PHYSICAL MAPPING AND EXPRESSION OF GENE FAMILIES ENCODING THE N-ACETYL D-GALACTOSAMINE ADHERENCE LECTIN OF ENTAMOEBA-HISTOLYTICA

Adherence of the enteric protozoan parasite Entamoeba histolytica is m ediated by an N-acetyl D-galactosamine (GalNAc)-specific lectin, a het erodimer of heavy (170 kDa) and light (35/31 kDa) subunits. The gene f amilies encoding the lectin subunits were characterized using clamped homogeneous electric field (CHEF) gel electrophoresis in the strain HM 1:IMSS. The heavy subunit was shown to be encoded by a family of five hgl genes, which were physically mapped to five distinct Hindlll restr iction fragments. The light subunit was shown to be encoded by a famil y of lgl genes located at six loci in the genome. Heavy and light subu nit genes did not appear to be linked. Partial sequences of new member s of the hgl and lgl gene families were obtained. Several different st rains of E. histolytica were found to contain multiple hgl loci in the ir genomes. Expression of hgl and lgl genes in HM1:IMSS trophozoites w as examined under different growth conditions using the reverse transc ription-polymerase chain reaction (RT-PCR). mRNA transcripts were dete cted from three hgl genes and three lgl genes, with no significant dif ferences between cultured amoebae and amoebae from liver abscesses. Th e complexity of GalNAc lectin gene expression observed suggests distin ct biological functions for the products of the individual genes durin g pathogenesis.