Project description:Pneumocystis pneumonia is the most common serious opportunistic infection in patients with HIV/AIDS. Furthermore, Pneumocystis pneumonia is a feared complication of the immunosuppressive drug regimens used to treat autoimmunity, malignancy, and post-transplantation rejection. With an increasing at-risk population, there is a strong need for novel approaches to discover diagnostic and vaccine targets. There are multiple challenges to finding these targets, however. First, Pneumocystis has a largely unannotated genome. To address this, we evaluated each protein encoded within the Pneumocystis genome to that of other fungi using NCBI Blast. Second, Pneumocystis relies on a multiphasic life cycle, as both the transmissible form, the ascus, and the replicative form, the troph, reside within the alveolar space of the host. Towards that end, we purified asci and trophs from Pneumocystis murina and utilized transcriptomics to identify differentially regulated genes. Two such genes, Arp9 and Sp, are differentially regulated in the ascus and the troph, respectively, and can be utilized to characterize the state of the Pneumocystis life cycle in vivo. Gsc1, a β-1,3-glucan synthase with a large extracellular domain previously identified using surface proteomics, was more highly expressed on the ascus form of Pneumocystis. GSC-1 ectodomain immunization generated a strong antibody response capable of recognizing the surface of the Pneumocystis asci. GSC-1 ectodomain immunization was also capable of reducing ascus burden following primary challenge with Pneumocystis murina. Finally, mice immunized with the GSC-1 ectodomain had limited burden following natural transmission of Pneumocystis using a co-housing model. Pneumocystis asci and trophs were separated via flow cytometry and the transcriptome was sequenced, allowing to further understand the differential expression of various RNA transcripts. These data can be mined for life-form specific diagnostics and therapeutic targets.
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.