title: Sexual cycle of Cryptococcus neoformans var. grubii and virulence of congenic a and alpha isolates.
abstract: 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 alpha 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 alpha 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 alpha mating type serotype A strains. Virulence tests with rabbit and murine models of cryptococcal meningitis showed that the serotype A congenic a and alpha mating type strains had equivalent virulence in animal models, in contrast to previous studies linking the alpha 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.
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Nielsen
authors.forename: Gary M
authors.initials: GM
authors.lastname: Cox
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.forename: Dena L
authors.initials: DL
authors.lastname: Toffaletti
authors.forename: John R
authors.initials: JR
authors.lastname: Perfect
authors.forename: Joseph
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000818:Animals; D001483:Base Sequence; D003455:Cryptococcus neoformans / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology*; D004271:DNA, Fungal / Q000235:genetics; D005260:Female; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D006238:Haploidy; D006801:Humans; D008297:Male; D016919:Meningitis, Cryptococcal / Q000209:etiology / Q000382:microbiology; D051379:Mice; D008805:Mice, Inbred A; D008969:Molecular Sequence Data; D009154:Mutation; D009894:Opportunistic Infections / Q000209:etiology / Q000382:microbiology; D011817:Rabbits; D011995:Recombination, Genetic; D012703:Serotyping; D014774:Virulence / Q000235:genetics
chemical_list: D004271:DNA, Fungal