A missense mutation in the highly conserved TNF-like domain of Ectodysplasin A is the candidate causative variant for X-linked hypohidrotic ectodermal dysplasia in Limousin cattle: Clinical, histological, and molecular analyses.

Ectodysplasin A related hypohidrotic ectodermal dysplasia (XLHED) is a well-studied fetal developmental disorder in mammals that mainly affects ectodermal structures. It has been identified in a variety of species, including mice, rats, dogs, cattle, and humans. Here, we report the clinical, histological, and molecular biological analyses of a case of XLHED in Limousin cattle. An affected Limousin calf showed pathognomonic signs of ectodermal dysplasia, i.e. sparse hair and characteristic dental aplasia. Histopathologic comparison of hairy and glabrous skin and computed tomography of the mandible confirmed the phenotypic diagnosis. In addition, a keratoconjunctivitis sicca was noted in one eye, which was also confirmed histopathologically. To identify the causative variant, we resequenced the bovine X-chromosomal ectodysplasin A gene (EDA) of the affected calf and compared the sequences to the bovine reference genome. A single missense variant (rs439722471) at position X:g.80411716T>C (ARS-UCD1.3) was identified. The variant resulted in an amino acid substitution from glutamic acid to glycine within the highly conserved TNF-like domain. To rule out the possibility that the variant was relatively common in the cattle population we genotyped 2,016 individuals including 40% Limousin cattle by fluorescence resonance energy transfer analysis. We also tested 5,116 multibreed samples from Run9 of the 1000 Bull Genomes Project for the said variant. The variant was not detected in any of the cattle tested, confirming the assumption that it was the causative variant. This is the first report of Ectodysplasin A related hypohidrotic ectodermal dysplasia in Limousin cattle and the description of a novel causal variant in cattle.

A large deletion encompassing exon 2 of the ectodysplasin A (EDA) gene in a British blue crossbred calf with hypohidrotic ectodermal dysplasia.

BACKGROUND: Hypohidrotic ectodermal dysplasia (HED) is a congenital syndrome of mammals affecting organs and tissues of ectodermal origin characterized by absence or hypoplasia of hair, teeth, and eccrine glands. The disorder has been reported in several species, including humans, mice, dogs and cattle, associated with variants in genes affecting the ectodysplasin pathway, including the X-linked ectodysplasin A (EDA) gene. Until now, nine pathogenic variants have been found in the bovine EDA gene. Here we report a novel variant in EDA in a crossbreed male Belgian Blue calf with HED, and provide an overview of the phenotypic and allelic heterogeneity of EDA-related forms of HED in cattle. CASE PRESENTATION: A 45-day-old male crossbreed British Blue calf was referred with congenital hypotrichosis, oligodontia and omphalitis. On histopathological examination of the nasal planum, nasolabial glands and ducts were not observed. The density of hair follicles was low, and they were small, with a predominance of telogen-phase hairs, and some serocellular crusts. The phenotype of the calf resembled that of HED. Whole-genome sequencing (WGS) was performed and revealed a 21,899 base-pair deletion encompassing the coding exon 2 of EDA, predicted to result in an altered transcript and aberrant protein. CONCLUSIONS: The clinicopathological and genetic findings were consistent with a case of X-linked HED. A very similar EDA deletion has been previously reported in a family of Holstein cattle with HED. The newly identified hemizygous EDA loss-of-function variant is certainly pathogenic and therefore is the genetic cause for the observed phenotype. This case report provides an additional example of the potential of WGS-based precise diagnostics in livestock species such as cattle to increase the diagnostic yield in rare diseases.

Genetic analysis of a possible case of canine X-linked ectodermal dysplasia.

In the present report, we describe targeted next-generation sequencing of the EDA gene of a male poodle with a clinical and histopathological diagnosis of X-linked hypohidrotic ectodermal dysplasia. The result was compared with the reference sequence and with the result of the sequencing of a normal dog's EDA gene. No point variant, small deletion or insertion were found in the exons and splice sites, but a transition and a transversion were found in the intron 6' and 3' UTR, respectively. The cause of the dysplasia of the affected dog in this study is neither a point variant nor a small deletion or insertion in the exons and splice sites of the EDA gene. Therefore, patients with phenotype of XLHED may have other types of variants in the EDA gene or variants in other genes of the EDA signalling pathway.

X-Linked Hypohidrotic Ectodermal Dysplasia-General Features and Dental Abnormalities in Affected Dogs Compared With Human Dental Abnormalities.

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disorder characterized by abnormalities in ectodermal derivatives such as sweat glands, hair, and teeth. In animals, the highest number of cases has been reported in dogs, which show characteristic congenital alopecia and develop abnormalities in the shape and number of teeth. Although the clinical phenotype of the affected individuals is typical, this disorder remains almost unknown in veterinary clinical practice. With the aim of making it better known, we gathered in this review the main clinical and genetic aspects of XLHED, placing emphasis on dental abnormalities.

