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  • 1
    Electronic Resource
    Electronic Resource
    Isolation of DNA and RNA from ascidians (1988)
    Springer
    Marine biology 98 (1988), S. 95-100 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A procedure is described for the extraction of DNA and RNA from solitary and colonial ascidians obtained on the east coast of Australia. Modifications to more established procedures have been made to avoid nuclease digestion, binding to polyphenolic compounds and other less well characterized pigments that interfere with the use of nucleic acids for restriction-enzyme analysis and gene-cloning. Tissue is homogenized in liquid nitrogen to produce a powder which is washed three times in 0.25 M ammonium acetate, pH 5.0, to remove a variety of contaminants. This is followed by lysis and immediate extraction in a number of different phenol/CHCl3/isoamyl alcohol mixtures. Additional steps are similar to those described in previous methods. Extraction of RNA by this procedure precludes the necessity for addition of ribonuclease inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392663
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  • 2
    Electronic Resource
    Electronic Resource
    Induction of metamorphosis with potassium ions requires development of competence and an anterior signalling centre in the ascidian Herdmania momus (1997)
    Springer
    Development genes and evolution 206 (1997), S. 370-376 
    Details
    ISSN: 1432-041X
    Keywords: Key words Ascidian ; Competence ; Metamorphosis ; Settlement ; Urochordate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Increased K+ concentration in seawater induces metamorphosis in the ascidian Herdmania momus. Larvae cultivated at 24°C exhibit highest rates of metamorphosis when treated with 40 mM KCl-elevated seawater at 21°C. At 24°C, H. momus larvae develop competence to respond to KCl-seawater and initiate metamorphosis approximately 3 h after hatching. Larval trunks and tails separated from the anterior papillae region, but maintained in a common tunic at a distance of greater than 60 μm, do not undergo metamorphosis when treated with KCl-seawater; normal muscle degradation does not occur in separated tails while ampullae develop from papillae-containing anterior fragments. Normal programmed degradation of myofibrils occurs when posterior fragments are fused to papillae-containing anterior fragments. These data indicate that H. momus settlement and metamorphosis only occurs when larvae have attained competence, and suggest that an anterior signalling centre is stimulated to release a factor that induces metamorphosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050066
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  • 3
    Electronic Resource
    Electronic Resource
    Neuroectodermal and endodermal expression of the ascidian Cdx gene is separated by metamorphosis (2000)
    Springer
    Development genes and evolution 210 (2000), S. 212-216 
    Details
    ISSN: 1432-041X
    Keywords: Key words Chordate evolution ; Heterochrony Urochordate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Ascidians are a group of invertebrate chordates that exhibit a biphasic life history, with chordate-specific structures developing during embryogenesis (dorsal neural tube and notochord) and metamorphosis (pharyngeal gill slits and endostyle). Here we characterize the expression of a caudal/Cdx gene homologue, Hec-Cdx, from the ascidian Herdmania curvata. Vertebrate Cdx genes are expressed at gastrulation and in the posterior of the developing neural tube and endoderm. Hec-Cdx expression is initiated at the earliest stages of gastrulation, with peaks in RNA abundance occurring first during neurulation and tailbud extension and then in 3- to 5-day-old juveniles. Hec-Cdx is expressed in a pair of cells in the anterior lip of the blastopore in the late gastrula which form the most posterior portion of the neural plate. During tailbud formation expression is maintained in and solely restricted to these cells. During metamorphosis expression is localized to the intestine of the juvenile. These data, along with data for the H. curvata Otx gene, suggest that the evolution of the novel ascidian biphasic body plan was not accompanied by a deployment of these genes into new pathways but by a temporal separation of tissue-specific expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050306
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  • 4
    Electronic Resource
    Electronic Resource
    Retinoic acid perturbs Otx gene expression in the ascidian pharynx (2000)
    Springer
    Development genes and evolution 210 (2000), S. 129-139 
    Details
    ISSN: 1432-041X
    Keywords: Key words Ascidian ; Chordate evolution ; Herdmania curvata ; Otx ; Retinoic acid ; Pharynx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In vertebrate embryos, ectopic application of all-trans retinoic acid (RA) alters the expression of Otx genes in the developing midbrain. In conjunction with RA-induced misexpression of other regulatory genes this leads to a loss of anterior CNS. In the ascidian Herdmania curvata, RA primarily inhibits the development of the juvenile pharynx. An ascidian Otx gene, Hec-Otx, is expressed largely in this tissue, associated stomodeal structures and the anterior endostyle of the juvenile. Treatment with 10–6 M RA reduces Hec-Otx mRNA levels in the juvenile to about 12% of normal and is correlated closely with the loss of pharyngeal structures. During embryogenesis the expression of Hec-Otx becomes restricted to cell lineages fated to give rise to the anterior-most nervous