P63‐related disorders: Dermatological characteristics in 22 patients

Modulating OCA2 Expression as a Promising Approach to Enhance Skin Brightness and Reduce Dark Spots

The oculocutaneous albinism II (OCA2) gene encodes a melanosomal transmembrane protein involved in melanogenesis. Recent genome-wide association studies have identified several single nucleotide polymorphisms within OCA2 genes that are involved in skin pigmentation. Nevertheless, there have been no attempts to modulate this gene to improve skin discoloration. Accordingly, our aim was to identify compounds that can reduce OCA2 expression and to develop a formula that can improve skin brightness and reduce hyperpigmented spots. In this study, we investigated the effects of OCA2 expression reduction on melanin levels, melanosome pH, and autophagy induction through siRNA knockdown. Additionally, we identified several bioactives that effectively reduce OCA2 expression. Ultimately, in a clinical trial, we demonstrated that topical application of those compounds significantly improved skin tone and dark spots compared to vitamin C, a typical brightening agent. These findings demonstrate that OCA2 is a promising target for the development of efficacious cosmetics and therapeutics designed to treat hyperpigmentation.

Molecular and Cellular Function of p63 in Skin Development and Genetic Diseases

The transcription factor p63 is a master regulator of multiple ectodermal derivatives. During epidermal commitment, p63 interacts with several chromatin remodeling complexes to transactivate epidermal-specific genes and repress transcription of simple epithelial and nonepithelial genes. In the postnatal epidermis, p63 is required to control the proliferative potential of progenitor cells, maintain epidermal integrity, and contribute to epidermal differentiation. Autosomal dominant sequence variant in p63 cause a spectrum of syndromic disorders that affect several tissues, including or derived from stratified epithelia. In this review, we describe the recent studies that have provided novel insights into disease pathogenesis and potential therapeutic targets.

A spectrum of TP63-related disorders with eight affected individuals in five unrelated families

TP63-related disdorders broadly involve varying combinations of ectodermal dysplasia (sparse hair, hypohydrosis, tooth abnormalities, nail dysplasia), cleft lip/palate, acromelic malformation, split-hand/foot malformation/syndactyly, ankyloblepharon filiforme adnatum, lacrimal duct obstruction, hypopigmentation, and hypoplastic breasts and/or nipples. TP63-related disorders are associated with heterozygous pathogenic variants in TP63 and include seven overlapping phenotypes; Ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC), Ectrodactyly-ectodermal dysplasia-cleft lip/palate syndrome 3 (EEC3), Limb-mammary syndrome (LMS), Acro-dermo-ungual-lacrimal-tooth syndrome (ADULT), Rapp-Hodgkin syndrome (RHS), Split-hand/foot malformation 4 (SHFM4), and Orofacial cleft 8. We report on five unrelated families with 8 affected individuals in which the probands presented with varying combinations of ectodermal dysplasia, cleft lip/palate, split-hand/foot malformation, lacrimal duct obstruction, and ankyloblepharon filiforme adnatum. The clinical diagnosis involved AEC syndrome (2 patients), EEC3 syndrome (2 patients), and a yet hitherto unclassified TP63-related disorder. Sanger sequence analysis of the TP63 gene was performed revealing five different variants among which four were novel and three were de novo. The identificated TP63 variants co-segregated with the other affected individuals in the families. The abnormalities of ectoderm derived structures including hair, nails, sweat glands, and teeth should alert the physician to the possibility of TP63-related disorders particularly in the presence of orofacial clefting.

The Ectodermal Dysplasias-Burden of Disease Score: Development and Validation of an Ectodermal Dysplasia Family/Parental Burden Score

Ectodermal dysplasias are genetic conditions affecting the development and/or homeostasis of 2 or more ectodermal derivatives, including hair, teeth, nails, and certain glands. No tool is available to assess the burden of ectodermal dysplasias and its multidimensional impact on patients and their families. This study developed and validated a familial/parental 19-item burden questionnaire designed specifically for ectodermal dysplasias. Each group of questions was linked to 1 of the following dimensions: (i) Impact of the disease on social life and hobbies; (ii) Future prospects; (iii) Restraint of the disease on outdoor activities; (iv) Financial burden of the disease; (v) Acceptance of the disease. Cronbach's alpha was 0.91 for the entire Ectodermal Dysplasias-Burden of Disease (ED-BD) scale, confirming excellent internal coherence. Intradimensional coherences all demonstrated excellent reliability (α > 0.76). The ED-BD questionnaire was highly correlated with the Short Form-12 and Psychological General Well Being Index validated questionnaires. Cultural and linguistic validation in US English was conducted. Development and validation of the questionnaire was based on data from patients with the 2 main ectodermal dysplasias subtypes. This ED-BD questionnaire represents the first specific assessment tool for evaluating the familial/parental burden of ectodermal dysplasias.

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.

Ectodermal dysplasias: New perspectives on the treatment of so far immedicable genetic disorders

The past decade has witnessed an expansion of molecular approaches facilitating the differential diagnosis of ectodermal dysplasias, a group of genetic diseases characterized by the lack or malformation of hair, teeth, nails, and certain eccrine glands. Moreover, advances in translational research have increased the therapeutic opportunities for such rare diseases, and new dental, surgical, and ophthalmic treatment options are likely to offer relief to many individuals affected by ectodermal dysplasias. In X-linked hypohidrotic ectodermal dysplasia (XLHED), the genetic deficiency of the signaling molecule ectodysplasin A1 (EDA1) may even be overcome before birth by administration of a recombinant replacement protein. This has been shown at least for the key problem of male subjects with XLHED, the nearly complete absence of sweat glands and perspiration which can lead to life-threatening hyperthermia. Prenatal treatment of six boys by injection of an EDA1 replacement protein into the amniotic fluid consistently induced the development of functional sweat glands. Normal ability to sweat has so far persisted for >5 years in the two oldest boys treated in utero. Thus, timely replacement of a missing protein appears to be a promising therapeutic strategy for the most frequent ectodermal dysplasia and possibly additional congenital disorders.

Rare Genetic Disorders: Novel Treatment Strategies and Insights Into Human Biology

The last decade has seen a dramatic increase in innovative ideas for the treatment of genetic disorders for which no curative therapies exist. Gene and protein replacement therapies stand out as novel approaches to treat a select group of these diseases, such as certain tissue fragility disorders. Further, the advent of stem cell approaches, such as induced pluripotent stem cells (iPSC) technology, has led to the development of new methods of creating replacement tissues for regenerative medicine. This coincided with the discovery of genome editing techniques, which allow for the correction of disease-causing mutations. The culmination of these discoveries suggests that new and innovative therapies for monogenetic disorders affecting single organs or tissues are on the horizon. Challenges remain, however, especially with diseases that simultaneously affect several tissues and organs during development. Examples of this group of diseases include ectodermal dysplasias, genetic disorders affecting the development of tissues and organs such as the skin, cornea, and epithelial appendages. Gene or protein replacement strategies are unlikely to be successful in addressing the multiorgan phenotype of these diseases. Instead, we believe that a more effective approach will be to focus on correcting phenotypes in the most severely affected tissues. This could include the generation of replacement tissues or the identification of pharmaceutical compounds that correct disease pathways in specific tissues.

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.