Pattern of p63 mutations and their phenotypes--update

Absent meibomian glands and cone dystrophy in ADULT syndrome: identification by whole exome sequencing of pathogenic variants in two causal genes TP63 and CNGB3

BACKGROUND

Ectrodactyly is a rare congenital limb malformation characterized by a deep median cleft of the hand and/or foot due to the absence of central rays. It could be isolated or depicts a part of diverse syndromic forms. Heterozygous pathogenic variants in the TP63 gene are responsible for at least four rare syndromic human disorders associated with ectrodactyly. Among them, ADULT (Acro-Dermato-Ungual-Lacrimal-Tooth) syndrome is characterized by ectodermal dysplasia, excessive freckling, nail dysplasia, and lacrimal duct obstruction, in addition to ectrodactyly and/or syndactyly. Ophthalmic findings are very common in TP63-related disorders, consisting mainly of lacrimal duct hypoplasia. Absent meibomian glands have also been well documented in EEC3 (Ectrodactyly Ectodermal dysplasia Cleft lip/palate) syndrome but not in ADULT syndrome.

METHODS

We report a case of syndromic ectrodactyly consistent with ADULT syndrome, with an additional ophthalmic manifestation of agenesis of meibomian glands. The proband, as well as her elder sister, presented with congenital cone dystrophy.The molecular investigation was performed in the proband using Whole Exome Sequencing. Family segregation of the identified variants was confirmed by Sanger sequencing.

RESULTS

Two clinically relevant variants were found in the proband: the novel de novo heterozygous missense c.931A > G (p.Ser311Gly) in the TP63 gene classified as pathogenic, and the homozygous nonsense pathogenic c.1810C > T (p.Arg604Ter) in the CNGB3 gene. The same homozygous CNGB3 variation was also found in the sister, explaining the cone dystrophy in both cases.

CONCLUSIONS

Whole Exome Sequencing allowed dual molecular diagnoses: de novo TP63-related syndromic ectrodactyly and familial CNGB3-related congenital cone dystrophy.

Case report: ADULT syndrome: a rare case of congenital lacrimal duct abnormality

Acro-dermato-ungual-lacrimal-tooth (ADULT) syndrome is a rare autosomal dominant inherited disease caused due to mutations in the TP63 gene. More commonly, mutations in the TP63 gene result in ectodermal dysplasia and/or orofacial cleft. ADULT syndrome is a type of ectoderm-related tissue dysplasia. This case report describes a patient with chronic tearing, congenital atresia, and obstruction of the lacrimal ducts, which are the main clinical manifestations of ADULT syndrome. This patient also presented with some clinical manifestations that were different from those of ADULT syndrome, namely, mild eyelid fusion and abnormal development of the fifth finger (a stiff fifth finger with camptodactyly that was shortened in length). The gene mutation in this patient was also at a site different from those usually reported in the literature. In this patient, c.518G > T resulted in p. G173V (accession number: NM_003722; exon4). We performed successful dacryocystorhinostomy and artificial lacrimal duct implantation. As shown above, we discussed the clinical characteristics and genetics of the disease in detail. In sharing this case, we aim to contribute to the current understanding of the genes and clinical manifestations of ADULT syndrome and to assist clinicians in the clinical diagnosis of TP63 mutation-related diseases.

Identification of the regulatory circuit governing corneal epithelial fate determination and disease

The transparent corneal epithelium in the eye is maintained through the homeostasis regulated by limbal stem cells (LSCs), while the nontransparent epidermis relies on epidermal keratinocytes for renewal. Despite their cellular similarities, the precise cell fates of these two types of epithelial stem cells, which give rise to functionally distinct epithelia, remain unknown. We performed a multi-omics analysis of human LSCs from the cornea and keratinocytes from the epidermis and characterized their molecular signatures, highlighting their similarities and differences. Through gene regulatory network analyses, we identified shared and cell type-specific transcription factors (TFs) that define specific cell fates and established their regulatory hierarchy. Single-cell RNA-seq (scRNA-seq) analyses of the cornea and the epidermis confirmed these shared and cell type-specific TFs. Notably, the shared and LSC-specific TFs can cooperatively target genes associated with corneal opacity. Importantly, we discovered that FOSL2, a direct PAX6 target gene, is a novel candidate associated with corneal opacity, and it regulates genes implicated in corneal diseases. By characterizing molecular signatures, our study unveils the regulatory circuitry governing the LSC fate and its association with corneal opacity.

[Congenital anomalies in lacrimal drainage]

Congenital dacryostenosis is the most common reason for ophthalmic consultation in childhood. It is most often caused by persisting of Hasner's membrane. However, congenital malformations of the lacrimal drainage system can also occur in rare cases. In the area of the proximal lacrimal drainage system, supernumerary lacrimal puncta and canaliculi can arise as well as diverticula, fistula, and atresia. The distal lacrimal drainage system can be affected by fistulas, amniotoceles, and cysts. Association of lacrimal malformations with congenital systemic diseases is reported in about 10% of cases. Depending on the severity of the symptoms, surgical rehabilitation can be performed, and endoscopic procedures and modern lacrimal drainage intubation systems may be employed.

Amelogenesis imperfecta: Next-generation sequencing sheds light on Witkop's classification

