Investigating basic biological mechanisms underlying human diseases relies on the availability of sufficient quantities of patient cells. As most primary somatic cells have a limited lifespan, obtaining sufficient material for biological studies has been a challenge. The development of induced pluripotent stem cell (iPSC) technology has been a game changer, especially in the field of rare genetic disorders. iPSC are essentially immortal, can be stored indefinitely, and can thus be used to generate defined somatic cells in unlimited quantities. Further, the availability of genome editing technologies, such as CRISPR/CAS, has provided us with the opportunity to create “designer” iPSC lines with defined genetic characteristics. A major advancement in biological research stems from the development of methods to direct iPSC differentiation into defined cell types. In this article, we provide the basic protocol for the generation of human iPSC‐derived keratinocytes (iPSC‐K). These cells have the characteristics of basal epidermal keratinocytes and represent a tool for the investigation of normal epidermal biology, as well as genetic and acquired skin disorders. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Directed differentiation of human iPSC into keratinocytes Support Protocol 1: Coating cell culture dishes or plates with Vitronectin XF™ Support Protocol 2: Freezing iPSC Support Protocol 3: Preparing AggreWell™400 6‐well plates for EB formation Support Protocol 4: Coating cell culture dishes or plates with Collagen IV Support Protocol 5: Immunofluorescence staining of cells

Heritable conditions known as ectodermal dysplasias are rare and can be associated with marked morbidity, mortality, and a reduced quality of life. The diagnosis and care of individuals affected by one of the many ectodermal dysplasias presents myriad challenges due to their rarity and the diverse phenotypes. These conditions are caused by abnormalities in multiple genes and signaling pathways that are essential for the development and function of ectodermal derivatives. During a 2021 international conference focused on translating discovery to therapy, researchers and clinicians gathered with the goal of advancing the diagnosis and treatment of conditions affecting ectodermal tissues with an emphasis on skin, hair, tooth, and eye phenotypes. Conference participants presented a variety of promising treatment strategies including gene or protein replacement, gene editing, cell therapy, and the identification of druggable targets. Further, barriers that negatively influence the current development of novel therapeutics were identified. These barriers include a lack of accurate prevalence data for rare conditions, absence of an inclusive patient registry with deep phenotyping data, and insufficient animal models and cell lines. Overcoming these barriers will need to be prioritized in order to facilitate the development of novel treatments for genetic disorders of the ectoderm.

The goal of this study was to investigate the molecular mechanisms responsible for the formation of skin erosions in patients affected by Ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC). This ectodermal dysplasia is caused by mutations in the TP63 gene, which encodes several transcription factors that control epidermal development and homeostasis. We generated induced pluripotent stem cells (iPSC) from AEC patients and corrected the TP63 mutations using genome editing tools. Three pairs of the resulting conisogenic iPSC lines were differentiated into keratinocytes (iPSC-K). We identified a significant downregulation of key components of hemidesmosomes and focal adhesions in AEC iPSC-K compared to their gene-corrected counterparts. Further, we demonstrated reduced iPSC-K migration, suggesting the possibility that a process critical for cutaneous wound healing might be impaired in AEC patients. Next, we generated chimeric mice expressing a TP63-AEC transgene and confirmed a downregulation of these genes in transgene-expressing cells in vivo. Finally, we also observed these abnormalities in AEC patient skin. Our findings suggest that integrin defects in AEC patients might weaken the adhesion of keratinocytes to the basement membrane. We propose that reduced expression of extracellular matrix adhesion receptors, potentially in conjunction with previously identified desmosomal protein defects, contribute to skin erosions in AEC.

The goal of this study was to investigate the molecular mechanisms responsible for the formation of skin erosions in patients affected by Ankyloblepharon‐ectodermal defects‐cleft lip/palate syndrome (AEC). This ectodermal dysplasia is caused by mutations in the TP63 gene, which encodes several transcription factors that control epidermal development and homeostasis. We generated induced pluripotent stem cells (iPSC) from AEC patients and corrected the TP63 mutations using genome editing tools. Three pairs of the resulting conisogenic iPSC lines were differentiated into keratinocytes (iPSC‐K). We identified a significant downregulation of key components of hemidesmosomes and focal adhesions in AEC iPSC‐K compared to their gene‐corrected counterparts. Further, we demonstrated reduced AEC iPSC‐K migration, suggesting the possibility that a process critical for cutaneous wound healing might be impaired in AEC patients. Next, we generated chimeric mice expressing a TP63‐AEC transgene and confirmed a downregulation of these genes in transgene‐expressing cells in vivo. Finally, we also observed these abnormalities in AEC patient skin. Our findings suggest that integrin defects in AEC patients might weaken the adhesion of keratinocytes to the basement membrane. We propose that reduced expression of extracellular matrix adhesion receptors, potentially in conjunction with previously identified desmosomal protein defects, contribute to skin erosions in AEC.