Conserved and novel Wnt clusters in the basal eumetazoan Nematostella vectensis
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Evolutionarily conserved gene clusters are interesting for two reasons: (1) they may illuminate ancient events in genome evolution and (2) they may reveal ongoing stabilizing selection; that is, the conservation of gene clusters may have functional significance. To test if the Wnt family of signaling factors exhibits conserved clustering in basal metazoans and if those clusters are of functional importance, we searched the genomic sequence of the sea anemone Nematostella vectensis for Wnt clusters and correlated the clustering we observed with published expression patterns. Our results indicate that the Wnt1–Wnt6–Wnt10 cluster observed in Drosophila melanogaster is partially conserved in the cnidarian lineage; Wnt6 and Wnt10 are separated by less than 4,500 nucleotides in Nematostella. A novel cluster comprised of Wnt5–Wnt7/Wnt7b was observed in Nematostella. Clustered Wnt genes do not exhibit Hox-like colinearity nor is the expression of linked Wnt genes more similar than the expression of nonlinked Wnt genes. Wnt6 and Wnt10 are not expressed in a spatially or temporally contiguous manner, and Wnt5 and Wnt7 are expressed in different germ layers.