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BMC Evol Biol
2008 May 09;8:136. doi: 10.1186/1471-2148-8-136.
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Unexpected diversity of cnidarian integrins: expression during coral gastrulation.
Knack BA
,
Iguchi A
,
Shinzato C
,
Hayward DC
,
Ball EE
,
Miller DJ
.
Abstract
BACKGROUND: Adhesion mediated through the integrin family of cell surface receptors is central to early development throughout the Metazoa, playing key roles in cell-extra cellular matrix adhesion and modulation of cadherin activity during the convergence and extension movements of gastrulation. It has been suggested that Caenorhabditis elegans, which has a single beta and two alpha integrins, might reflect the ancestral integrin complement. Investigation of the integrin repertoire of anthozoan cnidarians such as the coral Acropora millepora is required to test this hypothesis and may provide insights into the original roles of these molecules.
RESULTS: Two novel integrins were identified in Acropora. AmItgalpha1 shows features characteristic of alpha integrins lacking an I-domain, but phylogenetic analysis gives no clear indication of its likely binding specificity. AmItgbeta2 lacks consensus cysteine residues at positions 8 and 9, but is otherwise a typical beta integrin. In situ hybridization revealed that AmItgalpha1, AmItgbeta1, and AmItgbeta2 are expressed in the presumptive endoderm during gastrulation. A second anthozoan, the sea anemone Nematostella vectensis, has at least four beta integrins, two resembling AmItgbeta1 and two like AmItgbeta2, and at least three alpha integrins, based on its genomic sequence.
CONCLUSION: In two respects, the cnidarian data do not fit expectations. First, the cnidarian integrin repertoire is more complex than predicted: at least two betas in Acropora, and at least three alphas and four betas in Nematostella. Second, whereas the bilaterian alphas resolve into well-supported groups corresponding to those specific for RGD-containing or laminin-type ligands, the known cnidarian alphas are distinct from these. During early development in Acropora, the expression patterns of the three known integrins parallel those of amphibian and echinoderm integrins.
Figure 1. β integrin alignments (amino terminal end of the molecules). Amino acid sequence of AmItgβ2 aligned with representative β integrin sequences. Atypical absence of cysteines (yellow, numbered) from positions 8 and 9 suggests orthology between AmItgβ2 and Podocoryne IntB (PcIntB). Structural features including the MIDAS motif (DLSXS, underlined), transmembrane region (long wavy line), membrane proximal motif (short wavy line), and two NPxY/F motifs (double underline) are conserved. The ADMIDAS motif (DDL, underlined) is changed to EDL in AmItgβ2. An arrow indicates the position where a deletion was made in the sponge sequence (OtItgβ1) to facilitate alignment. Abbreviations and database accession numbers for sequences used in the alignment are: Acropora AmItgβ2 (AmItgβ2; EU239372); Podocoryne IntB (PcIntB; AAG25994); Acropora AmItgβ1 (AmItgβ1; AAB66910); Human β1 (HsItgβ1; P05556); Strongylocentrotus βG (Urchin SpItgβG; AAB39739); Strongylocentrotus βL (SpItgβL; AAC28382); Ophlitaspongia βPo1 (Sponge OtItgβ1; AAB66911).
Figure 2. β integrin alignments (carboxy terminal end of the molecules). See legend for Fig. 1.
Figure 3. α integrin alignments (amino terminal end of the molecules). The major structural features of alpha integrins lacking an alpha-A domain are conserved in AmItgα1 including seven FG-GAP repeats (underlined, roman numerals), three DxD/NxD/NxxxD cation binding sites (double underline), the transmembrane region (long wavy line) and the cytosolic membrane proximal domain (short wavy line). The position of a putative fourth cation binding site in the Podocoryne sequence is indicated in red. Arrows mark the positions where regions that could not be unambiguously aligned were removed from the Drosophila (DmPS2; 219 residues), Caenorhabditis (CePat2; 132 residues) and human (HsItgαV; 6 residues) sequences. Abbreviations and database accession numbers for sequences used in the alignment are: Acropora AmItgα1 (AmItgα1; EU239371); Podocoryne IntA (PcIntA; AAG25993); Drosophila αPS2 (DmPS2; P12080); Mouse α9 (MmItgα9; NP_598482); Human αV (HsItgαV; P06756); Caenorhabditis αPat2 (CePat2; P34446).
Figure 4. α integrin alignments (carboxy terminal end of the molecules). See legend for Fig. 3.
