Masayuki Hatta

Identification of a Hydra homologue of the β-catenin/plakoglobin/armadillo gene family

The beta-catenin/plakoglobin/armadillo gene family encodes a group of highly conserved proteins which play important roles in cadherin-mediated cell adhesion and in signal transduction mechanisms involved in regulating development. This gene family previously had been isolated only from higher metazoans. Here, we describe the isolation and characterization of a beta-catenin (beta Ctn) homologue from Hydra magnipapillata, a diploblastic lower metazoan. Comparison of the putative amino acid (aa) sequence of Hydra beta Ctn, with its homologues in higher metazoans, shows that a repeating 42-aa motif present in its central domain is highly conserved throughout the metazoa. This suggests that beta Ctn appeared very early in metazoan evolution, possibly when primitive multicellular animals started to form epithelial cell layers.

Isolation and characterization of a mini-collagen gene encoding a nematocyst capsule protein from a reef-building coral, acropora donei

Genomic and cDNA clones of a mcol gene encoding mini-collagen (MCOL), a nematocyst capsule protein, have been isolated from a reef-building coral, Acropora donei (Anthozoa). The gene and its flanking regions, comprising 5382 bp and covering three exons and two introns, were sequenced. Exons 2 and 3 together have an open reading frame which can encode a MCOL of 176 amino acids (aa). The coral MCOL has all the characteristic regions present in the four hydra MCOL specified by the four mcol cDNA clones previously isolated from Hydra magnipapillata (Hydrozoa) by Kurz et al. [J. Cell Biol. 115 (1991) 1159-1169], including a central Gly-Xaa-Yaa region and flanking Pro-rich and Cys-repeat regions. This observation suggests that a mcol family is highly conserved in Anthozoa and Hydrozoa, and also that the characteristic regions present in MCOL are essential for the structure and function of these peptides.

The structure and expression of a preprohormone of a neuropeptide, Hym‐176 in Hydra magnipapillata

Hym‐176 (APFIFPGPKVamide) is a novel myoactive neuropeptide which was identified in systematic screening of signaling peptides in Hydra magnipapillata. By using PCR and library screening, we cloned and sequenced a full length cDNA which encoded a preprohormone of Hym‐176. In the preprohormone, a typical signal sequence, one copy of Hym‐176 precursor peptide and one copy of precursor sequence of another novel peptide, Hym‐357 (KPAFLFKGYKPamide), were detected. In situ hybridization analysis revealed a strong signal in peduncle neurons. Signals were also detected, though weaker, in neurons in the gastric region and around the mouth. No signals were detected in the two extremities of the body, tentacles and basal disk. The expression pattern is correlated with the distribution of Hym‐176 and its myoactive function.

Identification of a Homolog of Actin-Binding Protein, ABP-280, Localized at Epithelial Cell-Cell Boundaries in Hydra

Abstract ABP-280 cross-links actin filaments and connects membrane glycoproteins and actin filaments in mammalian blood cells. We isolated cDNA clones for ABP-280 from hydra by screening a cDNA expression library with an antiserum against a cell membrane-enriched crude fraction. The amino acid sequences deduced from the cDNA clones showed significant similarity to human ABP-280, including intramolecular repetition of a unique sequence motif, suggesting similar tertiary structure and molecular activity. Monospecific antibodies were purified from the antiserum, by affinity to fusion proteins produced from the cDNA clones, and used for immunohistochemistry. Specific staining was detected at epithelial cell-cell boundaries in the hydra. The signals were restricted to the subapico-lateral regions corresponding to the locations of septate junctions. These results suggest that the identified molecule is a possible component of the septate junction, and presumably connects membrane cell adhesion molecules to actin filaments in the epithelial cells of hydra. This is the first report describing the subcellular distribution of ABP-280-related molecules in epithelial cells.