User:Ilya/Yeast/Phylogeny/Cryptococcus neoformans


 * a fungal pathogen that causes meningitis in immunocompromised patients

pathogenic basidiomycete Cryptococcus neoformans has two mating type specific STE12 genes STE12a and STE12α which play different roles in haploid fruiting mating and the regulation of genes 1

C. neoformans causes meningoencephalitis in humans and animals Strains of the fungus exist in five serotypes (A, B, C, D and AD) and the WM276 strain represents the serotype B group. In general, cryptococcal infections occur at high frequency (10 - 25%) in immunocompromised people such as those individuals infected with the human immunodeficiency virus (HIV). However, serotype B strains also infect immunocompetent (otherwise healthy) people. GSC - C. neoformans summary

It is a heterothallic yeast-like basidiomycete with two mating types, MATalpha and MAT a The S. cerevisiae pheromone response pathway appears to be conserved in C. neoformans. Preliminary molecular studies of mating in C. neoformans have identified a number of genes bearing substantial sequence similarity to S. cerevisiae mating-associated genes. These genes include homologues of GPA1 Tolkacheva1994,Alspaugh1997, GPB1 Wang2000 , STE12 Wickes1997 , STE4 (Wang et al., 2000) and a pheromone (Moore and Edman, 1993). 2

Additionally, a phenotype that parallels the S. cerevisiae pseudohyphal response has been identified in C. neoformans. 2

In spite of the fact that the C. neoformans mating pathway appears to be conserved, which is noteworthy because of the phylogenetic distance from S. cerevisiae, the importance of mating and mating type in this organism lies in virulence. Regardless of serotype or geographical location, the overwhelming majority of C. neoformans infections are caused by the MATalpha mating type 2. This may be due to the overwhelming prevalence of MATalpha in the evironment Litvintseva2003. In C. neoformans var. grubii it appears that the mating type is not linked to virulence Nielsen2005 in contrast to results in C. neoformans var. neoformans Kwon-Chung1992. The prevalence of MATalpha individuals in nature may be due to the haploid fruiting which can occur in haploid MATalpha cells Hull2002.