Clinical, genetic, epidemiologic, evolutionary, and functional delineation of TSPEAR-related autosomal recessive ectodermal dysplasia 14

TSPEAR variants cause autosomal recessive ectodermal dysplasia (ARED) 14. The function of TSPEAR is unknown. The clinical features, the mutation spectrum, and the underlying mechanisms of ARED14 are poorly understood. Combining data from new and previously published individuals established that ARED14 is primarily characterized by dental anomalies such as conical tooth cusps and hypodontia, like those seen in individuals with WNT10A-related odontoonychodermal dysplasia. AlphaFold-predicted structure-based analysis showed that most of the pathogenic TSPEAR missense variants likely destabilize the β-propeller of the protein. Analysis of 100000 Genomes Project (100KGP) data revealed multiple founder TSPEAR variants across different populations. Mutational and recombination clock analyses demonstrated that non-Finnish European founder variants likely originated around the end of the last ice age, a period of major climatic transition. Analysis of gnomAD data showed that the non-Finnish European population TSPEAR gene-carrier rate is ∼1/140, making it one of the commonest AREDs. Phylogenetic and AlphaFold structural analyses showed that TSPEAR is an ortholog of drosophila Closca, an extracellular matrix-dependent signaling regulator. We, therefore, hypothesized that TSPEAR could have a role in enamel knot, a structure that coordinates patterning of developing tooth cusps. Analysis of mouse single-cell RNA sequencing (scRNA-seq) data revealed highly restricted expression of Tspear in clusters representing enamel knots. A tspeara -/-;tspearb -/- double-knockout zebrafish model recapitulated the clinical features of ARED14 and fin regeneration abnormalities of wnt10a knockout fish, thus suggesting interaction between tspear and wnt10a. In summary, we provide insights into the role of TSPEAR in ectodermal development and the evolutionary history, epidemiology, mechanisms, and consequences of its loss of function variants.

Different degree of loss-of-function among four missense mutations in the EDAR gene responsible for autosomal recessive hypohidrotic ectodermal dysplasia may be associated with the phenotypic severity

Hypohidrotic ectodermal dysplasia is a rare condition characterized by hypohidrosis, hypodontia, and hypotrichosis. The disease can show X-linked recessive, autosomal dominant or autosomal recessive inheritance trait. Of these, the autosomal forms are caused by mutations in either EDAR or EDARADD. To date, the underlying pathomechanisms or genotype-phenotype correlations for autosomal forms have not completely been disclosed. In this study, we performed a series of in vitro studies for four missense mutations in the death domain of EDAR protein: p.R358Q, p.G382S, p.I388T, and p.T403M. The results revealed that p.R358Q- and p.T403M-mutant EDAR showed different expression patterns from wild-type EDAR in both western blots and immunostainings. NF-κB reporter assays demonstrated that all the mutant EDAR showed reduced activation of NF-κB, but the reduction by p.G382S- and p.I388T-mutant EDAR was moderate. Co-immunoprecipitation assays showed that p.R358Q- and p.T403M-mutant EDAR did not bind with EDARADD at all, whereas p.G382S- and p.I388T-mutant EDAR maintained the affinity to some extent. Furthermore, we demonstrated that all the mutant EDAR proteins analyzed aberrantly bound with TRAF6. Sum of the data suggest that the degree of loss-of-function is different among the mutant EDAR proteins, which may be associated with the severity of the disease.

