Isolation, Characterization, and Localization of a Capsule-Associated Gene, <i>CAP10</i> , of <i>Cryptococcus neoformans</i>

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:italic>Cryptococcus neoformans</jats:italic> is a pathogenic fungus which most commonly affects the central nervous system and causes fatal meningoencephalitis primarily in patients with AIDS. This fungus produces a thick extracellular polysaccharide capsule which is well recognized as a virulence factor. Here, we describe the isolation and characterization of a novel gene, <jats:italic>CAP10</jats:italic> , which is required for capsule formation. Complementation of the acapsular <jats:italic>cap10</jats:italic> mutant produced an encapsulated strain and the deletion of <jats:italic>CAP10</jats:italic> from a wild strain resulted in an acapsular phenotype. The molecular mass of the hemagglutinin epitope-tagged Cap10p is about 73 kDa, which is similar to the size predicted from sequence analysis. When <jats:italic>CAP10</jats:italic> was fused with a hybrid green fluorescent protein construct, the fluorescence signals appeared as patches in the cytoplasm. Using a reporter gene construct, we found that <jats:italic>CAP10</jats:italic> was expressed at high levels in late-stationary-phase cells. In addition, we found that the expression levels of <jats:italic>CAP10</jats:italic> are modulated by the transcriptional factor <jats:italic>STE12</jats:italic> α. Deletion of <jats:italic>STE12</jats:italic> α downregulated the expression levels of <jats:italic>CAP10</jats:italic> while overexpression of <jats:italic>STE12</jats:italic> α upregulated the expression levels of <jats:italic>CAP10</jats:italic> . Animal model studies indicate that deletion of the <jats:italic>CAP10</jats:italic> gene results in the loss of virulence, and complementation of the acapsular phenotype of <jats:italic>cap10</jats:italic> restores virulence. Thus, <jats:italic>CAP10</jats:italic> is required for capsule formation and virulence. </jats:p>