X-linked hypohidrotic ectodermal dysplasia: DNA probe linkage analysis and gene localization

Ectodysplasin Signaling through XEDAR Is Required for Mammary Gland Morphogenesis

XEDAR is a member of the TNF receptor subfamily and a mediator of the ectodysplasin (EDA) pathway. EDA signaling plays evolutionarily conserved roles in the development of the ectodermal appendage organ class, which includes hair, eccrine sweat glands, and mammary glands. Loss-of-function sequence variants of EDA, which encodes the two major ligand isoforms, EDA-A1 and EDA-A2, result in X-linked hypohidrotic ectodermal dysplasia characterized by defects in two or more types of ectodermal appendages. EDA-A1 and EDA-A2 signal through the receptors EDAR and XEDAR, respectively. Although the contributions of the EDA-A1/EDAR signaling pathway to EDA-dependent ectodermal appendage phenotypes have been extensively characterized, the significance of the EDA-A2/XEDAR branch of the pathway has remained obscure. In this study, we report the phenotypic consequences of disrupting the EDA-A2/XEDAR pathway on mammary gland differentiation and growth. Using a mouse Xedar knockout model, we show that Xedar has a specific and temporally restricted role in promoting late pubertal growth and branching of the mammary epithelium that can be influenced by genetic background. Our findings implicate Xedar in ectodermal appendage development and suggest that the EDA-A2/XEDAR signaling axis contributes to the etiology of EDA-dependent mammary phenotypes.

Neonatal treatment with recombinant ectodysplasin prevents respiratory disease in dogs with X-linked ectodermal dysplasia

Patients with defective ectodysplasin A (EDA) have X-linked hypohidrotic ectodermal dysplasia (XLHED; OMIM#305100), a condition comprising hypotrichosis, inability to sweat, abnormal teeth, and frequent pulmonary infections. The XLHED dogs show the same clinical signs as humans with the disorder, including frequent respiratory infections that can be fatal. The respiratory disease in humans and dogs is thought to be due to the absence of tracheal and bronchial glands which are a vital part of the mucociliary clearance mechanism. In our XLHED model, the genetically missing EDA was replaced by postnatal intravenous administration of recombinant EDA resulting in long-term, durable corrective effect on adult, permanent dentition. After treatment with EDA, significant correction of the missing tracheal and bronchial glands was achieved in those dogs that received higher doses of EDA. Moreover, successful treatment resulted in the presence of esophageal glands, improved mucociliary clearance, and the absence of respiratory infection. These results demonstrate that a short-term treatment at a neonatal age with a recombinant protein can reverse a developmental disease and result in vastly improved quality of life.

[Associated diseases and differential diagnostic considerations in childhood atopic eczema]

Atopic eczema (AE) is a chronic inflammatory skin disease which affects 10 to 20% of children and 1 to 3% of adults. AE is usually diagnosed based on standard criteria such as those of Hanifin and Rajka, whereby the age-related variation must be considered. There are numerous other diseases which go along with AE or show a very similar clinical picture and represent important differential diagnostic considerations including parasitic diseases, immunodeficiency, nutritional diseases, certain neoplastic disorders and various corneal abnormalities. Additionally, it is important to consider diseases which can occur in association with AE, such as keratosis pilaris, alopecia areata or sweat disturbances.

Psychosocial stress and adaptive functioning in children and adolescents suffering from hypohidrotic ectodermal dysplasia

In its fully manifest form, hypohidrotic ectodermal dysplasia (HED) leads to a typical dysmorphia of the face, referred to as "old man" facies. Few studies have been conducted on how children and adolescents deal with and adapt to the effects of this illness. The psychosocial stress and adaptive functioning of such patients was investigated by means of a semistructured interview conducted on a sample of 14 children and adolescents with varying degrees of this disease. The results revealed that adaptive functioning is not only dependent on the severity of symptoms. The child's intellectual potential and personality, how the disease is dealt with within the family, and reactions from the child's environment influence adaptive functioning in different ways.