Dental Phenotype with Minor Ectodermal Symptoms Suggestive of WNT10A Deficiency

Ectodermal dysplasias (EDs) represent a heterogeneous group of genetic disorders characterized by the abnormal development of ectodermal-derived tissues. They include the involvement of the hair, nails, skin, sweat glands, and teeth. Pathogenic variants in EDA1 (Xq12-13.1; OMIM*300451), EDAR (2q11-q13; OMIM*604095), EDARADD (1q42-q43, OMIM*606603), and WNT10A (2q35; OMIM*606268) genes are responsible for most EDs. Bi-allelic pathogenic variants of WNT10A have been associated with autosomal recessive forms of ED, as well as non-syndromic tooth agenesis (NSTA). The potential phenotypic impact of associated modifier mutations in other ectodysplasin pathway genes has also been pointed out. We present on an 11-year-old Chinese boy with oligodontia, with conical-shaped teeth as the main phenotype, and other very mild ED signs. The genetic study identified the pathogenic variants WNT10A (NM_025216.3): c.310C > T; p. (Arg104Cys) and c.742C > T; p. (Arg248Ter) in compound heterozygosis, confirmed by parental segregation. In addition, the patient had the polymorphism EDAR (NM_022336.4): c.1109T > C, p. (Val370Ala) in homozygosis, named EDAR370. A prominent dental phenotype with minor ectodermal symptoms is very suggestive of WNT10A mutations. In this case, the EDAR370A allele might also attenuate the severity of other ED signs.

A novel EDAR variant identified in non-syndromic tooth agenesis: Insights from molecular dynamics

OBJECTIVE

This study aims to investigate a novel pathogenic variant in a Chinese family of non-syndromic tooth agenesis (NSTA) and study the impact of the variant on related protein and pathway.

DESIGN

One NSTA family was collected. Whole exome sequencing and Sanger sequencing were performed on the proband with NSTA and his 5 family members. The pathogenic influence of the mutant is evaluated by bioinformatics analyses including evolutionary conservation analysis and secondary structure prediction. Molecular dynamics (MD) simulations and binding free energy calculations were then performed to explore changes in the tertiary structure and binding ability of the protein.

RESULTS

We found a novel missense ectodysplasin A receptor (EDAR) variant (c .1292 T > G; p.Ile431Arg) in all affected family members. The results of bioinformatics analyses revealed that the EDAR had harmful changes after mutation. MD simulations and the binding free energy calculations results showed that the mutant EDAR protein and EDAR/ectodysplasin-A receptor-associated adapter (EDARADD) complex displayed tertiary structural change, and EDAR possessed a lower affinity to EDARADD after mutation.

CONCLUSIONS

We found a novel EDAR variant (c.1292 T > G; p.Ile431Arg) in one NSTA family, which affects the binding of EDAR and EDARADD.

A homozygous loss-of-function variant in the MPO gene is associated with generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare form of psoriasis, which is characterized by sudden onset of repeated erythema and pustule formation with generalized inflammation. Recent advances in molecular genetics have led to the identification of several genes associated with GPP, including IL36RN, CARD14, AP1S3, SERPINA3, and MPO. Of these, only limited cases of GPP have been reported to carry mutations in the AP1S3, SERPINA3, or MPO to date. In the present study, we investigated a Japanese patient with GPP and found a homozygous missense mutation c.1769G>T (p.Arg590Leu) in the MPO gene. Structural analysis predicted that the mutant MPO protein would abolish its ability to bind with heme protein. In vitro studies using cultured cells revealed that the mutant MPO was stably expressed, but completely lost its myeloperoxidase activity. Immunohistochemistry (IHC) using an anti-MPO antibody showed markedly reduced expression of MPO protein in the patient's skin, suggesting that the mutation would lead to an instability of the MPO protein in vivo. Finally, IHC with an anti-citrullinated Histone H3 antibody demonstrated a sparse formation of neutrophil extracellular traps within a Kogoj's spongiform pustule of the patient's skin. Collectively, we conclude that the c.1769G>T (p.Arg590Leu) in the MPO is a complete loss-of-function mutation associated with GPP in the patient. Our data further underscore critical roles of the MPO gene in the pathogenesis of GPP.