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic rare diseases disrupting enamel development (Smith et al., Front Physiol, 2017a, 8, 333). The clinical enamel phenotypes can be described as hypoplastic, hypomineralized or hypomature and serve as a basis, together with the mode of inheritance, to Witkop's classification (Witkop, J Oral Pathol, 1988, 17, 547-553). AI can be described in isolation or associated with others symptoms in syndromes. Its occurrence was estimated to range from 1/700 to 1/14,000. More than 70 genes have currently been identified as causative. Objectives: We analyzed using next-generation sequencing (NGS) a heterogeneous cohort of AI patients in order to determine the molecular etiology of AI and to improve diagnosis and disease management. Methods: Individuals presenting with so called "isolated" or syndromic AI were enrolled and examined at the Reference Centre for Rare Oral and Dental Diseases (O-Rares) using D4/phenodent protocol (www.phenodent.org). Families gave written informed consents for both phenotyping and molecular analysis and diagnosis using a dedicated NGS panel named GenoDENT. This panel explores currently simultaneously 567 genes. The study is registered under NCT01746121 and NCT02397824 (https://clinicaltrials.gov/). Results: GenoDENT obtained a 60% diagnostic rate. We reported genetics results for 221 persons divided between 115 AI index cases and their 106 associated relatives from a total of 111 families. From this index cohort, 73% were diagnosed with non-syndromic amelogenesis imperfecta and 27% with syndromic amelogenesis imperfecta. Each individual was classified according to the AI phenotype. Type I hypoplastic AI represented 61 individuals (53%), Type II hypomature AI affected 31 individuals (27%), Type III hypomineralized AI was diagnosed in 18 individuals (16%) and Type IV hypoplastic-hypomature AI with taurodontism concerned 5 individuals (4%). We validated the genetic diagnosis, with class 4 (likely pathogenic) or class 5 (pathogenic) variants, for 81% of the cohort, and identified candidate variants (variant of uncertain significance or VUS) for 19% of index cases. Among the 151 sequenced variants, 47 are newly reported and classified as class 4 or 5. The most frequently discovered genotypes were associated with MMP20 and FAM83H for isolated AI. FAM20A and LTBP3 genes were the most frequent genes identified for syndromic AI. Patients negative to the panel were resolved with exome sequencing elucidating for example the gene involved ie ACP4 or digenic inheritance. Conclusion: NGS GenoDENT panel is a validated and cost-efficient technique offering new perspectives to understand underlying molecular mechanisms of AI. Discovering variants in genes involved in syndromic AI (CNNM4, WDR72, FAM20A … ) transformed patient overall care. Unravelling the genetic basis of AI sheds light on Witkop's AI classification.

Disease-related p63 DBD mutations impair DNA binding by distinct mechanisms and varying degree

The transcription factor p63 shares a high sequence identity with the tumour suppressor p53 which manifests itself in high structural similarity and preference for DNA sequences. Mutations in the DNA binding domain (DBD) of p53 have been studied in great detail, enabling a general mechanism-based classification. In this study we provide a detailed investigation of all currently known mutations in the p63 DBD, which are associated with developmental syndromes, by measuring their impact on transcriptional activity, DNA binding affinity, zinc binding capacity and thermodynamic stability. Some of the mutations we have further characterized with respect to their ability to convert human dermal fibroblasts into induced keratinocytes. Here we propose a classification of the p63 DBD mutations based on the four different mechanisms of DNA binding impairment which we identified: direct DNA contact, zinc finger region, H2 region, and dimer interface mutations. The data also demonstrate that, in contrast to p53 cancer mutations, no p63 mutation induces global unfolding and subsequent aggregation of the domain. The dimer interface mutations that affect the DNA binding affinity by disturbing the interaction between the individual DBDs retain partial DNA binding capacity which correlates with a milder patient phenotype.

Overlap between EEC and AEC syndrome and immunodeficiency in a preterm infant with a TP63 variant

Pathogenic variants in the transcription factor TP63 gene cause a variety of clinical phenotypes, such as ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome and ankyloblepharon-ectodermal dysplasia-clefting (AEC) syndrome. Historically, TP63-related phenotypes have been divided into several syndromes based on both the clinical presentation and location of the pathogenic variant on the TP63 gene. This division is complicated by significant overlap between syndromes. Here we describe a patient with clinical characteristics of different TP63-associated syndromes (cleft lip and palate, split feet, ectropion, erosions of the skin and corneas), associated with a de novo heterozygous pathogenic variant c.1681 T>C, p.(Cys561Arg) in exon 13 of the TP63 gene. Our patient also developed enlargement of the left-sided cardiac compartments and secondary mitral insufficiency, which is a novel finding, and immune deficiency, which has only rarely been reported. The clinical course was further complicated by prematurity and very low birth weight. We illustrate the overlapping features of EEC and AEC syndrome and multidisciplinary care needed to address the various clinical challenges.

Broad spectrum of anomalies including quadricuspid aortic valve associated with a novel frameshift SALL4 variant

Each family member had a SALL4 variant. This is the first report of quadricuspid aortic valve and a genetic variant. The variation in phenotype caused by SALL4 mutations questions the division of SALL4-related phenotypes in three different entities.

Identification of a novel heterozygous missense TP63 variant in a Chinese pedigree with split-hand/foot malformation

BACKGROUND

Tumor protein p63 is an important transcription factor regulating epithelial morphogenesis. Variants associated with the TP63 gene are known to cause multiple disorders. In this study, we determined the genetic cause of split-hand/foot malformation in a Chinese pedigree.

METHODS

For this study, we have recruited a Chinese family and collected samples from affected and normal individuals of the family (three affected and two normal). Whole exome sequencing was performed to detect the underlying genetic defect in this family. The potential variant was validated using the Sanger sequencing approach.

RESULTS

Using whole-exome and Sanger sequencing, we identified a novel heterozygous pathogenic missense variant in TP63 (NM_003722.5: c.921G > T; p.Met307Ile). This variant resulted in the substitution of methionine with isoleucine. Structural analysis suggested a resulting change in the structure of a key functional domain of the p63 protein.

CONCLUSION

This novel missense variant expands the TP63 variant spectrum and provides a basis for genetic counseling and prenatal diagnosis of families with split-hand/foot malformation or other TP63-related diseases.

A novel TP63 variant in a patient with ankyloblepharon-ectodermal defect-cleft lip/palate syndrome and Rapp-Hodgkin syndrome-like ectodermal dysplasia

Ankyloblepharon-ectodermal defect-cleft lip/palate syndrome and Rapp-Hodgkin syndrome are well-known TP63-related autosomal-dominant genetic disorders with various similar ectodermal dysplasias. In this study, whole-exome sequencing revealed a novel, potentially pathogenic TP63 nonsense variant (NM_001114980.2:c.25 C > T: p.Gln9Ter) in a patient with an atypical clinical phenotype. This variant was detected near translation initiation sites and has an effect only on ΔNp63α, the short isoform protein product of the TP63 gene.

Congenital Anomalies in Lacrimal Drainage

Congenital dacryostenosis is the most common reason for ophthalmic consultation in childhood. It is most often caused by persisting of Hasner's membrane. However, congenital malformations of the lacrimal drainage system can also occur in rare cases. In the area of the proximal lacrimal drainage system, supernumerary lacrimal puncta and canaliculi can arise as well as diverticula, fistula, and atresia. The distal lacrimal drainage system can be affected by fistulas, amniotoceles, and cysts. Association of lacrimal malformations with congenital systemic diseases is reported in about 10% of cases. Depending on the severity of the symptoms, surgical rehabilitation can be performed, and endoscopic procedures and modern lacrimal drainage intubation systems may be employed.

