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Cited by 99Developmental Biology and Gene RegulationMarine Invertebrate Physiology and EcologyPlanarian Biology and Electrostimulation

Conservation of Hox/ParaHox-Related Genes in the Early Development of a Cnidarian

Open access
Yanze, Nathalie, Spring, Jürg, Schmidli, Corinne, Schmid, Volker·2001·Developmental Biology
DOI 10.1006/dbio.2001.0299
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Abstract

To clarify the relationship between axial patterning in cnidarians and bilaterians, we have investigated the embryonic development of the hydrozoan Podocoryne carnea. The expression of Hox-like homeobox genes was analyzed by RT-PCR and in situ hybridization. Cnox1-Pc, an anterior Hox gene, is a maternal message. It is present throughout larval development, first weakly in all blastomeres and later restricted mostly to the anterior pole of the planula. Gsx, an anterior ParaHox gene, is first seen in the anterior endoderm but also extends into posterior regions. Cnox4-Pc, an orphan Hox-like gene, is expressed in the egg as a ring-shaped cloud around the germinal vesicle. After fertilization, the message remains in most animal blastomeres. When the embryo elongates in late blastula, staining is restricted to a few cells at the posterior pole where gastrulation will start. However, once gastrulation starts, the Cnox4-Pc signal disappears and is absent in later stages of larval development. Phylogenetic analysis shows that not all cnidarian Hox-like genes have recognizable orthologues in bilaterian groups. However, the expression analysis of Cnox1-Pc and Gsx correlates to some extent with the expression pattern of cognate genes of bilaterians, confirming the conservation of genes involved in organizing animal body plans and their putative common ancestral origin.

Integrity signals

Registry

Crossref · 10.1006/dbio.2001.0299

Cites

10 of 10 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 52 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In all larval stages, Gsx staining remains much stronger in the anterior endoderm.

    “Nevertheless, in all larval stages, the staining remains much stronger in the anterior endoderm.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Gsx signal later extends into posterior regions.

    “It is first expressed in the developing anterior endoderm (Figs.5D and 5E); later the signal extends also to the posterior region (Figs.5F and 5G).”
    Quote in the paperNot a substantial claim
  • Findingown data

    During cleavage, Cnox1-Pc expression is weak and uniform in all blastomeres.

    “It is present throughout larval development, first weakly in all blastomeres and later restricted mostly to the anterior pole of the planula.”
    • Also stated in: § Differential Expression of Hox-Like Genes during Embryogenesis · boosted
      “In situ hybridization analysis demonstrates a weak staining localized in the central cytoplasm of the egg and blastomeres (Figs.4A-4C).”
    Quote in the paperNot a substantial claim
  • Findingown data

    In the first cleavage, Cnox4-Pc message remains localized at the animal pole.

    “In the first cleavage, which in Podocoryne is unilateral and occurs where the polar bodies are formed (Freeman, 1981), the message remains localized at the animal pole (Figs.6D and 6E).”
    Quote in the paperNot a substantial claim
  • Findingown data

    Cnox1-Pc message is continuously present from the unfertilized egg through cleavage stages to the planula larva.

    “The RT-PCR data demonstrate the continuous presence of the Cnox1-Pc message from the unfertilized egg throughout the cleavage stages up to the formation of the planula larva (Fig. 3).”
    Quote in the paperSubstantial claim
  • May combine two claims. 32
  • The quote only partly states this claim. 8
  • Classified as probably not a substantial claim. 17

  • May combine two claims.

    Findingown data

    In the blastula, Cnox4-Pc signal is weaker but still localized to the pole where gastrulation starts and where the posterior pole of the larva will form.

    “In the blastula stage, the embryo elongates and although the signal becomes weaker it is still clearly localized to the pole where gastrulation starts by unipolar immigration and where the posterior pole of the larva will form (Fig. 6H).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cnox4-Pc message is absent in later larval stages and in the feeding polyp.

    “The message is seen neither in later larval stages nor in the feeding polyp (Fig. 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    In older planulae, Cnox1-Pc signal decreases and is absent in the polyp.