Figure 5. Maximum likelihood phylogenetic analysis of representative α and β integrin proteins. Numbers at branch points indicate the percentage of 1000 bootstrap replicates supporting the topology shown (using MolPhy version 2.3; see [14]). (A) α integrins. Whereas integrins from Bilateria group in a ligand specific manner, consistent with previous phylogenies, the cnidarian sequences form an independent clade, reflecting their early divergence. These groupings suggest that functional divergence of α integrins had already occurred in the Urbilateria. Sequences aligned, abbreviations, and accession numbers are: Lytechinus SU2 (LvSU2; AAC23572); Strongylocentrotus αP (SpαP; AAD55724); Drosophila αPS2 (DmPS2; P12080); Human α5 (HsItgα5; P08648); Human αV (HsItgαV; P06756); Human α8 (HsItgα8; P53708); Human αIIb (HsItgαllb; P08514); Human α6 (HsItgα6; P23229); Human α7 (HsItgα7; Q13683); Human α3 (HsItgα3; P26006); Drosophila αPS3 (DmPS3; O44386); Acropora AmItgα1 (AmItgα1; EU239371); Human α4 (HsItgα4; P13612); Human α9 (HsItgα9; Q13797); Nematostella NvItgα1 (NvItgα1; XP_001641435); Caenorhabditis αPat2 (CePat2; P34446); Drosophila αPS1 (DmPS1; Q24247); Podocoryne IntA (PcIntA; AAG25993); Caenorhabditis αIna1 (CeIna1; Q03600); Geodia α (GcItgα; CAA65943). (B) β integrins. Major clades resolved here are consistent with previous phylogenies. The position of sequences within the cnidarian clade is consistent with orthology between Podocoryne IntB (PcIntB) and AmItgβ2, and groups two Nematostella βs with each Acropora β. Unlike the α integrins, the β integrins appear to have diverged independently in several bilaterian lineages. Sequences aligned, abbreviations, and accession numbers are: Human β3 (HsItgβ3; P05106); Human β5 (HsItgβ5; P18084); Human β6 (HsItgβ6; P18564); Human β2 (HsItgβ2; P05107); Human β7 (HsItgβ7; P26010); Human β1 (HsItgβ1; P05556); Strongylocentrotus βG (Urchin SpItgβG; AAB39739); Strongylocentrotus βL (SpItgβL; AAC28382); Strongylocentrotus βC (SpItgβC; AAB39740); Drosophila βPS (DmβPS P11584); Caenorhabditis βPat3 (CePat3; Q27874); Acropora AmItgβ2 (AmItgβ2; EU239372); Nematostella β1 (NvItgβ1; XP_001641468); Nematostella β2 (NvItgβ2; XP_001627336); Podocoryne IntB (PcIntB; AAG25994); Acropora AmItgβ1(AmItgβ1; AAB66910); Nematostella β3 (NvItgβ3; XP_001637894); Nematostella β4 (NvItgβ4; XP_001621822); Ophlitaspongia βPo1 (Sponge OtItgβ1; AAB66911); Suberites β (Sponge SdItgβ; CAB38100); Geodia β (Sponge GcItgβ; CAA77071); Human β4 (HsItgβ4; P16144); Drosophila β-nu (Dmβ-nu; Q27591); Human β8 (HsItgβ8; P26012).
Figure 6. Reverse transcriptase PCR analysis of integrin expression during Acropora development. Time points: 1-Prawn Chip, 2-Gastrula, 3-Pear, 4-Planula, 5-Settlement. All three Acropora integrin subunits show constant levels of expression throughout development.
Figure 7. Comparison of AmItgα1, AmItgβ1 and AmItgβ2 mRNA distribution patterns during gastrulation in Acropora. At the prawn chip stage, the AmItgα1 and AmItgβ1 mRNAs are clearly restricted to one side of the flattened cell bilayer (A, A', D). During gastrulation, these mRNAs are tightly restricted to the area of the blastopore (asterisks) lip (B, B', C, C', E, F), and throughout development remain endodermal. The distribution of AmItgβ2 mRNA (G, H, I) is broadly similar to that of AmItgα1, but is less tightly restricted, as indicated by weak general staining. Arrow heads in A, B, and C indicate the plane of the sections shown as A', B' and C'.
Adachi,
Instability of quartet analyses of molecular sequence data by the maximum likelihood method: the Cetacea/Artiodactyla relationships.
1996, Pubmed
Adachi,
Instability of quartet analyses of molecular sequence data by the maximum likelihood method: the Cetacea/Artiodactyla relationships.
1996,
Pubmed
Adams,
The genome sequence of Drosophila melanogaster.
2000,
Pubmed
Ball,
A simple plan--cnidarians and the origins of developmental mechanisms.
2004,
Pubmed
Barrallo-Gimeno,
The Snail genes as inducers of cell movement and survival: implications in development and cancer.
2005,
Pubmed
Bellipanni,
Expression of Otx homeodomain proteins induces cell aggregation in developing zebrafish embryos.
2000,
Pubmed
Brower,
Molecular evolution of integrins: genes encoding integrin beta subunits from a coral and a sponge.
1997,
Pubmed
Bunch,
Analysis of the Drosophila betaPS subunit indicates that regulation of integrin activity is a primal function of the C8-C9 loop.
2004,
Pubmed
C. elegans Sequencing Consortium,
Genome sequence of the nematode C. elegans: a platform for investigating biology.
1998,
Pubmed
Carver,
The mouse snail gene encodes a key regulator of the epithelial-mesenchymal transition.
