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PubMed2001

Fatal outcome in a female monozygotic twin with X-linked hypohydrotic ectodermal dysplasia (XLHED) due to a de novo t(X;9) translocation with probable disruption of the EDA gene.

UNLABELLED: Ectodermal dysplasias are a group of congenital disorders with defective development of the epidermis and its appendages. X-linked hypohydrotic ectodermal dysplasia (XLHED; OMIM 305100) is the most common form of ectodermal dysplasia. We report on two monozygotic twin girls with XLHED due to a t(X;9) translocation causing a disruption of the EDA gene and non random inactivation of the normal X chromosome. One of the girls died unexpectedly at 2.5 years of age. Autopsy revealed that lack of normal tracheobronchial secretions leading to complete tracheal obstruction by mucous debris was the probable cause of death. CONCLUSION: Morbidity and mortality of ectodermal dysplasias in infancy and early childhood can be significant. Early diagnosis by paediatricians is important and complications should be anticipated.

Child, Preschool↗
PubMed2006

Ectodysplasin regulates the lymphotoxin-beta pathway for hair differentiation.

Mutations in the EDA gene cause anhidrotic/hypohidrotic ectodermal dysplasia, a disorder characterized by defective formation of hair, sweat glands, and teeth in humans and in a mouse model, "Tabby" (Ta). The gene encodes ectodysplasin, a TNF ligand family member that activates the NF-kappaB-signaling pathway, but downstream targets and the mechanism of skin appendage formation have been only partially analyzed. Comparative transcription profiling of embryonic skin during hair follicle development in WT and Ta mice identified critical anhidrotic/hypohidrotic ectodermal dysplasia (EDA) effectors in four pathways, three already implicated in follicle formation. They included Shh and its effectors, as well as antagonists for the Wnt (Dkk4) and BMP (Sostdc1) pathways. The fourth pathway was unexpected, a variant NF-kappaB-signaling cascade based on lymphotoxin-beta (LTbeta)/RelB. Previously known to participate only in lymphoid organogenesis, LTbeta was enriched in developing hair follicles of WT but not in Ta mice. Furthermore, in mice lacking LTbeta, all three types of mouse hair were still formed, but all were structurally abnormal. Guard hairs became wavy and irregular, zigzag/auchen hairs lost their kinks, and in a phenocopy of features of Ta animals, the awl hairs doubled in number and were characteristically distorted and pinched. LTbeta-null mice that received WT bone marrow transplants maintained mutant hair phenotypes, consistent with autonomous LTbeta action in skin independent of its expression in lymphoid cells. Thus, as an EDA target, LTbeta regulates the form of hair in developing hair follicles; and when EDA is defective, failure of LTbeta activation can account for part of the Ta phenotype.

Animals↗
PubMed1976

[Genesis of malformations of the distal parts of chick embryo extremities (adactylia, hemimelia)].

Two series of experiments were carried out on chick embryos, stages 24 to 28 pairs of somites. (1) Denuded mesenchyme obtained from leg presumptive area previously treated with nitrogen mustard, was grafted into the right flank of embryos, stages 15 to 24 pairs of somites. (2) Conversely, denuded mesenchyme was implanted into the flank of nitrogen mustard-treated embryos. In most of the embryos, a supernumerary abnormal limb appeared; 58% of the legs produced in the first set of experiments had distal parts, whereas only 15% of the legs in the second set of experiments showed toes. Most of these legs had a hemimelic aspect or were reduced to stumps. This study demonstrates that deficiencies localised in the ectodermal apical part of the bud may be responsible for the stumpy limb defect.

Animals↗
PubMed1992

Dissection of the faint little ball (flb) phenotype: determination of the development of the Drosophila central nervous system by early interactions in the ectoderm.