    “In the older planula, the signal is decreasing and is absent in the polyp (Fig. 3; Aerne et al., 1995).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Aerne et al., 1995

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    Gsx is not expressed before endoderm forms; its expression begins after gastrulation.

    “RT-PCR and in situ hybridization analysis show that Gsx is expressed after gastrulation (Figs. 3 and 5).”
    • Also stated in: § INTRODUCTION · plain
      “Gsx, however, is not expressed before the endoderm forms and from then on persists throughout larval development, mostly in the anterior endoderm.”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    In the planula, Cnox1-Pc expression is prominent at the anterior pole and stains both anterior ectoderm and endoderm.

    “In the planula larva, both the anterior ectoderm and endoderm stain (Figs.4D-4F).”
    • Also stated in: § INTRODUCTION · plain
      “In the planula, expression is prominent at the anterior pole.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    A total of 23 sequenced clones represented fragments of four homeobox genes; two were Cnox1-Pc and Cnox2-Pc, and two were new sequences named Cnox4-Pc and Gsx.

    “A total of 23 individual clones were sequenced representing fragments of four homeobox genes.”
    • Also stated in: § Isolation and Characterization of Cnox4-Pc and Gsx · plain
      “Two were previously characterized: Cnox1-Pc (Aerne et al., 1995) and Cnox2-Pc (Masuda-Nakagawa et al., 2000), and two were new sequences, later named Cnox4-Pc and Gsx.”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    Cnox1-Pc is related to paralog group 1 and clusters with human HOXA1 and Drosophila labial.

    “As previously described, Cnox1-Pc is related to the paralog group 1 (PG-1) (Aerne et al., 1995;Martinez et al., 1998;Kuhn et al., 1999;Gauchat et al., 2000).”
    • Also stated in: § Hox, ParaHox, and Orphan Hox-Like Genes in Podocoryne · plain
      “The Podocoryne sequence is closely related to the antpC sequence from Acropora formosa (Fig. 2), and both cluster with human HOXA1 and Drosophila labial.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In developing planula, Cnox1-Pc signal becomes strong and more locally restricted, with anterior ectoderm and endoderm staining.

    “the signal becomes strong and more locally restricted in the developing planula where the anterior ectoderm and the endoderm stain (Figs.4D-4F).”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    The Cnox4-Pc genomic clone is 15.7 kb and contains two introns upstream of the homeobox.

    “Subsequent screens of a genomic library led to the characterization of one clone of 15.7 kb for Cnox4-Pc and 14 kb for Gsx.”
    • Also stated in: § Isolation and Characterization of Cnox4-Pc and Gsx · plain
      “Cnox4-Pc displays two introns located upstream of the homeobox, whereas the Gsx gene contains only one intron.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In eggs and blastomeres, Cnox1-Pc staining is weak and located in the central cytoplasm.

    “Whereas some weak staining is observed in the central cytoplasm of the egg and blastomeres (Figs.4A-4C)”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    Gsx cDNA is 901 bp, with an open reading frame of 798 bp encoding 266 amino acids.

    “The compilation of the 5Ј and 3Ј RACE gave rise to a 1201-bp sequence for Cnox4-Pc and to a 901-bp sequence for Gsx.”
    • Also stated in: § Isolation and Characterization of Cnox4-Pc and Gsx · plain
      “Analysis of the two sequences revealed open reading frames of 1068 bp and 798 bp, respectively, and predicted amino acid sequences of 356 and 266 amino acids.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Larval development within a batch is asynchronous; first cleavage times can vary by over 2 h.

    “Within each batch of larvae, development is not synchronized, even the time of first cleavage can differ for more than 2 h.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cnox4-Pc cDNA is 1201 bp, with an open reading frame of 1068 bp encoding 356 amino acids.

    “The compilation of the 5Ј and 3Ј RACE gave rise to a 1201-bp sequence for Cnox4-Pc and to a 901-bp sequence for Gsx.”
    • Also stated in: § Isolation and Characterization of Cnox4-Pc and Gsx · plain
      “Analysis of the two sequences revealed open reading frames of 1068 bp and 798 bp, respectively, and predicted amino acid sequences of 356 and 266 amino acids.”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingcitation

    Cnox4-Pc cannot be placed reliably into bilaterian groups but belongs to the heterogeneous cnidarian Cnox-3 class or Cnox-1 family.

