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At least 19 recordsLinked to original sources
PubMed2005

TAB2, TRAF6 and TAK1 are involved in NF-kappaB activation induced by the TNF-receptor, Edar and its adaptator Edaradd.

Activation of the NF-kappaB pathway by the TNF-receptor Edar (Ectodysplasin receptor) and its downstream adaptator Edaradd (Edar-associated death domain) is essential for the development of hair follicles, teeth, exocrine glands and other ectodermal derivatives. Dysfunction of Edar signalling causes hypohidrotic/anhidrotic ectodermal dysplasia (ED), a disorder characterized by sparse hair, lack of sweat glands and malformation of teeth. The Edar signalling pathway stimulates NF-kappaB transcription factors via an activation of the IkappaB kinase (IKK) complex. To gain further insight into the mechanism of IKK activation by Edar and Edaradd, we performed a yeast two-hybrid screen and isolated TAB2 (TAK1-binding protein 2) as a binding partner of Edaradd. TAB2 is an adaptator protein that brigdes TRAF6 (TNF-receptor-associated factor 6) to TAK1 (TGFbeta-activated kinase 1), allowing TAK1 activation and subsequent IKK activation. Here, we show that endogenous and overexpressed TAB2, TRAF6 and TAK1 co-immunoprecipitated with Edaradd in 293 cells. Moreover, we show that dominant negative forms of TAB2, TRAF6 and TAK1 blocked the NF-kappaB activation induced by Edaradd. These results support the involvement of the TAB2/TRAF6/TAK1 signalling complex in the Edar signal transduction pathway and have important implications for our understanding of NF-kappaB activation and EDs in human.

Adaptor Proteins, Signal Transducing↗
PubMed2004

The activation level of the TNF family receptor, Edar, determines cusp number and tooth number during tooth development.

Mutations in members of the ectodysplasin (TNF-related) signalling pathway, EDA, EDAR, and EDARADD in mice and humans produce an ectodermal dysplasia phenotype that includes missing teeth and smaller teeth with reduced cusps. Using the keratin 14 promoter to target expression of an activated form of Edar in transgenic mice, we show that expression of this transgene is able to rescue the tooth phenotype in Tabby (Eda) and Sleek (Edar) mutant mice. High levels of expression of the transgene in wild-type mice result in molar teeth with extra cusps, and in some cases supernumerary teeth, the opposite of the mutant phenotype. The level of activation of Edar thus determines cusp number and tooth number during tooth development.

Animals↗
PubMed2002

Regulation of hair follicle development by the TNF signal ectodysplasin and its receptor Edar.

X-linked and autosomal forms of anhidrotic ectodermal dysplasia syndromes (HED) are characterized by deficient development of several ectodermal organs, including hair, teeth and exocrine glands. The recent cloning of the genes that underlie these syndromes, ectodysplasin (ED1) and the ectodysplasin A receptor (EDAR), and their identification as a novel TNF ligand-receptor pair suggested a role for TNF signaling in embryonic morphogenesis. In the mouse, the genes of the spontaneous mutations Tabby (Ta) and downless (dl) were identified as homologs of ED1 and EDAR, respectively. To gain insight into the function of this signaling pathway in development of skin and hair follicles, we analyzed the expression and regulation of Eda and Edar in wild type as well as Tabby and Lef1 mutant mouse embryos. We show that Eda and Edar expression is confined to the ectoderm and occurs in a pattern that suggests a role of ectodysplasin/Edar signaling in the interactions between the ectodermal compartments and the formation and function of hair placodes. By using skin explant cultures, we further show that this signaling pathway is intimately associated with interactions between the epithelial and mesenchymal tissues. We also find that Ta mutants lack completely the placodes of the first developing tylotrich hairs, and that they do not show patterned expression of placodal genes, including Bmp4, Lef1, Shh, Ptch and Edar, and the genes for beta-catenin and activin A. Finally, we identified activin as a mesenchymal signal that stimulates Edar expression and WNT as a signal that induces Eda expression, suggesting a hierarchy of distinct signaling pathways in the development of skin and hair follicles. In conclusion, we suggest that Eda and Edar are associated with the onset of ectodermal patterning and that ectodysplasin/edar signaling also regulates the morphogenesis of hair follicles.

Activins↗
PubMed2004

Tooth patterning and enamel formation can be manipulated by misexpression of TNF receptor Edar.

