THE FRESH-WATER PLANARIAN DUGESIA-(G)-TIGRINA CONTAINS A GREAT DIVERSITY OF HOMEOBOX GENES

To identify potential pattern control and cell determination and/or di fferentiation genes in the freshwater planarian Dugesial (G.) tigrina, we searched for homeobox genes of different types in the genome of th is primitive metazoan. We applied two basic approaches: 1) Screening t he cDNA library with degenerate oligonucleotides corresponding to the most conserved amino acid sequence from helix-3 of the homeodomain of each family; and 2) PCR amplification of genomic DNA or cDNA, using tw o sets of degenerated oligonucleotides corresponding to helices 1 and 3 of the homeodomain or two specific domains of the POU family. Using the first strategy we have identified and characterized two tissue-spe cific cell determination and/or differentiation NK-type homeobox genes . Using the second strategy we have identified several homeobox genes that belong to the HOM/Hox, paired (prd) or POU families.