    “The situation is similar concerning Cnox4-Pc for which no obvious grouping can be seen.”
    • Also stated in: § Hox, ParaHox, and Orphan Hox-Like Genes in Podocoryne · plain
      “However, Cnox4-Pc is placed in the very heterogeneous cnidarian Cnox-3 class (Gauchat et al., 2000) or Cnox-1 family (Kuhn et al., 1999).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Gauchat et al., 2000

      Not checked in the free run.

    • cites Kuhn et al., 1999

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The previous classification of Cnox2-Pc as Deformed-like cannot be confirmed; its homeodomain lacks specific residues that would group it clearly with anterior or intermediate paralog groups.

    “The position of Cnox2-Pc (Masuda-Nakagawa et al., 2000), previously described as a Deformed-like gene, can not be confirmed in our analysis.”
    • Also stated in: § Hox, ParaHox, and Orphan Hox-Like Genes in Podocoryne · plain
      “The homeodomain of Cnox2-Pc does not display specific residues that would allow to group it clearly with one of the anterior or intermediate paralog groups.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Masuda-Nakagawa et al., 2000

      Not checked in the free run.

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    The Gsx genomic clone is 14 kb and contains one intron.

    “Subsequent screens of a genomic library led to the characterization of one clone of 15.7 kb for Cnox4-Pc and 14 kb for Gsx.”
    • Also stated in: § Isolation and Characterization of Cnox4-Pc and Gsx · plain
      “Cnox4-Pc displays two introns located upstream of the homeobox, whereas the Gsx gene contains only one intron.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    Cnox4-Pc belongs to the heterogeneous Cnox-3 family, which has no clear bilaterian representative.

    “Classification of Cnox4-Pc is more problematic (Figs. 1 and 2), it belongs to the heterogeneous Cnox-3 family, which has no clear bilaterian representative (Sharkey et al., 1997;Gauchat et al., 2000).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Sharkey et al., 1997

      Not checked in the free run.

    • cites Gauchat et al., 2000

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    Cnox4-Pc message is strongly stained in the unfertilized egg and localized at the animal pole where the first polar body is given off.

    “Strong staining of the unfertilized egg (B) localized at the animal pole where first polar body is given off (A).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Posterior expression of Gsx and Cnox1-Pc coincides with the larva becoming competent for polyp formation.

    “and coincides with the competence of the larva to undergo polyp formation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The RT-PCR experiments were repeated twice on two different mRNA samples.

    “Experiments were repeated twice on two different mRNA samples.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The phylogenetic tree was calculated with neighbor-joining and 1000 bootstrap replicates.

    “A phylogenetic neighbor-joining tree of the homeodomains was calculated with Clustal X and 1000 bootstrap replicates (Jeanmougin et al., 1998).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Jeanmougin et al., 1998 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In Podocoryne, the first cleavage is unilateral and occurs where the polar bodies are formed.

    “In the first cleavage, which in Podocoryne is unilateral and occurs where the polar bodies are formed (Freeman, 1981), the message remains localized at the animal pole (Figs.6D and 6E).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Freeman, 1981

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    During Hydra regeneration, cnox-1 is expressed in a head-specific way.

    “During regeneration, the gene is expressed in a”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gauchat et al., 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    For each gene, several primer sets were tested and selected for suitability with SYBR Green I technology.

    “For each gene, several primer sets have been tested and selected to be suited for the SYBR Green I technology.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The conservation of genes involved in organizing animal body plans and their putative common ancestral origin is confirmed.

    “However, the expression analysis of Cnox1-Pc and Gsx correlates to some extent with the expression pattern of cognate genes of bilaterians, confirming the conservation of genes involved in organizing animal body plans and their putative common ancestral origin.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Podocoryne has three distinct life stages: a lecitotrophic planula larva, a sessile colonial polyp, and a sexual free-swimming medusa.