Familial cleft tongue caused by a unique translation initiation codon variant in TP63

Variants in transcription factor p63 have been linked to several autosomal dominantly inherited malformation syndromes. These disorders show overlapping phenotypic characteristics with various combinations of the following features: ectodermal dysplasia, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypoplastic breasts and/or nipples, ankyloblepharon filiforme adnatum, hypospadias and cleft lip/palate. We describe a family with six individuals presenting with a striking novel phenotype characterized by a furrowed or cleft tongue, a narrow face, reddish hair, freckles and various foot deformities. Whole-exome sequencing (WES) identified a novel heterozygous variant, c.3G>T, in TP63 affecting the translation initiation codon (p.1Met?). Sanger sequencing confirmed dominant inheritance of this unique variant in all six affected family members. In summary, our findings indicate that heterozygous variants in TP63 affecting the first translation initiation codon result in a novel phenotype dominated by a cleft tongue, expanding the complex genotypic and phenotypic spectrum of TP63-associated disorders.

Spontaneous resolution of nonimmune hydrops fetalis in a fetus with TP63 gene mutation and LZTR1 gene variants

In cases of fetal hydrops, searching for an etiology is essential to evaluate the fetal prognosis and propose the most appropriate management.

Cereblon-Based Small-Molecule Compounds to Control Neural Stem Cell Proliferation in Regenerative Medicine

Thalidomide, a sedative drug that was once excluded from the market owing to its teratogenic properties, was later found to be effective in treating multiple myeloma. We had previously demonstrated that cereblon (CRBN) is the target of thalidomide embryopathy and acts as a substrate receptor for the E3 ubiquitin ligase complex, Cullin-Ring ligase 4 (CRL4^CRBN) in zebrafish and chicks. CRBN was originally identified as a gene responsible for mild intellectual disability in humans. Fetuses exposed to thalidomide in early pregnancy were at risk of neurodevelopmental disorders such as autism, suggesting that CRBN is involved in prenatal brain development. Recently, we found that CRBN controls the proliferation of neural stem cells in the developing zebrafish brain, leading to changes in brain size. Our findings imply that CRBN is involved in neural stem cell growth in humans. Accumulating evidence shows that CRBN is essential not only for the teratogenic effects but also for the therapeutic effects of thalidomide. This review summarizes recent progress in thalidomide and CRBN research, focusing on the teratogenic and therapeutic effects. Investigation of the molecular mechanisms underlying the therapeutic effects of thalidomide and its derivatives, CRBN E3 ligase modulators (CELMoDs), reveals that these modulators provide CRBN the ability to recognize neosubstrates depending on their structure. Understanding the therapeutic effects leads to the development of a novel technology called CRBN-based proteolysis-targeting chimeras (PROTACs) for target protein knockdown. These studies raise the possibility that CRBN-based small-molecule compounds regulating the proliferation of neural stem cells may be developed for application in regenerative medicine.

Isoform-Specific Roles of Mutant p63 in Human Diseases

Simple Summary

The protein p63 belongs to the family of the p53 tumor suppressor. Mouse models have, however, shown that it is not a classical tumor suppressor but instead involved in developmental processes. Mutations in the p63 gene cause several developmental defects in human patients characterized by limb deformation, cleft lip/palate, and ectodermal dysplasia due to p63’s role as a master regulator of epidermal development. In addition, p63 plays a key role as a quality control factor in oocytes and p63 mutations can result either in compromised genetic quality control or premature cell death of all oocytes.

Abstract

The p63 gene encodes a master regulator of epidermal commitment, development, and differentiation. Heterozygous mutations in the DNA binding domain cause Ectrodactyly, Ectodermal Dysplasia, characterized by limb deformation, cleft lip/palate, and ectodermal dysplasia while mutations in in the C-terminal domain of the α-isoform cause Ankyloblepharon-Ectodermal defects-Cleft lip/palate (AEC) syndrome, a life-threatening disorder characterized by skin fragility, severe, long-lasting skin erosions, and cleft lip/palate. The molecular disease mechanisms of these syndromes have recently become elucidated and have enhanced our understanding of the role of p63 in epidermal development. Here we review the molecular cause and functional consequences of these p63-mutations for skin development and discuss the consequences of p63 mutations for female fertility.

EEC-LM-ADULT syndrome caused by R319H mutation in TP63 with ectrodactyly, syndactyly, and teeth anomaly: A case report

RATIONALE

Ectrodactyly ectodermal dysplasia-cleft lip/palate (EEC) syndrome, limb-mammary syndrome (LMS), and acro-dermato-ungual-lacrimal-tooth (ADULT) syndrome are caused by a TP63 gene disorder and have similar features. In the present article, a R319H mutation in TP63 is reported, and the correlation between genotype and phenotype is discussed based on the current case and previous literature.

PATIENT CONCERNS

A 13-year-old Japanese boy had ectrodactyly in the right hand and left foot and syndactyly in the left and right foot, and tooth shape abnormalities.

DIAGNOSES

Peripheral blood samples were obtained, and mutation analysis was performed. A heterozygous G>A transition at cDNA position 956 of the TP63 gene was found. The patient was diagnosed with ELA (EEC/LM/ADULT) syndrome based on his clinical features and mutation analysis results.

INTERVENTIONS

The patient underwent surgery to correct the left foot malformation at 1 year of age and the right foot syndactyly at 11 years of age.

OUTCOMES

No complications were observed after the first and second operations. He can walk comfortably after them, and no additional interventions will be planned in him. We continued to follow up with him up to the present.

LESSONS

The concept of ELA syndrome, which is the original concept of combining 3 syndromes (EEC syndrome/LMS/ADULT syndrome) into a unique clinical entity, can help clinicians to better understand TP63-related syndromes and improve the differential diagnosis of these syndromes.

TP63-mutation as a cause of prenatal lethal multicystic dysplastic kidneys

Background

Ectrodactyly‐ectodermal dysplasia‐clefting syndrome 3 (EEC) is one of the six overlapping syndromes caused by mutations in the tumor protein p63 gene (TP63). EEC is suspected when patients have cleft hands or feet, polydactyly, and syndactyly, abnormal development of the ectodermally derived structures, and orofacial clefting. Genitourinary (GU) anomalies have been identified in patients with EEC, yet these are often under‐recognized and under‐reported. The available literature on sonographic prenatal findings is sparse, especially when considering GU anomalies.

