Tandem repeats a new tools for Anaplasma marginale epidemiological studies

RUYBAL PAULA; MORETTA ROSALIA; PETRIGH ROMINA; ALCARAZ ELVA; ECHAIDE SUSANA; FARBER MARISA

Montevideo, Uruguay

Simposio; 12º Simposio Internacional de la Asociación Mundial de Laboratorios de Diagnóstico Veterinario; 2005

MSP1 is a dimer of two structurally unrelated polypeptides, MSP1a and MSP1b.  MSP1a is encoded by a single copy gene (msp1a). Because of different number of tandem repeats (28- or 29- aminoacids) located in the amino-terminal portion of the protein presents a molecular weight variation among isolates. The msp1a gene is conserved during acute and persistent rickettsemia in cattle and also during multiplication in ticks and has been used as a stable genetic marker for identification of Anaplasma marginale isolates. Eighty different repeated forms have been described from European, Australian, and American isolates. However, only two Argentinian isolates (Salta and Virasoro) were analyzed so far. In our study we describe 11 new repeats from different geographical regions of Argentina including enzootic and non-enzootic regions. Short nucleotide sequences repeated in tandem, microsatellite (up to 6 nucleotides) or minisatellite elements are very frequent in eukaryotic organisms. The accumulating bacterial genomic data have revealed that these elements are also frequent in bacteria. Moreover, tandem repeats have potentially high variability in repeated units number allowing great strain discrimination capacity. Two different minisatellite elements were found after complete Anaplasma marginale genome analysis using “Tandem Repeat Finder” software. AMTR11 consists in an 11bp sequence repeated up to 19 times while AMTR15 (15bp) is repeated up 13 to times in the several isolates analysed so far . Both minisatellites are excluded from ORFs and AMTR11 seemed to have higher variability rate than AMTR15. Furthermore, AMTR11 and AMTR15 showed higher polymorphism than MSP1a. Finally, these studies suggest that the analysis of AMTR11 and AMTR15 minisatellites may provide a new tool to further discriminate among Anaplasma marginale isolates.