The complex embryonic phenotype of mutations in the faint little ball (flb) locus, encoding the Drosophila EGF receptor homolog (DER), was dissected by temperature shifts of a temperature-sensitive allele. We show that the phenotype can be resolved into at least five components, which are temporally and spatially distinct. Most notably, the central nervous system (CNS) phenotype is determined at two separate phases. A severe collapse results from early defects in the DER-expressing ectodermal cells from which neuroblasts and midline glial cells deaminate. We thus suggest that DER activity is crucial for interactions that occur in the ectoderm at an early stage, and determine the fate of neuronal and glial cell lineages. This finding explains how a severe CNS phenotype is generated in flb embryos, in spite of the absence of expression of the protein in neuronal cells. In a second phase, during germ band retraction, the flb function is required specifically in the three pairs of midline glial cells (MG). In the absence of a functional DER protein, these cells die or fail to differentiate correctly, resulting in a fused commissure phenotype.

Animals↗
PubMed1979

[Jadassohn's nevus sebaceus and nevus unius lateris. Report of an observation with multiple dysplasia (author's transl)].

The case of a female patient with multiple ectodermal and mesodermal malformations present since birth is reported. The cutaneous lesions were of two types: Jadassohn's nevus sebaceus and nevus unius lateris. These entities have been described in the literature as congenital dermatologic alterations of nevoid character and organoid structure. They can be considered as congenital epidermal nevi. In many cases, including this one, there are various associated disorders especially of the nervous system, eyes, and skeleton. Both syndromes are cutaneous hamartomas which can be differentiated histologically but not by the anomalies accompanying them. Their dermatologic aspects are very similar. The histopathologic characteristics of the skin lesions of nevus unius lateris consist of hyperkeratosis, acanthosis, and epidermal papillomatosis. In Jadassohn's nevus sebaceus there are also alterations of the skin adnexa, namely the absence of hair follicles and the presence of numerous mature sebaceus and hyperplastic glands. In general, the presence of organoid nevus may be a sign of multiple ectodermal and mesodermal malformations. Both syndromes are often present in the same patient, as in the case described here, and their etiology is the same. It is based on an alteration in embryogenic development affecting primarily, though not exclusively, the formations of ectodermal origin. Thus Jadassohn's nevus sebaceus and nevus unius lateris are both forms of phacomatosis. Clinical cases have in common the cutaneous cited above, either in combination or singly. The other possible signs and symptoms are variable, depending on which stage of embryogenic development is affected. There may be defects in the structures of both ectodermal and mesodermal origin.

Adult↗
PubMed1987

Growth hormone deficiency associated with the ectrodactyly-ectodermal dysplasia-clefting syndrome and isolated absent septum pellucidum.

Two growth hormone-deficient patients with particular developmental defects are presented. One patient had the ectrodactyly-ectodermal dysplasia-clefting syndrome with lobster-claw deformities of the hands; thin, blond, and dry hair and enamel hypoplasia; and a facial raphe on the right side of the philtrum. The other patient had isolated absence of the septum pellucidum. The facial raphe and the absent septum pellucidum are related to cleft lip and septooptic dysplasia, conditions that have been associated with growth hormone failure. The association of the ectrodactyly-ectodermal dysplasia-clefting syndrome with isolated growth hormone deficiency has not been described previously.

Abnormalities, Multiple↗
PubMed1988

The carpal bones in congenital hand anomalies: a radiographic study in patients older than ten years.

Abnormalities of the carpal bones in 192 anomalous hands of 154 patients older than 10 years were examined. Judging from the time of appearance of the pisiform, there was no delay of carpal bone maturation in these anomalies. There were differences between the carpal bones of three distinct groups: which included central polydactyly, syndactyly, and typical cleft hand; the group which included radial and ulnar deficiency, and the group which included symbrachydactyly and transverse defect. This suggests that there were differences between these groups in the timing and degree of injury to the limb bud or the hand plate in the course of development. It is thought that the first group originates from maldistribution of mesenchymal tissue of the limb bud (or of the apical ectodermal ridge), the second group from defects of that tissue, and the last group from defects of the mesenchymal tissue of the hand plate.

Adolescent↗
PubMed2005

Three successive generations of women with anhidrotic/hypohidrotic ectodermal dysplasia.

