LAUSR

Genes encoding Wnt ligands, which have important roles in cell communication and organ development, are restricted to multicellular animals. We systematically studied Wnt genes from eumetazoan genomes, with emphasis on the poorly studied superphylum Lophotrochozoa (four annelids, seven mollusks, eight platyhelminths, one bdelloid rotifer, and one brachiopod species). Between 3 and 39 Wnt loci were identified in each genome, and the protostome-specific loss of Wnt3 genes was confirmed. We identified gastropod-specific loss of Wnt8, refining the previously proposed mollusk-specific loss. Some duplicated Wnt genes belonging to a same subfamily or closely related subfamilies showed tandem distribution in the lophotrochozoan genomes, indicating tandem duplication events during Wnt family evolution. Members of the conserved Wnt10 - Wnt6 - Wnt1 - Wnt9 cluster showed highly correlated expression patterns over time in two assayed lophotrochozoans, the oyster Crassostrea gigas and the brachiopod Lingula anatina, reflecting the possible similar function of the clustered Wnt genes.