Medical Mycology
- Molecular Pathogenesis
- Fungal Biology
Background:
- Aspergillus fumigatus is a significant human fungal pathogen.
- Inhaled conidia adhere to pulmonary cells, leading to opportunistic infections.
- The molecular mechanisms of resting conidia adherence are poorly understood.
Purpose of the Study:
- To identify molecular mechanisms and genes involved in Aspergillus fumigatus conidia adherence to human pulmonary cells.
- To investigate the role of differential gene expression in conidial surface properties and host cell adhesion.
Main Methods:
- Comparative analysis of A. fumigatus strains with high and low adherence phenotypes.
- Gene expression profiling using K-means cluster analysis.
- Gene knockout studies of differentially expressed genes (AFUA_4G01030, AFUA_4G08805).
- Morphological and adherence assays on human pulmonary A549 cells.
Main Results:
- Reduced conidia size, hydrophobicity, or number correlated with decreased adherence.
- 31 differentially expressed genes were identified in high-adherence strains.
- Knockout of AFUA_4G01030 and AFUA_4G08805 significantly reduced conidia adherence.
- Knockout strains exhibited lower hydrophobicity and fewer surface spikes.
Conclusions:
- Selectively expressed genes, including those encoding a hypothetical protein and a haemolysin-like protein, play crucial roles in conidia adherence.
- These gene products likely have synergistic roles in mediating fungal adhesion to pulmonary epithelial cells.
- Findings provide insights into the molecular basis of A. fumigatus pathogenesis.
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