STRUCTURAL ORGANIZATION OF MICROSATELLITE FAMILIES IN THE LEISHMANIA GENOME AND POLYMORPHISMS AT 2 (CA)(N) LOCI

In the present study, we have analysed the frequency and distribution of several microsatellite DNAs [(CA)(n), (GGT)(n) and (GCA)(n)] in the genome of Leishmania. Hybridisation analysis on the molecular karyoty pes of different Leishmania strains showed the presence of these three microsatellites on all chromosomes of the parasite. The number of mic rosatellite clusters appeared grossly similar among strains from diffe rent Old World complexes. However, these three microsatellite families showed an uneven distribution among heterologous chromosomes of the s ame strain. Moreover, restriction analysis of chromosome I in various strains of Leishmania infantum showed a strong clustering of these mic rosatellites in the same chromosomal region. A partial genomic library was screened with a (CA)(n) probe, and 21 positive clones were isolat ed. The sequencing of these clones confirmed the association of variou s microsatellites such as (CA)(n), (CT)(n) and (GCA)(n). Finally, spec ific polymerase chain reaction amplification of two cloned (CA)(n) loc i demonstrated allelic size polymorphisms among strains within L. infa ntum and Leishmania donovani. Most of the 34 strains analysed were fou nd to be monoallelic, while two alleles were found in a small number o f strains. The interest of these sequences for studies on ploidy and p opulation genetics of the parasite is discussed.