X-linked anhidrotic (hypohidrotic) ectodermal dysplasia is caused by mutation in a novel transmembrane protein

Ectodermal dysplasias comprise over 150 syndromes of unknown pathogenesis. X-linked anhidrotic ectodermal dysplasia (EDA) is characterized by abnormal hair, teeth and sweat glands. We now describe the positional cloning of the gene mutated in EDA. Two exons, separated by a 200-kilobase intron, encode a predicted 135-residue transmembrane protein. The gene is disrupted in six patients with X;autosome translocations or submicroscopic deletions; nine patients had point mutations. The gene is expressed in keratinocytes, hair follicles, and sweat glands, and in other adult and fetal tissues. The predicted EDA protein may belong to a novel class with a role in epithelial-mesenchymal signalling.

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.

Mapping around the Xq13.1 breakpoints of two X/A translocations in hypohidrotic ectodermal dysplasia (EDA) female patients

Cellular hybrids were obtained from a t(X;12) identified in a female patient with hypohidrotic ectodermal dysplasia (EDA). This rearrangement had the same Xq13.1 cytogenetic breakpoint as a t(X;9) found in a previously observed EDA patient. A comparative analysis of these two rearrangements with nine probes was performed at the molecular level. These probes could define three subregions: three are proximal, two are distal, and four are between the two breakpoints. These last probes should prove useful for cloning the gene.

Gene mapping of ocular diseases

Increasing awareness of the role of genetic factors in the causation of many human eye diseases has made ocular genetics one of the fastest growing areas of ophthalmology. The objective of this paper is to present the basic principles of gene mapping and their application to ophthalmology. The techniques used to map the genome are reviewed with emphasis placed on molecular genetics. The advances in this area have already provided the major impetus to the areas of diagnosis and prevention of some genetic eye disorders. Tables are presented that list the autosomal, X-linked and mitochondrial assignment of eye genes and disorders with ocular involvement.

X-linked anhidrotic ectodermal dysplasia and de novo t(X;1) in a female

A de novo translocation (X;1)(q13.1;p36.33) was found in a 2-year-old girl with typical clinical features of X-linked anhidrotic ectodermal dysplasia (EDA). The breakpoint at Xq13.1 is approximately the same as has been described in 2 other EDA females with X;autosome translocations.

Possible genetic heterogeneity in X linked hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia has been mapped to Xq11-q13 by linkage studies and by a translocation in a manifesting female. We report a family with hypohidrotic ectodermal dysplasia in which the disease did not segregate with this region of the X chromosome as expected. Ten DNA probes which are localised between Xp11 and Xq22 were used in the investigation. The difficulties in diagnosing the carrier state in this condition and the possibility of non-allelic heterogeneity are discussed.

Rapp-Hodgkin ectodermal dysplasia

Rapp-Hodgkin syndrome is an uncommon, autosomal dominant condition characterized by distinctive craniofacial anomalies, cleft lip or palate, poor dentition, poor hair growth, dystrophic nails, and hypohidrosis, and hypospadias in boys. Since the original report in 1968, fewer than 20 other patients have been described. We report a new sporadic case, a 12-year-old boy who had erythrodermia and scaling skin at birth, and later developed most of the symptoms and findings previously described.

Female with hypohidrotic ectodermal dysplasia and de novo (X;9) translocation. Clinical documentation of the AnLy cell line case

We present here a historical documentation of a female with X-linked hypohidrotic ectodermal dysplasia (XHED) and a de novo X/9 chromosome translocation. The patient was verbally reported by Dr. P.L. J. Cook to the HGM conference in 1973, but was subsequently lost to follow up. We have since traced her and confirmed the diagnosis of XHED with moderately severe mental retardation. According to Dr. P. L. J. Cook's records, fibroblast cell line AnLy GMO 705, was derived from this patient. Another female with a de novo X/12 chromosome translocation and hypohidrotic ectodermal dysplasia was recently reported. In both cases, the X chromosome breakpoint appears to be at Xq13.1.

