Genetic profiling of the isoprenoid and sterol biosynthesis pathway genes of Trypanosoma cruzi.
In Trypanosoma cruzi the isoprenoid and sterol biosynthesis pathways are validated targets for chemotherapeutic intervention. In this work we present a study of the genetic diversity observed in genes from these pathways. Using a number of bioinformatic strategies, we first identified genes that were missing and/or were truncated in the T. cruzi genome. Based on this analysis we obtained the complete sequence of the ortholog of the yeast ERG26 gene and identified a non-orthologous homolog of the yeast ERG25 gene (sterol methyl oxidase, SMO), and we propose that the orthologs of ERG25 have been lost in trypanosomes (but not in Leishmanias). Next, starting from a set of 16 T. cruzi strains representative of all extant evolutionary lineages, we amplified and sequenced ∼ 24 Kbp from 22 genes, identifying a total of 975 SNPs or fixed differences, of which 28% represent non-synonymous changes. We observed genes with a density of substitutions ranging from those close to the average (∼ 2.5/100 bp) to some showing a high number of changes (11.4/100 bp, for the putative lathosterol oxidase gene). All the genes of the pathway are under apparent purifying selection, but genes coding for the sterol C14-demethylase, the HMG-CoA synthase, and the HMG-CoA reductase have the lowest density of missense SNPs in the panel. Other genes (TcPMK, TcSMO-like) have a relatively high density of non-synonymous SNPs (2.5 and 1.9 every 100 bp, respectively). However, none of the non-synonymous changes identified affect a catalytic or ligand binding site residue. A comparative analysis of the corresponding genes from African trypanosomes and Leishmania shows similar levels of apparent selection for each gene. This information will be essential for future drug development studies focused on this pathway.
Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús, Universidad de San Martín - CONICET, Sede San Martín, Buenos Aires, Argentina.
Raúl O
RO
Cosentino
Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico de Chascomús, Universidad de San Martín - CONICET, Sede San Martín, Buenos Aires, Argentina.
Fernán
F
Agüero
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D014644:Genetic Variation; D018503:Genome, Protozoan; D007891:Leishmania / Q000235:genetics; D008565:Membrane Proteins; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D006899:Mixed Function Oxygenases / Q000235:genetics; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D015800:Protozoan Proteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013261:Sterols / Q000096:biosynthesis*; D013729:Terpenes / Q000378:metabolism*; D014345:Trypanosoma / Q000235:genetics; D014349:Trypanosoma cruzi / Q000235:genetics*
C438144:ASI1 protein, S cerevisiae; D008565:Membrane Proteins; D015800:Protozoan Proteins; D029701:Saccharomyces cerevisiae Proteins; D013261:Sterols; D013729:Terpenes; D006899:Mixed Function Oxygenases; D015096:3-Hydroxysteroid Dehydrogenases; C069942:ERG26 protein, S cerevisiae; C547779:ERG25 protein, S cerevisiae