However the Non-Reference SNP potentially predisposed the asymptomatic infection to initiate an amebic liver abscess rather than amebic colitis (p = 0.0182) as the Non-Reference EHI_080100 SNPs, were present with even higher prevalence, in samples from amebic liver abscess (p = 0.0003, q = 0.0144). Additional studies are needed to identify additional amebic biomarkers associated with invasive disease. In both EHI_065250 and EHI_080100 the consequence of the Non-Reference polymorphisms AG-881 clinical trial was to change two amino acids within the C-terminal domains. The reason behind the association of these SNPs with invasive disease is not yet clear. The polymorphic genes have not previously been associated with a virulent
phenotype, and other than the previously discussed change in at a potential phosphorylation site, there were no other predicted changes in protein function using the currently check details available bioinformatics tools (PolyPhen http://genetics.bwh.harvard.edu/pph2/ http://sift.jcvi.org/www/SIFT_seq_submit2.html)[47, 48]. EHI_080100 (cyclin-2) is present on a short region of contiguous
DNA in the E. histolytica HM-1:IMSS genome assembly that could not be assembled into a larger contiguous DNA segment or sequence scaffold (Table 4). This suggests that the gene may be present in proximity to highly repetitive regions that prevent unambiguous assembly. Lorenzi et al. suggest that repeats and repeat-clusters are found at syntenic break points between E. histolytica and E. dispar and could act as recombination hot spots promoting genome rearrangement [49]. This “informative” locus could therefore reside in regions of DNA prone to allelic imbalance. In addition, no E. dispar homologue has been found for EHI_080100, making this gene an interesting candidate for further studies. Table 4 Locations of informative SNPs Gene id ContiguousE. Carnitine palmitoyltransferase II histolytica DNA region ID Length (bp) Location of SNP(s) (bp) EHI_080100 DS571720 5179 2725-2730 EHI_065250 DS571302 38246 10296-10318 Genomic Location of the SNPS in the EHI_080100 and EHI_065250
genes. The currently identified SNPs could act as genetic “markers” in incomplete linkage disequilibrium with neighboring DNA that contains causative or regulatory SNP (r-SNP) mutations that result in a modulation of gene expression. It is interesting to note that contiguous with the EHI_065250 gene is one of the genes encoding the intermediate subunit of the Epoxomicin Galactose- and N-acetyl-D-galactosamine (Gal/GalNAc) inhibitable lectin (igl2) [50]. The Gal/GalNAc inhibitable lectinis a well-characterised virulence factor in E. histolytica[51]. It is also possible that amino acids changes resulting from the SNPs directly influence the biological activity of the encoded protein and that these changes affect the ability of the trophozoite to invade its host. What has never been clear is the advantage to the E. histolytica parasite to the causation of invasive disease [41].