    “Podocoryne exhibits three distinct life stages: the lecitotrophic planula larva, the sessile colonial polyp, and the sexual free-swimming medusa stage (Tardent, 1978).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tardent, 1978

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The expression data presented do not permit linking the function of the studied genes to the histological differentiation events discussed.

    “The presented expression data do not allow to make a link between the gene function and the discussed histological differentiation events.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Early axis specification depends on asymmetries that are either preexisting in the egg or triggered by external cues.

    “The establishment of the early axis specification relies on asymmetries, which are either preexisting in the egg or triggered by external cues (Goldstein and Freeman, 1997).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Goldstein and Freeman, 1997

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Elongation Factor 1 alpha was used as an endogenous control to compensate for variation in the quantity and quality of the preparations.

    “Elongation Factor 1␣ (EF1␣) was used as endogenous control to compensate for variations in the quantity and quality of the preparations.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Bilaterians and cnidarians diverged from their last common ancestor about 600 million years ago with the same inventory of regulatory developmental genes.

    “Both groups have diverged from their last common ancestor approximately 600 million years ago with the same inventory of regulatory developmental genes as a”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Valentine et al., 1999 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In Hydra, cnox-1 appears to be involved in tentacle formation.

    “It appears that the gene is involved in tentacle formation (Bode, 2001).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bode, 2001

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    DIG-RNA-labeled probes were synthesized from regions excluding the homeobox.

    “DIG-RNA-labeled probes were synthesized from regions excluding the homeobox (DIG-RNA labeling, Roche).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Many regulatory and developmental gene families known from bilaterians have representatives in cnidarians.

    “Many of the regulatory and developmental gene families known from bilaterians have representatives in cnidarians (Galliot, 2000;Hobmayer et al., 2000).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Galliot, 2000 source

      Not checked in the free run.

    • cites Hobmayer et al., 2000

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    At least part of the molecular control of anterior-posterior body axis patterning is conserved between cnidarians and bilaterians and must originate from a common ancestor.

    “Our data suggest that at least part of the molecular control of the A-P body axis patterning is conserved between cnidarians and bilaterians and therefore must originate from a common ancestor.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Cnidarians have shown little change in axial complexity since Precambrian times.

  • May combine two claims.

    Premisecitation

    Most Podocoryne cell types differentiate in a nonpolarized pattern, while a nerve net develops from anterior to posterior and large nematocytes differentiate only at the posterior end.

    “Whereas most of these cell types differentiate in a nonpolarized pattern, a nerve net which stains positive with a tyrosine-tubulin antibody gradually develops from anterior to posterior, the large nematocytes, however, differentiate only at the posterior end (Gro ¨ger and Schmid, 2001).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gro ¨ger and Schmid, 2001

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Hydra, cnox-1 (or cnox-3) is found in ectoderm, weakly in the body column, a little more strongly in the hypostome, and strongly in the future head area of developing buds.

    “In Hydra, cnox-1 (or cnox-3; Bode, 2001) is expressed always in the ectodermal layer, at low levels in the body column, slightly higher in the hypostome, and at high levels in the future”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bode, 2001

      Not checked in the free run.

    • cites Gauchat et al., 2000

      Not checked in the free run.

  • The quote only partly states this claim.

    Interpretationreasoning

    The absence of cnidarian middle-group Hox genes correlates with the absence of middle Hox gene expression during embryogenesis in nematodes and sea urchins.

    “The absence of cnidarian”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Cnox2-Pc shows graded ectodermal anterior expression.

    “A graded ectodermal anterior expression is reported for Cnox2-Pc, a Hox-like gene (Masuda-Nakagawa et al., 2000).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Masuda-Nakagawa et al., 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    Body-plan comparisons face a basic limit when approaching the origin of the metazoan ancestor, probably a planula-like creature.

    “A fundamental limitation of body plan comparison is reached, however, as we approach the original invention of the metazoan ancestor, most probably a planula-like creature.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Hydrozoan embryo A-P axis definition cannot rely on gut formation and instead uses criteria such as cell-type differentiation, gene expression dynamics, body shape, and swimming behavior.