Methods

We present the case of a male stillborn fetus, who was found antenatally to have multicystic dysplastic kidneys and anhydramnios. Following the termination of pregnancy, examination and autopsy further revealed unilateral polydactyly and bilateral syndactyly which had not been previously identified on antenatal ultrasound.

Results

Whole‐exome sequencing (WES) revealed a de novo heterozygous pathogenic variant in exon 5 of the TP63 gene: p.His247Arg: c.740A>G (NM_003722.4) which has been reported in the literature. The His247Arg variant has been published as a pathogenic variant in association with EEC, both with and without orofacial clefting.

Conclusion

Our prenatal case expands the phenotypic spectrum of TP63‐related disorders in general. In addition, it adds to the phenotype associated with the His247Arg pathogenic variant responsible for EEC. Further, we highlight the importance of WES as a postnatal tool to help clarify unexpected findings, and as a way to add to the spectrum of existing phenotypes of known single‐gene disorders.

Cleft Lip and Palate in Ectodermal Dysplasia

OBJECTIVE

Ectodermal dysplasia (ED) comprises multiple syndromes that affect skin, hair, nails, and teeth, and sometimes are associated with orofacial clefting. The purpose of this study is to (1) identify the prevalence and characteristics of cleft lip and/or palate (CL/P) in patients with ED and (2) describe the management and outcomes.

DESIGN

Retrospective review from 1990 to 2019.

PATIENTS

All patients with ED treated at Boston Children's Hospital.

MAIN OUTCOMES MEASURES

Prevalence of CL/P was calculated and clinical details recorded: phenotypic anomalies, cleft type, operative treatment, and results of repair.

RESULTS

Of 170 patients with a purported diagnosis of ED, 24 (14%) had CL/P. Anatomic categories were bilateral CL/P (67%), unilateral CL/P (8%), and cleft palate only (25%). The most common ED syndrome (37%) was ectrodactyly, ectodermal dysplasia, and cleft lip/palate (EEC). Pathogenic variants in TP63 were the most frequent finding in the 11 patients who had genetic testing. Aberrations from a typical clinical course included failure of presurgical dentofacial orthopedics, dehiscence of nasolabial adhesion, and total palatal absence requiring free-flap construction. Two patients had prolonged postoperative admission for respiratory infection. High fistula (8%) and velopharyngeal insufficiency (33%) rates reflected the predominance of bilateral complete forms.

CONCLUSIONS

As in other types of syndromic CL/P, cleft phenotypic expression in ED is more severe than the general cleft population. Further studies are needed to correlate genotype and phenotype for the distinct syndromes included in the ED spectrum.

Ectrodactyly-ectodermal dysplasia-clefting syndrome presenting with bilateral choanal atresia and rectal stenosis

We present the case of a male who shortly after birth developed acute respiratory distress due to bilateral choanal atresia, following which he was found to have rectal stenosis. Genetic testing for CHARGE syndrome was negative, but whole genome sequencing identified heterozygosity for a pathogenic missense variant in TP63 (c.727C > T, p.(Arg243Trp). He also has partial cutaneous syndactyly of the third and fourth fingers of the right hand, and bilateral lacrimal duct stenosis/aplasia. A later maxillofacial review identified a palpable submucousal cleft and his scalp hair is blond and slightly sparse. Choanal atresia and rectal stenosis are recognized features of ectrodactyly-ectodermal dysplasia-clefting syndrome, but we believe this is the first report of a case presenting with these features in the absence of the cardinal features.

Molecular Mechanisms of the Teratogenic Effects of Thalidomide

Thalidomide was sold worldwide as a sedative over 60 years ago, but it was quickly withdrawn from the market due to its teratogenic effects. Thalidomide was later found to have therapeutic effects in several diseases, although the molecular mechanisms remained unclear. The discovery of cereblon (CRBN), the direct target of thalidomide, a decade ago greatly improved our understanding of its mechanism of action. Accumulating evidence has shown that CRBN functions as a substrate of Cullin RING E3 ligase (CRL4^CRBN), whose specificity is controlled by ligands such as thalidomide. For example, lenalidomide and pomalidomide, well-known thalidomide derivatives, degrade the neosubstrates Ikaros and Aiolos, resulting in anti-proliferative effects in multiple myeloma. Recently, novel CRBN-binding drugs have been developed. However, for the safe handling of thalidomide and its derivatives, a greater understanding of the mechanisms of its adverse effects is required. The teratogenic effects of thalidomide occur in multiple tissues in the developing fetus and vary in phenotype, making it difficult to clarify this issue. Recently, several CRBN neosubstrates (e.g., SALL4 (Spalt Like Transcription Factor 4) and p63 (Tumor Protein P63)) have been identified as candidate mediators of thalidomide teratogenicity. In this review, we describe the current understanding of molecular mechanisms of thalidomide, particularly in the context of its teratogenicity.

Recent advances in the molecular mechanism of thalidomide teratogenicity

Thalidomide was first marketed in 1957 but soon withdrawn because of its notorious teratogenicity. Studies on the mechanism of action of thalidomide revealed the pleiotropic properties of this class of drugs, including their anti-inflammatory, antiangiogenic and immunomodulatory activities. Based on their notable activities, thalidomide and its analogues, lenalidomide and pomalidomide, have been repurposed to treat erythema nodosum leprosum, multiple myeloma and other haematological malignancies. Thalidomide analogues were recently found to hijack CRL4^CRBN ubiquitin ligase to target a number of cellular proteins for ubiquitination and proteasomal degradation. Thalidomide-mediated degradation of SALL4 and p63, transcription factors essential for embryonic development, very likely plays a critical role in thalidomide embryopathy. In this review, we provide a brief retrospective summary of thalidomide-induced teratogenesis, the mechanism of thalidomide activity, and the latest advances in the molecular mechanism of thalidomide-induced birth malformations.

Sam Domains in Multiple Diseases

BACKGROUND

The sterile alpha motif (Sam) domain is a small helical protein module, able to undergo homo- and hetero-oligomerization, as well as polymerization, thus forming different types of protein architectures. A few Sam domains are involved in pathological processes and consequently, they represent valuable targets for the development of new potential therapeutic routes. This study intends to collect state-of-the-art knowledge on the different modes by which Sam domains can favor disease onset and progression.

METHODS

This review was build up by searching throughout the literature, for: a) the structural properties of Sam domains, b) interactions mediated by a Sam module, c) presence of a Sam domain in proteins relevant for a specific disease.

