Two small RNAs regulate the timing of Caenorhabditis elegans development. Transition from the first to the second larval stage fates
requires the 22-nucleotide lin-4 RNA, and transition
from late ...larval to adult cell fates requires the 21-nucleotide let-7
RNA. The lin-4 and let-7 RNA genes are not homologous
to each other, but are each complementary to sequences in the 3′ untranslated
regions of a set of protein-coding target genes that are normally negatively
regulated by the RNAs. Here we have detected let-7
RNAs of ∼21 nucleotides in samples from a wide range of animal
species, including vertebrate, ascidian, hemichordate, mollusc, annelid and
arthropod, but not in RNAs from several cnidarian and poriferan species,
Saccharomyces cerevisiae, Escherichia coli or Arabidopsis.
We did not detect lin-4 RNA in these species. We found that let-7
temporal regulation is also conserved: let-7 RNA expression is
first detected at late larval stages in C. elegans and Drosophila
, at 48 hours after fertilization in zebrafish, and in adult stages
of annelids and molluscs. The let-7 regulatory RNA may control late temporal
transitions during development across animal phylogeny.
Full text
Available for:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Human obesity is a main cause of morbidity and mortality. Recently, several studies have demonstrated an association between the FTO gene locus and early onset and severe obesity. To date, the FTO ...gene has only been discovered in vertebrates. We identified FTO homologs in the complete genome sequences of various evolutionary diverse marine eukaryotic algae, ranging from unicellular photosynthetic picoplankton to a multicellular seaweed. However, FTO homologs appear to be absent from all other completely sequenced genomes of plants, fungi, and invertebrate animals. Although the biological roles of these marine algal FTO homologs are still unknown, these genes will be useful for exploring basic protein features and could hence help unravel the function of the FTO gene in vertebrates and its inferred link with obesity in humans.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Most animals are classified as Bilateria and only four phyla are still extant as outgroups, namely Porifera, Placozoa, Cnidaria and Ctenophora. These non-bilaterians were not considered to have a ...mesoderm and hence mesoderm-specific genes. However, the T-box gene
Brachyury could be isolated from sponges, placozoans and cnidarians. Here, we describe the first
Brachyury and a
Tbx2/3 homologue from a ctenophore. In addition, analysing T-box and homeobox genes under comparable conditions in all four basal phyla lead to the discovery of novel T-box genes in sponges and cnidarians and a
Tlx homeobox gene in the ctenophore
Pleurobrachia pileus . The conservation of the T-box and the homeobox genes suggest that distinct subfamilies with different roles in bilaterians were already split in non-bilaterians.
Full text
Available for:
BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
One major difference between simple metazoans such as cnidarians and all the bilaterian animals is thought to involve the invention of mesoderm. The terms diploblasts and triploblasts are therefore, ...often used to group prebilaterian and bilaterian animals, respectively. However, jellyfish contain well developed striated and smooth muscle tissues that derive from the entocodon, a mesoderm-like tissue formed during medusa development. We investigated the hypothesis, that the entocodon could be homologous to the third germ layer of bilaterians by analyzing the structures and expression patterns of the homologues of Brachyury, Mef2, and Snail in the jellyfish Podocoryne carnea. These are regulatory genes from the T-box, MADS-box and zinc finger families known to play important roles in bilaterian mesoderm patterning and muscle differentiation. The sequence and expression data demonstrate that the genes are structurally and functionally conserved and even more similar to humans or other deuterostomes than to protostome model organisms such as Drosophila or Caenorhabditis elegans. Based on these data we conclude that the common ancestor of the cnidarians and bilaterians not only shared genes that play a role in regulating myogenesis but already used them to develop and differentiate muscle systems similar to those of triploblasts.