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At least 343 records · Page 19Linked to original sources
PubMed2003

Pax6 autoregulation mediated by direct interaction of Pax6 protein with the head surface ectoderm-specific enhancer of the mouse Pax6 gene.

The Pax6 gene plays crucial roles in eye development and encodes a transcription factor containing both a paired domain and a homeodomain. During embryogenesis, Pax6 is expressed in restricted tissues under the direction of distinct cis-regulatory regions. The head surface ectoderm-specific enhancer of mouse Pax6 directs reporter expression in the derivatives of the ectoderm in the eye, such as lens and cornea, but the molecular mechanism of its control remains largely unknown. We identified a Pax6 protein-responsive element termed LE9 (52 bp in length) within the head surface ectoderm-specific enhancer. LE9, a sequence well conserved across vertebrates, acted as a highly effective enhancer in reporter analyses. Pax6 protein formed in vitro a complex with the distal half of LE9 in a manner dependent on the paired domain. The proximal half of the LE9 sequence contains three plausible sites of HMG domain recognition, and HMG domain-containing transcription factors Sox2 and Sox3 activated LE9 synergistically with Pax6. A scanning mutagenesis experiment indicated that the central site is most important among the three presumptive HMG domain recognition sites. Furthermore, Pax6 and Sox2 proteins formed a complex when they were expressed together. Based on these findings, we propose a model in which Pax6 protein directly and positively regulates its own gene expression, and Sox2 and Sox3 proteins interact with Pax6 protein, resulting in modification of the transcriptional activation by Pax6 protein.

Animals↗
PubMed1981

Hypohidrotic ectodermal dysplasia with hypothyroidism.

Two brothers with hypohidrotic ectodermal dysplasia were found to have urticaria pigmentosa-like skin pigmentation with increased mast cells and melanin depositions in the dermis. Structural ciliary abnormalities of the respiratory tract were seen, and these may contribute to their severe recurrent chest infections. Primary hypothyroidism occurred in both by 3 years of age and responded to replacement therapy. The abnormalities seen appear to be the result of a common genetic aberration causing a particular sequence of maldevelopments during embryogenesis. This form of hypohidrotic ectodermal dysplasia associated with hypothyroidism gives a unique insight into the potential extent of structural defects of ectodermal dysplasias.

Biopsy↗
PubMed1998

A case of probable autosomal recessive ectodermal dysplasia with corkscrew hairs and mental retardation in a family with tuberous sclerosis.

We describe a woman with a probable autosomal recessive ectodermal dysplasia with corkscrew hairs and mental retardation in a family with tuberous sclerosis. Other findings included syndactyly, typical facies, dental abnormalities, dermatoglyphic hypoplasia, epidermal ridge sweat pore count slightly below normal, and keratosis pilaris. Clinical studies and genetic analysis excluded the diagnosis of tuberous sclerosis in our patient. We conclude that she has ectodermal dysplasia associated with mental retardation. This association has been described previously; it suggests the possible interrelationship of a community of ectodermal dysplasia syndromes with a distinctive structural hair abnormality (pili torti et canaliculi), variable midfacial malformations, limb defects, and other features such as mental retardation. The similarity of our patient to that described by Whiting et al. and Abramovits-Ackerman et al. suggests the autonomy of this syndrome.

Adult↗
PubMed1997

A graded response to BMP-4 spatially coordinates patterning of the mesoderm and ectoderm in the zebrafish.

The effects of signal perturbation on expression domains of molecular markers for the mesoderm and ectoderm have been analysed across the dorso-ventral axis in zebrafish embryos. Injection of RNA encoding bone morphogenetic protein-4 (BMP-4) ventralised the embryo, expanding the intermediate mesoderm and non-neural ectoderm at the expense of the dorso-anterior mesoderm and neural plate. A dose-dependent response was observed both morphologically and in expression of gta3, MyoD and pax2. Conversely, increases in dorso-anterior mesoderm and neurectoderm were generated by injection of RNA encoding either a dominant-negative BMP receptor (delta BMPR) or noggin, as demonstrated by goosecoid and pax2 expression. Ventral BMP-4 expression was also inhibited. Thus, patterning of both the mesoderm and the ectoderm during gastrulation appears to depend, directly or indirectly, on the level of BMP activity. Consistent with their locations prior to formation of the neural tube, elevated BMP-4 increased the number of dorsal spinal cord neurons whilst sonic hedgehog and islet1 expression in the ventral spinal cord were reduced. However, the ectopic neurons were not positioned more ventrally, implicating a prepattern in the dorsal neural tube that is independent of the ventral central nervous system.