Signaling by Edar, a tumor necrosis factor receptor, is required for the development of ectodermal organs. Mutations in Edar or other molecules of the same signaling pathway cause ectodermal dysplasias in humans and mice. In these diseases, teeth are missing or malformed, and the development of hairs and several glands is hypoplastic. During tooth and hair development, Edar expression becomes patterned to ectodermal placodes and signaling centers. This localization has been suggested to be required for organogenesis. We have expressed Edar throughout the ectoderm using the keratin 14 promoter and show that this misexpression disrupts tooth patterning and differentiation. Tooth shape and cusp number are differentially affected, depending on the amount of transgene expression. In addition, tooth enamel formation is defective in a dose-dependent manner. We speculate that the tooth patterning defects are caused by ectopic Edar activity outside the signaling centers.

Amelogenesis↗
PubMed2001

Signaling and subcellular localization of the TNF receptor Edar.

Tabby and downless mutant mice have identical phenotypes characterized by deficient development of several ectodermally derived organs such as teeth, hair, and sweat glands. Edar, encoded by the mouse downless gene and defective in human dominant and recessive forms of autosomal hypohidrotic ectodermal dysplasia (EDA) syndrome, is a new member of the tumor necrosis factor (TNF) receptor superfamily. The ligand of Edar is ectodysplasin, a TNF-like molecule mutated in the X-linked form of EDA and in the spontaneous mouse mutant Tabby. We have analyzed the response of Edar signaling in transfected cells and show that it activates nuclear factor-kappaB (NF-kappaB) in a dose-dependent manner. When Edar was expressed at low levels, the NF-kappaB response was enhanced by coexpression of ectodysplasin. The activation of NF-kappaB was greatly reduced in cells expressing mutant forms of Edar associated with the downless phenotype. Overexpression of Edar did not activate SAPK/JNK nor p38 kinase. Even though Edar harbors a death domain its overexpression did not induce apoptosis in any of the four cell lines analyzed, nor was there any difference in apoptosis in developing teeth of wild-type and Tabby mice. Additionally, we show that the subcellular localization of dominant negative alleles of downless is dramatically different from that of recessive or wild-type alleles. This together with differences in NF-kappaB responses suggests an explanation for the different mode of inheritance of the different downless alleles.

Alleles↗
PubMed2002

TRAF6-deficient mice display hypohidrotic ectodermal dysplasia.

Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) is an adapter protein that links signals from members of the TNFR superfamily and Toll/IL-1 receptor family to activation of transcription factors NFkappaB and AP-1. Analysis of TRAF6-deficient mice revealed that TRAF6 is essential for normal bone formation and establishment of immune and inflammatory systems. Here we report that TRAF6 deficiency results in defective development of epidermal appendixes, including guard hair follicles, sweat glands, sebaceous glands of back skin, and modified sebaceous glands such as meibomian glands, anal glands, and preputial glands. Except the sebaceous gland impairment, these abnormal phenotypes are identical to those observed in Tabby (Ta), downless (dl), and crinkled (cr) mice, which are models of hypohidrotic (anhidrotic) ectodermal dysplasia in human. beta-catenin and mucosal addressin cell adhesion molecule-1, an early marker of developing guard-hair follicles is absent in the skin of TRAF6-deficient embryos. Thus, TRAF6 is essential for development of epidermal appendixes. TRAF6 does not associate with the cytoplasmic tail of the dl protein (DL)/ectodysplasin receptor (EDAR) receptor, which, when mutated, results in hypohidrotic (anhidrotic) ectodermal dysplasia. However, TRAF6 associates with X-linked ectodysplasin-A2 receptor (XEDAR) and TNFR super family expressed on the mouse embryo (TROY/toxicity and JNK inducer (TAJ), which are EDAR-related members of the TNFR superfamily that are expressed at high level in epidermal appendixes. Furthermore, TRAF6 is essential for the XEDAR-mediated NFkappaB activation. Our results suggest that TRAF6 may transduce signals emanating from XEDAR or TROY/TAJ that are associated with development of epidermal appendixes.

Animals↗
PubMed2006

Repertoire of mouse ectodysplasin-A (EDA-A) isoforms.

Mutations in ectodysplasin-A (EDA) cause loss of hair, sweat glands, and teeth in man and mouse. Isoform EDA-A1 protein shows partial rescue of the affected Tabby mouse phenotypes, suggesting that other isoforms may be required for full function. We describe genomic structure for five EDA isoforms, EDA-A1', A5, A5', A6, and A6', in addition to the previously known EDA-A1, A2, A3, and A4. The novel isoforms together account for approximately 12% of total EDA transcripts. The most different, EDA-A6 and A6', which lack the critical domain for interaction with NF-kappaB-activating receptors, were nevertheless confirmed to be present in mouse and human skin tissue. Other isoforms, EDA-A5 and A5', for example, activated NF-kappaB through receptors EDAR and XEDAR. These properties make new isoforms candidates for modulators of EDA function.