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The basic helix-loop-helix (bHLH) transcription factor Twist is highly conserved from Drosophila to vertebrates and plays a major role in mesoderm specification of triploblasts. The presence of a ...Twist homologue in diploblasts such as the cnidarian Podocoryne carnea raises questions on the evolution of mesoderm, the third cell layer characteristic for triploblasts. Podocoryne Twist is expressed in the early embryo until the myoepithelial cells of the larva differentiate and then again during medusa development. There, the gene is detected first when the myoepithelial cells of the polyp dedifferentiate to form the medusa bud and later Twist is found transiently in the entocodon, a mesoderm-like cell layer which differentiates into the smooth muscle and striated muscle of the bell. On the other hand, in later bud stages and the medusa, expression is seen where non-muscle tissues differentiate. Experimental analysis of in vitro transdifferentiation and regeneration demonstrates that Twist activity is not needed when isolated striated muscle regenerate medusa organs. Developmental roles of Twist are discussed with respect to early animal evolution from a common ancestor of cnidarians and bilaterians.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
For the growing fraction of human genes with identified functions there are often homologues known from invertebrates such as
Drosophila. A survey of well established gene families from aldolases to ...zinc finger transcription factors reveals that usually a single invertebrate gene corresponds to up to four equally related vertebrate genes on different chromosomes. This pattern was before widely noticed for the
Hox gene clusters but appears to be more general. Genome quadruplication by two rounds of hybridisation is discussed as a simple biological mechanism that could have provided the necessary raw material for the success of vertebrate evolution.
Full text
Available for:
BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The Okinawan sea anemone
Actineria villosa causes severe cases of stinging. We isolated the 60 kDa
A. villosa toxin (AvTX-60A) as the major toxin from the isolated nematocysts of this species. ...AvTX-60A showed fatal toxicity to mice with intraperitoneal injection at a minimum lethal dose of less than 250 μg/kg. The N-terminal amino acid sequence was determined and the corresponding cDNA encoding AvTX-60A was sequenced. The deduced amino acid sequence of AvTX-60A showed high similarity with PsTX-60A, which had been isolated as one of the major toxins from the venomous sea anemone
Phyllodiscus semoni. These sea anemone toxins are new members of the family of proteins containing membrane-attack complex/perforin (MACPF) domains, best known in pore forming proteins such as perforin. These are the first examples of MACPF domain proteins as toxins for prey acquisition or repelling predators in nature.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
In many bilaterian animals members of the Otx gene family are expressed in head or brain structures. Cnidarians, however, have no clearly homologous head and no distinct brain; but an Otx homolog ...from the jellyfish Podocoryne carnea is highly conserved in sequence and domain structure. Sequence similarities extend well beyond the homeodomain and Podocoryne Otx can be aligned over its entire length to human OTX1, OTX2, and CRX. The overall structure of Otx is better conserved from Podocoryne to deuterostomes while protostomes appear to be more derived. In contrast, functions seem to be conserved from protostomes to vertebrates but not in Podocoryne or echinoderms. Podocoryne Otx is expressed only during medusa bud formation and becomes restricted to the striated muscle of medusae. Cnidaria are the most basal animals with striated muscle. Podocoryne polyps have no striated muscle and no Otx expression; both appear only during the asexual medusa budding process. The common ancestor of all animals that gave rise to cnidarians, protostomes, and deuterostomes already had an Otx gene more similar to today's Podocoryne and human homologs than to Drosophila otd, while the head-specific function appears to have evolved only later.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
A structural and functional model of tenascin was elaborated using recombinant parts of three alternatively spliced tenascin variants and anti-tenascin monoclonal antibodies. The fusion proteins were ...compared with intact tenascin for their functions and by electron microscopy. A strong cell binding site was localized within 104 amino acids. This fragment also contains the epitope of the monoclonal antibody anti-Tn68, which inhibits cell attachment to tenascin and binds near the tips of the six arms of tenascin. In contrast, constructs containing the 13 1/2 EGF-like repeats of tenascin showed an antiadhesive effect. The coexistence of the two contrary signals on the same molecule might be responsible for the versatile features of tenascin.
PDF