Animals↗
PubMed1998

A constitutively activated mutant of galphaq down-regulates EP-cadherin expression and decreases adhesion between ectodermal cells at gastrulation.

We have examined the expression and function of the heterotrimeric GTP-binding protein Gq during early Xenopus embryogenesis. Abundant XGalphaq transcripts were detected in oocytes and early embryos by Northern blot analysis. In situ hybridization revealed that these transcripts are confined to the animal hemisphere of the mature oocyte and to the presumptive ectoderm of cleaving embryos. Microinjection at the two-cell stage of alphaq and Q209Lalphaq, a constitutively activated mutant, causes a disruption in ectodermal cell adhesion at late gastrulation. Dissociation/reaggregation experiments performed on animal cap explants clearly demonstrate that the Q209Lalphaq-induced phenotype occurs after reaggregation of the explants with a time-course similar to that observed in whole embryos. RT-PCR experiments performed on the explants from Q209Lalphaq-injected embryos revealed a selective decrease in the amount of EP-cadherin mRNA. Co-injection of EP-cadherin RNA, but also E-cadherin RNA, rescued the disaggregated phenotype. These data emphasize the functional link between Gq protein-coupled signalling pathways and cadherin molecules in the ectodermal layer during the morphogenetic movements of gastrulation.

Animals↗
PubMed2002

Ectodermal syndecan-2 mediates left-right axis formation in migrating mesoderm as a cell-nonautonomous Vg1 cofactor.

Heparan sulfate proteoglycans expressed on the Xenopus animal cap ectoderm have been implicated in transmitting left-right information to heart and gut primordia. We report here that syndecan-2 functions in the ectoderm to mediate cardiac and visceral situs, upstream of known asymmetrically expressed genes but independently of its ability to mediate fibronectin fibrillogenesis. Left-right development is dependent on a distinct subset of glycosaminoglycan attachment sites on syndecan-2. A novel in vivo approach with enterokinase demonstrates that syndecan-2 functions in left-right patterning during early gastrulation. We describe a cell-nonautonomous role for ectodermal syndecan-2 in transmitting left-right information to migrating mesoderm. The results further suggest that this function may be related to the transduction of Vg1-related signals.

Activin Receptors, Type I↗
PubMed2003

PCP4 is highly expressed in ectoderm and particularly in neuroectoderm derivatives during mouse embryogenesis.

PCP4 (PEP-19) belongs to a family of proteins involved in calcium transduction signals and binds calmodulin via an IQ motif, in a calcium independent manner. PCP4 gene maps to murine chromosome 16 and in human to chromosome 21. Murine PCP4 expression in the brain has been detected by Northern blot analysis to be mainly post-natal and in the adult to have a neuronal pattern. To investigate if it might have a role earlier in development, we analyzed its expression during mouse embryogenesis by in situ hybridization from E7.5 post-coitum (p.c.) to E17.5 p.c., and in P0 brain. Early, at E7.5, a high expression is restricted to the extra embryonic ectoderm. Embryonic expression starts at E9.5. At E10.5, PCP4 shows a strong signal in the post-mitotic cells of the diencephalon, the metencephalon and the myelencephalon and in the dorsal and cranial ganglia. The floor plate is also densely labelled. At E17.5, PCP4 is expressed in the central nervous system, in the myenteric plexus, and in other ectoderm derivatives, for instance the lens, the hairy cells of the cochlea, the enamel organ and the hair follicles. Thus, during embryogenesis PCP4 is mainly expressed in ectoderm and neuroectoderm comprising neural crest derived cells.

Animals↗
PubMed1997

Radical fringe positions the apical ectodermal ridge at the dorsoventral boundary of the vertebrate limb.

Vertebrate limb outgrowth requires a structure called the apical ectodermal ridge, formation of which follows the previous establishment of the dorsoventral limb axis. Radical fringe is expressed in the dorsal ectoderm before the ridge appears, and is repressed by Engrailed-1, which is expressed in the ventral ectoderm. Misexpression of these genes indicates that a ridge is formed wherever there is a boundary between cells expressing and not expressing Radical fringe. Thus, as in Drosophila, Radical fringe positions the ridge at the dorsoventral limb boundary.

Animals↗
PubMed1997

Msx1 expressing mesoderm is important for the apical ectodermal ridge (AER)-signal transfer in chick limb development.

