Phenotypic characterization of HAM1 , a novel mating regulator of the fungal pathogen Cryptococcus neoformans

• Published in: Microbiology spectrum Vol. 12; no. 7; p. e0341923
• Main Authors: Arsenault Yee, Elizabeth, Ross, Robbi L, Santiago-Tirado, Felipe H
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 02-07-2024
• Subjects: Animals; Cryptococcosis - microbiology; Cryptococcus neoformans; Cryptococcus neoformans - genetics; Cryptococcus neoformans - metabolism; Cryptococcus neoformans - pathogenicity; Cryptococcus neoformans - physiology; fungal mating; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Expression Regulation, Fungal; Genes, Mating Type, Fungal - genetics; Hyphae - genetics; Hyphae - growth & development; Hyphae - metabolism; Mice; Microbial Pathogenesis; Phenotype; polysaccharide capsule; Research Article; Virulence - genetics; Virulence Factors - genetics; Virulence Factors - metabolism; polysaccharide capsule; Cryptococcus neoformans; fungal mating
• ISSN: 2165-0497; 2165-0497
• DOI: 10.1128/spectrum.03419-23

is a fungal pathogen responsible for >200,000 yearly cases with a mortality as high as 81%. This burden results, in part, from an incomplete understanding of its pathogenesis and ineffective antifungal treatments; hence, there is a pressing need to understand the biology and host interactions of this yeast to develop improved treatments. Protein palmitoylation is important for cryptococcal virulence, and we previously identified the substrates of its main palmitoyl transferase. One of them was encoded by the uncharacterized gene CNAG_02129. In the filamentous fungus
, a homolog of this gene named hyphal anastomosis protein 13 plays a role in proper cellular communication and filament fusion. In
, cellular communication is essential during mating; therefore, we hypothesized that CNAG_02129, which we named hyphal anastomosis protein 1 (
), may play a role in mating. We found that
Δ mutants produce more fusion products during mating, filament more robustly, and exhibit competitive fitness defects under mating and non-mating conditions. Additionally, we found several differences with the major virulence factor, the polysaccharide capsule, that may affect virulence, consistent with prior studies linking virulence to mating. We observed that
Δ mutants have decreased capsule attachment and transfer but exhibit higher amounts of exopolysaccharide shedding and biofilm production. Finally,
expression is significantly lower in mating media relative to non-mating conditions, consistent with it acting as a negative regulator of mating. Understanding the connection between mating and virulence in
may open new avenues of investigation into ways to improve the treatment of this disease.
Fungal mating is a vital part of the lifecycle of the pathogenic yeast
. More than just ensuring the propagation of the species, mating allows for sexual reproduction to occur and generates genetic diversity as well as infectious propagules that can invade mammalian hosts. Despite its importance in the biology of this pathogen, we still do not know all of the major players regulating the mating process and if they are involved or impact its pathogenesis. Here, we identified a novel negative regulator of mating that also affects certain cellular characteristics known to be important for virulence. This gene, which we call
, is widely conserved across the cryptococcal family as well as in many pathogenic fungal species. This study will open new avenues of exploration regarding the function of uncharacterized but conserved genes in a variety of pathogenic fungal species and specifically in serotype A of
.