    “Therefore, the definition of the A-P axis in hydrozoan embryos does not use gut formation but must rely on other criteria, like differentiation of cell types, gene expression dynamics, body shape, and swimming behavior.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Formation of the inner cell layer in hydrozoans follows highly variable patterns without blastopore formation.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Study design and conductnone given

    A direct comparison of the authors' data with Hydra embryos is not possible.

    “Again, a direct comparison of our data with Hydra embryos is not possible.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The expression pattern of Cnox-1 (cnox-3) during Hydra embryogenesis is not known.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In Acropora larva, Cnox-2Am is expressed in scattered ectodermal cells, possibly a subset of neurons.

    “Interestingly, Cnox-2Am is expressed in scattered ectodermal cells of the Acropora larva, possibly a subset of neurons (Hayward et al., 2001).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hayward et al., 2001

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Clear A-P polarity appears in histology and gene expression during planula development, polyp formation and regeneration, and medusa budding.

    “On the other hand, a clear A-P polarity in histology and gene expression patterns is observed in the development of the planula, in the formation and regeneration of polyps, and in budding of medusae.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Cnidarians in sensu stricto have no head.
    • Rests on an assumption: Polyps have no specific sense organs.
    • Rests on an assumption: In medusae, statocysts and lens eyes may form at the bell margin, but nerve cells do not form brain-like structures.

  • May combine two claims.

    Premisecitation

    In Podocoryne, the mouth-area nervous system is net-like, with neuronal density not much higher than elsewhere in the mid body column.

    “and, in Podocoryne, the nervous system in the mouth area is net-like and not much more increased in neuronal density than at other places of the mid body column (Gro ¨ger and Schmid, 2001).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gröger and Schmid, 2001

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Hydra, cnox-2 transcripts occur in ectoderm along the body column, in a subset of head-specific epithelial cells, and during regeneration as the polyp head differentiates.

    “In Hydra, transcripts are always found in the ectodermal layer along the body column in a specific subset of head-specific epithelial cells and in regeneration when the polyp”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gauchat et al., 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    cnox-2 may function as an inhibitor of head formation.

    “and appears to act as a negative regulator of head formation (Endl et al., 1999).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Endl et al., 1999

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Regeneration from vegetal half embryos suggests either an undetected Cnox4-Pc gradient in the vegetal region or other genes ensuring normal development in those half embryos.

    “On the other hand, the reported full regeneration from vegetal half embryos (Freeman, 1990) indicates that either a gradient of some undetected Cnox4-Pc message extends into the vegetal part or that this or other genes are used to guarantee normal development in the regenerating half embryos.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Freeman, 1990

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Axis determination through localized maternal message appears to operate in bilaterian phyla and in Cnidaria.

    “In summary, it appears that the principle of axis determination by localized distribution of maternal message is not only used in the different bilaterian phyla but also in Cnidaria.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In other phyla with planctotrophic larvae, a gut forms before metamorphosis, and substrate adhesion occurs at the posterior/blastopore area rather than the anterior pole as in hydrozoan larvae, usually with later body-axis reorientation.

    “In all the other phyla with planctotrophic larvae, a gut develops prior to metamorphosis, substrate adhesion does not occur at the anterior pole like in hydrozoan larvae but with the posterior/blastopore area, usually followed by a reorientation of body axis (Nielsen, 1997;personal communication).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Nielsen, 1997

      Not checked in the free run.

49 of 49

  • The authors state this as an assumption.

    Regeneration or asexual reproduction and embryonic development could be regulated differently.

    “However, there are good reasons to assume that both processes could be differently regulated when compared with embryonic development (Gardiner et al., 1995;Bayascas et al., 1998;Torok et al., 1998;Orii et al., 1999;Spring et al., 2000).”

  • The paper relies on this without support.

    Cnidarians have shown little change in axial complexity since Precambrian times.

    “They are the best-studied outgroup to the bilaterians and appear to show little change in axial complexity since the precambrian times.”

