Kindler syndrome pathogenesis and fermitin family homologue 1 (kindlin-1) function

Identification of a novel FERMT1 variant causing kindler syndrome and a review of the clinical and molecular genetic features in Chinese patients

Background

Kindler Syndrome (KS, OMIM #173650), a rare autosomal recessive genetic disorder, is characterized by a spectrum of symptoms such as cutaneous fragility, blistering, photosensitivity, and mucosal involvement. These symptoms result from variations in the FERMT1 gene (Fermitin family member 1, OMIM: 607900), encoding kindlin-1, an essential component of focal adhesions.

Objective

This study aims to ascertain the potential pathogenicity of a FERMT1 variant identified in a Chinese patient and to explore the phenotypic and molecular genetic characteristics of all reported cases of Kindler Syndrome in the Chinese population.

Methods

Whole-exome sequencing (WES) was performed on the patient to identify candidate variants associated with KS, and Sanger sequencing was utilized to authenticate their presence and origin. To further assess the potential impact of these genetic variants, we employed a variety of in silico prediction tools. Concurrently, a review of various databases was undertaken to ascertain and consolidate information regarding cases of KS in Chinese families.

Results

We identified a novel likely pathogenic frameshift variant in the FERMT1 gene, specifically c.567_579delTATATATGACCCC (p.Ile190Serfs*10). The clinical presentation of this patient aligns with the diagnostic criteria for KS. The literature review reveals that the core clinical features of KS reported in the Chinese population include skin abnormalities (100%), as well as hyperkeratosis of the palms and soles (91.70%). Other clinical phenotypes encompass nail abnormalities (77.78%), abnormalities of the fingers/toes (75.00%), oral damage (70.00%), eye abnormalities (57.14%), and constipation (50.00%).

Conclusion

Our study enriches the genetic landscape of KS in the Chinese population and augments the understanding of phenotypic variability resulting from FERMT1 gene variants. The findings hold considerable significance for refining variant-based screening, genetic diagnosis, and comprehending the molecular pathogenesis underlying FERMT1-related disorders.

Dermoscopic Correlation of an Eccentric Case of Kindler Syndrome

Kindler syndrome (KS) is a rare autosomal recessive skin condition. The FERMT1 gene mutates and causes symptoms such as blistering and epidermal atrophy, as well as an increased risk of cancer and poor wound healing. A male in his 20s sought treatment for his hyper-hypopigmentation over the body with poikiloderma of the face with thin wrinkled cigarette paper skin in association with photosensitivity. He gave a history of developing blisters all over the body during his childhood, which formed raw areas and eventually healed forming atrophic scars. The objective is to assess the correlation of clinical findings with dermoscopy in a case of KS. KS is a rare disorder with poikiloderma, photosensitivity, and acral bullae in infancy as predominant features. Dermoscopy proves to be a useful tool in the diagnosis of this rare disorder as it helps in the identification of poikiloderma, adermatoglyphia, and cigarette paper scarring.

A tEMTing target? Clinical and experimental evidence for epithelial-mesenchymal transition in the progression of cutaneous squamous cell carcinoma (a scoping systematic review)

Cutaneous squamous cell carcinoma (cSCC) is a disease with globally rising incidence and poor prognosis for patients with advanced or metastatic disease. Epithelial-mesenchymal transition (EMT) is a driver of metastasis in many carcinomas, and cSCC is no exception. We aimed to provide a systematic overview of the clinical and experimental evidence for EMT in cSCC, with critical appraisal of type and quality of the methodology used. We then used this information as rationale for potential drug targets against advanced and metastatic cSCC. All primary literature encompassing clinical and cell-based or xenograft experimental studies reporting on the role of EMT markers or related signalling pathways in the progression of cSCC were considered. A screen of 3443 search results yielded 86 eligible studies comprising 44 experimental studies, 22 clinical studies, and 20 studies integrating both. From the clinical studies a timeline illustrating the alteration of EMT markers and related signalling was evident based on clinical progression of the disease. The experimental studies reveal connections of EMT with a multitude of factors such as genetic disorders, cancer-associated fibroblasts, and matrix remodelling via matrix metalloproteinases and urokinase plasminogen activator. Additionally, EMT was found to be closely tied to environmental factors as well as to stemness in cSCC via NFκB and β-catenin. We conclude that the canonical EGFR, canonical TGF-βR, PI3K/AKT and NFκB signalling are the four signalling pillars that induce EMT in cSCC and could be valuable therapeutic targets. Despite the complexity, EMT markers and pathways are desirable biomarkers and drug targets for the treatment of advanced or metastatic cSCC.