2001,
Pubmed
Davidson,
Mesendoderm extension and mantle closure in Xenopus laevis gastrulation: combined roles for integrin alpha(5)beta(1), fibronectin, and tissue geometry.
2002,
Pubmed
De Arcangelis,
Integrin and ECM functions: roles in vertebrate development.
2000,
Pubmed
Ewan,
The integrins of the urochordate Ciona intestinalis provide novel insights into the molecular evolution of the vertebrate integrin family.
2005,
Pubmed
Hayward,
Localized expression of a dpp/BMP2/4 ortholog in a coral embryo.
2002,
Pubmed
Hayward,
snail expression during embryonic development of the coral Acropora: blurring the diploblast/triploblast divide?
2004,
Pubmed
Hayward,
Gene structure and larval expression of cnox-2Am from the coral Acropora millepora.
2001,
Pubmed
Hertzler,
alphaSU2, an epithelial integrin that binds laminin in the sea urchin embryo.
1999,
Pubmed
,
Echinobase
Hughes,
Evolution of the integrin alpha and beta protein families.
2001,
Pubmed
Huhtala,
Integrin evolution: insights from ascidian and teleost fish genomes.
2005,
Pubmed
Hynes,
Integrins: bidirectional, allosteric signaling machines.
2002,
Pubmed
Iguchi,
Apparent involvement of a beta1 type integrin in coral fertilization.
2007,
Pubmed
Ip,
Cell movements during gastrulation: snail dependent and independent pathways.
2002,
Pubmed
Kortschak,
EST analysis of the cnidarian Acropora millepora reveals extensive gene loss and rapid sequence divergence in the model invertebrates.
2003,
Pubmed
Lichtneckert,
Insights into the urbilaterian brain: conserved genetic patterning mechanisms in insect and vertebrate brain development.
2005,
Pubmed
Lin,
Identification of the human alpha6 integrin gene promoter.
1997,
Pubmed
Marsden,
Integrin-ECM interactions regulate cadherin-dependent cell adhesion and are required for convergent extension in Xenopus.
2003,
Pubmed
Marsden,
The betaL integrin subunit is necessary for gastrulation in sea urchin embryos.
1998,
Pubmed
,
Echinobase
Miao,
Differential regulation of Rho GTPases by beta1 and beta3 integrins: the role of an extracellular domain of integrin in intracellular signaling.
2002,
Pubmed
Müller,
Origin of metazoan adhesion molecules and adhesion receptors as deduced from cDNA analyses in the marine sponge Geodia cydonium: a review.
1997,
Pubmed
Nieto,
The snail superfamily of zinc-finger transcription factors.
2002,
Pubmed
Pancer,
On the origin of Metazoan adhesion receptors: cloning of integrin alpha subunit from the sponge Geodia cydonium.
1997,
Pubmed
Perea-Gomez,
Otx2 is required for visceral endoderm movement and for the restriction of posterior signals in the epiblast of the mouse embryo.
2001,
Pubmed
Ramos,
Xenopus embryonic cell adhesion to fibronectin: position-specific activation of RGD/synergy site-dependent migratory behavior at gastrulation.
1996,
Pubmed
Reber-Müller,
Integrin and talin in the jellyfish Podocoryne carnea.
2001,
Pubmed
Roote,
Functions for PS integrins in tissue adhesion, migration, and shape changes during early embryonic development in Drosophila.
1995,
Pubmed
Smith,
CnOtx, a member of the Otx gene family, has a role in cell movement in hydra.
1999,
Pubmed
Takagi,
Changing ligand specificities of alphavbeta1 and alphavbeta3 integrins by swapping a short diverse sequence of the beta subunit.
1997,
Pubmed
Takagi,
The role of the specificity-determining loop of the integrin beta subunit I-like domain in autonomous expression, association with the alpha subunit, and ligand binding.
2002,
Pubmed
Technau,
Maintenance of ancestral complexity and non-metazoan genes in two basal cnidarians.
2005,
Pubmed
Tozer,
Ligand binding and affinity modulation of integrins.
1996,
Pubmed
Tuckwell,
Homology modelling of integrin EF-hands. Evidence for widespread use of a conserved cation-binding site.
1992,
Pubmed
Turner,
Slug regulates integrin expression and cell proliferation in human epidermal keratinocytes.
2006,
Pubmed
Whittaker,
Distribution and evolution of von Willebrand/integrin A domains: widely dispersed domains with roles in cell adhesion and elsewhere.
2002,
Pubmed
Whittaker,
Integrin alpha subunit mRNAs are differentially expressed in early Xenopus embryos.
1993,
Pubmed
Wimmer,
Origin of the integrin-mediated signal transduction. Functional studies with cell cultures from the sponge Suberites domuncula.
1999,
Pubmed
de Jong,
Components of both major axial patterning systems of the Bilateria are differentially expressed along the primary axis of a 'radiate' animal, the anthozoan cnidarian Acropora millepora.
2006,
Pubmed