RESULTS

Sam domains appear crucial in many diseases including cancer, renal disorders, cataracts. Often pathologies are linked to mutations directly positioned in the Sam domains that alter their stability and/or affect interactions that are crucial for proper protein functions. In only a few diseases, the Sam motif plays a kind of "side role" and cooperates to the pathological event by enhancing the action of a different protein domain.

CONCLUSION

Considering the many roles of the Sam domain into a significant variety of diseases, more efforts and novel drug discovery campaigns need to be engaged to find out small molecules and/or peptides targeting Sam domains. Such compounds may represent the pillars on which to build novel therapeutic strategies to cure different pathologies.

Novel phenotype of syndromic premature ovarian insufficiency associated with TP63 molecular defect

There is growing evidence that TP63 is associated with isolated as well as syndromic premature ovarian insufficiency (POI). We report two adolescent sisters diagnosed with undetectable ovaries, uterine hypoplasia, and mammary gland hypoplasia. A novel paternally inherited nonsense variant in TP63 [NM_003722.4 c.1927C > T,p.(Arg643*)] in exon 14 was identified by exome sequencing. One of the syndromes linked to TP63 is limb mammary syndrome (LMS), an autosomal dominant inherited disorder characterized by ectrodactyly, hypoplasia of mammary-gland and nipple, lacrimal duct stenosis, nail dysplasia, dental anomalies, cleft palate and/or cleft lip and absence of skin and hair defects. The TP63 variant segregated with symptoms of LMS in the family, however, no affected individual had limb defects. The phenotype reported here represents a novel syndromic phenotype associated with TP63. Reported cases with TP63 associated POI are reviewed.

Phenotypic expansion of KMT2D-related disorder: Beyond Kabuki syndrome

Pathogenic variants in KMT2D, which encodes lysine specific methyltransferase 2D, cause autosomal dominant Kabuki syndrome, associated with distinctive dysmorphic features including arched eyebrows, long palpebral fissures with eversion of the lower lid, large protuberant ears, and fetal finger pads. Most disease-causing variants identified to date are putative loss-of-function alleles, although 15-20% of cases are attributed to missense variants. We describe here four patients (including one previously published patient) with de novo KMT2D missense variants and with shared but unusual clinical findings not typically seen in Kabuki syndrome, including athelia (absent nipples), choanal atresia, hypoparathyroidism, delayed or absent pubertal development, and extreme short stature. These individuals also lack the typical dysmorphic facial features found in Kabuki syndrome. Two of the four patients had severe interstitial lung disease. All of these variants cluster within a 40-amino-acid region of the protein that is located just N-terminal of an annotated coiled coil domain. These findings significantly expand the phenotypic spectrum of features associated with variants in KMT2D beyond those seen in Kabuki syndrome and suggest a possible new underlying disease mechanism for these patients.

Molecular mechanisms of thalidomide and its derivatives

Thalidomide, originally developed as a sedative drug, causes multiple defects due to severe teratogenicity, but it has been re-purposed for treating multiple myeloma, and derivatives such as lenalidomide and pomalidomide have been developed for treating blood cancers. Although the molecular mechanisms of thalidomide and its derivatives remained poorly understood until recently, we identified cereblon (CRBN), a primary direct target of thalidomide, using ferrite glycidyl methacrylate (FG) beads. CRBN is a ligand-dependent substrate receptor of the E3 ubiquitin ligase complex cullin-RING ligase 4 (CRL4^CRBN). When a ligand such as thalidomide binds to CRBN, it recognizes various 'neosubstrates' depending on the shape of the ligand. CRL4^CRBN binds many neosubstrates in the presence of various ligands. CRBN has been utilized in a novel protein knockdown technology named proteolysis targeting chimeras (PROTACs). Heterobifunctional molecules such as dBET1 are being developed to specifically degrade proteins of interest. Herein, we review recent advances in CRBN research.

A novel mutation (c.1010G>T; p.R337L) in TP63 as a cause of split-hand/foot malformation with hypodontia

BACKGROUND

Tumor protein p63 (TP63)-related disorders can be divided into at least six categories, including ectrodactyly-ectodermal dysplasia-cleft lip/palate syndrome 3 (EEC syndrome 3), ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC syndrome), acro-dermo-ungual-lacrimal-tooth syndrome (ADULT syndrome), limb-mammary syndrome (LMS), Rapp-Hodgkin syndrome (RHS) and split-hand/foot malformation 4 (SHFM4), and are all a result of heterozygous mutations of TP63. The phenotypes of TP63-related disorders broadly involve ectodermal dysplasias, acromelic malformation and orofacial cleft. SHFM and hypodontia are prominent clinical manifestations of TP63-related disorders.

METHODS

The present study investigated a family with SHFM and hypodontia; determined the sequences of DLX5, WNT8B, WNT10B, BHLHA9, CDH3, DYNC1I1 and FGFR1; and performed single nucleotide polymorphism-array analysis. We detected the mutation by multiple sequence alignments and a bioinformatic prediction.

RESULTS

We identified a novel missense mutation of TP63 (c.1010G>T; R337L) in the family without mutations of DLX5, WNT8B, WNT10B, BHLHA9, CDH3, DYNC1I1, FGFR1 and copy number variants causing SHFM.

CONCLUSIONS

A mutation of TP63 (c.1010G>T; R337L) leads to SHFM with hypodontia. The identification of this mutation expands the spectrum of known TP63 mutations and also may contribute to novel approaches for the genetic diagnosis and counseling of families with TP63-related disorders.

Pioneer and repressive functions of p63 during zebrafish embryonic ectoderm specification

The transcription factor p63 is a master regulator of ectoderm development. Although previous studies show that p63 triggers epidermal differentiation in vitro, the roles of p63 in developing embryos remain poorly understood. Here, we use zebrafish embryos to analyze in vivo how p63 regulates gene expression during development. We generate tp63-knock-out mutants that recapitulate human phenotypes and show down-regulated epidermal gene expression. Following p63-binding dynamics, we find two distinct functions clearly separated in space and time. During early development, p63 binds enhancers associated to neural genes, limiting Sox3 binding and reducing neural gene expression. Indeed, we show that p63 and Sox3 are co-expressed in the neural plate border. On the other hand, p63 acts as a pioneer factor by binding non-accessible chromatin at epidermal enhancers, promoting their opening and epidermal gene expression in later developmental stages. Therefore, our results suggest that p63 regulates cell fate decisions during vertebrate ectoderm specification.

p63 cooperates with CTCF to modulate chromatin architecture in skin keratinocytes

The transcription factor p63 regulates epidermal genes and the enhancer landscape in skin keratinocytes. Its molecular function in controlling the chromatin structure is, however, not yet completely understood. Here, we integrated multi-omics profiles, including the transcriptome, transcription factor DNA-binding and chromatin accessibility, in skin keratinocytes isolated from EEC syndrome patients carrying p63 mutations, to examine the role of p63 in shaping the chromatin architecture. We found decreased chromatin accessibility in p63- and CTCF-bound open chromatin regions that potentially contributed to gene deregulation in mutant keratinocytes. Cooperation of p63 and CTCF seemed to assist chromatin interactions between p63-bound enhancers and gene promoters in skin keratinocytes. Our study suggests an intriguing model where cell type-specific transcription factors such as p63 cooperate with the genome organizer CTCF in the three-dimensional chromatin space to regulate the transcription program important for the proper cell identity.

