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Results for “ECTODERMAL DEFECT”

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PubMed1996

The Drosophila embryonic midline is the site of Spitz processing, and induces activation of the EGF receptor in the ventral ectoderm.

The Drosophila EGF receptor (DER) is activated by secreted Spitz to induce different cell fates in the ventral ectoderm. Processing of the precursor transmembrane Spitz to generate the secreted form was shown to be the limiting event, but the cells in which processing takes place and the mechanism that may generate a gradient of secreted Spitz in the ectoderm were not known. The ectodermal defects in single minded (sim) mutant embryos, in which the midline fails to develop, suggested that the midline cells contribute to patterning of the ventral ectoderm. This work shows that the midline provides the site for Spitz expression and processing. The Rhomboid and Star proteins are also expressed and required in the midline. The ectodermal defects of spitz, rho or Star mutant embryos could be rescued by inducing the expression of the respective normal genes only in the midline cells. Rho and Star thus function non-autonomously, and may be required for the production or processing of the Spitz precursor. Secreted Spitz is the only sim-dependent contribution of the midline to patterning the ectoderm, since the ventral defects observed in sim mutant embryos can be overcome by expression of secreted Spitz in the ectoderm. While ectopic expression of secreted Spitz in the ectoderm or mesoderm gave rise to ventralization of the embryo, increased expression of secreted Spitz in the midline did not lead to alterations in ectoderm patterning. A mechanism for adjustment to variable levels of secreted Spitz emanating from the midline may be provided by Argos, which forms an inhibitory feedback loop for DER activation. The production of secreted Spitz in the midline, may provide a stable source for graded DER activation in the ventral ectoderm.

Animals↗
PubMed2002

Bilateral nephroblastoma in familial Hay-Wells syndrome associated with familial reticulate pigmentation of the skin.

We report on a girl with maxillary hypoplasia, prominent ears, dry sparse hair, palmar and plantar keratoderma, dystrophic nails, patchy pigmented skin lesions in hands and feet and bilateral Wilms tumor. She was born with bilateral ankyloblepharon. The mother and maternal grandmother presented similar ectodermal defects. Skin biopsies of the patient and her mother proved to contain cells overexpressing p63 by immunohistochemistry. Karyotypes of the patient and her mother, and FISH studies on lymphocytes and tumor cells of the girl demonstrated a mosaic 11p15.5 deletion. These findings suggest a relationship between familial ankyloblepharon, ectodermal defects and cleft lip and palate (AEC) syndrome (Hay-Wells syndrome) and familial reticulate pigmentation of the skin. In addition the development of Wilms tumor and 11p15.5 region involvement expand the genetic relationship between these conditions and the enlarging group of genetic entities related to nephroblastoma.

Abnormalities, Multiple↗
PubMedDate not supplied

Gene defect in ectodermal dysplasia implicates a death domain adapter in development.

Members of the tumour-necrosis factor receptor (TNFR) family that contain an intracellular death domain initiate signalling by recruiting cytoplasmic death domain adapter proteins. Edar is a death domain protein of the TNFR family that is required for the development of hair, teeth and other ectodermal derivatives. Mutations in Edar-or its ligand, Eda-cause hypohidrotic ectodermal dysplasia in humans and mice. This disorder is characterized by sparse hair, a lack of sweat glands and malformation of teeth. Here we report the identification of a death domain adapter encoded by the mouse crinkled locus. The crinkled mutant has an hypohidrotic ectodermal dysplasia phenotype identical to that of the edar (downless) and eda (Tabby) mutants. This adapter, which we have called Edaradd (for Edar-associated death domain), interacts with the death domain of Edar and links the receptor to downstream signalling pathways. We also identify a missense mutation in its human orthologue, EDARADD, that is present in a family affected with hypohidrotic ectodermal dysplasia. Our findings show that the death receptor/adapter signalling mechanism is conserved in developmental, as well as apoptotic, signalling.

Amino Acid Sequence↗
PubMed1998

Björnstad syndrome in a patient with mental retardation.

Björnstad syndrome in a patient with mental retardation: Pili torti or twisted hair can appear as an isolated defect, in association with other ectodermal defects, in association with other clinical features or can be acquired. Björnstad syndrome is a rare condition with apparent autosomal recessive inheritance, characterized by hearing loss and twisted hairs (pili torti). All patients with Björnstad syndrome reported thusfar have normal intelligence. We report on a patient with severe mental retardation and review the literature.