Three Variants Affecting Exon 1 of Ectodysplasin A Cause X-Linked Hypohidrotic Ectodermal Dysplasia: Clinical and Molecular Characteristics

Background: Ectodysplasin A (EDA) variations are major pathogenic factors for hypohidrotic ectodermal dysplasia (HED), the most common form of ectodermal dysplasia (ED), characterized by hypotrichosis, hypohidrosis, hypodontia, and other oral features. Methods: Molecular genetic defects in three HED families were detected by whole-exome sequencing and confirmed by Sanger sequencing or multiplex ligation-dependent probe amplification. The effect of splicing variant was further verified by EDA minigene in vitro analysis. De novo deletion was confirmed by chromosomal microarray analysis. Results: Three variants (c.396 + 1 G > C, c.171-173 del GTT, and exon 1 deletion) were identified, all affecting exon 1 of the EDA gene. Variants c.396 + 1 G > C and c.171-173 del GTT were first identified. Minigene analysis of the splicing variant (c.396 + 1 G > C) displayed a prolonged EDA-A1 transcript containing extra 699 bp at the start of intron 1, representing a functional cryptic splice site formation in vitro. Combining the results of chromosomal microarray analysis and whole-exome sequencing, the deletion variant was over 87 kb. Three variants were predicted to affect protein function to differing degrees, and were responsible for X-linked HED with varying phenotype. Conclusion: Investigating the clinical and molecular characteristics of these variations broadens our understanding of EDA gene variants, supporting clinical diagnosis, genetic counseling, and prenatal diagnosis of HED.

Identification of a novel missense heterozygous mutation in the KDF1 gene for non-syndromic congenital anodontia

OBJECTIVES

KDF1 is a recently identified gene related to tooth development, but it has been little studied. To date, only three cases have been reported in which KDF1 mutations are related to tooth development, including two ectodermal dysplasia cases accompanied by tooth loss and one non-syndromic case with tooth agenesis. However, no KDF1 mutations have been reported as associated with non-syndromic anodontia. Here, the aim was to investigate the genetic etiology of this condition and explore the functional role of a novel KDF1 mutation in a Chinese patient with non-syndromic anodontia.

MATERIALS AND METHODS

Pathogenic variants were identified by whole-exome and Sanger sequencing. Meanwhile, we conducted a literature review of the reported KDF1 mutations and performed an in vitro functional analysis of four anodontia-causing KDF1 mutations (one novel and three known).

RESULTS

We identified a novel de novo missense mutation (c.911 T > A, p.I304N) in the KDF1 gene in a Chinese patient with severe non-syndromic anodontia. In vitro functional studies showed altered mRNA and protein expression levels of the mutant KDF1.

CONCLUSIONS

Our results are the first report of KDF1 missense mutation causing non-syndromic anodontia.

CLINICAL RELEVANCE

This study not only further supports the important role of KDF1 in non-syndromic congenital anodontia, but also expands the spectrum of KDF1 mutations and will contribute to the genetic diagnosis and counselling of families with anodontia.

ANOTHER syndrome-Familial presentations of progressive lung disease leading to double lung transplantation: A case report and literature review

Ectodermal dysplasias (EDs) are a heterogeneous rare group of disorders with an incidence at 1/100,000 live births. Currently, there are limited case reports of patients requiring lung transplantation. Here, we report two brothers who present with a constellation of features including alopecia, nail dystrophy, ophthalmic complications, thyroid disease, hypohidrosis, ephelides, enteropathy and recurrent respiratory tract infections, known as ANOTHER syndrome, a rare autosomal recessive variant of ED. Both presented in early childhood with progressive respiratory decline and eventual failure. Chronic respiratory decline was refractory to standard therapy. Both patients required lung transplantation for sequelae of end-stage lung disease. Pathology demonstrated multifocal bronchiectasis with areas of fibrosis and small airway obstruction. ANOTHER syndrome is rare with a paucity of data in the literature. Given the limited therapeutic options available with natural progression towards respiratory failure, lung transplantation may be considered.

Update of recent findings in genetic hair disorders

Genetic hair disorders, although unusual, are not very rare, and dermatologists often have opportunities to see patients. Significant advances in molecular genetics have led to identifying many causative genes for genetic hair disorders, including the recently identified causative genes, such as LSS and C3ORF52. Many patients have been detected with autosomal recessive woolly hair/hypotrichosis in the Japanese population caused by founder mutations in the LIPH gene. Additionally, many patients with genetic hair disorders caused by other genes have been reported in East Asia including Japan. Understanding genetic hair disorders is essential for dermatologists, and the findings obtained from analyzing these diseases will contribute to revealing the mechanisms of hair follicle morphogenesis and development in humans.

