MAZZA, M.E.**; RYAN, J.F.; MULLIKIN, J.C.; ROKSHAR, D.S.; FINNERTY, J.R.; Boston University, MA; Boston University, MA; National Human Genome Research Institute, Bethesda, MD; DOE, Joint Genome Institute, Walnut Creek, CA; Boston University, MA: Evolutionarily conserved and derived homeobox clusters in the starlet sea anemone Nematostella vectensis

Sequencing of the first non-bilaterian metazoan genome, the starlet sea anemone, Nematostella vectensis, provides an opportunity to study the early evolution of homeobox gene clusters. It has been proposed that early in metazoan evolution a single UrArchHox gene underwent a series of tandem duplication events resulting in an array of three homeobox gene clusters, a ProtoHox cluster, an NKL cluster and an EHGbox cluster. The ProtoHox cluster subsequently duplicated into the Hox and ParaHox clusters. The duplication events that gave rise to the Hox and ParaHox clusters are the subjects of debate. Two alternate models have been proposed to explain the genomic organization of metazoan Hox and ParaHox clusters. One suggests that an extended Hox (which includes Hox, Mox and Evx) and ParaHox cluster arose via trans duplication of the ProtoHox cluster, while an alternate scenario proposes that the ProtoHox cluster, in conjunction with an Evx/Mox ancestor, underwent cis duplication events that produced a ParaHox cluster and a Hox cluster flanked by Evx and Mox. Using the most recent assembly of the Nematostella genome we have mapped the genomic organization of cnidarian homeobox clusters, including the extended Hox cluster, ParaHox cluster, NKL cluster, and EHGbox cluster. The genomic organization of these gene clusters in cnidarians should provide further insight into the evolution of metazoan homeobox clusters.