  • The paper relies on this without support.

    The expression pattern of Cnox-1 (cnox-3) during Hydra embryogenesis is not known.

    “Cnox-1 (cnox-3) expression pattern during Hydra embryogenesis is not known and, therefore, a direct comparison not possible.”

  • The paper relies on this without support.

    Cnox-1 family members are related to labial, the Drosophila anterior Hox gene.

    “Members of the Cnox-1 family are related to the Drosophila anterior Hox gene labial”

  • The paper relies on this without support.

    The Gsx of Podocoryne corresponds to Hydra cnox-2 and Acropora millepora cnox-2Am.

    “The Gsx of Podocoryne corresponds to the Hydra cnox-2 and the cnox-2Am of the anthozoan Acropora millepora.”

  • The paper relies on this without support.

    As larvae settle and form polyps, the larval posterior pole becomes the anterior/head region of the sessile polyp.

    “During larva settlement and polyp formation, the posterior pole of the larva becomes the anterior or”

  • The paper relies on this without support.

    In all bilaterian protostomes, gastrulation site becomes the adult mouth opening.

    “Additionally, as in all bilaterian protostomes, the site of gastrulation will become the mouth opening of the adult.”

  • The paper relies on this without support.

    Formation of the inner cell layer in hydrozoans follows highly variable patterns without blastopore formation.

    “However, formation of the inner cell layer in the hydrozoans follows highly variable patterns without blastopore formation.”

  • The paper relies on this without support.

    Cnidarians in sensu stricto have no head.

    “Cnidarians in sensu stricto have no head.”

  • The paper relies on this without support.

    Polyps have no specific sense organs.

    “Polyps have no specific sense organs”

  • The paper relies on this without support.

    In medusae, statocysts and lens eyes may form at the bell margin, but nerve cells do not form brain-like structures.

    “In the medusa stage, statocysts and lens eyes can differentiate at the bell margin of many medusae, but nerve cells never form brain-like structures.”
11 of 11

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Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Figure 6F is assigned two different embryo stages

    Minor

    The results identify the embryo shown in Figure 6F as being at the 8-cell stage, but the figure caption identifies it as a 16-cell-stage embryo.

1 of 1

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Research works printed but not linked: 45

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Cited by

Sorted by citations

Authors
Yanze, N., Spring, J., Schmidli, C., & Schmid, V.
Affiliations
University of Basel (CH)
Corresponding author
Schmid, Volker
ORCID
Schmid, Volker
Venue
Developmental Biology
Publisher
Elsevier BV
Published
2001-08
Volume
236
Issue
1
Pages
89-98
ISSN
0012-1606 (ISSN-L)
DOI
10.1006/dbio.2001.0299
OpenAlex
W2011655218
Semantic Scholar
9b1333ee2a07c4bbb84f08b5d83e4b0d62e0fcee
Cited by
99
References
10
Citations by year
2026: 1 · 2023: 2 · 2022: 1 · 2020: 1 · 2019: 1 · 2018: 2 · 2017: 1 · 2016: 3 · 2015: 4 · 2013: 2 · 2012: 5
FWCI
3.61
Type
journal article
Language
en
Open access
Licence
Locations
  • Developmental Biology (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Science Foundation
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (61443)
  • National Eye Institute
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Developmental Biology and Gene Regulation
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Marine Invertebrate Physiology and Ecology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Planarian Biology and Electrostimulation
Keywords
Hox genes, ParaHox genes, Podocoryne carnea, axial patterning, maternal mRNA, planula, gastrulation, gene expression, phylogenetic analysis, bilaterian evolution, body plan evolution, homeobox genes
MeSH terms
Amino Acid Sequence, Animals, Cloning, Molecular, Cnidaria, Genes, Homeobox, Models, Biological, Molecular Sequence Data, Phylogeny, Time Factors, Conserved Sequence, Caenorhabditis elegans, Sequence Homology, Amino Acid, In Situ Hybridization, Homeodomain Proteins, Gene Expression Regulation, Developmental, Evolution, Molecular, Reverse Transcriptase Polymerase Chain Reaction

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