A frameshift variant in the EDA gene in Dachshunds with X-linked hypohidrotic ectodermal dysplasia.

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disease characterized by hypoplasia or absence of hair, teeth and sweat glands. The EDA gene, located on the X chromosome, encodes the type II transmembrane protein ectodysplasin A. Variants in the EDA gene can lead to XLHED in humans, mice, cattle and dogs. In the present study, we investigated a litter of Dachshund puppies, of which four male puppies showed clinical signs of XLHED. We performed a candidate gene analysis in one affected puppy and several non-affected relatives. This analysis revealed a single base-pair deletion in the coding sequence of the EDA gene in the affected puppy (NM_001014770.2:c.842delT). The deletion is predicted to cause a frameshift, NP_001014770.1:p.(Leu281HisfsTer22), leading to a premature stop codon which truncates more than one quarter of the EDA protein. Sanger sequencing results confirmed that this variant was inherited from the dam. Based on knowledge about the functional impact of EDA variants in dogs and other species, c.842delT is a convincing candidate causative variant for the observed XLHED in the male puppies.

Exonization of a LINE1 fragment implicated in X-linked hypohidrotic ectodermal dysplasia in cattle.

A case of X-linked hypohidrotic ectodermal dysplasia (XHED) was identified in a family of Danish Red Holstein cattle. The ectodysplasin-signalling protein (EDA) is known to be central in the normal development of ectodermal structures, and mutations in the ectodysplasin A (EDA) gene have been reported to cause XHED. In this study, we analysed different EDA transcript variants in affected and unaffected cattle and identified a new transcript variant including a LINE1-derived pseudoexon between EDA exons 1 and 2. The 161-bp-long pseudoexon introduces a shift in reading frame and a premature stop codon early in EDA exon 2 and is probably the cause of XHED in this Danish Red Holstein family.

A novel point mutation within the EDA gene causes an exon dropping in mature RNA in Holstein Friesian cattle breed affected by X-linked anhidrotic ectodermal dysplasia.

BACKGROUND: X-linked anhidrotic ectodermal dysplasia is a disorder characterized by abnormal development of tissues and organs of ectodermal origin caused by mutations in the EDA gene. The bovine EDA gene encodes the ectodysplasin A, a membrane protein expressed in keratinocytes, hair follicles and sweat glands, which is involved in the interactions between cell and cell and/or cell and matrix. Four mutations causing ectodermal dysplasia in cattle have been described so far. RESULTS: We identified a new single nucleotide polymorphism (SNP) at the 9th base of exon 8 in the EDA gene in two calves of Holstein Friesian cattle breed affected by ectodermal dysplasia. This SNP is located in the exonic splicing enhancer (ESEs) recognized by SRp40 protein. As a consequence, the spliceosome machinery is no longer able to recognize the sequence as exonic and causes exon skipping. The mutation determines the deletion of the entire exon (131 bp) in the RNA processing, causing a severe alteration of the protein structure and thus the disease. CONCLUSION: We identified a mutation, never described before, that changes the regulation of alternative splicing in the EDA gene and causes ectodermal dysplasia in cattle. The analysis of the SNP allows the identification of carriers that can transmit the disease to the offspring. This mutation can thus be exploited for a rational and efficient selection of unequivocally healthy cows for breeding.

Dental abnormalities associated with X-linked hypohidrotic ectodermal dysplasia in dogs.

OBJECTIVES: X-linked hypohidrotic ectodermal dysplasia (XLHED) occurs in several species, including humans, mice, cattle and dogs. The orofacial manifestations of ectodermal dysplasia in humans and mice have been extensively studied, but documentation of dental abnormalities in dogs is lacking. The current study describes the results of clinical and radiographic examinations of XLHED-affected dogs and demonstrates profound similarities to findings of XLHED-affected humans. SETTING AND SAMPLE POPULATION: Section of Medical Genetics at the University of Pennsylvania, School of Veterinary Medicine. Clinical and radiographic oral examinations were performed on 17 dogs with XLHED, three normal dogs, and two dogs heterozygous for XLHED. MATERIALS AND METHODS: The prevalence and severity of orofacial and dental abnormalities were evaluated by means of a sedated examination, photographs, and full-mouth intraoral radiographs. RESULTS: Crown and root abnormalities were common in dogs affected by XLHED, including hypodontia, oligodontia, conical crown shape, decreased number of cusps, decreased number of roots, and dilacerated roots. Persistent deciduous teeth were frequently encountered. Malocclusion was common, with Angle Class I mesioversion of the maxillary and/or mandibular canine teeth noted in 15 of 17 dogs. Angle Class III malocclusion (maxillary brachygnathism) was seen in one affected dog. CONCLUSION: Dental abnormalities are common and severe in dogs with XLHED. Dental manifestations of canine XLHED share characteristics of brachyodont tooth type and diphyodont dentition, confirming this species to be an orthologous animal model for study of human disease.