Forty-two novel COL7A1 mutations and the role of a frequent single nucleotide polymorphism in the MMP1 promoter in modulation of disease severity in a large European dystrophic epidermolysis bullosa cohort

Descriptive Study of the Clinical and Molecular Features of Epidermolysis Bullosa Patients in a Romanian European Reference Network-Skin Affiliated Reference Center

BACKGROUND

During the last 10 years, in Romania, progress has been made for the welfare of patients suffering from epidermolysis bullosa (EB). In five university hospitals, affiliated with the National Program for the Treatment of Rare Diseases, highly trained specialists diagnose and treat patients with this rare condition. Regarding diagnosis, limitations still exist as immunofluorescence mapping and molecular genetic analysis are not accessible, and generally not reimbursed. Our objective is to present the experience in diagnosing EB patients at Colentina Clinical Hospital, highlighting genotype-phenotype correlations observed in our cohort of patients.

METHODS

The records of the patients enrolled between 2012 and 2024 were analyzed considering clinical aspects, and, when available, immunofluorescence mapping, transmission electron microscopy, and genetic molecular analysis.

RESULTS

Fifty-six patients were identified, of whom 31 cases were of dystrophic EB, three were of junctional EB, and 11 were of simplex EB. For 11 cases, the EB type could not be determined. Regarding EB simplex, two patients with KRT5 mutations and three patients with KRT14 mutations with various clinical expressions, from mild phenotype to severe forms, were identified. Three severe junctional EB patients were registered in our database and for one of the patients, two previously unreported mutations in the LAMA3 gene were identified. Regarding dystrophic EB, 31 cases were identified, of which 25 were recessive dystrophic cases and six were dominant dystrophic cases. Molecular genetic testing was performed for 15 patients, and the most common variant was c.425A>G, identified in six cases.

DISCUSSIONS

Two previously unreported mutations were identified, namely, COL7A1 c.5416G>C, a heterozygous missense variant in a patient with a mild phenotype, mainly with nail involvement, and COL7A1 c.5960del, a variant that generates a frameshift in exon 72 resulting in a premature stop codon; this variant was identified in two siblings with a severe recessive dystrophic.

CONCLUSION

Important steps have been made in identifying the correct and complete diagnosis, as well as the characterization of EB patients addressing our reference center. The findings underscore the pivotal role of molecular genetic testing in confirming diagnoses and elucidating inheritance patterns, especially in cases with atypical presentations or de novo mutations.

Dystonin modifiers of junctional epidermolysis bullosa and models of epidermolysis bullosa simplex without dystonia musculorum

The Lamc2jeb junctional epidermolysis bullosa (EB) mouse model has been used to demonstrate that significant genetic modification of EB symptoms is possible, identifying as modifiers Col17a1 and six other quantitative trait loci, several with strong candidate genes including dystonin (Dst/Bpag1). Here, CRISPR/Cas9 was used to alter exon 23 in mouse skin specific isoform Dst-e (Ensembl GRCm38 transcript name Dst-213, transcript ID ENSMUST00000183302.5, protein size 2639AA) and validate a proposed arginine/glutamine difference at amino acid p1226 in B6 versus 129 mice as a modifier of EB. Frame shift deletions (FSD) in mouse Dst-e exon 23 (Dst-eFSD/FSD) were also identified that cause mice carrying wild-type Lamc2 to develop a phenotype similar to human EB simplex without dystonia musculorum. When combined, Dst-eFSD/FSD modifies Lamc2jeb/jeb (FSD+jeb) induced disease in unexpected ways implicating an altered balance between DST-e (BPAG1e) and a rarely reported rodless DST-eS (BPAG1eS) in epithelium as a possible mechanism. Further, FSD+jeb mice with pinnae removed are found to provide a test bed for studying internal epithelium EB disease and treatment without severe skin disease as a limiting factor while also revealing and accelerating significant nasopharynx symptoms present but not previously noted in Lamc2jeb/jeb mice.

Clinical and allelic heterogeneity in dystrophic epidermolysis bullosa- lessons from an Indian cohort

BACKGROUND

Dystrophic epidermolysis bullosa (DEB) is due to variation in the COL7A1 gene. The clinical phenotype and severity depends on the type of variation and domain of the affected protein.