Animals↗
PubMed2001

The medaka rs-3 locus required for scale development encodes ectodysplasin-A receptor.

The bodies of most teleost fish species are covered with specialized subepithelial structures known as scales. The scale is an epithelial appendage that differentiates from the dermal mesenchyme. Mammals, on the other hand, have no scales, but instead their bodies are covered with hair. Although their appearances are quite different, scales and hair can be considered structurally similar in that both of them are epithelial appendages distributed over the body surface in an orderly pattern. This analogy suggests that they may have the same evolutionary origin. But, to date, no molecular evidence has been presented that links scales and hair. A mutation at the rs-3 locus of medaka (Oryzias latipes) leads to almost complete loss of scales. We demonstrated that the rs-3 locus encodes ectodysplasin-A receptor (EDAR), which is required for the initiation of hair development in mammals. We identified a novel transposon inserted in the first intron of EDAR, which causes aberrant splicing. This work shows that EDAR is required for scale development in fish and suggests that it is an evolutionarily conserved molecule that is required for the development of epithelial appendages in vertebrates.

Amino Acid Sequence↗
PubMed2006

Generation of the primary hair follicle pattern.

Hair follicles are spaced apart from one another at regular intervals through the skin. Although follicles are predominantly epidermal structures, classical tissue recombination experiments indicated that the underlying dermis defines their location during development. Although many molecules involved in hair follicle formation have been identified, the molecular interactions that determine the emergent property of pattern formation have remained elusive. We have used embryonic skin cultures to dissect signaling responses and patterning outcomes as the skin spatially organizes itself. We find that ectodysplasin receptor (Edar)-bone morphogenetic protein (BMP) signaling and transcriptional interactions are central to generation of the primary hair follicle pattern, with restriction of responsiveness, rather than localization of an inducing ligand, being the key driver in this process. The crux of this patterning mechanism is rapid Edar-positive feedback in the epidermis coupled with induction of dermal BMP4/7. The BMPs in turn repress epidermal Edar and hence follicle fate. Edar activation also induces connective tissue growth factor, an inhibitor of BMP signaling, allowing BMP action only at a distance from their site of synthesis. Consistent with this model, transgenic hyperactivation of Edar signaling leads to widespread overproduction of hair follicles. This Edar-BMP activation-inhibition mechanism appears to operate alongside a labile prepattern, suggesting that Edar-mediated stabilization of beta-catenin active foci is a key event in determining definitive follicle locations.

Animals↗
PubMed2005

The ectodysplasin pathway in feather tract development.

The ectodysplasin pathway, comprising the ligand ectodysplasin, its receptor Edar and a dedicated death domain adaptor protein Edaradd, plays an important role in epidermal organ formation in mammals. Mutations in the genes encoding these proteins cause dysplasia or absence of teeth, sweat glands and hair follicles. However, the relative position of this pathway in the regulatory hierarchy directing follicle formation remains unclear. In this work, the chicken orthologs of Eda, Edar and Edaradd were cloned to exploit the temporal precision of the feather tract system in order to study the role of the ectodysplasin pathway. We find that these genes are expressed in a similar pattern during feather and hair development, with the notable difference that the ligand Eda, which is expressed in the epidermis of the mouse, is expressed in the dermis of the feather tract. Contrary to conclusions reached from the analysis of mutant mice, we find that localization of Edar expression to the nascent placode is coincident or subsequent to the local expression of other markers of placodal differentiation, and not an upstream event in tract patterning. Furthermore, forced expression of BMP and activated beta-catenin demonstrate that local expression of Edar is dictated by the interaction between these two pathways. These results suggest that activation of the ectodysplasin pathway may be permissive for activating signals to overcome signals that inhibit placode formation, but the function of this pathway in the specification of follicle initiation lies downstream of other patterning events.

Amino Acid Sequence↗
PubMed2006

NF-kappaB transmits Eda A1/EdaR signalling to activate Shh and cyclin D1 expression, and controls post-initiation hair placode down growth.

