Sexual cycle of Cryptococcus neoformans var. grubii and Virulence of congenic a and α isolates

Kirsten Nielsen, Gary M. Cox, Ping Wang, Dena L. Toffaletti, John R. Perfect, Joseph Heitman

Research output: Contribution to journalArticlepeer-review

303 Scopus citations


Cryptococcus neoformans is a human-pathogenic fungus that has evolved into three distinct varieties that infect most prominently the central nervous system. A sexual cycle involving haploid cells of a and α mating types has been reported for two varieties (C. neoformans var. neoformans, serotype D, and C. neoformans var. gattii, serotypes B and C), yet the vast majority of infections involve a distinct variety (C. neoformans var. grubii, serotype A) that has been thought to be clonal and restricted to the a mating type. We recently identified the first serotype A isolate of the a mating type which had been thought to be extinct (strain 125.91). Here we report that this unusual strain can mate with a subset of pathogenic serotype A strains to produce a filamentous dikaryon with fused clamp connections, basidia, and viable recombinant basidiospores. One meiotic segregant mated poorly with the serotype A reference strain H99 but robustly with a crg1 mutant that lacks a regulator of G protein signaling and is hyperresponsive to mating pheromone. This meiotic segregant was used to create congenic a and α mating type serotype A strains. Virulence tests with rabbit and murine models of cryptococcal meningitis showed that the serotype A congenic a and α mating type strains had equivalent virulence in animal models, in contrast to previous studies linking the a mating type to increased virulence in congenic serotype D strains. Our studies highlight a role for sexual recombination in the evolution of a human fungal pathogen and provide a robust genetic platform to establish the molecular determinants of virulence.

Original languageEnglish (US)
Pages (from-to)4831-4841
Number of pages11
JournalInfection and immunity
Issue number9
StatePublished - Sep 1 2003


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