Focal adhesion molecule Kindlin-1 mediates activation of TGF-β signaling by interacting with TGF-βRI, SARA and Smad3 in colorectal cancer cells

Kindlin-1, an integrin-interacting protein, has been implicated in TGF-β/Smad3 signaling. However, the molecular mechanism underlying Kindlin-1 regulation of TGF-β/Smad3 signaling remains elusive. Here, we reported that Kindlin-1 is an important mediator of TGF-β/Smad3 signaling by showing that Kindlin-1 physically interacts with TGF-β receptor I (TβRI), Smad anchor for receptor activation (SARA) and Smad3. Kindlin-1 is required for the interaction of Smad3 with TβRI, Smad3 phosphorylation, nuclear translocation, and finally the activation of TGF-β/Smad3 signaling pathway. Functionally, Kindlin-1 promoted colorectal cancer (CRC) cell proliferation in vitro and tumor growth in vivo, and was also required for CRC cell migration and invasion via an epithelial to mesenchymal transition. Kindlin-1 was found to be increased with the CRC progression from stages I to IV. Importantly, raised expression level of Kindlin-1 correlates with poor outcome in CRC patients. Taken together, we demonstrated that Kindlin-1 promotes CRC progression by recruiting SARA and Smad3 to TβRI and thereby activates TGF-β/Smad3 signaling. Thus, Kindlin-1 is a novel regulator of TGF-β/Smad3 signaling and may also be a potential target for CRC therapeutics.

Kindlin-2 interacts with endothelial adherens junctions to support vascular barrier integrity

KEY POINTS

A reduction in Kindlin-2 levels in endothelial cells compromises vascular barrier function. Kindlin-2 is a previously unrecognized component of endothelial adherens junctions. By interacting directly and simultaneously with β- or γ-catenin and cortical actin filaments, Kindlin-2 stabilizes adherens junctions. The Kindlin-2 binding sites for β- and γ-catenin reside within its F1 and F3 subdomains. Although Kindlin-2 does not associate directly with tight junctions, its downregulation also destabilizes these junctions. Thus, impairment of both adherens and tight junctions may contribute to enhanced leakiness of vasculature in Kindlin-2^+/- mice.

ABSTRACT

Endothelial cells (EC) establish a physical barrier between the blood and surrounding tissue. Impairment of this barrier can occur during inflammation, ischaemia or sepsis and cause severe organ dysfunction. Kindlin-2, which is primarily recognized as a focal adhesion protein in EC, was not anticipated to have a role in vascular barrier. We tested the role of Kindlin-2 in regulating vascular integrity using several different approaches to decrease Kindlin-2 levels in EC. Reduced levels of Kindlin-2 in Kindlin-2^+/- mice aortic endothelial cells (MAECs) from these mice, and human umbilical ECs (HUVEC) treated with Kindlin-2 siRNA showed enhanced basal and platelet-activating factor (PAF) or lipopolysaccharide-stimulated vascular leakage compared to wild-type (WT) counterparts. PAF preferentially disrupted the Kindlin-2^+/- MAECs barrier to BSA and dextran and reduced transendothelial resistance compared to WT cells. Kindlin-2 co-localized and co-immunoprecipitated with vascular endothelial cadherin-based complexes, including β- and γ-catenin and actin, components of adherens junctions (AJ). Direct interaction of Kindlin-2 with β- and γ-catenin and actin was demonstrated in co-immunoprecipitation and surface plasmon resonance experiments. In thrombin-stimulated HUVECs, Kindlin-2 and cortical actin dissociated from stable AJs and redistributed to radial actin stress fibres of remodelling focal AJs. The β- and γ-catenin binding site resides within the F1 and F3 subdomains of Kindlin-2 but not the integrin binding site in F3. These results establish a previously unrecognized and vital role of Kindlin-2 with respect to maintaining the vascular barrier by linking Vascuar endothelial cadherin-based complexes to cortical actin and thereby stabilizing AJ.

The integrin adhesome: from genes and proteins to human disease

The adhesive interactions of cells with their environment through the integrin family of transmembrane receptors have key roles in regulating multiple aspects of cellular physiology, including cell proliferation, viability, differentiation and migration. Consequently, failure to establish functional cell adhesions, and thus the assembly of associated cytoplasmic scaffolding and signalling networks, can have severe pathological effects. The roles of specific constituents of integrin-mediated adhesions, which are collectively known as the 'integrin adhesome', in diverse pathological states are becoming clear. Indeed, the prominence of mutations in specific adhesome molecules in various human diseases is now appreciated, and experimental as well as in silico approaches provide insights into the molecular mechanisms underlying these pathological conditions.

Sporadic Kindler syndrome with a novel mutation

We report the case of a 28-year-old woman with Kindler syndrome, a rare form of epidermolysis bullosa. Clinically, since childhood, she had widespread pigmentary changes in her skin as well as photosensitivity and fragility of the skin and mucous membranes. The mucosal involvement led to an erosive stomatitis as well as esophageal, anal and vaginal stenoses, requiring surgical intervention. The diagnosis of Kindler syndrome was confirmed by DNA sequencing with compound heterozygosity for a nonsense/frameshift combination of mutations (p.Arg110X; p.Ala289GlyfsX7) in the FERMT1 gene.

