Localization and potential function of kindlin-1 in periodontal tissues

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.

Cell Junctions in Periodontal Health and Disease: An Insight

Cells are the building blocks of all living organisms. The presence of cell junctions such as tight junctions, gap junctions, and anchoring junctions between cells play a role in cell-to-cell communication in periodontal health and disease. A literature search was done in Scopus, PubMed, and Web of Science to gather information about the effect of cell junctions on periodontal health and disease. The presence of tight junction in the oral cavity helps in cell-to-cell adhesiveness and assists in the barrier function. The gap junctions help in controlling growth and development and in the cell signaling process. The presence of desmosomes and hemidesmosomes as anchoring junctions aid in mechanical strength and tissue integrity. Periodontitis is a biofilm-induced disease leading to the destruction of the supporting structures of the tooth. The structures of the periodontium possess multiple cell junctions that play a significant role in periodontal health and disease as well as periodontal tissue healing. This review article provides an insight into the role of cell junctions in periodontal disease and health, and offers concepts for development of therapeutic strategies through manipulation of cell junctions.

Migfilin: Cell Adhesion Effect and Comorbidities

Cell adhesion manifests as cell linkages to neighboring cells and/or the extracellular matrix (ECM). Migfilin is a widely expressed adhesion protein. It comprises three LIM domains in the C-terminal region and one proline-rich sequence in the N-terminal region. Through interplay with its various binding partners, such as Kindlin-2, Filamin, vasodilator-stimulated phosphoprotein (VASP) protein and the transcription factor CSX, Migfilin facilitates the dynamic association of connecting actomyosin fibers, orchestrating cell morphogenetic movement and cell adhesion, proliferation, migration, invasion, differentiation and signal transduction. In this review, to further elucidate the functional contributions of and pathogenesis induced by Migfilin, we focused on the structure of Migfilin and the targets which it directly binds with. We also summarized the role of Migfilin and its binding partners in the progression of different diseases and malignancies. As a possible candidate for coordinating various cellular processes and because of its association with both the pathogenesis and progression of certain tumors, Migfilin likely has utility as a therapeutic target against multiple diseases in the clinic.

Rare Genetic Disorders Affecting the Periodontal Supporting Tissues in Adolescence

In adolescents periodontal destruction may be the primary manifestation of an as yet unrecognized rare systemic disease, and it may be up to the periodontist to make the correct tentative diagnosis. Many genetic diseases that present with primary periodontal manifestations in adolescence affect immune function, sometimes with only mild or absent systemic features. They include periodontal Ehlers-Danlos syndrome (lack of attached gingiva, various connective tissue abnormalities), Papillon-Lefèvre syndrome (palmoplantar hyperkeratosis), and plasminogen deficiency (fibrin deposition within mucous membranes). Other immune disorders with severe periodontitis manifesting in adolescence are usually diagnosed in early childhood due to unmistakeable systemic features. They include Cohen syndrome (developmental disorder, truncal obesity, and microcephaly), Hermansky-Pudlak Syndrome (oculocutaneous albinism, bleeding diathesis, and other systemic manifestations), glycogen storage disease type 1b, and Chediak-Higashi syndrome (pyogenic infections, albinism, and neuropathy). The structural integrity of periodontal tissue is affected in genodermatoses such as Kindler syndrome, a type of epidermolysis bullosa. In primary hyperoxaluria, inflammatory periodontal destruction is associated with renal calculi. Breakdown of periodontal tissues independent of dental plaque biofilm-induced periodontitis is found in hypophosphatasia (highly variable skeletal hypomineralization) or isolated odontohypophosphatasia, hypophosphatemic rickets and primary hyperparathyroidism. Finally, alveolar osteolysis mimicking localized periodontitis may be due to neoplastic processes, e.g., in neurofibromatosis type 1 (typical skin features including café au lait macules and neurofibromas), Langerhans cell histiocytosis (locally destructive proliferation of bone marrow-derived immature myeloid dendritic cells), and Gorham-Stout disease (diffuse cystic angiomatosis of bone).

Periodontal Manifestation in a Patient with Kindler Syndrome

Kindler syndrome is a rare subtype of inherited epidermolysis bullosa. A 42-year-old female patient was admitted to our clinic with a complaint of tooth mobility. Multiple hypo- and hyperpigmented macules dissipated all over her body, prominent poikilodermatous changes, xerosis of the skin, and atrophy were seen in the clinical extraoral examination. Intraoral examination showed atrophy of the buccal mucosa, limited oral opening, epidermal tissue easily separated from the connective tissue, painful ulcers of the hard palate, severe periodontitis, and keratosis of the lips. All of the teeth showed mobility. After dermatologist consultation, the diagnosis of the patient was clinically identified as “Kindler syndrome.” All of her teeth were extracted due to her progressive periodontal disease and late admission to our clinic. Periodontal treatment might be effective in treating and controlling oral symptoms related to the syndrome and in improving the patient's quality of life.