Hair↗
PubMed2003

The cytoplasmic domain of Xenopus NF-protocadherin interacts with TAF1/set.

Protocadherins are members of the cadherin superfamily of cell adhesion molecules proposed to play important roles in early development, but whose mechanisms of action are largely unknown. We examined the function of NF-protocadherin (NFPC), a novel cell adhesion molecule essential for the histogenesis of the embryonic ectoderm in Xenopus, and demonstrate that the cellular protein TAF1, previously identified as a histone-associated protein, binds the NFPC cytoplasmic domain. NFPC and TAF1 coprecipitate from embryo extracts when ectopically expressed, and TAF1 can rescue the ectodermal disruptions caused by a dominant-negative NFPC construct lacking the extracellular domain. Furthermore, disruptions in either NFPC or TAF1 expression, using NFPC- or TAF1-specific antisense morpholinos, result in essentially identical ectodermal defects. These results indicate a role for TAF1 in the differentiation of the embryonic ectoderm, as a cytosolic cofactor of NFPC.

Amino Acid Sequence↗
PubMed1988

Familial occurrence of eccrine tumours in a family with ectodermal dysplasia.

In two brothers and their sister, ectodermal defects including hypodontia, onychodystrophia, trichodysplasia and palmoplantar keratosis were observed. In addition to the ectodermal dysplasia a diffuse palmoplantar eccrine hyperplasia was noted as well as tumours and cysts of eccrine origin. This seems to be the first report of familial occurrence of eccrine tumours.

Adenocarcinoma↗
PubMed2003

Penetrating keratoplasty and keratolimbal allograft transplantation for corneal perforations associated with the ectodermal dysplasia syndrome.

PURPOSE: To report two patients with ectodermal dysplasia-associated keratopathy treated with keratolimbal allograft transplantation and penetrating keratoplasty. METHODS: Two patients with ectodermal dysplasia suffered multiple corneal perforations. In both patients, keratolimbal allograft transplantation was performed along with penetrating keratoplasty. Histopathology of the corneal buttons was obtained. RESULTS: Histopathologic examination showed chronic inflammation with thin, irregular epithelium, loss of stromal tissue, and thin or absent Bowman's membrane. Both patients had multiple contributing factors predisposing them to corneal perforations including an inherent ectodermal defect, trichiasis, poor tear film, and limbal stem cell deficiency. CONCLUSIONS: Patients with keratopathy and corneal perforations associated with the ectodermal dysplasia syndrome has a poor prognosis. Keratolimbal allograft transplantation may have a role in the treatment of this disease. Longer follow-up and additional case reports will determine whether this technique confers a better prognosis than keratoplasty alone.

Adult↗
PubMed2001

Hedgehog signaling patterns the tracheal branches.

The elaborate branching pattern of the Drosophila tracheal system originates from ten tracheal placodes on both sides of the embryo, each consisting of about 80 cells. Simultaneous cell migration from each tracheal pit in six different directions gives rise to the stereotyped branching pattern. Each branch contains a fixed number of cells. Previous work has shown that in the dorsoventral axis, localized activation of the Dpp, Wnt and EGF receptor (DER) pathways, subdivides the tracheal pit into distinct domains. We present the role of the Hedgehog (Hh) signaling system in patterning the tracheal branches. Hh is expressed in segmental stripes abutting the anterior border of the tracheal placodes. Induction of patched expression, which results from activation by Hh, demonstrates that cells in the anterior half of the tracheal pit are activated. In hh-mutant embryos migration of all tracheal branches is absent or stalled. These defects arise from a direct effect of Hh on tracheal cells, rather than by indirect effects on patterning of the ectoderm. Tracheal cell migration could be rescued by expressing Hh only in the tracheal cells, without rescuing the ectodermal defects. Signaling by several pathways, including the Hh pathway, thus serves to subdivide the uniform population of tracheal cells into distinct cell types that will subsequently be recruited into the different branches.

Animals↗
PubMed1982

The conditions manifesting taurodontism.

Taurodontism is a trait that has captured the interests of evolutionists and clinical geneticists. This paper reviews the reported cases of taurodontism as an isolated trait and as a component of malformation syndromes. Because of the nature of the syndromes with which it is associated and its frequency in the general population, it is concluded that taurodontism is the result of an ectodermal defect and may be useful as an indicator of development instability.