system and the stomodeal component of the primordial pharynx. In hatched larvae Hec-Otx transcripts are detected only in the sensory (brain) vesicle. RA reduces Hec-Otx expression in the tailbud stomodeal pharynx primordium/anterior nervous system cell line but not in the larval sensory vesicle, suggesting that RA regulation of Hec-Otx expression is restricted to pharyngeal tissues throughout embryonic and postlarval development. RA does not affect expression of Hec-Pax2/5/8, which is normally expressed within the developing nervous system immediately posterior to Hec-Otx at the tailbud stage, lending support to the proposition that RA does not impact CNS axial patterning. These data combined with those from other chordates suggest that RA regulation of Otx expression in the anterior nerve cord and pharynx is a primitive chordate feature which has been maintained predominantly in pharyngeal tissues in the ascidian.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050019
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  • 5
    Electronic Resource
    Electronic Resource
    Retinoic acid disrupts anterior ectodermal and endodermal development in ascidian larvae and postlarvae (1998)
    Springer
    Development genes and evolution 208 (1998), S. 336-345 
    Details
    ISSN: 1432-041X
    Keywords: Key words Retinoic acid ; Ascidian ; Anteroposterior Patterning ; Herdmania curvata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In vertebrates, excess all-trans retinoic acid (RA) applied during axis formation leads to the apparent truncation of anterior structures. In this study we sought to determine the type of defects caused by ectopic RA on the development of the ascidian Herdmania curvata. We demonstrate that H. curvata embryos cultured in the presence of RA develop into larvae whose trunks are shortened and superficially resemble those of early metamorphosing postlarvae. Despite RA-treated larvae lacking papillar structures they respond normally to natural cues that induce metamorphosis, indicating that chemosensory functionality previously mapped to the most anterior region of normal larvae is unaffected by RA. Excess RA applied during postlarval development leads to a graded loss of the juvenile pharynx, apparently by respecifying anterior endoderm to a more posterior fate. This structure is considered homologous to the gill slits of amphioxus, which are also lost upon RA treatment. This suggests that RA may have had a role in the development of the pharynx of the ancestral chordate and that this function has been maintained in ascidians and cephalochordates and lost in vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050189
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  • 6
    Electronic Resource
    Electronic Resource
    Muscle-specific regulation of tropomyosin gene expression and myofibrillogenesis differs among muscle systems examined at metamorphosis of the gastropod Haliotis rufescens (1997)
    Springer
    Development genes and evolution 206 (1997), S. 464-471 
    Details
    ISSN: 1432-041X
    Keywords: Key words Abalone ; Competence ; In situ hybridization ; Larva ; Muscle cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The spatial and temporal association of muscle-specific tropomyosin gene expression, and myofibril assembly and degradation during metamorphosis is analyzed in the gastropod mollusc, Haliotis rufescens. Metamorphosis of the planktonic larva to the benthic juvenile includes rearrangement and atrophy of specific larval muscles, and biogenesis of the new juvenile muscle system. The major muscle of the larva – the larval retractor muscle – reorganizes at metamorphosis, with two suites of cells having different fates. The ventral cells degenerate, while the dorsal cells become part of the developing juvenile mantle musculature. Prior to these changes in myofibrillar structure, tropomyosin mRNA prevalence declines until undetectable in the ventral cells, while increasing markedly in the dorsal cells. In the foot muscle and right shell muscle, tropomyosin mRNA levels remain relatively stable, even though myofibril content increases. In a population of median mesoderm cells destined to form de novo the major muscle of the juvenile and adult (the columellar muscle), tropomyosin expression is initiated at 45 h after induction of metamorphosis. Myofibrillar filamentous actin is not detected in these cells until about 7 days later. Given that patterns of tropomyosin mRNA accumulation in relation to myofibril assembly and disassembly differ significantly among the four major muscle systems examined, we suggest that different regulatory mechanisms, probably operating at both transcriptional and post-transcriptional levels, control the biogenesis and atrophy of different larval and postlarval muscles at metamorphosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050076
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  • 7
    Electronic Resource
    Electronic Resource
    Highly repetitive DNA sequences provide evidence for a lack of gene flow between two morphological forms of Herdmania momus (Ascidiacea: Stolidobranchia) (1995)
    Springer