Metabolic syndrome and masticatory hypofunction: a cross-sectional study

The objective of this paper is to clarify the rate of abdominal obesity (AO), waist-to-height ratio (WHtR), metabolic syndrome (MetS) and determine the relationship with the masticatory capacity (MC) in terms of total functional tooth units (t-FTU) in a representative sample of older Spanish adults. This cross-sectional study included 544 adult subjects aged 50 or over, who were prospectively selected and who had participated in a survey conducted in a primary dental care service in a Public Oral Health Service in Spain. Anthropometric, clinical variables and t-FTUs were obtained through a calibrated and well-established protocol. Univariate and multivariate binary and multinomial logistic regression analyses were developed. With regards to the t-FTU or MC, it was poor in 60.3%, good in 17.6%, and complete in 22.1% of the sample. The univariate odss ratio (OR) for MetS and AO increased as the MC decreased and as the age group increased. With regards to gender, women presented with an OR of 5.56 (CI 95% 3.70-8.38). With regards to the WHtR-a3 (WHtR grouped into three categories), the univariate ORs were all significant for morbid obesity compared to the healthy group, with a risk of 6.86 (CI 95% 3.23-14.58) for patients with poor MC compared to those with complete MC. Masticatory hypofunctionality could be associated with the presence of MetS. Clinical relevance: The number of t-FTUs is directly related to AO.

Manifestations of systemic diseases and conditions that affect the periodontal attachment apparatus: Case definitions and diagnostic considerations

OBJECTIVES

This review proposes case definitions and diagnostic considerations of systemic disorders and conditions that affect the periodontal attachment apparatus.

IMPORTANCE

Periodontal diseases and certain systemic disorders share similar genetic and/or environmental etiological factors, and affected patients may show manifestations of both diseases. Characterizing these diseases and the nature of the association between them could have important diagnostic value and therapeutic implications for patients.

FINDINGS

Numerous systemic disorders and certain medications can affect the periodontal attachment apparatus and cause loss of periodontal attachment and alveolar bone. Although many of these disorders are rare or uncommon, they often cause significant loss of periodontal tissue by influencing periodontal inflammation or through mechanisms distinct from periodontitis. Most of these disorders are due to innate mechanisms and some are acquired via environmental factors or lifestyle. Several disorders affect periodontal inflammation through alterations in the host immune response to periodontal infection; others cause defects in the gingiva or periodontal connective tissue, instigate metabolic changes in the host that affect various tissues of the periodontal apparatus, or operate by other mechanisms. For some systemic disorders that are more common, their contribution to the loss of periodontal tissue is modest, while for others, contribution is not supported by clear evidence. Few systemic medications are associated with increased loss of periodontal tissue, and these are typically medications used in the treatment of malignancies.

CONCLUSIONS

This review identifies systemic diseases and conditions that can affect the periodontal attachment apparatus and cause loss of periodontal supporting tissues and, where possible, presents case definitions for these. Many of these diseases are associated with a profound loss of periodontal attachment and alveolar bone, and for some of these disorders the periodontal manifestations may be among the first signs of the disease. These case definitions may be useful in the early diagnosis of these diseases and may contribute to an improvement in the management of periodontal manifestations and improve the quality of life for these patients.

Assessment of the risk and characterization of non-melanoma skin cancer in Kindler syndrome: study of a series of 91 patients

BACKGROUND

Kindler Syndrome (KS) is a rare genodermatosis characterized by skin fragility, skin atrophy, premature aging and poikiloderma. It is caused by mutations in the FERMT1 gene, which encodes kindlin-1, a protein involved in integrin signalling and the formation of focal adhesions. Several reports have shown the presence of non-melanoma skin cancers in KS patients but a systematic study evaluating the risk of these tumors at different ages and their potential outcome has not yet been published. We have here addressed this condition in a retrospective study of 91 adult KS patients, characterizing frequency, metastatic potential and body distribution of squamous cell carcinoma (SCC) in these patients. SCC developed in 13 of the 91 patients.

RESULTS

The youngest case arose in a 29-year-old patient; however, the cumulative risk of SCC increased to 66.7% in patients over 60 years of age. The highly aggressive nature of SCCs in KS was confirmed showing that 53.8% of the patients bearing SCCs develop metastatic disease. Our data also showed there are no specific mutations that correlate directly with the development of SCC; however, the mutational distribution along the gene appears to be different in patients bearing SCC from SCC-free patients. The body distribution of the tumor appearance was also unique and different from other bullous diseases, being concentrated in the hands and around the oral cavity, which are areas of high inflammation in this disease.

