Document Type


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Date of Submission

November 2014




Cryptosporidiosis is a ubiquitous infectious disease, caused by the protozoan parasitesCryptosporidium hominis and C. parvum, leading to acute, persistent and chronic diarrhea worldwide. Although the complications of this disease can be serious, even fatal, in immunocompromised patients of any age, they have also been found to lead to long term effects, including growth inhibition and impaired cognitive development, in infected immunocompetent children. The Cryptosporidium life cycle alternates between a dormant stage, the oocyst, and a highly replicative phase that includes both asexual vegetative stages as well as sexual stages, implying fine genetic regulatory mechanisms. The parasite is extremely difficult to study because it cannot be cultured in vitro and animal models are equally challenging. The recent publication of the genome sequence of C. hominis and C. parvum has, however, significantly advanced our understanding of the biology and pathogenesis of this parasite.

Methodology/Principal Findings

Herein, our goal was to identify cis-regulatory elements associated with heat shock response in Cryptosporidium using a combination of in silico and real time RT-PCR strategies. Analysis with Gibbs-Sampling algorithms of upstream non-translated regions of twelve genes annotated as heat shock proteins in the Cryptosporidium genome identified a highly conserved over-represented sequence motif in eleven of them. RT-PCR analyses, described herein and also by others, show that these eleven genes bearing the putative element are induced concurrent with excystation of parasite oocysts via heat shock.


Our analyses suggest that occurrences of a motif identified in the upstream regions of theCryptosporidium heat shock genes represent parts of the transcriptional apparatus and function as stress response elements that activate expression of these genes during excystation, and possibly at other stages in the life cycle of the parasite. Since heat shock and excystation represent a critical step in the development of the infectious sporozoite form ofCryptosporidium, these results provide important insight into the pathogenicity of the parasite.


Copyright: © 2010 Cohn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Is Part Of

VCU Microbiology and Immunology Publications

Figure_S1.tif (1994 kB)
Occurrences of motif identified by FIMO.

Figure_S2.tif (1959 kB)
Segregation of FIMO-identified motifs by false discovery rate.

Table_S1.doc (36 kB)
Probes and Primers used in quantitative real-time RT-PCR experiments. Gene-specific primers and probes used in RT PCR experiments to show the up regulation of the indicated heat shock genes.