Year: 2023
Type: article
Abstract: Most microscopic fungal species respond to their surrounding conditions with morphological changes, including transitions between yeast, pseudohyphal, and hyphal forms.In some cases, cells may undergo more subtle yet effective transformations that alter the size, shape, and biophysical barriers of the cells [1].Cryptococcus neoformans is an encapsulated human fungal pathogen and the etiological agent of cryptococcosis and cryptococcal meningitis [2].Cryptococcal infections begin with the inhalation of basidiospores, which initiate mostly asymptomatic lung infections in immunologically intact hosts [3].In immunocompromised patients, infections can disseminate to the central nervous system (CNS), promoting life-threatening meningitis.In recent years, evidence has accumulated that morphological changes are key mechanisms that allow C. neoformans to persist in tissues in the form of enlarged cells and disseminate within the host organism as microcells [4]. Mating and hypha formationThe mating cycle of C. neoformans produces hyphae, a result of the fusion of two yeast cells.These branching segments later form basidia and spores (Fig 1).C. neoformans is a heterothallic fungus, with two mating types of yeast cells (MATa and MATα) [5].The bipolar mating system is distinguished by two alleles at the MAT locus.Contact between MATa and MATα mating types produces zygotes that undergo filamentous growth.If opposite mating types, the hyphae are dikaryotic and parental nuclei remain separate; if same mating type, the hyphae are monokaryotic and the parental nuclei undergo fusion to produce diploids.[6].Both types of fruiting can lead to basidiospore production.Transition to hyphal morphotypes is triggered by environmental changes, such as low temperature and moisture, as well as limited nutrient availability [6].While pseudohyphae display resistance to amoeba and phagocytic predators, it is unknown whether the sexual hyphal forms of C. neoformans are resistant to phagocytosis.Interestingly, mating and the formation of hyphae are influenced by the nutrients sourced from the Cryptococcus environmental niche.For instance, C. neoformans can be sourced from bird guano and trees, and mating can be stimulated using a variety of media formulations, including plant-derived media, as well as live plants [7,8].This suggests that the availability and source of nutrients drive sexual reproduction, which can increase genetic variety and lead to enhanced survival and virulence [7,9].Recently, identified genes that are important to hyphal formation include OLP1, which produces an oxidoreductase-like protein and is necessary for proper hyphae formation, and MKT1, which is involved in pheromone gene expression and hyphal growth [10,11].
Source: PLoS Pathogens
Institution: Johns Hopkins University
Language: English
Subfield: Epidemiology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,655
OpenAlex ID: W4313535147