Analyses of oligodontia phenotypes and genetic etiologies

Oligodontia is the congenital absence of six or more teeth and comprises the more severe forms of tooth agenesis. Many genes have been implicated in the etiology of tooth agenesis, which is highly variable in its clinical presentation. The purpose of this study was to identify associations between genetic mutations and clinical features of oligodontia patients. An online systematic search of papers published from January 1992 to June 2021 identified 381 oligodontia cases meeting the eligibility criteria of causative gene mutation, phenotype description, and radiographic records. Additionally, ten families with oligodontia were recruited and their genetic etiologies were determined by whole-exome sequence analyses. We identified a novel mutation in WNT10A (c.99_105dup) and eight previously reported mutations in WNT10A (c.433 G > A; c.682 T > A; c.318 C > G; c.511.C > T; c.321 C > A), EDAR (c.581 C > T), and LRP6 (c.1003 C > T, c.2747 G > T). Collectively, 20 different causative genes were implicated among those 393 cases with oligodontia. For each causative gene, the mean number of missing teeth per case and the frequency of teeth missing at each position were calculated. Genotype-phenotype correlation analysis indicated that molars agenesis is more likely linked to PAX9 mutations, mandibular first premolar agenesis is least associated with PAX9 mutations. Mandibular incisors and maxillary lateral incisor agenesis are most closely linked to EDA mutations.

Characterization of EDARADD gene mutations responsible for hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterized by hypohidrosis, hypodontia, and hypotrichosis. Autosomal forms of the disease are caused by mutations in either EDAR or EDARADD. To date, the underlying pathomechanisms for HED resulting from EDARADD mutations have not fully been disclosed. In this study, we performed detailed in vitro analyses in order to characterize three dominantly inherited missense mutations, p.D120Y, p.L122R, and p.D123N, and one recessively inherited missense mutation, p.E152K, in the EDARADD gene. Nuclear factor (NF)-κB reporter assays demonstrated that all the mutant EDARADD showed reduction in activation of NF-κB. Importantly, p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD slightly reduced the NF-κB activity induced by wild-type EDARADD in a dominant negative manner. Co-immunoprecipitation assays showed that all of the mutant EDARADD were capable of binding to EDAR and wild-type EDARADD. Additional co-immunoprecipitation assays revealed that p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD markedly prevented the interaction between EDAR and wild-type EDARADD, which further indicated a dominant negative effect by these mutations. Finally, we found that p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD completely lost the ability to bind with TRAF6, while p.E152K-mutant EDARADD showed a mild reduction in the affinity. Our findings will provide crucial information toward unraveling the molecular mechanisms how EDARADD gene mutations cause the disease.

A novel EDAR missense mutation identified by whole-exome sequencing with non-syndromic tooth agenesis in a Chinese family

Background

Causative variants in genes of the EDA/EDAR/NF‐κB pathway, such as EDA and EDARADD, have been widely identified in patients with non‐syndromic tooth agenesis (NSTA). However, few cases of NSTA are due to ectodysplasin‐A receptor (EDAR) variants. In this study, we investigated NSTA‐associated variants in Chinese families.

Methods

Peripheral blood samples were collected from the family members of 24 individuals with NSTA for DNA extraction. The coding region of the EDA gene of the 24 probands was amplified by PCR and sequenced to investigate new variants. Whole‐exome sequencing and Sanger sequencing were then performed for probands without EDA variants detected by PCR.

Results

A novel missense variant EDAR c.338G>A (p.(Cys113Tyr)) was identified in one family. In addition, three known EDA variants (c.865C>T, c.866G>A, and c.1013C>T) were identified in three families. Genotype–phenotype correlation analysis of EDAR gene mutation showed that NSTA patients were most likely to lose the maxillary lateral incisors and the maxillary central incisors were the least affected. The phenotype of mutations at codon 289 of EDA in NSTA affected patients was characterized by lateral incisors loss, rarely affecting the maxillary first molars.

