Catalogus

UGT1B genes are also present in pufferfish (Tetraodon nigroviridis) and zebrafish (Danio rerio) genomes, but they differ in their genic organisation. Pufferfish possess multiple (repeated) complete UGT1 genes and Southern blots indicate that the homologous plaice UGT1B gene may also be organised in this way. In contrast, zebrafish appear to have two UGT1 loci whose sequences and intron/exon structures are closely related to that of plaice, however, the organisation of these genes is similar to the mammalian UGT1 family since each has multiple repeated exon 1's which are alternatively spliced to a common set of exons encoding the aglycone binding domain. Taken together with evidence from phylogenetic comparison of fish sequences with UGT1 and UGT2 families in mammals, we suggest these homologous fish UGTs should all be included within the vertebrate UGT1 family and designated as UGT1B.