Physical mapping of a 670-kb region of chromosomes XVI and XVII from the human protozoan parasite Trypanosoma cruzi encompassing the genes for two immunodominant antigens

As part of the Trypanosoma cruzi Genome Initiative, we have mapped a large portion of the chromosomal bands XVI (2.3 Mb) and XVII (2.6 Mb) containing the highly repetitive and immunodominant antigenic gene families h49 and j1 8. Restriction mapping of the isolated chromosomal bands and hybridization with chromosome specific gene probes showed that genes h49 and j18 are loca ted in a pair of size-polymorphic homologous chromosomes. To construct the integrated map of the chromosomes harboring the h49 and j18 loci, we used Y AC, cosmid, slid lambda phage overlapping clones, and long range restrictio n analysis using a variety of probes (i.e., known gene sequences, ESTs, pol ymorphic repetitive sequences, anonymous sequences, STSs generated from the YAC ends). The total length covered by the YAC contig was approximately 67 0 kb, and its map agreed and was complementary to the one obtained by long- range restriction Fragment analysis. Average genetic marker spacing in a 10 5 kb region around h49 and j18 genes was estimated to be 6.2 kb/marker. We have detected some polymorphism in the H49/JL8 antigens-encoding chromosome s, affecting also the coding regions. The physical map of this region, toge ther with the isolation of specific chromosome markers, will contribute in the global effort to sequence the nuclear genome of this parasite.