We describe the findings of anhidrotic/hypohidrotic ectodermal dysplasia in three successive generations of a family. All three women had variable alopecia, anhidrosis, hypodontia and malar hypoplasia. Chromosomal studies revealed a defect of the 2q12 region in all three patients. Previous studies have reported rare cases of autosomal dominant ectodermal dysplasia associated with defects in the 2q11-13 region1. These rare disorders are characterized by common anomalies of at least two elements of the ectoderm and its appendages--namely, the skin, teeth, hair, nails and sweat glands. These patients also frequently have chronic dental problems with early loss of teeth and recurrent lung, ear and nose infections secondary to a defect in mucous membrane function. The majority of reported cases of ectodermal dysplasias have historically been X-linked recessive, but our findings indicate that an autosomal version may be more prevalent than previously thought.

Adult↗
PubMed2002

Mouse Twist is required for fibroblast growth factor-mediated epithelial-mesenchymal signalling and cell survival during limb morphogenesis.

Mouse Twist is essential for cranial neural tube, limb and somite development. [Genes Dev. 9 (1995) 686]. To identify the molecular defects disrupting limb morphogenesis, we have analysed expression of mesenchymal transcription factors involved in patterning and the cell-cell signalling cascades controlling limb bud development. These studies establish that Twist is essential for maintenance and progression of limb bud morphogenesis. In particular, the SHH/FGF signalling feedback loop operating between the polarizing region and the apical ectodermal ridge (AER) is disrupted. These defects in epithelial-mesenchymal signalling are most likely a direct consequence of disrupted fibroblast growth factor (FGF) signalling in Twist-deficient limb buds. In early limb buds, down-regulation of Fgf receptor 1 and Fgf10 expression in the mesenchyme occurs concurrent with loss of Fgf4 and Fgf8 expression in the AER. Finally, Twist function, most likely by regulating FGF signalling, is required for cell survival as apoptotic cells are detected in posterior and distal limb bud mesenchyme.

Animals↗
PubMed2004

The ectodermal dysplasia receptor represses the Lef-1/beta-catenin-dependent transcription independent of NF-kappaB activation.

EDAR plays a key role in the process of ectodermal differentiation via activation of the NF-kappaB pathway. We present evidence that EDAR also represses Lef-1/beta-catenin-dependent transcription and this ability is defective in EDAR mutants associated with anhidrotic ectodermal dysplasia. While IKK1/IKKalpha and IKK2/IKKbeta are required for EDAR-induced NF-kappaB activation, they are dispensable for its ability to repress Lef-1/beta-catenin-dependent transcription. In contrast, NIK is not involved in EDAR-induced NF-kappaB activation or Lef-1/beta-catenin transcriptional repression. As Lef-1/beta-catenin pathway controls the expression of EDAR ligand, ectodysplasin-A (EDA), our results point to a negative feedback regulation of EDA-EDAR axis.

Animals↗
PubMed1985

Aplasia cutis congenita associated with valvular heart disease.

We present a patient with a congenital scalp lesion compatible with aplasia cutis congenita (ACC) and associated congenital heart disease (CHD). This interesting combined entity is briefly reviewed and associated defects that can occur are discussed.

Ectodermal Dysplasia↗
PubMed2003

PTPN11 mutations are not responsible for the Cardiofaciocutaneous (CFC) syndrome.

Cardiofaciocutaneous (CFC) syndrome is a multiple congenital anomalies/mental retardation syndrome characterized by congenital heart defects, characteristic facial appearance, short stature, ectodermal abnormalities and mental retardation. It was described in 1986, and to date is of unknown genetic etiology. All reported cases are sporadic, born to non-consanguineous parents and have apparently normal chromosomes. Noonan and Costello syndromes remain its main differential diagnosis. The recent finding of PTPN11 missense mutations in 45-50% of the Noonan patients studied with penetrance of almost 100% and the fact that in animals mutations of this gene cause defects of semilunar valvulogenesis, made PTPN11 mutation screening in CFC patients a matter of interest. We sequenced the entire coding region of the PTPN11 gene in ten well-characterised CFC patients and found no base changes. We also studied PTPN11 cDNA in our patients and demonstrated that there are no interstitial deletions either. The genetic cause of CFC syndrome remains unknown, and PTPN11 can be reasonably excluded as a candidate gene for the CFC syndrome, which we regard as molecular evidence that CFC and Noonan syndromes are distinct genetic entities.

