Morphological variations of a hypha-forming strain of<i>Cryptococcus neoformans</i>(Coward strain) in tissues of mice

Lurie, H. I.; Shadomy, H. Jean

doi:10.1080/00362177185190041

Cited by 33 publications

(16 citation statements)

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“…Research on different morphological forms has implicated positive roles for cell gigantism in disease (11)(12)(13)(14)(15)(16) and negative roles for filaments in disease and conversely inducing a protective response from the host (17)(18)(19)(20)(21)(22). Accordingly, the filamentous form is only occasionally observed in host tissues and is considered an atypical form for Cryptococcus in vivo (5)(6)(7)(8)(9)(10). The association between morphogenesis and virulence in Cryptococcus is thus similar to that observed in other conventional dimorphic fungal pathogens, such as Histoplasma capsulatum and Blastomyces dermatitidis (23)(24)(25)(26).…”

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confidence: 65%

Congenic Strains of the Filamentous Form of Cryptococcus neoformans for Studies of Fungal Morphogenesis and Virulence

et al. 2013

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cCryptococcus neoformans is an unconventional dimorphic fungus that can grow either as a yeast or in a filamentous form. To facilitate investigation of genetic factors important for its morphogenesis and pathogenicity, congenic a and ␣ strains for a filamentous form were constructed. XL280 (␣) was selected as the background strain because of its robust ability to undergo the morphological transition from yeast to the filamentous form. The MATa allele from a sequenced strain JEC20 was introgressed into the XL280 background to generate the congenic a and ␣ pair strains. The resulting congenic strains were then used to test the impact of mating type on virulence. In both the inhalation and the intravenous infection models of murine cryptococcosis, the congenic a and ␣ strains displayed comparable levels of high virulence. The a-␣ coinfections displayed equivalent virulence to the individual a or ␣ infections in both animal models. Further analyses of the mating type distribution in a-␣ coinfected mice suggested no influence of a-␣ interactions on cryptococcal neurotropism, irrespective of the route of inoculation. Furthermore, deletion or overexpression of a known transcription factor, Znf2, in XL280 abolished or enhanced filamentation and biofilm formation, consistent with its established role. Overexpression of Znf2 in XL280 led to attenuation of virulence and a reduced abundance in the brain but not in other organs, suggesting that Znf2 might interfere with cryptococcal neurotropism upon extrapulmonary dissemination. In summary, the congenic strains provide a new resource for the exploration of the relationship in Cryptococcus between cellular morphology and pathogenesis.

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confidence: 65%

Congenic Strains of the Filamentous Form of Cryptococcus neoformans for Studies of Fungal Morphogenesis and Virulence

et al. 2013

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“…C. neoformans, although capable of producing true hyphae, was not generally considered to be dimorphic because the hyphal phase is usually transient and is observed exclusively during mating. The few reports of hyphal production in C. neoformans occurring under nonmating conditions (5,16,27,28) are the result of diploids or aneuploids which are self-fertile (5,29).…”

Section: Resultsmentioning

confidence: 99%

Dimorphism and haploid fruiting in Cryptococcus neoformans: association with the alpha-mating type.

Wickes

Mayorga

Edman

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

295

298

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Cryptococcus neoformans is a major opportunistic fungal pathogen in AIDS and other immunosuppressed patients. We have shown that wild-type haploid C. neoformans can develop an extensive hyphal phase under appropriate conditions. Hyphae produced under these conditions are monokaryotic, possess unfused clamp connections, and develop basidia with viable basidiospores. The ability to undergo this transition is determined by the presence of the a-mating type locus and is independent of serotype. The association of the hyphal phase with the a-mating type may explain the preponderance of this mating type in the environment and the nature of the infectious propagule of C. neoformans.Since the discovery of the sexual or perfect state of the human fungal pathogen Cryptococcus neoformans by Kwon-Chung (1, 2), it has been considered a bipolar heterothallic basidiomycete with two mating types, a and a (MA Ta and MA Ta The ability of hyphae to form fruiting body-like structures in the vegetative phase is called monokaryotic, homokaryotic, or haploid fruiting (13). Although haploid fruiting is common in the higher basidiomycetes (13-15), it has not been characterized in C. neoformans, and association with mating type has never been described. Recent observations made in this laboratory and a reassessment of past studies (5, 10, 16) allow us to propose a new hypothesis for the biased mating type ratios and the nature of the infectious propagule of C. neoformans. We show here that a strains of C. neoformans can undergo a true dimorphic transition from a haploid yeast phase to a hyphal phase from which vegetative growth can continue indefinitely. The hyphal phase is induced by nitrogen starvation on a solid surface. Basidia bearing viable basidiospores are also produced, all of which are a in mating type. The ability of a but not a cells to form basidiospores under these conditions provides an attractive explanation for both the mating type bias and the nature of the infectious propagule of C. neoformans. MATERIALS AND METHODSStrains. The strains used in this study are listed in Table 1. Auxotrophic strains were derived from JEC20 (MA Ta) and JEC21 (MA Ta). JEC20 and JEC21 are a well-characterized, haploid, congenic pair of prototrophic laboratory strains that presumably differ only at the mating type locus (17).Media 7327The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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“…Other reports describe the identification of variant forms having pseudohyphae 2,19 , germ-tube like structures and hyphae-forming structures 6 , all identified in an India ink preparation of CSF. In a review of prior necropsy specimens, a case was discovered in which germ tubes and hyphae were observed in brain tissues 15 . Rare germinating forms of Cryptococcus spp.…”

Section: Discussionmentioning

confidence: 99%

Unusual morphologies of Cryptococcus spp. in tissue specimens: report of 10 cases

Gazzoni

Oliveira

Salles

et al. 2010

Rev. Inst. Med. trop. S. Paulo

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SUMMARYTen cases of cryptococcosis due to unusual microscopic forms of Cryptococcus sp. observed over a twenty-eight year period ) are presented. The most important clinicopathological and laboratory data are tabulated. The uncommon forms of cryptococcal cells given are: structures resembling germ tube (one case), chains of budding yeasts (one case), pseudohyphae (two cases) and nonencapsulated yeast-like organisms (eight cases). The diagnosis was based on the histopathological findings. The causative organism was isolated and identified in seven cases; five were due to C. neoformans, and two to C. gattii. In addition, the importance of using staining histochemical techniques -Grocott's silver stain (GMS), Mayer's mucicarmine stain (MM) and Fontana-Masson stain (FM) -in the diagnosis of cryptococcosis is argued.

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Morphological variations of a hypha-forming strain ofCryptococcus neoformans(Coward strain) in tissues of mice

Cited by 33 publications

References 7 publications

Congenic Strains of the Filamentous Form of Cryptococcus neoformans for Studies of Fungal Morphogenesis and Virulence

Congenic Strains of the Filamentous Form of Cryptococcus neoformans for Studies of Fungal Morphogenesis and Virulence

Dimorphism and haploid fruiting in Cryptococcus neoformans: association with the alpha-mating type.

Unusual morphologies of Cryptococcus spp. in tissue specimens: report of 10 cases

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