The apical ectodermal ridge (AER) is a specialized thickening of the distal limb ectoderm, and its signals are known to support limb morphogenesis. The expression of a homeobox gene, Msx1, in the distal limb mesoderm depends on signals from the AER. In the present paper it is reported that Msx1 expression in the distal mesoderm is necessary for the transfer of AER signals in chick limb buds. Interruption of AER-mesoderm interaction by insertion of a thick filter led to the inhibition of pattern specification in the mesoderm just under the filter. In such cases, the expression of Msx1 disappeared in the mesoderm under the filter, suggesting that AER is able to signal over short ranges. In advanced limb buds, Msx1 is also expressed in the proximal mesoderm under the anterior ectoderm. However, it was found that a grafted antero-proximal mesoderm shows no inhibitory effects on pattern specification of the host mesoderm, as is the case with the distal mesoderm. On the other hand, grafted mesoderms without potent Msx1 re-expression, even underneath AER, disturbed normal limb development. In such cases, the expression of Msx1 disappeared in the mesoderm under the grafts, whereas Fgf-8 expression was maintained in the AER above the graft. These results indicate that the expression of Msx1 in the mesoderm is important for the transfer of AER signals.

Animals↗
PubMed1999

FGF10 can induce Fgf8 expression concomitantly with En1 and R-fng expression in chick limb ectoderm, independent of its dorsoventral specification.

The limb bud has a thickened epithelium at the dorsal-ventral boundary, the apical ectodermal ridge (AER), which sustains limb outgrowth and patterning. A secreted molecule fibroblast growth factor (FGF)10 is involved in inducing Fgf8 expression in the prospective AER and mutual interaction between mesenchymal FGF10 and FGF8 in the AER is essential for limb outgrowth. A secreted factor Wnt7a and a homeobox protein Lmx1 are involved in the dorsal patterning of the limb, whereas a homeobox protein Engrailed 1 (En1) is involved in the dorsal-ventral patterning as well as AER formation. Radical fringe (R-fng), a vertebrate homolog of Drosophila fringe was also found to elaborate AER formation in chicks. However, little is known about the molecular interactions between these factors during AER formation. The present study clarified the relationship between FGF10, Wnt7a, Lmx1, R-fng and En1 during limb development using a foil-barrier insertion experiment. It was found that a foil-barrier inserted into the chick prospective wing mesenchyme lateral to the mesonephric duct blocks AER induction. This experiment was expanded by implanting Fgf10-expressing cells lateral to the barrier and examined whether FGF10 could rescue the expression of the limb-patterning genes reported in AER formation. It was found that FGF10 is sufficient to induce Fgf8 expression in the ectoderm of the foil-inserted limb bud, concomitantly with R-fng and En1 expression. However, FGF10 could not rescue the expression of the dorsal marker genes, Wnt7a or Lmx1. Thus, it is suggested that epithelial factors of En1 and R-fng can induce Fgf8 expression in the limb ectoderm in cooperation with a mesenchymal factor FGF10. Some factor(s) other than FGF10, possibly from the paraxial structures medial to the limb mesoderm, is responsible for the initial dorsal-ventral specification of the limb bud.

Animals↗
PubMed1999

Dorsoventral differential distribution of collagen type XIV around the spinal cord is regulated by the ectoderm.

Regional specification in the nervous system is a critical issue in nervous system morphogenesis. Along the dorsoventral axis of the spinal cord, ventral inductive signals of the notochord and floor plate, and dorsal ones of the epidermal ectoderm are essential. Collagen type XIV is uniquely distributed around the spinal cord with a gradient of dorsal high and ventral low at the early developmental stages of the chick embryo. In the present study it was found that collagen type XIV expression around the spinal cord was entirely regulated by the ectoderm and that even the ventralizing tissues, the notochord and floor plate, themselves could be influenced to express this molecule by the ectoderm.

Animals↗
PubMed2001

An RGDS peptide-binding receptor, FR-1R, localizes to the basal side of the ectoderm and to primary mesenchyme cells in sand dollar embryos.