A novel function of NF-kappaB in the development of most ectodermal appendages, including two types of murine pelage hair follicles, was detected in a mouse model with suppressed NF-kappaB activity (c(IkappaBalphaDeltaN)). However, the developmental processes regulated by NF-kappaB in hair follicles has remained unknown. Furthermore, the similarity between the phenotypes of c(IkappaBADeltaN) mice and mice deficient in Eda A1 (tabby) or its receptor EdaR (downless) raised the issue of whether in vivo NF-kappaB regulates or is regulated by these novel TNF family members. We now demonstrate that epidermal NF-kappaB activity is first observed in placodes of primary guard hair follicles at day E14.5, and that in vivo NF-kappaB signalling is activated downstream of Eda A1 and EdaR. Importantly, ectopic signals which activate NF-kappaB can also stimulate guard hair placode formation, suggesting a crucial role for NF-kappaB in placode development. In downless and c(IkappaBalphaDeltaN) mice, placodes start to develop, but rapidly abort in the absence of EdaR/NF-kappaB signalling. We show that NF-kappaB activation is essential for induction of Shh and cyclin D1 expression and subsequent placode down growth. However, cyclin D1 induction appears to be indirectly regulated by NF-kappaB, probably via Shh and Wnt. The strongly decreased number of hair follicles observed in c(IkappaBalphaDeltaN) mice compared with tabby mice, indicates that additional signals, such as TROY, must regulate NF-kappaB activity in specific hair follicle subtypes.

Animals↗
PubMed2007

Ectodysplasin has a dual role in ectodermal organogenesis: inhibition of Bmp activity and induction of Shh expression.

Ectodermal organogenesis is regulated by inductive and reciprocal signalling cascades that involve multiple signal molecules in several conserved families. Ectodysplasin-A (Eda), a tumour necrosis factor-like signalling molecule, and its receptor Edar are required for the development of a number of ectodermal organs in vertebrates. In mice, lack of Eda leads to failure in primary hair placode formation and missing or abnormally shaped teeth, whereas mice overexpressing Eda are characterized by enlarged hair placodes and supernumerary teeth and mammary glands. Here, we report two signalling outcomes of the Eda pathway: suppression of bone morphogenetic protein (Bmp) activity and upregulation of sonic hedgehog (Shh) signalling. Recombinant Eda counteracted Bmp4 activity in developing teeth and, importantly, inhibition of BMP activity by exogenous noggin partially restored primary hair placode formation in Eda-deficient skin in vitro, indicating that suppression of Bmp activity was compromised in the absence of Eda. The downstream effects of the Eda pathway are likely to be mediated by transcription factor nuclear factor-kappaB (NF-kappaB), but the transcriptional targets of Edar have remained unknown. Using a quantitative approach, we show in cultured embryonic skin that Eda induced the expression of two Bmp inhibitors, Ccn2/Ctgf (CCN family protein 2/connective tissue growth factor) and follistatin. Moreover, our data indicate that Shh is a likely transcriptional target of Edar, but, unlike noggin, recombinant Shh was unable to rescue primary hair placode formation in Eda-deficient skin explants.

Animals↗
PubMed2003

Death receptors.

Death receptors [Fas/Apo-1/CD95, TNF-R1 [tumour necrosis factor (TNF) receptor 1], DR3 [death receptor 3], TRAIL-R1 [TNF-related apoptosis-inducing ligand receptor 1], TRAIL-R2, DR6, p75-NGFR [p75-nerve growth factor receptor], EDAR [ectodermal dysplasia receptor]] form a subgroup of the TNF-R superfamily that can induce apoptosis (programmed cell death) via a conserved cytoplasmic signalling module termed the death domain. Although death receptors have been recognized mainly as apoptosis inducers, there is growing evidence that these receptors also fulfil a variety of nonapoptotic functions. This review is focused on the molecular mechanisms of apoptotic and non-apoptotic death receptor signalling in light of the phenotype of mice deficient in the various death receptors.

Animals↗
PubMedDate not supplied

Ectodysplasin signaling in development.

Ectodysplasin (Eda), a signaling molecule belonging to the tumor necrosis factor family, is required for normal development of several ectodermally derived organs in humans and mice. Two closely related isoforms of ectodysplasin, Eda-A1 and Eda-A2, have been described which bind to and activate two different receptors, Edar and X-linked Eda-A2 receptor (Xedar), respectively. Mutations in Eda, Edar or other molecules of this signaling pathway cause ectodermal dysplasias characterized by defective development of teeth, hairs, and several exocrine glands such as sweat glands presumably due to impaired NF-kappaB response. Studies with mice either lacking the functional proteins of Edar pathway or overexpressing the ligand or receptor suggest that Eda-A1-Edar signaling has multiple roles in ectodermal organ development regulating their initiation, morphogenesis, and differentiation.

Animals↗
PubMed2003

Stimulation of ectodermal organ development by Ectodysplasin-A1.