Abnormalities, Multiple↗
PubMed1978

Lack of correlation between mesenchymal cell death and morphogenesis after different extents of apical ectodermal ridge/rim ectoderm removal in the chick embryo wing bud.

The removal of the apical ectodermal ridge (A.E.R.) subsequently causes distal deletion defects in the limb. There have been contradictory reports as to the appearance of cell death in the mesenchyme after A.E.R. removal, as well as to its morphogenetic significance. In our study the A.E.R./ rim ectoderm removal was varied to test whether different degrees of cell death would correlate with different degrees of distal deletions. From the right wing bud of stage 19 and 20 (HH) embryos the rim ectoderm was removed in four ways: all of the rim, the anterior third, the middle third (most of the A.E.R.), or its posterior third. The removal of all or of the anterior third caused a definite band of subwound mesenchymal cell death to appear. There was little or no cell death after removal of the middle or posterior thirds. Removal of the anterior third caused no distal deletion defects, and only a few were noted after removal of the posterior third. The proximo-distal level of the distal deletions, however, was the same after removal of all of the rim or only its middle third. As there was no difference in the degree of distal deletions after the removal of all or of the middle third of the rim but a definite difference in the mesenchymal cell death patterns we conclude that cell death is not part of the mechanisms of the distal deletion defect. Our findings also suggest that cell death does not play a role in the A.E.R.-mesenchyme reciprocal interaction that controls limb proximo-distal morphogenesis.

Animals↗
PubMed1996

Heartless, a Drosophila FGF receptor homolog, is essential for cell migration and establishment of several mesodermal lineages.

A Drosophila FGF receptor homolog (DFGF-R2/DFRI) termed Heartless (Htl) is expressed in the embryonic mesoderm. The phenotypes of null mutant embryos demonstrated that Htl is a central player that is required for the development of several mesodermal lineages. No abnormalities in the primary specification of the mesoderm were observed. The first defects were seen as irregular migration and spreading of the mesoderm over the ectoderm. Subsequently, cell fates were not induced in several lineages including the visceral mesoderm, heart, and the dorsal somatic muscles. The defects in the induction of cell fates are likely to result from failure of the mesoderm to spread over the ectoderm and receive patterning signals. The defective spreading could be circumvented in htl mutant embryos by providing an ectopic Dpp patterning signal, leading to the formation of heart and dorsal muscle cells. Htl appears to be required also subsequently during the migration and morphogenesis of the different lineages. Expression of a dominant-negative htl construct after the initial induction of cell fates gave rise to aberrant migration and organization of the visceral mesoderm, heart, and somatic muscles. Thus, a common role for Htl in cell migration and tissue organization may account for the pleiotropic defects of the htl mutation.

Animals↗
PubMed1995

'Membranous aplasia cutis' with hair collars. Congenital absence of skin or neuroectodermal defect?

BACKGROUND: The skin and the nervous system are both derived from ectoderm. Separation of neural ectoderm from epithelial ectoderm occurs concurrently with the closure of the neural tube. This chronologic association may explain the cutaneous abnormalities often found overlying neural tube defects. A ring of dark long hair encircling a congenital scalp lesion (the hair collar sign) is one such marker and is often associated with encephaloceles, meningoceles, and heterotopic brain tissue. OBSERVATIONS: We describe six children with aplasia cutis who displayed the hair collar sign. Aplasia cutis is a relatively heterogeneous disorder; however, these lesions had a unique and strikingly similar appearance. This subtype of aplasia cutis, which we have termed membranous aplasia cutis, shares several clinical and histologic features with cranial neural tube defects. CONCLUSIONS: We propose that membranous aplasia cutis is a form fruste of a neural tube defect and may be derived from a similar embryological defect. Recent advances in the understanding of cranial neural tube closure may provide support for this hypothesis.

Atrophy↗
PubMed2004

Retinoic acid synthesis controlled by Raldh2 is required early for limb bud initiation and then later as a proximodistal signal during apical ectodermal ridge formation.