Immunoblotting using polyclonal antibodies (pAb) raised against an FR-1 receptor (FR-1R), a 57 kDa Arg-Gly-Asp-Ser (RGDS)-binding protein, of the sand dollar Clypeaster japonicus showed that the pAb monospecifically bound to the protein. FR-1R was present in purified plasma membrane, suggesting that the protein is a membrane-bound protein. The molecular structure of FR-1R did not change throughout the early embryogenesis, whereas its expression changed significantly during this period. FR-1R was present in the cortex of unfertilized eggs and was then transferred to the hyaline layer soon after the fertilization. The hyaline layer retained FR-1R immunoreactivity during early embryogenesis. FR-1R appeared on the basal side of the ectoderm at the morula stage and was retained basolaterally, at least, to the early gastrula stage. In mesenchyme blastulae, FR-1R was also present on the surface of primary mesenchyme cells (PMC). FR-1R was localized on the basal side of the ectoderm in early gastrulae, exclusively at the place where PMC formed ventrolateral aggregates, and at the apical tuft ectoderm. In vitro, PMC bound to FR-1R and its binding was inhibited in the presence of a synthetic RGDS peptide or the pAb. The pAb introduced into the blastocoele perturbed PMC migration and gastrulation. FR-1R was weakly recognized by antihuman integrin beta5 subunit pAb.

Animals↗
PubMed1998

Limb development and evolution: a frog embryo with no apical ectodermal ridge (AER).

The treefrog Eleutherodactylus coqui is a direct developer--it has no tadpole stage. The limb buds develop earlier than in metamorphosing species (indirect developers, such as Xenopus laevis). Previous molecular studies suggest that at least some mechanisms of limb development in E. coqui are similar to those of other vertebrates and we wished to see how limb morphogenesis in this species compares with that in other vertebrates. We found that the hind limb buds are larger and more advanced than the forelimbs at all stages examined, thus differing from the typical amniote pattern. The limb buds were also small compared to those in the chick. Scanning and transmission electron microscopy showed that although the apical ectoderm is thickened, there was no apical ectodermal ridge (AER). In addition, the limb buds lacked the dorsoventral flattening seen in many amniotes. These findings could suggest a mechanical function for the AER in maintaining dorsoventral flattening, although not all data are consistent with this view. Removal of distal ectoderm from E. coqui hindlimb buds does not stop outgrowth, although it does produce anterior defects in the skeletal pattern. The defects are less severe when the excisions are performed earlier. These results contrast with the chick, in which AER excision leads to loss of distal structures. We suggest that an AER was present in the common ancestor of anurans and amniotes and has been lost in at least some direct developers including E. coqui.

Animals↗
PubMed1998

Surface ectodermal wound healing in the chick embryo.

Wound healing has been studied in the surface ectoderm overlying the midbrain region of stages 16-20 chick embryos by light microscopy, scanning and transmission electron microscopy, and immunofluorescent techniques. The embryos were divided into 6 groups, i.e. stages 16-17 for groups I, V and VI, and stages 19-20 for groups II, III and IV. For groups I and II embryos, a longitudinal incision about 0.6 mm was made close to the dorsal midline and the embryos incubated for varying periods of time up to 24 h. To determine the role of actin in the process of healing, selected groups I and II embryos were stained with FITC phalloidin and the wound margins examined using a confocal microscope. Wounds of all embryos in group I and about 20% in group II healed completely within 24 h of reincubation. The process of healing involved a change in the shapes of the ectodermal cells at the wound ends. This appeared as a zipping-up of the wound from both ends. In about 80% of group II embryos where healing did not occur, wound gaping was marked. Intense actin staining (actin cable) was observed at the wound margins of groups I and II embryos suggesting that the actin purse-string mechanism may play a role during wound healing in this epithelial model. The role of tension in wound healing was also determined by placing 2 secondary wounds about 0.5-0.7 mm long close to, and at right angles to the ends of the primary wound in groups III and V embryos. The procedure decreased the tension within the ectodermal cells at the wound ends. Groups IV and VI embryos served as controls for groups III and V embryos, respectively. Healing of both primary and secondary wounds after reduction of tension was rapid. Most primary wounds in group V embryos healed completely within 3 h of reincubation and the rate of reepithelialisation after the reduction of tension was about 160% more than that in group VI (control) embryos. Similarly, most primary wounds in group III embryos were almost closed within 6 h of reincubation. Here, the rate of reepithelialisation was 80 % more than that in group IV (controls). Thus tension is an important factor in wound healing in this model.

Animals↗
PubMedDate not supplied

[Polysaccharide specific humoral immunodeficiency in ectodermal dysplasia. Case report of a boy with two affected brothers].

We report a now three year old male patient with ectodermal dysplasia and a polysaccharide specific humoral immunodeficiency. Immunological investigations showed compromised production of IgA, IgM, and IgG2. Isohaemagglutinins still were not detectable at the age of three years. Repeated vaccination with polyvalent pneumococcal polysaccharide vaccine did not result in production of specific antibodies. Two brothers showed clinical signs of ectodermal dysplasia. The elder brother died from pneumococcal sepsis at the age of 3 years. The younger brother suffers from chronic inflammatory gastrointestinal disease with ulcerations in all parts of the gastrointestinal system. Thus, a possible association between polysaccharide specific humoral immunodeficiency and ectodermal dysplasia may be considered.