X-linked hypohidrotic ectodermal dysplasia and t(X;12) in a female

A female patient with features of hypohidrotic ectodermal dysplasia (HED) was found to be a carrier of a de novo t(X;12) with a breakpoint in Xq13.1. This is the second instance of an X/autosome translocation, with apparently the same X breakpoint, reported in HED.

Localization of the gene for classic Alport syndrome

The inheritance of Alport syndrome has been controversial for 30 years because no clear diagnostic criteria were established to define a clinically homogeneous group of patients. In this study, 41 families with "classic" Alport syndrome were identified and studied. All the pedigrees are compatible with X-linked inheritance. A formal genetic study confirmed linkage to probe S21 (DXS17), with a maximum LOD score of 4.72 at a recombination frequency of 0.06.

Genetic mapping of anhidrotic ectodermal dysplasia: DXS159, a closely linked proximal marker

Three families with anhidrotic ectodermal dysplasia (AED) have been studied by linkage analysis with seven polymorphic DNA markers from the Xp11-q21 region. Previously reported linkage to DXYS1 (Xq13-q21) has been confirmed (z (theta) = 4.08 at theta = 0.05) and we have also established linkage to another polymorphic locus, DXS159, located in Xq11-q12 (z (theta) = 4.28 at theta = 0.05). Physical mapping places DSX159 proximal to the Xq12 breakpoint of an X autosome translocation found in a female with clinical signs of ectodermal dysplasia. Of all markers that have been used in linkage analysis of AED, DXS159 would appear the closest on the proximal side of the disease locus.

Recognition and reanalysis of a cell line from a manifesting female with X linked hypohidrotic ectodermal dysplasia and an X; autosome balanced translocation

We have restudied a fibroblast cell line from a female with marked manifestations of X linked hypohidrotic ectodermal dysplasia (HED) and a balanced X;9 translocation. Chromosome analysis showed a karyotype of 46,X,t(X;9)(q13.1;p24) with an Xq breakpoint distal to the one previously reported. The significance of the cell line, previously unrecognised, for the mapping and eventual cloning of the HED locus is discussed.

A primary genetic map of the pericentromeric region of the human X chromosome

We report a genetic linkage map of the pericentromeric region of the human X chromosome, extending from Xp11 to Xq13. Genetic analysis with five polymorphic markers, including centromeric alpha satellite DNA, spanned a distance of approximately 38 cM. Significant lod scores were obtained with linkage analysis in 26 families from the Centre d'Etude du Polymorphisme Humain, establishing estimates of genetic distances between these markers and across the centromere. Physical mapping experiments, using a panel of somatic cell hybrids segregating portions of the X chromosome due to translocations or deletions, are in agreement with the multilocus linkage analysis and indicate the order Xp11 . . . DXS7(L1.28)-TIMP- DXZ1(alpha satellite, cen)- DXS159(cpX73)-PGK1 . . . Xq13. The frequency of recombination in the two approximately 20-cM intervals flanking alpha satellite on either chromosome arm was roughly proportional to the estimated physical distance between markers; no evidence for a reduced crossover frequency was found in the intervals adjacent to the centromere. However, significant interfamilial variations in recombination rates were noted in this region. This primary map should be useful both as a foundation for a higher resolution centromere-based linkage map of the X chromosome and in the localization of genes to the pericentromeric region.

Clinical aspects of X-linked hypohidrotic ectodermal dysplasia

Boys with X-linked hypohidrotic ectodermal dysplasia and their families were studied. Many suffered severe illness in early childhood and nearly 30% died; many had feeding problems, severe fever, atopic disease, and recurrent respiratory infections. Some infants failed to thrive. We found no consistent common endocrine or immunological abnormality, although, most had abnormal immunoglobulin production. This may be related to the abnormal mucosa of the gastrointestinal and respiratory tracts which exacerbates the chronic obstructive airways disease found later in life in those who smoke. Mental handicap was not a feature, although convulsions sometimes occurred during fever. Early diagnosis is important to avoid attacks of severe fever and so that rational management may be planned for other problems that arise. Dental advice should be sought before school age and genetic counselling may also be required. Many female carriers may be recognised at clinical examination: their affected sons can then be diagnosed more readily.