ANCIENT GENE DUPLICATION AND DOMAIN SHUFFLING IN THE ANIMAL CYCLIC-NUCLEOTIDE PHOSPHODIESTERASE FAMILY

The animal cyclic nucleotide phosphodiesterases (PDEs) comprise at lea st seven subtypes, PDE1-7, which differ from each other in domain orga nization and primary function, and they diverged from an ancestral gen e by gene duplication and domain shuffling during animal evolution. To obtain rough estimates for the divergence times of these subtypes, cl oning of PDE cDNAs from Ephydatia fluviatilis (freshwater sponge) by R T-PCR was carried out. We obtained four cDNAs, EFPDE1, EFPDE2, EFPDE3, and EFPDE4, which are possibly homologs of the vertebrate PDE1, PDE2, PDE3, and PDE4, respectively, judging from the sequence similarity, d omain organization, and branching pattern in the phylogenetic tree. Th e phylogenetic tree of the PDE family revealed that most gene duplicat ions and domain shufflings that gave rise to different subtypes had be en completed in the early evolution of animals before the separation o f sponges and eumetazoans, (C) 1998 Federation of European Biochemical Societies.