Anti-Bacterial Agents↗
PubMed2001

Mutations within a furin consensus sequence block proteolytic release of ectodysplasin-A and cause X-linked hypohidrotic ectodermal dysplasia.

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a heritable disorder of the ED-1 gene disrupting the morphogenesis of ectodermal structures. The ED-1 gene product, ectodysplasin-A (EDA), is a tumor necrosis factor (TNF) family member and is synthesized as a membrane-anchored precursor protein with the TNF core motif located in the C-terminal domain. The stalk region of EDA contains the sequence -Arg-Val-Arg-Arg156-Asn-Lys-Arg159-, representing overlapping consensus cleavage sites (Arg-X-Lys/Arg-Arg( downward arrow)) for the proprotein convertase furin. Missense mutations in four of the five basic residues within this sequence account for approximately 20% of all known XLHED cases, with mutations occurring most frequently at Arg156, which is shared by the two consensus furin sites. These analyses suggest that cleavage at the furin site(s) in the stalk region is required for the EDA-mediated cell-to-cell signaling that regulates the morphogenesis of ectodermal appendages. Here we show that the 50-kDa EDA parent molecule is cleaved at -Arg156Asn-Lys-Arg(159 downward arrow)- to release the soluble C-terminal fragment containing the TNF core domain. This cleavage appears to be catalyzed by furin, as release of the TNF domain was blocked either by expression of the furin inhibitor alpha1-PDX or by expression of EDA in furin-deficient LoVo cells. These results demonstrate that mutation of a functional furin cleavage site in a developmental signaling molecule is a basis for human disease (XLHED) and raise the possibility that furin cleavage may regulate the ability of EDA to act as a juxtacrine or paracrine factor.

Amino Acid Sequence↗
PubMed2002

Activin A induces craniofacial cartilage from undifferentiated Xenopus ectoderm in vitro.

Activin A has potent mesoderm-inducing activity in amphibian embryos and induces various mesodermal tissues in vitro from the isolated presumptive ectoderm. By using a sandwich culture method established to examine activin A activity, we previously demonstrated that activin-treated ectoderm can function as both a head and trunk-tail organizer, depending on the concentration of activin A. By using activin A and undifferentiated presumptive ectoderm, it is theoretically possible to reproduce embryonic induction. Here, we test this hypothesis by studying the induction of cartilage tissue by using the sandwich-culture method. In the sandwiched explants, the mesenchymal cell condensation expressed type II collagen and cartilage homeoprotein-1 mRNA, and subsequently, cartilage were induced as they are in vivo. goosecoid (gsc) mRNA was prominently expressed in the cartilage in the explants. Xenopus distal-less 4 (X-dll4) mRNA was expressed throughout the explants. In Xenopus embryos, gsc expression is restricted to the cartilage of the lower jaw, and X-dll4 is widely expressed in the ventral head region, including craniofacial cartilage. These finding suggest that the craniofacial cartilage, especially lower jaw cartilage, was induced in the activin-treated sandwiched explants. In addition, a normal developmental pattern was recapitulated at the histological and genetic level. This work also suggests that the craniofacial cartilage-induction pathway is downstream of activin A. This study presents a model system suitable for the in vitro analysis of craniofacial cartilage induction in vertebrates.

Activins↗
PubMed2000

The ectodermal dysplasia receptor activates the nuclear factor-kappaB, JNK, and cell death pathways and binds to ectodysplasin A.

The ectodermal dysplasia receptor (EDAR) is a recently isolated member of the tumor necrosis factor receptor family that has been shown to play a key role in the process of ectodermal differentiation. We present evidence that EDAR is capable of activating the nuclear factor-kappaB, JNK, and caspase-independent cell death pathways and that these activities are impaired in mutants lacking its death domain or those associated with anhidrotic ectodermal dysplasia and the downless phenotype. Although EDAR possesses a death domain, it did not interact with the death domain-containing adaptor proteins TRADD and FADD. EDAR successfully interacted with various TRAF family members; however, a dominant-negative mutant of TRAF2 was incapable of blocking EDAR-induced nuclear factor-kappaB or JNK activation. Collectively, the above results suggest that EDAR utilizes a novel signal transduction pathway. Finally, ectodysplasin A can physically interact with the extracellular domain of EDAR and thus represents its biological ligand.

Cell Death↗