OBJECTIVES

To characterize the spectrum of COL7A1 variations in a cohort of DEB patients from India, to correlate these findings with clinical phenotypes and to establish a genotype-phenotype correlation.

METHODS

This was a retrospective, observational study involving patients with DEB diagnosed on the basis of clinical manifestations, Immuno-fluorescence antigen mapping (IFM) and genetic analysis. A genotype-phenotype correlation was attempted and observations were further explained using IFM on skin biopsies and molecular dynamic simulations. Descriptive statistics were performed using SPSS version 20.0 with P values of <0.05 considered significant.

RESULTS

We report 68 unrelated Indian DEB patients classified as RDEB-Intermediate (RDEB-I), RDEB-Severe (RDEB-S) or DDEB based on the EB diagnostic matrix, immunofluorescence antigen mapping and genetic data. Of 68 DEB patients, 59 (86.76%) were inherited in a recessive pattern (RDEB) and 9 (13.24%) in a dominant pattern (DDEB). Limbal stem cell deficiency was seen in four cases of RDEB-S very early in the course of the disease. A total of 88 variants were detected of which 66 were novel. There were no hotspots and recurrent variations were seen in a very small group of patients. We found a high frequency of compound heterozygotes (CH) in RDEB patients born out of non-consanguineous marriage. RDEB patients older than two years who had oral mucosal involvement, and/or deformities, were more likely to have esophageal involvement. Genotype phenotype correlation showed a higher frequency of extracutaneous manifestations and deformities in patients with Premature Termination Codons (PTCs) than in patients with other variations. Molecular simulation studies in patients with missense mutations showed severe phenotype when they were localized in interrupted regions of GLY-X-Y repeats.

CONCLUSION

This large study of DEB patients in South Asia adds to the continually expanding genetic database of this condition. This study has direct implications on management as this group of patients can be screened early and managed appropriately.

Seven naturally variant loci serve as genetic modifiers of Lamc2jeb induced non-Herlitz junctional Epidermolysis Bullosa in mice

Epidermolysis Bullosa (EB) is a group of rare genetic disorders that compromise the structural integrity of the skin such that blisters and subsequent erosions occur after minor trauma. While primary genetic risk of all subforms of EB adhere to Mendelian patterns of inheritance, their clinical presentations and severities can vary greatly, implying genetic modifiers. The Lamc2jeb mouse model of non-Herlitz junctional EB (JEB-nH) demonstrated that genetic modifiers can contribute substantially to the phenotypic variability of JEB and likely other forms of EB. The innocuous changes in an 'EB related gene', Col17a1, have shown it to be a dominant modifier of Lamc2jeb. This work identifies six additional Quantitative Trait Loci (QTL) that modify disease in Lamc2jeb/jeb mice. Three QTL include other known 'EB related genes', with the strongest modifier effect mapping to a region including the epidermal hemi-desmosomal structural gene dystonin (Dst-e/Bpag1-e). Three other QTL map to intervals devoid of known EB-associated genes. Of these, one contains the nuclear receptor coactivator Ppargc1a as its primary candidate and the others contain related genes Pparg and Igf1, suggesting modifier pathways. These results, demonstrating the potent disease modifying effects of normally innocuous genetic variants, greatly expand the landscape of genetic modifiers of EB and therapeutic approaches that may be applied.

Recessive Dystrophic Epidermolysis bullosa due to Hemizygous 40 kb Deletion of COL7A1 and the Proximate PFKFB4 Gene Focusing on the Mutation c.425A>G Mimicking Homozygous Status

Background: Dystrophic Epidermolysis bullosa (DEB) is a rare inherited mechanobullous disease characterised by the hyperfragility of the skin and mucous membranes. It is (typically) caused by (loss-of-function) mutations in the COL7A1 gene that impair the formation of collagen type VII, which represents the major constituent of anchoring fibrils within the basement membrane zone of epithelialised tissues. In a 4-year-old patient diagnosed with the clinical features of recessive DEB, genotyping via Next-Generation EB Panel Sequencing initially revealed the homozygosity of the maternal c.425A>G mutation, while the paternal heterozygosity in exon 3 was lacking. This genetic profile suggested incongruent gene transmission due to uniparental isodisomy (UPD) or the occurrence of a hemizygous deletion of unknown size. Methods: Thus, the EB panel sequencing of genomic DNA, followed by a paternity test and analysis of microsatellite markers, as well as multiplex ligation-dependent probe amplification (MLPA) copy number analysis using patient and parental DNA, were performed. Results: This approach revealed a paternally derived hemizygous deletion spanning from exon 3 to exon 118. Linear amplification-mediated PCR (LAM-PCR) determined the breaking points within intron 2 of the COL7A1 gene, comprising a 40kb segment within intron 1 of the adjacent PFKFB4 gene. Conclusion: This report highlights the relevance of advanced molecular profiling to determine new/exceptional/unusual genotypes and the accurate mode of genetic transmission in DEB.