    Marine biology 124 (1995), S. 293-299 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genomic structure of two morphological forms of the pyurid ascidian Herdmania momus — H. momus forma curvata and H. momus forma grandis—are compared using a rapidly evolving highly repetitive element isolated from the genome of H. momus forma curvata. A 663 bp (base pair) Cla I satellite sequence is present only in the genome of H. momus forma curvata, and hence can be used as a form-specific marker. Low-stringency Southern blot analyses, using the Cla I satellite as a probe, revealed that the genomes of H. momus forma grandis and another pyurid ascidian, Pyura stolonifera, do not contain similar sequences to the H. momus forma curvata repetitive element. In addition to this genomic dissimilarity, there are a number of significant reproductive and developmental differences between the two H. momus forms, and interform fertilisation rates are significantly lower than intraform rates. The molecular, reproductive and developmental differences between H. momus forma curvata and H. momus forma grandis indicate the presence of strong barriers to gene flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00347133
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  • 8
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    Functionalization of a protosynaptic gene expression network (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-06-20
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Origin and Evolution of Laminin Gene Family Diversity (2012)
    Oxford University Press
    Details
    Publication Date: 2012-06-16
    Description: Laminins are a family of multidomain glycoproteins that are important contributors to the structure of metazoan extracellular matrices. To investigate the origin and evolution of the laminin family, we characterized the full complement of laminin-related genes in the genome of the sponge, Amphimedon queenslandica . As a representative of the Demospongiae, a group consistently placed within the earliest diverging branch of animals by molecular phylogenies, Amphimedon is uniquely placed to provide insight into early steps in the evolution of metazoan gene families. Five Amphimedon laminin-related genes possess the conserved molecular features, and most of the domains found in bilaterian laminins, but all display domain architectures distinct from those of the canonical laminin chain types known from model bilaterians. This finding prompted us to perform a comparative genomic analysis of laminins and related genes from a choanoflagellate and diverse metazoans and to conduct phylogenetic analyses using the conserved Laminin N-terminal domain in order to explore the relationships between genes with distinct architectures. Laminin-like genes appear to have originated in the holozoan lineage (choanoflagellates + metazoans + several other unicellular opisthokont taxa), with several laminin domains originating later and appearing only in metazoan (animal) or eumetazoan (placozoans + ctenophores + cnidarians + bilaterians) laminins. Typical bilaterian α, β, and laminin chain forms arose in the eumetazoan stem and another chain type that is conserved in Amphimedon , the cnidarian, Nematostella vectensis , and the echinoderm, Strongylocentrotus purpuratus , appears to have been lost independently from the placozoan, Trichoplax adhaerens , and from multiple bilaterians. Phylogenetic analysis did not clearly reconstruct relationships between the distinct laminin chain types (with the exception of the α chains) but did reveal how several members of the netrin family were generated independently from within the laminin family by duplication and domain shuffling and by domain loss. Together, our results suggest that gene duplication and loss and domain shuffling and loss all played a role in the evolution of the laminin family and contributed to the generation of lineage-specific diversity in the laminin gene complements of extant metazoans.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    Dynamic and Widespread lncRNA Expression in a Sponge and the Origin of Animal Complexity (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-20
    Description: Long noncoding RNAs (lncRNAs) are important developmental regulators in bilaterian animals. A correlation has been claimed between the lncRNA repertoire expansion and morphological complexity in vertebrate evolution. However, this claim has not been tested by examining morphologically simple animals. Here, we undertake a systematic investigation of lncRNAs in the demosponge Amphimedon queenslandica, a morphologically simple, early-branching metazoan. We combine RNA-Seq data across multiple developmental stages of Amphimedon with a filtering pipeline to conservatively predict 2,935 lncRNAs. These include intronic overlapping lncRNAs, exonic antisense overlapping lncRNAs, long intergenic nonprotein coding RNAs, and precursors for small RNAs. Sponge lncRNAs are remarkably similar to their bilaterian counterparts in being relatively short with few exons and having low primary sequence conservation relative to protein-coding genes. As in bilaterians, a majority of sponge lncRNAs exhibit typical hallmarks of regulatory molecules, including high temporal specificity and dynamic developmental expression. Specific lncRNA expression profiles correlate tightly with conserved protein-coding genes likely involved in a range of developmental and physiological processes, such as the Wnt signaling pathway. Although the majority of Amphimedon lncRNAs appears to be taxonomically restricted with no identifiable orthologs, we find a few cases of conservation between demosponges in lncRNAs that are antisense to coding sequences. Based on the high similarity in the structure, organization, and dynamic expression of sponge lncRNAs to their bilaterian counterparts, we propose that these noncoding RNAs are an ancient feature of the metazoan genome. These results are consistent with lncRNAs regulating the development of animals, regardless of their level of morphological complexity.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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