Cryptosporidium Muris Genome Project

Status

The initial version of the C. muris WGS sequence has been deposited at GenBank.

Background

The genus Cryptosporidium, a group of single-celled eukaryotic organisms in the phylum Apicomplexa, comprises an unknown number of species infecting numerous vertebrate species. It includes two groups of parasites that have adapted to different environments in the gastrointestinal (GI) tract: the small intestine/colon, where the majority of species multiply, and the stomach, which only a few species are able to infect. Cryptosporidium species are significant sources of gastrointestinal infection worldwide. Particularly in underdeveloped nations, cryptosporidiosis is common in children, where it is frequently associated with persistent diarrhea, malnutrition and stunted growth (Guerrant 1997). In immune compromised individuals, persistent infection with Cryptosporidium can lead to wasting and is often fatal. Effective drugs or vaccines against this infection are not available (Tzipori 1998). The human-infecting species C. parvum and C. hominis, which colonize the lower GI tract, are classified as class B agents of bioterrorism. Their genome sequences have been recently published, and revealed a 95-98% similarity at the DNA level between the two species (Abrahamsen et al. 2004, Xu et al. 2004).

C. muris is a rodent parasite and one of the species that have adapted to the harsh conditions of the stomach. The evolutionary distance between the gastric species C. muris and the intestinal C. parvum/C. hominis species (~20% divergence at the DNA level in coding sequences) will enable comparative genomic studies which are not feasible with the very closely related species C. parvum and C. hominis.

Goals

The goals of the project are as follows: (1) to shotgun sequence the C. murisgenome to 8X coverage; (2) to sequence 20,000 clones from a C. muris cDNA library to provide gene prediction training and verification data; and (3) to manually annotate the C. muris genome sequence in comparison with the genome sequence data for C. parvum and C. hominis. Completion of this project will provide the community with high quality annotated sequence for a third species of Cryptosporidium, as well as a comparative reannotation of the existing Cryptosporidium genomes.

References

1. Abrahamsen MS, Templeton TJ, Enomoto S, Abrahante JE, Zhu G, Lancto CA, Deng M, Liu C, Widmer G, Tzipori S, Buck GA, Xu P, Bankier AT, Dear PH, Konfortov BA, Spriggs HF, Iyer L, Anantharaman V, Aravind L, Kapur V, 2004. Complete genome sequence of the apicomplexan, Cryptosporidium parvum. Science 304: 441-5.
2. Guerrant RL., 1997. Cryptosporidiosis: an emerging, highly infectious threat. Emerg Infect Dis. 3:51-7.
3. Tzipori, S., 1998. Cryptosporidiosis: laboratory investigations and chemotherapy. Adv. Parasitol. 40: 187-221.
4. Xu P, Widmer G, Wang Y, Ozaki LS, Alves JM, Serrano MG, Puiu D, Manque P, Akiyoshi D, Mackey AJ, Pearson WR, Dear PH, Bankier AT, Peterson DL, Abrahamsen MS, Kapur V, Tzipori S, Buck GA, 2004. The genome of Cryptosporidium hominis. Nature 431:1107-12.