CONCLUSIONS

This study characterizes SCCs in the largest series of KS patients reported so far, showing the high frequency and aggressiveness of these tumors. It also describes their particular body distribution and their relationship with mutations in the FERMT-1 gene. These data reinforce the need for close monitoring of premalignant or malignant lesions in KS patients.

Kindler syndrome with palmoplantar hyperhidrosis and blonde hair

Kindler syndrome (KS) is a very rare genodermatosis characterized by acral blistering starting in infancy along with photosensitivity, progressive poikiloderma, cutaneous atrophy, and a variable degree of mucosal involvement. A large number of other cutaneous and extracutaneous features have been described, which aid in diagnosing it. Generally KS has been found to be associated with hypohidrosis/anhidrosis. We herein present a rare case of KS with unique features.

Effect of maternal periodontitis and low birth weight--a case control study

INTRODUCTION

Since the 1990s, evidence has been raised that there is an association between maternal periodontal disease and undesirable gestational events, for example low birth weight; this issue is controversial.

OBJECTIVE

To evaluate whether there is an association between maternal periodontitis and low birth weight (LBW).

METHODS

A case-control study was carried out on 951 mothers that had been cared for by the Brazilian Unified Health System in Petrolina-PE and Juazeiro-BA, Brazil. The case group (n = 269) consisted of mothers of newborns with birth weight <2500 g and a control group (n = 682) of mothers of newborns with birth weight ≥2500 g. An interview was realized, using a questionnaire as well as a full mouth examination to diagnose the periodontal condition. Women who had at least four teeth with probing depth ≥4 mm and clinical attachment loss ≥3 mm, with bleeding on probing at the same site, were diagnosed with periodontitis. The birth weight was obtained through the hospital book record. The main association was evaluated using the multivariate regression model, considering confounders.

RESULTS

The frequency of periodontitis was 16.4% (case group) and 17.4% (control group). Periodontitis did not show an association with LBW (ORcrude = 0.92; 95% CI = 0.63-1.35), even after adjustment for the following confounders: maternal age, pre-gestational body mass index, number of pre-natal consultations, number of pregnancies, maternal schooling level, smoking habit during pregnancy and hypertension (ORadjusted = 1.00; 95% CI = 0.61-1.68).

CONCLUSION

The findings of this study showed no association between maternal periodontal disease and low birth weight, even after appropriate adjustments for confounding factors.

FERMT1 promoter mutations in patients with Kindler syndrome

Mutations in the FERMT1 gene, encoding the focal adhesion protein kindlin-1 underlie the Kindler syndrome (KS), an autosomal recessive skin disorder with a phenotype comprising skin blistering, photosensitivity, progressive poikiloderma with extensive skin atrophy, and propensity to skin cancer. The FERMT1 mutational spectrum comprises gross genomic deletions, splice site, nonsense, and frameshift mutations, which are scattered over the coding region spanning exon 2-15. We now report three KS families with mutations affecting the promoter region of FERMT1. Two of these mutations are large deletions (∼38.0 and 1.9 kb in size) and one is a single nucleotide variant (c.-20A>G) within the 5' untranslated region (UTR). Each mutation resulted in loss of gene expression in patient skin or cultured keratinocytes. Reporter assays showed the functional relevance of the genomic regions deleted in our patients for FERMT1 gene transcription and proved the causal role of the c.-20A>G variant in reducing transcriptional activity.

Diverse functions of kindlin/fermitin proteins during embryonic development in Xenopus laevis

The kindlin/fermitin family includes three proteins involved in regulating integrin ligand-binding activity and adhesion. Loss-of-function mutations in kindlins1 and 3 have been implicated in Kindler Syndrome and Leukocyte Adhesion Deficiency III (LAD-III) respectively, whereas kindlin2 null mice are embryonic lethal. Post translational regulation of cell-cell and cell-ECM adhesion has long been presumed to be important for morphogenesis, however, few specific examples of activation-dependent changes in adhesion molecule function in normal development have been reported. In this study, antisense morpholinos were used to reduce expression of individual kindlins in Xenopus laevis embryos in order to investigate their roles in early development. Kindlin1 knockdown resulted in developmental delays, gross malformations of the gut and eventual lethality by tadpole stages. Kindlin2 morphant embryos displayed late stage defects in vascular maintenance and angiogenic branching consistent with kindlin2 loss of function in the mouse. Antisense morpholinos were also used to deplete maternal kindlin2 protein in oocytes and eggs. Embryos lacking maternal kindlin2 arrested at early cleavage stages due to failures in cytokinesis. Kindlin3 morphant phenotypes included defects in epidermal ciliary beating and partial paralysis at tailbud stages but these embryos recovered eventually as morpholino levels decayed. These results indicate a remarkably diverse range of kindlin functions in vertebrate development.

