This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Giardia lamblia is an early branching protozoan parasite in the eukaryotic lineage. The organism is water transmitted and occurs as disease-causing (trophozoites) and environmental (cysts) forms. The human disease caused by G. lamblia is called giardiasis, a diarrheal illness that is the most common parasitic disease in the United States. The availability of the organism s genome sequence containing over 9,000 predicted genes as well as Serial Analysis of Gene Expression (SAGE) data from 11 life cycle stages provides basis to understand the structure and regulatory relationships of genes in the life cycle. An integrative and comparative bioinformatics approach incorporating differential expression statistics, reciprocal-BLAST algorithm and binary-encoding of SAGE tag types were used to prioritize Giardia lamblia genes. Over 30,828 SAGE Tags were evaluated for statistical significance of the differences between observed tag frequencies in the CYST library compared to that of 10 other libraries. Furthermore, each of the 6,243 genes with at least a SAGE tag was assigned into one of the 16 binary-encoded groups that indicate the mapping or otherwise of 4 SAGE tag types. A total of 63 genes were prioritized as cyst-upregulated genes, of which three genes were identified as having orthologs in the epidemiologically related human pathogen Cryptosporidium hominis. A total of 417 putative orthologous genes were identified between the two organisms. The SAGE tag types allowed the identification of outlier gene groups for example genes with only one SAGE tag type. Collectively, these observations are relevant to categorizing genes that could contribute to the annotation of the Giardia genome and allow future work on host-parasite and parasite-environment interactions of Giardia and Cryptosporidium.
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