Integrative analysis of multiple cancer genomic datasets under the heterogeneity model

In the analysis of cancer studies with high-dimensional genomic measurements, integrative analysis provides an effective way of pooling information across multiple heterogeneous datasets. The genomic basis of multiple independent datasets, which can be characterized by the sets of genomic markers, can be described using the homogeneity model or heterogeneity model. Under the homogeneity model, all datasets share the same set of markers associated with responses. In contrast, under the heterogeneity model, different studies have overlapping but possibly different sets of markers. The heterogeneity model contains the homogeneity model as a special case and can be much more flexible. Marker selection under the heterogeneity model calls for bi-level selection to determine whether a covariate is associated with response in any study at all as well as in which studies it is associated with responses. In this study, we consider two minimax concave penalty-based penalization approaches for marker selection under the heterogeneity model. For each approach, we describe its rationale and an effective computational algorithm. We conduct simulations to investigate their performance and compare with the existing alternatives. We also apply the proposed approaches to the analysis of gene expression data on multiple cancers.

Evaluation and treatment of the newborn with epidermolysis bullosa

Epidermolysis bullosa (EB) is a heterogeneous group of inherited skin diseases characterized by increased skin fragility and variable degrees of extracutaneous involvement. The clinical spectrum ranges from localized skin disease to a life-threatening and disabling disease with extensive extracutaneous involvement. All four major types of EB, namely EB simplex, Junctional EB, Dystrophic EB and Kindler syndrome, can present with blistering and erosions at birth and cannot be distinguished clinically in the newborn period. The extensive differential diagnosis of blistering and erosions in the neonate must be considered and common etiologies ruled out. The diagnosis of EB can be confirmed via a skin biopsy for immunoflourescence mapping. This review discusses the four major subtypes of EB and their associated extracutaneous features. The evaluation of a newborn suspected of having EB, including diagnosis and management, is also reviewed.

Photosensitivity disorders in children: part II

Photosensitivity disorders in children encompass a diverse group of diseases. Some inherited disorders manifest with photosensitivity early in life. Specific extracutaneous association may be the clue to diagnosis in this group of pediatric photodermatoses. Part II of this 2-part review covers hereditary photodermatoses caused by defects in nucleotide excision repair, double strand break repair, or localized or systemic biochemical abnormalities. Diagnosis and management of photoaggravated dermatoses are also discussed. Sun protection strategies are required in all patients with evidence of photosensitivity. Early recognition and prompt diagnosis is essential to minimize the long-term complications associated with inadequate photoprotection.

Ultrastructure and molecular pathogenesis of epidermolysis bullosa

Epidermolysis bullosa (EB) is classified into the three major subtypes depending on the level of skin cleavage within the epidermal keratinocyte or basement membrane zone. Tissue separation occurs within the intraepidermal cytoplasm of the basal keratinocyte, through the lamina lucida, or in sublamina densa regions of the basal lamina (basement membrane) in EB simplex, junctional EB, and dystrophic EB, respectively. Transmission electron microscopy (TEM) is an effective method for determining the level of tissue separation and hemidesmosome (HD) and anchoring fibril morphology if performed by experienced operators, and has proven to be a powerful technique for the diagnosis of new EB patients. Recent advances in genetic and immunofluorescence studies have enabled us to diagnose EB more easily and with greater accuracy. This contribution reviews TEM findings in the EB subtypes and discusses the importance of observations in the molecular morphology of HD and basement membrane associated structures.

Reconstruction of integrin activation

Integrins are integral membrane proteins that mediate cell-matrix and cell-cell adhesion. They are important for vascular development and hematopoiesis, immune and inflammatory responses, and hemostasis. Integrins are also signaling receptors that can transmit information bidirectionally across plasma membranes. Research in the past 2 decades has made progress in unraveling the mechanisms of integrin signaling and brings the field to the moment of attempting synthetic reconstruction of the signaling pathways in vitro. Reconstruction of biologic processes provides stringent tests of our understanding of the process, as evidenced by studies of other biologic machines, such as ATP synthase, lactose permease, and G-protein-coupled receptors. Here, we review recent progress in reconstructing integrin signaling and the insights that we have gained through these experiments.

[Kindler syndrome: clinical and ultra-structural particularities, a propos of three cases]

INTRODUCTION

Kindler's syndrome is a rare type of genetic skin condition belonging to the class of bullous poikilodermia. We report three new sibling cases of this rare syndrome.

CASES REPORTS

The condition was seen in three sisters aged 12, 16 and 20 years, born of a first-degree consanguineous marriage with no family history of Kindler's syndrome. The three patients presented spontaneously regressive bullous eruptions, poikilodermia of gradual onset, major cutaneous atrophy on the back of the hands and the feet, photosensitivity and gingival hypertrophy. Electron microscopy examination of poikilodermic skin showed normal anchoring filaments and intraepidermal cleavage.

DISCUSSION

Diagnosis of Kindler's syndrome is based upon clinical evidence. Kidler's syndrome is a well defined clinical entity. Ultra-structural studies show intraepidermal, junctional, and dermal cleavage. This syndrome must be differentiated from congenital epidermolysis bullosa, Weary's syndrome, and other bullous hereditary poikilodermas.