Unusual presentation of a severe autosomal recessive anhydrotic ectodermal dysplasia with a novel mutation in the EDAR gene

Attenuation of Mammary Gland Dysplasia and Feeding Difficulties in Tabby Mice by Fetal Therapy

Hypohidrotic ectodermal dysplasias (HED) are hereditary differentiation disorders of multiple ectodermal structures including the mammary gland. The X-linked form of HED (XLHED) is caused by a lack of the secreted signaling molecule ectodysplasin A1 (EDA1) which is encoded by the gene EDA and belongs to the tumor necrosis factor (TNF) superfamily. Although male patients (hemizygous) are usually more severely affected by XLHED, heterozygous female carriers of an EDA mutation may also suffer from a variety of symptoms, in particular from abnormal development of their breasts. In Tabby mice, a well-studied animal model of XLHED, EDA1 is absent. We investigated the effects of prenatal administration of Fc-EDA, a recombinant EDA1 replacement protein, on mammary gland development in female Tabby mice. Intra-amniotic delivery of Fc-EDA to fetal animals resulted later in improved breastfeeding and thus promoted the growth of their offspring. In detail, such treatment led to a normalization of the nipple shape (protrusion, tapering) that facilitated sucking. Mammary glands of treated female Tabby mice also showed internal changes, including enhanced branching morphogenesis and ductal elongation. Our findings indicate that EDA receptor stimulation during development has a stable impact on later stages of mammary gland differentiation, including lactation, but also show that intra-amniotic administration of an EDA1 replacement protein to fetal Tabby mice partially corrects the mammary gland phenotype in female adult animals.

Genome-wide association study in Japanese females identifies fifteen novel skin-related trait associations

Skin trait variation impacts quality-of-life, especially for females from the viewpoint of beauty. To investigate genetic variation related to these traits, we conducted a GWAS of various skin phenotypes in 11,311 Japanese women and identified associations for age-spots, freckles, double eyelids, straight/curly hair, eyebrow thickness, hairiness, and sweating. In silico annotation with RoadMap Epigenomics epigenetic state maps and colocalization analysis of GWAS and GTEx Project eQTL signals provided information about tissue specificity, candidate causal variants, and functional target genes. Novel signals for skin-spot traits neighboured AKAP1/MSI2 (rs17833789; P = 2.2 × 10-9), BNC2 (rs10810635; P = 2.1 × 10-22), HSPA12A (rs12259842; P = 7.1 × 10-11), PPARGC1B (rs251468; P = 1.3 × 10-21), and RAB11FIP2 (rs10444039; P = 5.6 × 10-21). HSPA12A SNPs were the only protein-coding gene eQTLs identified across skin-spot loci. Double edged eyelid analysis identified that a signal around EMX2 (rs12570134; P = 8.2 × 10-15) was also associated with expression of EMX2 and the antisense-RNA gene EMX2OS in brain putamen basal ganglia tissue. A known hair morphology signal in EDAR was associated with both eyebrow thickness (rs3827760; P = 1.7 × 10-9) and straight/curly hair (rs260643; P = 1.6 × 10-103). Excessive hairiness signals' top SNPs were also eQTLs for TBX15 (rs984225; P = 1.6 × 10-8), BCL2 (rs7226979; P = 7.3 × 10-11), and GCC2 and LIMS1 (rs6542772; P = 2.2 × 10-9). For excessive sweating, top variants in two signals in chr2:28.82-29.05 Mb (rs56089836; P = 1.7 × 10-11) were eQTLs for either PPP1CB or PLB1, while a top chr16:48.26-48.45 Mb locus SNP was a known ABCC11 missense variant (rs6500380; P = 6.8 × 10-10). In total, we identified twelve loci containing sixteen association signals, of which fifteen were novel. These findings will help dermatologic researchers better understand the genetic underpinnings of skin-related phenotypic variation in human populations.