Kindlin binds migfilin tandem LIM domains and regulates migfilin focal adhesion localization and recruitment dynamics

Focal adhesions (FAs), sites of tight adhesion to the extracellular matrix, are composed of clusters of transmembrane integrin adhesion receptors and intracellular proteins that link integrins to the actin cytoskeleton and signaling pathways. Two integrin-binding proteins present in FAs, kindlin-1 and kindlin-2, are important for integrin activation, FA formation, and signaling. Migfilin, originally identified in a yeast two-hybrid screen for kindlin-2-interacting proteins, is a LIM domain-containing adaptor protein found in FAs and implicated in control of cell adhesion, spreading, and migration. By binding filamin, migfilin provides a link between kindlin and the actin cytoskeleton. Here, using a combination of kindlin knockdown, biochemical pulldown assays, fluorescence microscopy, fluorescence resonance energy transfer (FRET), and fluorescence recovery after photobleaching (FRAP), we have established that the C-terminal LIM domains of migfilin dictate its FA localization, shown that these domains mediate an interaction with kindlin in vitro and in cells, and demonstrated that kindlin is important for normal migfilin dynamics in cells. We also show that when the C-terminal LIM domain region is deleted, then the N-terminal filamin-binding region of the protein, which is capable of targeting migfilin to actin-rich stress fibers, is the predominant driver of migfilin localization. Our work details a correlation between migfilin domains that drive kindlin binding and those that drive FA localization as well as a kindlin dependence on migfilin FA recruitment and mobility. We therefore suggest that the kindlin interaction with migfilin LIM domains drives migfilin FA recruitment, localization, and mobility.

Epithelial integrins with special reference to oral epithelia

Adhesion of epithelium to the extracellular matrix is crucial for the maintenance of systemic and oral health. In the oral cavity, teeth or artificial dental implants penetrate the soft tissue of the gingiva. In this interface, gingival soft tissue needs to be well attached via the epithelial seal to the tooth or implant surface to maintain health. After injury or wounding, epithelial tissue rapidly migrates to form the initial epithelial cover to restore the barrier against infection. These events are crucially dependent on deposition of extracellular matrix and proper activation and function of integrin receptors in the epithelial cells. Recent experimental evidence suggests that epithelial integrins also participate in the regulation of periodontal inflammation. In this review, we will discuss the structure and function of epithelial integrins and their extracellular ligands and elaborate on their potential role in disease and repair processes in the oral cavity.

Kindler syndrome: extension of FERMT1 mutational spectrum and natural history

Mutations in the FERMT1 gene (also known as KIND1), encoding the focal adhesion protein kindlin-1, underlie the Kindler syndrome (KS), an autosomal recessive skin disorder with an intriguing progressive phenotype comprising skin blistering, photosensitivity, progressive poikiloderma with extensive skin atrophy, and propensity to skin cancer. Herein we review the clinical and genetic data of 62 patients, and delineate the natural history of the disorder, for example, age at onset of symptoms, or risk of malignancy. Although most mutations are predicted to lead to premature termination of translation, and to loss of kindlin-1 function, significant clinical variability is observed among patients. There is an association of FERMT1 missense and in-frame deletion mutations with milder disease phenotypes, and later onset of complications. Nevertheless, the clinical variability is not fully explained by genotype-phenotype correlations. Environmental factors and yet unidentified modifiers may play a role. Better understanding of the molecular pathogenesis of KS should enable the development of prevention strategies for disease complications.

Induction of type XVI collagen expression facilitates proliferation of oral cancer cells

Type XVI collagen belongs to the family of fibril-associated collagens with interrupted triple helices (FACIT). Recently, high affinity to integrin alpha1beta1 has been shown allowing cells expressing those integrins to attach and spread on recombinant type XVI collagen. Here, we show that type XVI collagen is overexpressed in dysplastic areas of mucosal epithelium from oral squamous cell carcinoma (OSCC) patients. Induction of its expression in OSCC cell lines (COLXVI cells) leads to an increased expression of Kindlin-1. Moreover, we demonstrate a significantly increased Kindlin-1/beta1-integrin interaction. Additionally, we detected a higher number of activated beta1-integrins in COLXVI cells and found a neo-expression of alpha1 integrin subunit on these cells. FACS analysis revealed a significantly higher amount of COLXVI cells in S-phase and G2/M-phase 6h after synchronisation leading to a markedly higher proliferation activity. Blocking beta1-integrins with a specific antibody resulted in reduced proliferation of COLXVI cells. In summary, we demonstrate that overexpression of type XVI collagen in aberrant oral keratinocytes leads to Kindlin-1 induction, increased Kindlin-1/beta1-integrin interaction, integrin activation and subsequently to a proliferative cellular phenotype.