TP63-truncating variants cause isolated premature ovarian insufficiency

Premature ovarian insufficiency involves amenorrhea and elevated follicle-stimulating hormone before age 40, and its genetic basis is poorly understood. Here, we study 13 premature ovarian insufficiency (POI) patients using whole-exome sequencing. We identify PREPL and TP63 causative variants, and variants in other potentially novel POI genes. PREPL deficiency is a known cause of syndromic POI, matching the patients' phenotype. A role for TP63 in ovarian biology has previously been proposed but variants have been described in multiorgan syndromes, and not isolated POI. One patient with isolated POI harbored a de novo nonsense TP63 variant in the terminal exon and an unrelated patient had a different nonsense variant in the same exon. These variants interfere with the repression domain while leaving the activation domain intact. We expand the phenotypic spectrum of TP63-related disorders, provide a new genotype:phenotype correlation for TP63 and identify a new genetic cause of isolated POI.

Deletions and loss-of-function variants in TP63 associated with orofacial clefting

We aimed to identify novel deletions and variants of TP63 associated with orofacial clefting (OFC). Copy number variants were assessed in three OFC families using microarray analysis. Subsequently, we analyzed TP63 in a cohort of 1072 individuals affected with OFC and 706 population-based controls using molecular inversion probes (MIPs). We identified partial deletions of TP63 in individuals from three families affected with OFC. In the OFC cohort, we identified several TP63 variants predicting to cause loss-of-function alleles, including a frameshift variant c.569_576del (p.(Ala190Aspfs*5)) and a nonsense variant c.997C>T (p.(Gln333*)) that introduces a premature stop codon in the DNA-binding domain. In addition, we identified the first missense variants in the oligomerization domain c.1213G>A (p.(Val405Met)), which occurred in individuals with OFC. This variant was shown to abrogate oligomerization of mutant p63 protein into oligomeric complexes, and therefore likely represents a loss-of-function allele rather than a dominant-negative. All of these variants were inherited from an unaffected parent, suggesting reduced penetrance of such loss-of-function alleles. Our data indicate that loss-of-function alleles in TP63 can also give rise to OFC as the main phenotype. We have uncovered the dosage-dependent functions of p63, which were previously rejected.

Infrared meibography and molecular assessment of p63 gene mutations in a Mexican patient with EEC syndrome

OBJECTIVE

To report the finding of infrared meibography in a Mexican patient with EEC syndrome (Ectrodactyly-ectodermal dysplasia-cleft syndrome) confirmed by molecular analysis of the p63 gene.

CLINICAL CASE

A 31 year-old male patient was seen due to a history of progressive visual loss in both eyes associated with long-term photophobia. The patient was born with cleft lip and palate, ectrodactyly of right hand, and afterwards, displayed nail dysplasia, anodontia and alopecia, with which ectodermal dysplasia was diagnosed. The ophthalmological findings were limited to the adnexa and the ocular surface. In vivo infrared meibography showed total absence of Meibomian glands in the lower eyelids and severe deficiency in the upper eyelids. In addition, it was shown that the patient was a heterozygous carrier of a missense mutation R304W (C → T) in exon 8 of the p63 gene.

DISCUSSION

The R304W mutation in the p63 gene region is definitely related to characteristics such as the absence of Meibomian glands.

Oral Mucosa-Derived Induced Pluripotent Stem Cells from Patients with Ectrodactyly-Ectodermal Dysplasia-Clefting Syndrome

Ectrodactyly-Ectodermal dysplasia-Clefting (EEC) syndrome is a rare monogenic disease with autosomal dominant inheritance caused by mutations in the TP63 gene, leading to progressive corneal keratinocyte loss, limbal stem cell deficiency (LSCD), and eventually blindness. Currently, there is no treatment available to cure or slow down the keratinocyte loss. Human oral mucosal epithelial stem cells (hOMESCs), which are a mixed population of keratinocyte precursor stem cells, are used as source of autologous tissue for treatment of bilateral LSCD. However, hOMESCs from EEC patients have a reduced life span due to TP63 mutations and cannot be used for autologous transplantation. Human induced pluripotent stem cells (hiPSCs) represent a potentially unlimited source of autologous limbal stem cell for EEC patients and can be genetically modified by genome editing technologies to correct the disease ex vivo before transplantation. In this study, we describe for the first time the generation of integration-free EEC-hiPSCs from hOMESCs of EEC patients by Sendai virus vector and episomal vector-based reprogramming. The generated hiPSC clones expressed pluripotency markers and were successfully differentiated into derivatives of the three germ layers, as well as toward corneal epithelium. These cells may be used for EEC disease modeling and open perspectives for applications in cell therapy of LSCD.

p73 Alternative Splicing: Exploring a Biological Role for the C-Terminal Isoforms

p73 (encoded by TP73 gene) is a p53 related protein that functions as a transcriptional factor. Similarly to p53, following DNA damage, p73 is stabilized and activated and controls expression of target genes that are involved in the regulation of cycle arrest and apoptosis. However, great complexity to the function of this gene is given by the wide range of its non-tumor-related roles, which include neurological development, ciliogenesis and fertility. From the structural point of view, p73 displays an intricate range of regulations because it can be expressed both as an N-terminally deleted dominant-negative isoforms and as multiple alternatively spliced C-terminal isoforms, which can include or not a sterile alpha motif domain. More is known about the functions of the N-terminal isoforms of p73 (TAp73 and ΔNp73) and their opposing pro- and anti-apoptotic roles, whereas the functional differences of the distinct C-terminal splice forms of p73 are very far away from been defined. Here we summarize the current available literature regarding p73 C-terminal isoforms and the contribution of the sterile alpha motif domain to p73 function, trying to provide an unified view in this complex and sometime controversial field. Current data indicate that the full-length, TAp73α, is the major, if not the exclusive, isoform detected in physiological systems, indicating that detailed spatio-temporal expression analysis and functional studies are highly demanded to support a physiological role for the p73 alternative splicing. With this article, we also aim to emphasize the need to further investigation on the topic, refocusing the attention on what we believe are the most relevant unanswered questions.

