Capsule Polysaccharide Synthase 1 (CPS1) Homolog in Aspergillus fumigatus: A Gene Disruption Study

Introduction: Aspergillus fumigatus is the leading cause of invasive aspergillosis in immunocompromised patients with a high rate of mortality. Despite introduction of several classes of antifungal drugs, the limitations of current therapies have prompted an intense research toward the discovery of new antifungal compounds. In a recent study, several potential drug targets were identified based on in silico comparative proteome analyses of A. fumigatus and Saccharomyces cerevisiae. A potential target, capsule polysaccharide synthase1 (CPS1) homolog gene, was identified and chosen for further study. Methods: The genome sequence of CPS1 homolog in A.  fumigatus (AfuCPS1) was retrieved from the database and analyzed. The RT-PCR analysis was carried out to show the presence of the transcripts. A gene disruption cassette was prepared and subsequently transformed into A. fumigatus strain AF293. An AfuCPS1 disruptant strain was isolated and further analyzed. Results: The AfuCPS1 gene sequence was annotated, and the signal sequence and a glycosyltransferase motif were identified. The RT-PCR analysis showed that AfuCPS1 is expressed throughout the life cycle of the fungus. The AfuCPS1 mutant showed normal colony morphology. Antifungal susceptibility assay of the mutant using different classes of known antifungal drugs confirmed a similar susceptibility pattern to the wild-type strain. However, spore germination was affected, and a delay in germination was observed. Conclusion: The findings showed that the AfuCPS1 is not essential for the normal growth of A. fumigatus. More investigation is underway to elucidate the physiological role of this gene in spore germination process.