USE OF VNTRS WITHIN CODING SEQUENCES TO GENOTYPE TOXOPLASMA GONDII

MORETTA R; RUYBAL P; MARTIN V

CABA

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Toxoplasma gondii is an intracellular protozoan with a worldwideprevalence in human and animal populations. Infection occurs as aresult of ingestion of resistant forms present in meat products andexposure to cat faeces. In immunocompetent individuals is generallyasymptomatic. Severe disease may occur in immunocompromisedsubjects and in congenital toxoplasmosis, which is caused by transplacentalacquisition of Toxoplasma gondii.Genetic diversity of T. gondii has been studied using a PCR-RFLPscheme based on nine molecular markers. These studies led to thedescription of a clonal population structure with three main lineages,designated as type I, II and III.The aim of this study was to develop molecular markers that allowedthe discrimination of genetic variants within each clonal linageand therefore describe T. gondii population variability closer to strainlevel.We analyzed the genome of Toxoplasma gondii to identify genescontaining variable number tandem repeats (VNTRs). The codingsequences of T. gondii ME49 genome (www.toxodb.org) were processedwith Tandem Repeat Finder software. A panel of candidatemarkers was selected based on the following parameters: the repeatperiod (20), the repeat modulecomposition (to avoid single and dinucleotide runs) and the absenceof introns within the repeat region.The selected panel of eight molecular markers was analyzed inPRU (type II) and RH (type I) strains. As a first step, the variabilityof the PCR product size allowed us to differentiate PRU from ME49(both type II strains) and RH from GT1 (both type I strains). Additionally,amplification products from PRU and RH strains were sequencedto study intra-lineage variability. Polymorphic markers betweentype I and type II strains presented specific arranges of theVNTR pattern. Nonetheless, those markers that didn´t present sizepolymorphisms were also conserved at the sequence level.