Organs developing as ectodermal appendages share similar early morphogenesis and molecular mechanisms. Ectodysplasin, a signaling molecule belonging to the tumor necrosis factor family, and its receptor Edar are required for normal development of several ectodermal organs in humans and mice. We have overexpressed two splice forms of ectodysplasin, Eda-A1 and Eda-A2, binding to Edar and another TNF receptor, Xedar, respectively, under the keratin 14 (K14) promoter in the ectoderm of transgenic mice. Eda-A2 overexpression did not cause a detectable phenotype. On the contrary, overexpression of Eda-A1 resulted in alterations in a variety of ectodermal organs, most notably in extra organs. Hair development was initiated continuously from E14 until birth, and in addition, the transgenic mice had supernumerary teeth and mammary glands, phenotypes not reported previously in transgenic mice. Also, hair composition and structure was abnormal, and the cycling of hairs was altered so that the growth phase (anagen) was prolonged. Both hairs and nails grew longer than normal. Molar teeth were of abnormal shape, and enamel formation was severely disturbed in incisors. Furthermore, sweat gland function was stimulated and sebaceous glands were enlarged. We conclude that ectodysplasin-Edar signaling has several roles in ectodermal organ development controlling their initiation, as well as morphogenesis and differentiation.

Animals↗
PubMed2005

Edar signaling in the control of hair follicle development.

Ectodysplasin receptor Edar and its ligand Eda A1, as well as their related receptor Xedar and ligand Eda A2, are recently discovered members of the tumor necrosis factor superfamily that signal predominantly through the nuclear factor-kappaB and c-jun N-terminal kinases pathways. Mutations in genes that encode proteins involved in Edar signaling pathway cause hypohidrotic ectodermal displasias in humans and mice and characterized by severe defects in development of ectodermal appendages including hairs, teeth, and exocrine glands. Here, we summarize the current knowledge of molecular mechanisms underlying the involvement of Edar signaling pathway in controlling hair follicle (HF) development and cycling. Genetic and experimental studies suggest that Edar signaling is involved in the control of cell fate decision in embryonic epidermis, as well as in the regulation of cell differentiation programs in the HF. Loss or gain of Edar signaling affects the initiation of several HF types (guard and zig-zag HF), hair shaft formation, as well as sebaceous gland morphology. We also review data on the cross-talk between Edar and Wnt, transforming growth factor-beta/bone morphogenic protein/activin, and Shh signaling pathways in the control of HF development and cycling.

Animals↗
PubMed2006

Involvement of the Edar signaling in the control of hair follicle involution (catagen).

Ectodysplasin (Eda) and its receptor (Edar) are required for normal development of several ectodermal derivatives including hair follicles (HFs). Here, we show that during the murine hair cycle the expression of Eda A1, Edar, Edaradd, and TRAF6 transcripts are minimal in the resting phase and maximal during HF transition from active growth to regression (catagen). Eda A1 mRNA and Edar proteins were expressed in the hair matrix and outer and inner root sheaths of anagen HFs. During catagen, Eda A1 mRNA and Edar protein were expressed in the outer and inner root sheaths and later in the secondary hair germ. Catagen development accompanied by increased apoptosis in the outer root sheath was significantly accelerated in downless mice or after treatment of wild-type mice by a fusion protein that inhibits Edar signaling, compared with the corresponding controls. Microarray, real-time polymerase chain reaction, and immunohistochemical analyses of skin of downless mice revealed a strong decrease of expression of X-linked inhibitor of apoptosis protein (XIAP), compared with the controls, suggesting XIAP as a target for Edar signaling. Thus, our data demonstrate that in addition to its well-established role in HF morphogenesis, Edar signaling is also involved in hair cycle control and regulates apoptosis in HF keratinocytes during catagen.

Animals↗
PubMed2002

Recent advances in understanding of the molecular basis of anhidrotic ectodermal dysplasia: discovery of a ligand, ectodysplasin A and its two receptors.

Recent developments of the investigations on the molecular basis of anhidrotic ectodermal dysplasia are reviewed. Identification of the major product of the EDA gene (ectodysplasin A), a protein belonging to a group of TNF ligands, and molecular cloning of the cDNA, encoding its receptor (EDAR), a member of the TNF receptor family, are presented. The role of an alternative EDA receptor, localised on the X chromosome (XEDAR) in the developmental control of the differentiation of skin appendages, is discussed. Recent findings have elucidated the cause of the autosomal forms of EDA, both dominant and recessive, and indicated an important role of a signal transduction pathway involving a protein product of the NEMO gene and the transcription factor NFkappaB in the differentiation of skin appendages.

Cloning, Molecular↗