Conclusion

A novel EDAR missense variant c.338G>A (p.(Cys113Tyr)) was identified in a family with NSTA, extending the mutation spectrum of the EDAR gene. Genotype–phenotype correlation analyses of EDAR and EDA mutations could help to improve disease status prediction in NSTA families.

Evidence for a dominant-negative effect of a missense mutation in the SERPING1 gene responsible for hereditary angioedema type I

Hereditary angioedema (HAE) is a rare condition characterized by episodic local edema involving various organs, which can be life-threatening in some cases. Among the three subtypes of the disease, HAE types I and II are known to be caused by heterozygous mutations in the SERPING1 gene encoding C1 inhibitor (C1INH). Although a number of mutations in the SERPING1 gene have been identified to date, the mechanisms how these mutations cause HAE are not completely understood. We herein performed detailed in vitro studies for a missense SERPING1 gene mutation p.S150F which we recently identified in a Japanese patient with HAE type I. We showed that the p.S150F-mutant C1INH was stably expressed within the cultured cells, while it was not secreted into the medium at all. Furthermore, we demonstrated that the mutant C1INH significantly prevented secretion of wild-type C1INH. Finally, the results suggested that the wild-type protein was not only retained but also degraded within the cytoplasm through interacting with the mutant protein. Our study clearly revealed a dominant-negative effect of the p.S150F-mutant C1INH against the wild-type C1INH.

Cell signaling regulation in salivary gland development

The mammalian salivary gland develops as a highly branched structure designed to produce and secrete saliva. This review focuses on research conducted on mammalian salivary gland development, particularly on the differentiation of acinar, ductal, and myoepithelial cells. We discuss recent studies that provide conceptual advances in the understanding of the molecular mechanisms of salivary gland development. In addition, we describe the organogenesis of submandibular glands (SMGs), model systems used for the study of SMG development, and the key signaling pathways as well as cellular processes involved in salivary gland development. The findings from the recent studies elucidating the identity of stem/progenitor cells in the SMGs, and the process by which they are directed along a series of cell fate decisions to form functional glands, are also discussed. Advances in genetic tools and tissue engineering strategies will significantly increase our knowledge about the mechanisms by which signaling pathways and cells establish tissue architecture and function during salivary gland development, which may also be conserved in the growth and development of other organ systems. An increased knowledge of organ development mechanisms will have profound implications in the design of therapies for the regrowth or repair of injured tissues. In addition, understanding how the processes of cell survival, expansion, specification, movement, and communication with neighboring cells are regulated under physiological and pathological conditions is critical to the development of future treatments.

Characterisation of a second gain of function EDAR variant, encoding EDAR380R, in East Asia

Ectodysplasin A1 receptor (EDAR) is a TNF receptor family member with roles in the development and growth of hair, teeth and glands. A derived allele of EDAR, single-nucleotide variant rs3827760, encodes EDAR:p.(Val370Ala), a receptor with more potent signalling effects than the ancestral EDAR370Val. This allele of rs3827760 is at very high frequency in modern East Asian and Native American populations as a result of ancient positive selection and has been associated with straighter, thicker hair fibres, alteration of tooth and ear shape, reduced chin protrusion and increased fingertip sweat gland density. Here we report the characterisation of another SNV in EDAR, rs146567337, encoding EDAR:p.(Ser380Arg). The derived allele of this SNV is at its highest global frequency, of up to 5%, in populations of southern China, Vietnam, the Philippines, Malaysia and Indonesia. Using haplotype analyses, we find that the rs3827760 and rs146567337 SNVs arose on distinct haplotypes and that rs146567337 does not show the same signs of positive selection as rs3827760. From functional studies in cultured cells, we find that EDAR:p.(Ser380Arg) displays increased EDAR signalling output, at a similar level to that of EDAR:p.(Val370Ala). The existence of a second SNV with partly overlapping geographic distribution, the same in vitro functional effect and similar evolutionary age as the derived allele of rs3827760, but of independent origin and not exhibiting the same signs of strong selection, suggests a northern focus of positive selection on EDAR function in East Asia.