Neurocristopathies: New insights 150 years after the neural crest discovery

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

Hypohidrotic Ectodermal Dysplasia: Breastfeeding Complications Due to Impaired Breast Development

Background X-linked hypohidrotic ectodermal dysplasia (XLHED), the most common form of ectodermal dysplasia, is caused by mutations in the gene EDA. While only affected men develop the full-blown clinical picture, females who are heterozygous for an EDA mutation often also show symptoms such as hypodontia, hypotrichosis and hypohidrosis. These women may also suffer from malformations of the mammary gland which represent not just a cosmetic problem but can limit their breastfeeding capability. This paper summarizes the findings of the first systematic study on the impact of hypohidrotic ectodermal dysplasia on breastfeeding. Patients Thirty-eight adult female members of the German-Swiss-Austrian ectodermal dysplasia patient support group participated in a structured interview; most of them also agreed to a photodocumentation of their mammary region. Thirty-one women carried mutations in EDA (Group A) and seven were affected by other forms of hypohidrotic ectodermal dysplasia (Group B). Results 39 % of the women of Group A reported that their breasts were of different size or entirely absent on one side. In Group B, 86 % of the women reported differently sized or even absent breasts; two of these women lacked both breasts entirely. Most women described their nipples as exceptionally flat. 10 % of the women of Group A had more than two nipples. The high percentage of deviations from the norm was confirmed in the photodocumentation. Both groups had few or no sebaceous glands of Montgomery in the areolar region. Around 80 % of interviewed women had children and had attempted to breastfeed their first child. 67 % of the mothers in Group A had had difficulty in breastfeeding their infants and generally attributed this difficulty to their flat nipples. All of the mothers in Group B reported difficulties in breastfeeding; 60 % had not been able to breastfeed their first child. Conclusion Mothers with hypohidrotic ectodermal dysplasia very often have difficulty in breastfeeding because of their impaired breast development. This causal relationship needs to be taken into account in lactation counseling.

Ectodysplasin/NF-κB Promotes Mammary Cell Fate via Wnt/β-catenin Pathway

Mammary gland development commences during embryogenesis with the establishment of a species typical number of mammary primordia on each flank of the embryo. It is thought that mammary cell fate can only be induced along the mammary line, a narrow region of the ventro-lateral skin running from the axilla to the groin. Ectodysplasin (Eda) is a tumor necrosis factor family ligand that regulates morphogenesis of several ectodermal appendages. We have previously shown that transgenic overexpression of Eda (K14-Eda mice) induces formation of supernumerary mammary placodes along the mammary line. Here, we investigate in more detail the role of Eda and its downstream mediator transcription factor NF-κB in mammary cell fate specification. We report that K14-Eda mice harbor accessory mammary glands also in the neck region indicating wider epidermal cell plasticity that previously appreciated. We show that even though NF-κB is not required for formation of endogenous mammary placodes, it is indispensable for the ability of Eda to induce supernumerary placodes. A genome-wide profiling of Eda-induced genes in mammary buds identified several Wnt pathway components as potential transcriptional targets of Eda. Using an ex vivo culture system, we show that suppression of canonical Wnt signalling leads to a dose-dependent inhibition of supernumerary placodes in K14-Eda tissue explants.

Mammary glands are the most characteristic feature of all mammals. The successful growth and function of the mammary glands is vital for the survival of offspring since the secreted milk is the main nutritional source of a new-born. Ectodysplasin (Eda) is a signaling molecule that regulates the formation of skin appendages such as hair, teeth, feathers, scales, and several glands in all vertebrates studied so far. In humans, mutations in the EDA gene cause a congenital disorder characterized by sparse hair, missing teeth, and defects in exocrine glands including the breast. We have previously shown that excess Eda induces formation of supernumerary mammary glands in mice. Here, we show that Eda leads to extra mammary gland formation also in the neck, a region previously not thought to harbor capacity to support mammary development. Using Eda loss- and gain-of-function mouse models and transcriptional profiling we identify the downstream mediators of Eda. The presence of extra nipples is a fairly common developmental abnormality in humans. We suggest that misregulation of Eda or its effectors might account for some of these malformations. Further, the number and location of the mammary glands vary widely between different species. Tinkering with the Eda pathway activity could provide an evolutionary means to modulate the number of mammary glands.