We present evidence for the existence of two phases of retinoic acid (RA) signaling required for vertebrate limb development. Limb RA synthesis is under the control of retinaldehyde dehydrogenase-2 (Raldh2) expressed in the lateral plate mesoderm, which generates a proximodistal RA signal during limb outgrowth. We report that Raldh2(-/-) embryos lack trunk mesodermal RA activity and fail to initiate forelimb development. This is associated with deficient expression of important limb determinants Tbx5, Meis2, and dHand needed to establish forelimb bud initiation, proximal identity, and the zone of polarizing activity (ZPA), respectively. Limb expression of these genes can be rescued by maternal RA treatment limited to embryonic day 8 (E8) during limb field establishment, but the mutant forelimbs obtained at E10 display a significant growth defect associated with a smaller apical ectodermal ridge (AER), referred to here as an apical ectodermal mound (AEM). In these RA-deficient forelimbs, a ZPA expressing Shh forms, but it is located distally adjacent to the Fgf8 expression domain in the AEM rather than posteriorly as is normal. AER formation in Raldh2(-/-) forelimbs is rescued by continuous RA treatment through E10, which restores RA to distal ectoderm fated to become the AER. Our findings indicate the existence of an early phase of RA signaling acting upstream of Tbx5, Meis2, and dHand, followed by a late phase of RA signaling needed to expand AER structure fully along the distal ectoderm. During ZPA formation, RA acts early to activate expression of dHand, but it is not required later for Shh activation.

Aldehyde Oxidoreductases↗
PubMed1997

Frontoethmoidal encephaloceles, a study of their pathogenesis.

A prospective clinical study of 30 patients with frontoethmoidal encephaloceles was performed in order to find support for a proposed theory concerning its pathogenesis, based on a previously performed embryological study and relevant findings in the literature. According to this proposed theory the pathogenesis of frontoethmoidal encephaloceles is primarily based on a disturbance in separation of neural and surface ectoderm at the site of final closure of the rostral neuropore during the final phase of neurulation in the 4th week of gestation. An insufficient occurrence of apoptosis might cause this disturbance in separation. The nonseparation of neural and surface ectoderm will result secondarily in a midline mesodermal defect. This mesodermal defect is reflected in the median skull defect at the site of the foramen caecum. The outgrowth of the nasal septum with the concomitant forward displacement of epidermis (surface ectoderm) and attached brain tissue (neural ectoderm) may act as herniating force. The patient study consisted of a clinical investigation, radiological investigations (X skull and CT scans), and surgical treatment in order to obtain specimens which were examined histologically. Clinical findings supportive of the proposed hypothesis are (1) the consistency in the location of the internal skull defect, (2) the close relationship between epidermal structures and glial tissue in 15 out of 29 specimens, and (3) the presence of a normally developed nose in combination with interorbital hypertelorism in all patients. A discussion of these findings is presented with special reference to the embryological aspects.

Abnormalities, Multiple↗
PubMed2001

Desmosomes: structure and function in normal and diseased epidermis.

Desmosomes are important epidermal adhesion complexes that are characterized by a cell-specific expression of transmembrane cadherins and plaque-associated molecules. Desmosomes have so far, been implicated in three main disease types: autoimmune diseases that involve desmosome components (such as pemphigus vulgaris and pemphigus foliaceus), congenital diseases that affect intracellular calcium channels (such as Hailey-Hailey disease and Darier disease) and congenital diseases that directly affect desmosomal structural components. The identification of the first congenital defect affecting a desmosome component was in the gene for plakophilin I which caused an autosomal recessive skin fragility-ectodermal dysplasia syndrome with skin, hair and nail defects. Subsequently, either a haploinsufficiency of desmoplakin or a defect in desmoglein 1 was found to underlie the autosomal dominant condition Striate Palmoplantar Keratoderma. In addition, plakoglobin has been shown to be defective in Naxos disease, which results in a cardiomyopathy and growth of abnormal hair. These findings pave the way for the discovery of further cell cohesion-related diseases and will help to greatly increase our understanding of the specific function of desmosome and other epithelial junction components.

Animals↗