Abnormalities, Multiple↗
PubMed1990

Developmentally regulated lectin in dark versus white axolotl embryos.

The white mutant of the Mexican axolotl, A. mexicanum, involves an ectodermal defect which prevents melanophore colonization. Endogenous lectins have been suggested to function in neural crest-derived melanophore adhesion in other animals. To determine if differences in endogenous lectins exist in dark and white axolotls during melanophore colonization, white and dark ectoderm and carcass tissues have been assayed for lectin activity at premigratory, early migratory, and late migratory neural crest stages. Lectin content (specific for D-glucosamine, N-acetyl-D-glucosamine and D-mannose) increases significantly during early migration only in dark ectoderm and white carcass tissues, whereas white ectoderm and dark carcass lectin activities remain close to premigration levels. Neural crest cells in these embryos are associated with regions of high lectin activity suggesting that the differences in endogenous lectins may be involved in establishment of the dark/white phenotype.

Ambystoma↗
PubMed2000

Control of neurulation by the nucleosome assembly protein-1-like 2.

Neurulation is a complex process of histogenesis involving the precise temporal and spatial organization of gene expression. Genes influencing neurulation include proneural genes determining primary cell fate, neurogenic genes involved in lateral inhibition pathways and genes controlling the frequency of mitotic events. This is reflected in the aetiology and genetics of human and mouse neural tube defects, which are of both multifactorial and multigenic origin. The X-linked gene Nap1l2, specifically expressed in neurons, encodes a protein that is highly similar to the nucleosome assembly (NAP) and SET proteins. We inactivated Nap1l2 in mice by gene targeting, leading to embryonic lethality from mid-gestation onwards. Surviving mutant chimaeric embryos showed extensive surface ectoderm defects as well as the presence of open neural tubes and exposed brains similar to those observed in human spina bifida and anencephaly. These defects correlated with an overproduction of neuronal precursor cells. Protein expression studies showed that the Nap1l2 protein binds to condensing chromatin during S phase and in apoptotic cells, but remained cytoplasmic during G1 phase. Nap1l2 therefore likely represents a class of tissue-specific factors interacting with chromatin to regulate neuronal cell proliferation.

Animals↗
PubMed1986

Hay-Wells syndrome.

Hay-Wells syndrome is an autosomal dominant constellation of facial clefting, ankyloblepharon filiforme adnatum (fused eyelids), and ectodermal defects. Our patient, a child who had these unusual features at birth, led us to consider possible differential diagnoses based on clinical features and review of the literature.

Cleft Lip↗
PubMed1994

Selective disruption of E-cadherin function in early Xenopus embryos by a dominant negative mutant.

E-cadherin function was disrupted in vivo in developing Xenopus laevis embryos through the expression of a mutant E-cadherin protein lacking its cytoplasmic tail. This truncated form of E-cadherin was designed to act as a dominant negative mutant by competing with the extracellular interactions of wild-type endogenous E-cadherin. Expression of truncated E-cadherin in the early embryo causes lesions to develop in the ectoderm during gastrulation. In contrast, expression of a similarly truncated N-cadherin protein failed to cause the lesions. The ectodermal defect caused by the truncated E-cadherin is rescued by overexpression of wild-type E-cadherin, by co-injection of full-length E-cadherin RNA along with the RNA for the truncated form. Overexpression of full-length C-cadherin, however, is unable to compensate for the disruption of E-cadherin function and can actually cause similar ectodermal lesions when injected alone, suggesting that there is a specific requirement for E-cadherin. Therefore, E-cadherin seems to be specifically required for maintaining the integrity of the ectoderm during epiboly in the gastrulating Xenopus embryo. Differential cadherin expression reflects, therefore, the requirement for distinct adhesive properties during different morphogenetic cell behaviors.

Amino Acid Sequence↗
PubMed1997

Hypoplastic thymus and T-cell reduction in EECUT syndrome.