Molecular basis of hypohidrotic ectodermal dysplasia: an update

Recent advances in understanding the molecular events underlying hypohidrotic ectodermal dysplasia (HED) caused by mutations of the genes encoding proteins of the tumor necrosis factor α (TNFα)-related signaling pathway have been presented. These proteins are involved in signal transduction from ectoderm to mesenchyme during development of the fetus and are indispensable for the differentiation of ectoderm-derived structures such as eccrine sweat glands, teeth, hair, skin, and/or nails. Novel data were reviewed and discussed on the structure and functions of the components of TNFα-related signaling pathway, the consequences of mutations of the genes encoding these proteins, and the prospect for further investigations, which might elucidate the origin of HED.

In-silico QTL mapping of postpubertal mammary ductal development in the mouse uncovers potential human breast cancer risk loci

Genetic background plays a dominant role in mammary gland development and breast cancer (BrCa). Despite this, the role of genetics is only partially understood. This study used strain-dependent variation in an inbred mouse mapping panel, to identify quantitative trait loci (QTL) underlying structural variation in mammary ductal development, and determined if these QTL correlated with genomic intervals conferring BrCa susceptibility in humans. For about half of the traits, developmental variation among the complete set of strains in this study was greater (P < 0.05) than that of previously studied strains, or strains in current common use for mammary gland biology. Correlations were also detected with previously reported variation in mammary tumor latency and metastasis. In-silico genome-wide association identified 20 mammary development QTL (Mdq). Of these, five were syntenic with previously reported human BrCa loci. The most significant (P = 1 × 10(-11)) association of the study was on MMU6 and contained the genes Plxna4, Plxna4os1, and Chchd3. On MMU5, a QTL was detected (P = 8 × 10(-7)) that was syntenic to a human BrCa locus on h12q24.5 containing the genes Tbx3 and Tbx5. Intersection of linked SNP (r(2) > 0.8) with genomic and epigenomic features, and intersection of candidate genes with gene expression and survival data from human BrCa highlighted several for further study. These results support the conclusion that mammary tumorigenesis and normal ductal development are influenced by common genetic factors and that further studies of genetically diverse mice can improve our understanding of BrCa in humans.

A review of the diverse genetic disorders in the Lebanese population: highlighting the urgency for community genetic services

The review lists the genetic diseases reported in Lebanese individuals, surveys genetic programs and services, and highlights the absence of basic genetic health services at the individual and community level. The incidence of individual diseases is not determined, yet the variety of genetic diseases reported is tremendous, most of which follow autosomal recessive inheritance reflecting the social norms in the population, including high rates of consanguinity, which favor the increase in incidence of these diseases. Genetic services including all activities for the diagnosis, care, and prevention of genetic diseases at community level are extremely inadequate. Services are limited to some clinical and laboratory diagnostic services with no genetic counseling. These services are localized within the capital thus preventing their accessibility to high-risk communities. Screening programs, which are at the core of public health prevention services, are minimal and not nationally mandated. The absence of adequate genetic services is attributed to many factors undermining the importance of genetic diseases and their burden on society, the most important of which is genetic illiteracy at all levels of the population, including high-risk families, the general public, and most importantly health care providers and public health officials. Thus, a country like Lebanon, where genetic diseases are expected to be highly prevalent, is in utmost need for community genetics services. Strategies need to be developed to familiarize public health officials and medical professionals with medical genetics leading to a public health infrastructure that delivers community genetics services for the prevention and care of genetic disorders at community level.

Ectodysplasin/NF-κB signaling in embryonic mammary gland development

The ectodysplasin (Eda) signaling pathway consists of a TNF-like ligand Eda, its receptor Edar, and an adaptor protein Edaradd and its activation leads to NF-κB mediated transcription. In humans, mutations in the EDA pathway genes cause hypohidrotic ectodermal dysplasia, a disorder characterized by defective formation of hair follicles, teeth, and several exocrine glands including the breast. Embryonic mammary gland development proceeds via placode, bud, bulb and sprout stages before the onset of branching morphogenesis. Studies on mouse models have linked Eda with two aspects of embryonic mammary gland morphogenesis: placode induction and ductal growth and branching. Here we summarize the current knowledge on the role of Eda/NF-κB in mammary gland development.