Genetic analysis of a congenital split‑hand/split‑foot malformation 4 pedigree

In the present study whole-exome sequencing using the Complete Genomics platform was employed to scan a proband from a split-hand/split-foot malformation (SHFM) 4 family. The missense mutation c.728G>A (p.Arg243Gln) in the TP63 gene was revealed to be associated with SHFM. Sanger sequencing confirmed the sequences of the proband and his father. The father was diagnosed with SHFM and harbored a CGG-to-CAG mutation in exon 5, which produced a R243Q substitution in the zinc binding site and dimerization site of TP63. The R243Q mutation was predicted to be pathogenic by PolyPhen-2. The proband, who was diagnosed with four digit SHFM, exhibited a more severe phenotype. X-ray analysis returned the following results: Absence of third phalange bilaterally and third metacarpus of the left hand; absence of the second toes bilaterally and partial third toes; and partial fusion of the second, third and metatarsal bones of the right side with deformity of the second metatarsal of the right side. Osteochondroma was present in the fourth proximal radial metacarpal of the left hand and the basal and proximal parts of the second metatarsal of the right side. The proband's father had five digits in both feet. These results indicate that the R243Q mutation produces a novel phenotype named SHFM4. The present study revealed that the R243Q mutation in the TP63 gene produced a novel phenotype named SHFM4, thereby demonstrating the mutational overlap between ectrodactyly-ectodermal dysplasia-cleft syndrome and SHFM4.

Protein aggregation of the p63 transcription factor underlies severe skin fragility in AEC syndrome

The p63 gene encodes a master regulator of epidermal development and function. Specific mutations in p63 are causative of a life-threatening disorder mainly characterized by severe skin erosions and cleft palate. Little is known about the mechanisms underlying disease pathology and possible treatments. Based on biochemical studies, genetic mouse models, and functional assays, we demonstrate that these mutations cause p63 protein misfolding and aggregation. Protein aggregation lead to reduced DNA binding and impaired transcriptional activity. Importantly, genetic modifications of p63 that abolish aggregation of the mutant proteins rescue its function, revealing that ankyloblepharon-ectodermal defects-cleft lip/palate syndrome is a protein aggregation disorder and opening avenues for therapeutic intervention.

The p63 gene encodes a master regulator of epidermal commitment, development, and differentiation. Heterozygous mutations in the C-terminal domain of the p63 gene can cause ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome, a life-threatening disorder characterized by skin fragility and severe, long-lasting skin erosions. Despite deep knowledge of p63 functions, little is known about mechanisms underlying disease pathology and possible treatments. Here, we show that multiple AEC-associated p63 mutations, but not those causative of other diseases, lead to thermodynamic protein destabilization, misfolding, and aggregation, similar to the known p53 gain-of-function mutants found in cancer. AEC mutant proteins exhibit impaired DNA binding and transcriptional activity, leading to dominant negative effects due to coaggregation with wild-type p63 and p73. Importantly, p63 aggregation occurs also in a conditional knock-in mouse model for the disorder, in which the misfolded p63 mutant protein leads to severe epidermal defects. Variants of p63 that abolish aggregation of the mutant proteins are able to rescue p63’s transcriptional function in reporter assays as well as in a human fibroblast-to-keratinocyte conversion assay. Our studies reveal that AEC syndrome is a protein aggregation disorder and opens avenues for therapeutic intervention.

Update on 13 Syndromes Affecting Craniofacial and Dental Structures

Care of individuals with syndromes affecting craniofacial and dental structures are mostly treated by an interdisciplinary team from early childhood on. In addition to medical and dental specialists that have a vivid interest in these syndromes and for whom these syndromes are of evident interest, experts of scientific background-like molecular and developmental geneticists, but also computational biologists and bioinformaticians-, become more frequently involved in the refined diagnostic and etiological processes of these patients. Early diagnosis is often crucial for the effective treatment of functional and developmental aspects. However, not all syndromes can be clinically identified early, especially in cases of absence of known family history. Moreover, the treatment of these patients is often complicated because of insufficient medical knowledge, and because of the dental and craniofacial developmental variations. The role of the team is crucial for the prevention, proper function, and craniofacial development which is often combined with orthognathic surgery. Although the existing literature does not provide considerable insight into this topic, this descriptive review aims to provide tools for the interdisciplinary team by giving an update on the genetics and general features, and the oral and craniofacial manifestations for early diagnosis. Clinical phenotyping together with genetic data and pathway information will ultimately pave the way for preventive strategies and therapeutic options in the future. This will improve the prognosis for better functional and aesthetic outcome for these patients and lead to a better quality of life, not only for the patients themselves but also for their families. The aim of this review is to promote interdisciplinary interaction and mutual understanding among all specialists involved in the diagnosis and therapeutic guidance of patients with these syndromal conditions in order to provide optimal personalized care in an integrated approach.

Identification of a de novo variant in CHUK in a patient with an EEC/AEC syndrome-like phenotype and hypogammaglobulinemia

The cardinal features of Ectrodactyly, Ectodermal dysplasia, Cleft lip/palate (EEC), and Ankyloblepharon-Ectodermal defects-Cleft lip/palate (AEC) syndromes are ectodermal dysplasia (ED), orofacial clefting, and limb anomalies. EEC and AEC are caused by heterozygous mutations in the transcription factor p63 encoded by TP63. Here, we report a patient with an EEC/AEC syndrome-like phenotype, including ankyloblepharon, ED, cleft palate, ectrodactyly, syndactyly, additional hypogammaglobulinemia, and growth delay. Neither pathogenic mutations in TP63 nor CNVs at the TP63 locus were identified. Exome sequencing revealed de novo heterozygous variants in CHUK (conserved helix-loop-helix ubiquitous kinase), PTGER4, and IFIT2. While the variant in PTGER4 might contribute to the immunodeficiency and growth delay, the variant in CHUK appeared to be most relevant for the EEC/AEC-like phenotype. CHUK is a direct target gene of p63 and encodes a component of the IKK complex that plays a key role in NF-κB pathway activation. The identified CHUK variant (g.101980394T>C; c.425A>G; p.His142Arg) is located in the kinase domain which is responsible for the phosphorylation activity of the protein. The variant may affect CHUK function and thus contribute to the disease phenotype in three ways: (1) the variant exhibits a dominant negative effect and results in an inactive IKK complex that affects the canonical NF-κB pathway; (2) it affects the feedback loop of the canonical and non-canonical NF-κB pathways that are CHUK kinase activity-dependent; and (3) it disrupts NF-κB independent epidermal development that is often p63-dependent. Therefore, we propose that the heterozygous CHUK variant is highly likely to be causative to the EEC/AEC-like and additional hypogammaglobulinemia phenotypes in the patient presented here.