We report on a patient with EEC/EECUT syndrome and concomitant hypoplasia of the thymus and reduction of T cells in secondary lymphatic organs. The patient was born prematurely at 35 weeks of gestational age and exhibited ectodermal dysplasia, ectrodactyly, cleft palate and urinary tract abnormalities. On the left side, a large ureterocele was present. On the right side, an atretic ureter was found. Both conditions had led to intrauterine hydronephrosis, renal dysplasia, oligohydramnios, pulmonary hypoplasia, and death of the child. Ureteral malformations are thought to be of epithelial origin. Autopsy showed only small rudiments of thymic tissue containing single epithelial cells, but were completely devoid of Hassall corpuscules. Again, this clearly points to an ectodermal defect. Although there was severe reduction of T cells in secondary lymphatic organs, the thymic defect would not have necessarily led to immunological deficiency; perhaps this is the reason that an epithelial defect in the thymus of patients with EEC syndrome has not yet been reported. With regard to an updating of the diagnosis of the EEC/EECUT syndrome, an "EEC/EECUT plus" syndrome is suggested.

Abnormalities, Multiple↗
PubMed1996

Fibroblast growth factor 2 can replace ectodermal signaling for feather development.

The initiation and morphogenesis of cutaneous appendages depend on a series of reciprocal signaling events between the epithelium and mesenchyme of the embryonic skin. In the development of feather germs, early dermal signals induce the formation of epidermal placodes that in turn signal the mesoderm to form dermal condensations immediately beneath them. We find a spatially and temporally restricted pattern of transcription for the genes that encode fibroblast growth factor (FGF) 2 and FGF receptor (FGFR) 1 in developing feather germs of the chicken embryo. FGF-2 expression is restricted to the epidermal placodes, whereas FGFR-1 expression is limited to the dermal condensations. Transcription of these genes could not be detected in skins of scaleless (sc/sc) embryos that fail to develop feathers as a result of an ectodermal defect. Treatment of sc/sc skins with FGF-2 results in the formation of feathers at the site of application of the growth factor and the induced feathers express FGFR-1 in their dermal condensations. Thus, we have established FGF-2 as an epidermal signal in early feather germ formation. The observation that FGF-2 can rescue the mutant phenotype of sc/sc embryos suggests that FGF-2 either is, or is downstream from, the signal that the sc/sc mutant ectoderm fails to generate.

Animals↗
PubMed1992

Ectodermal dysplasias associated with clefting: significance of scalp dermatitis.

Several clinical syndromes are characterized by ectodermal dysplasia (ED) in association with clefting of the lip and/or palate. The three most commonly recognized entities are (1) the EEC syndrome (ectodermal dysplasia, ectrodactyly, cleft lip/palate); (2) the Rapp-Hodgkin syndrome with ectodermal dysplasia, cleft lip/palate, and mid facial hypoplasia; and (3) the Hay-Wells or AEC syndrome (ankyloblepharon, ectodermal defects, cleft lip/palate). The clinical characteristics of these entities as well as several less common syndromes are reviewed and summarized. The presence of scalp dermatitis in patients with the AEC syndrome and less often the Rapp-Hodgkin syndrome is emphasized.

Cleft Lip↗
PubMed1992

Neurotoxicology of PCBs and related compounds.

Polychlorinated biphenyls (PCBs) are a family of 209 chemicals with two linked phenyl rings and variable chlorination. They are clear oils at room temperature. They were produced from the 1930s until banned in the 1970s because of toxicity and evidence of widespread environmental contamination. They were used mostly as insulators in electrical equipment; their widespread occurrence in the environment is more a consequence of uncontrolled disposal than of deliberate dissemination. In Asia, there have been two outbreaks of poisoning due to cooking oil contaminated by thermally degraded PCBs. Studies in workers exposed chronically to "clean" PCBs, workers exposed acutely to thermally degraded PCBs in clean-up of fires, and adult patients in Asia who ingested contaminated rice oil consistently show slowed nerve conduction and sometimes show headache, lassitude, and other CNS symptoms. In children exposed to background levels in the US, those with the highest transplacental exposure show hypotonia and hyporeflexia at birth and slowed motor development through age two, a defect in visual memory processing at 7 mon, and defects in short term memory at 4 years. Despite the presence of PCBs in breast milk, no association between breast milk exposure and any measured outcome has been seen other than lower activity levels at 4 years among long term breast fed children at the highest PCB levels. In Asia, children who were in utero at or after the 1968 exposure in Japan or the 1979 exposure in Taiwan showed clinically evident developmental delay. In Taiwan, the children were shown to have a variety of ectodermal defects, but the association between these defects and developmental delay was weak.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