Ectodysplasin regulates hormone-independent mammary ductal morphogenesis via NF-κB

Ductal growth of the mammary gland occurs in two distinct stages. The first round of branching morphogenesis occurs during embryogenesis, and the second round commences at the onset of puberty. Currently, relatively little is known about the genetic networks that control the initial phases of ductal expansion, which, unlike pubertal development, proceeds independent of hormonal input in female mice. Here we identify NF-κB downstream of the TNF-like ligand ectodysplasin (Eda) as a unique regulator of embryonic and prepubertal ductal morphogenesis. Loss of Eda, or inhibition of NF-κB, led to smaller ductal trees with fewer branches. On the other hand, overexpression of Eda caused a dramatic NF-κB-dependent phenotype in both female and male mice characterized by precocious and highly increased ductal growth and branching that correlated with enhanced cell proliferation. We have identified several putative transcriptional target genes of Eda/NF-κB, including PTHrP, Wnt10a, and Wnt10b, as well as Egf family ligands amphiregulin and epigen. We developed a mammary bud culture system that allowed us to manipulate mammary development ex vivo and found that recombinant PTHrP, Wnt3A, and Egf family ligands stimulate embryonic branching morphogenesis, suggesting that these pathways may cooperatively mediate the effects of Eda.

Two novel mutations in the gene EDAR causing autosomal recessive hypohidrotic ectodermal dysplasia

INTRODUCTION

Hypohidrotic ectodermal dysplasia (HED) is a human heritable disorder characterized by sparse hair, reduced ability to sweat and hypodontia. The HED exhibits X-linked, autosomal recessive and autosomal dominant mode of inheritance. Mutations in four genes including EDA, EDAR, EDARADD, and WNT10A are known to cause hypohidrotic and anhidrotic ectodermal dysplasia.

MATERIALS AND METHODS

Genotyping of both affected and normal individuals of two consanguineous Pakistani families (A, B), showing autosomal recessive HED, was carried out using microsatellite markers linked to EDAR gene on chromosome 2q11-q13. To screen for mutations in the gene EDAR, all of its exons and splice junction were amplified and sequenced directly, using an automated DNA sequencer.

RESULTS

Genotyping using microsatellite markers analysis showed linkage of the two families to gene EDAR on chromosome 2q11-2q13. Subsequently, screening of all the 12 exons and splice junctions of gene EDAR revealed a novel missense mutation (c.1163T>C; p.Ile388Thr) in family A and a novel insertion mutation (c.1014insA; p.V339SfsX6) in family B.

CONCLUSION

Our findings extend the body of evidence supporting the role of EDAR signaling pathway as a powerful regulator of development of ectodermal appendages.

A compound heterozygous mutation in the EDAR gene in a Spanish family with autosomal recessive hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterised by sparse hair, lack of sweat glands and malformation of teeth. The X-linked form of the disease, caused by mutations in the EDA gene, represents the majority of HED cases. Autosomal forms result from mutations in either the EDAR or the EDARADD gene. The X-linked and autosomal forms are phenotypically indistinguishable. For the purpose of genetic counselling, it is, therefore, important to know which gene is involved. In this study, we ascertained a Spanish family demonstrating the autosomal recessive form of HED. Affected individuals in the family showed the characteristic features of HED, including fine and sparse scalp hair, sparse eyebrows and eyelashes, periorbital hyperpigmentation, prominent lips, hypodontia and conical teeth, reduced sweating, and dry and thin skin. Sequence analysis of the EDAR gene revealed a novel compound heterozygous mutation [c.52-2A>G; c.212G>A (p.Cys71Tyr)]. Our finding extends the body of evidence that supports the significance of the EDAR signalling pathway in the ectodermal morphogenesis.