Intermediate Phenotype between ADULT Syndrome and EEC Syndrome Caused by R243Q Mutation in TP63

A patient who had ectrodactyly, dry skin, exfoliative dermatitis, and hypodontia with peg-shaped teeth, but not cleft lip and palate, is described. Ectrodactyly with a tooth anomaly is recognized in both acro-dermato-ungual-lacrimal-tooth (ADULT) syndrome and ectrodactyly-ectodermal dysplasia-cleft (EEC) syndrome. These 2 syndromes are caused by heterozygous mutations in the transcriptional factor gene p63. Mutation analysis of p63 gene showed a heterozygous mutation c.728G>A, p.Arg243Gln (previously referred to as R204Q) in the patient, but not in his parents. Therefore, this was a sporadic case of the p63 mutation–associated disorder. Although the mutation has been mostly reported in EEC syndrome patients, the present case did not have cleft lip and palate. Furthermore, the present case did not exhibit freckling or some of the other ectodermal dysplasia phenotypes typical of ADULT syndrome. The concept of ELA syndrome proposed by Prontera in 2011 resolves the problem confronted in diagnosing the present case. ELA syndrome is an acronym of EEC/limb–mammary syndrome/ADULT syndromes, and these 3 syndromes are united into a unique entity. This system can classify p63 mutation–associated disorders simply without interfering with treatment.

A New Split Hand/Foot Malformation with Long Bone Deficiency Familial Case

Split hand/foot malformation with long bone deficiency (SHFLD) is a congenital limb anomaly where hands and/or feet cleft and syndactyly are associated with long bone defects, usually involving the tibia. Previously published data reported that 17p13.3 chromosomal duplication, including the BHLHA9 gene, has been associated with the distinct entity, termed SHFLD3 (OMIM 612576), inherited as an autosomal dominant trait. Here, we present a family with three members affected by SHFLD harboring BHLHA9 duplication. We exploited in vitro differentiation system to promote proband's skin fibroblasts toward osteoblastic lineage, and we observed a slight but consistent delay in the mineralization pattern. This result possibly suggests an impairment of the osteogenic process in the affected members.

Recurrence of split hand/foot malformation, cleft lip/palate, and severe urogenital abnormalities due to germline mosaicism for TP63 mutation

We describe two sibling fetuses with urogenital abnormalities detected by prenatal ultrasound, in which post-delivery examination showed split hand and foot malformation, and bilateral cleft lip and palate. These findings are consistent with ectrodactyly-ectodermal dysplasia-cleft lip with or without cleft palate syndrome (EEC). Both fetuses were found to have the same missense mutation in TP63 (c.1051G > A; p.D351N). Parental clinical examinations and lymphocyte DNA analyses were normal. This report illustrates the potential severity of urogenital defects in TP63-related disorders, which may be detectable with fetal ultrasonography. It highlights the need to counsel for the possibility of germline mosaicism in TP63-associated disorders. © 2016 Wiley Periodicals, Inc.

Allele-specific silencing of EEC p63 mutant R304W restores p63 transcriptional activity

EEC (ectrodactily-ectodermal dysplasia and cleft lip/palate) syndrome is a rare genetic disease, autosomal dominant inherited. It is part of the ectodermal dysplasia disorders caused by heterozygous mutations in TP63 gene. EEC patients present limb malformations, orofacial clefting, skin and skin's appendages defects, ocular abnormalities. The transcription factor p63, encoded by TP63, is a master gene for the commitment of ectodermal-derived tissues, being expressed in the apical ectodermal ridge is critical for vertebrate limb formation and, at a later stage, for skin and skin's appendages development. The ΔNp63α isoform is predominantly expressed in epithelial cells and it is indispensable for preserving the self-renewal capacity of adult stem cells and to engage specific epithelial differentiation programs. Small interfering RNA (siRNA) offers a potential therapy approach for EEC patients by selectively silencing the mutant allele. Here, using a systemic screening based on a dual-luciferase reported gene assay, we have successfully identified specific siRNAs for repressing the EEC-causing p63 mutant, R304W. Upon siRNA treatment, we were able to restore ΔNp63-WT allele transcriptional function in induced pluripotent stem cells that were derived from EEC patient biopsy. This study demonstrates that siRNAs approach is promising and, may pave the way for curing/delaying major symptoms, such as cornea degeneration and skin erosions in young EEC patients.

A recurrent TP63 mutation causing EEC3 and Rapp-Hodgkin syndromes

The ectrodactyly, ectodermal dysplasia, and cleft lip/palate syndrome 3 (EEC3; OMIM #604292), the Rapp-Hodgkin syndrome (RHS), and various other syndromes are caused by mutations in the TP63 gene, which encodes a p53-like transcription factor. Here, we report on a woman aged 37 years and her daughter aged 3 years with the previously reported c.1028G>A (p.Arg343Gln) mutation in exon 8 of TP63. The mother lacked ectrodactyly, indicating a diagnosis of RHS, whereas the girl presented with all three major features (ectrodactyly, ectodermal dysplasia, clefting) and different minor features (including small and brittle nails, and recurrent conjunctivitis believed to be because of stenotic and blocked nasolacrimal ducts) of the EEC3 syndrome. The EEC and EEC-like syndromes are usually distinguished on the basis of the clinical findings; however, these syndromes show a huge variability in features because of variable expressivity and incomplete penetrance, making the correct clinical assignment difficult. In EEC3 syndrome and RHS, a clustering of mutations in the different domains of TP63 can be observed. Our findings indicate the clinical variability with TP63 mutations and underline that in the case of two syndromes being clinically possible in a patient, the final diagnosis should be assigned only after molecular diagnostics.