Matrikines as mediators of tissue remodelling

Extracellular matrix (ECM) proteins confer biomechanical properties, maintain cell phenotype and mediate tissue repair (via release of sequestered cytokines and proteases). In contrast to intracellular proteomes, where proteins are monitored and replaced over short time periods, many ECM proteins function for years (decades in humans) without replacement. The longevity of abundant ECM proteins, such as collagen I and elastin, leaves them vulnerable to damage accumulation and their host organs prone to chronic, age-related diseases. However, ECM protein fragmentation can potentially produce peptide cytokines (matrikines) which may exacerbate and/or ameliorate age- and disease-related ECM remodelling. In this review, we discuss ECM composition, function and degradation and highlight examples of endogenous matrikines. We then critically and comprehensively analyse published studies of matrix-derived peptides used as topical skin treatments, before considering the potential for improvements in the discovery and delivery of novel matrix-derived peptides to skin and internal organs. From this, we conclude that while the translational impact of matrix-derived peptide therapeutics is evident, the mechanisms of action of these peptides are poorly defined. Further, well-designed, multimodal studies are required.

Cas9-guided haplotyping of three truncation variants in autosomal recessive disease

An autosomal recessive disease is caused by biallelic loss-of-function mutations. However, when more than two disease-causing variants are found in a patient's gene, it is challenging to determine which two of the variants are responsible for the disease phenotype. Here, to decipher the pathogenic variants by precise haplotyping, we applied nanopore Cas9-targeted sequencing (nCATS) to three truncation COL7A1 variants detected in a patient with recessive dystrophic epidermolysis bullosa (EB). The distance between the most 5' and 3' variants was approximately 19 kb at the level of genomic DNA. nCATS successfully demonstrated that the most 5' and 3' variants were located in one allele while the variant in between was located in the other allele. Interestingly, the proband's mother, who was phenotypically intact, was heterozygous for the allele that harbored the two truncation variants, which could otherwise be misinterpreted as those of typical recessive dystrophic EB. Our study highlights the usefulness of nCATS as a tool to determine haplotypes of complicated genetic cases. Haplotyping of multiple variants in a gene can determine which variant should be therapeutically targeted when nucleotide-specific gene therapy is applied. This article is protected by copyright. All rights reserved.

Availability of mRNA Obtained from Peripheral Blood Mononuclear Cells for Testing Mutation Consequences in Dystrophic Epidermolysis Bullosa

Dystrophic epidermolysis bullosa (DEB) is an inheritable blistering disease caused by mutations in COL7A1, which encodes type VII collagen. To address the issue of genotype-phenotype correlations in DEB, analyzing the consequences of COL7A1 mutations using mRNA is indispensable. Herein we established a novel method for testing the effect of mutations in DEB using COL7A1 mRNA extracted from peripheral blood mononuclear cells (PBMCs). We investigated the consequences of four COL7A1 mutations (c.6573 + 1G > C, c.6216 + 5G > T, c.7270C > T and c.2527C > T) in three Japanese individuals with recessive DEB. The novel method detected the consequences of two recurrent COL7A1 mutations (c.6573 + 1G > C, c.6216 + 5G > T) and a novel COL7A1 mutation (c.7270C > T) accurately. In addition, it detected aberrant splicing resulting from a COL7A1 mutation (c.2527C > T) which was previously reported as a nonsense mutation. Furthermore, we revealed that type VII collagen-expressing cells in PBMCs have similar cell surface markers as mesenchymal stem cells; they were CD105⁺, CD29⁺, CD45^-, and CD34^-, suggesting that a small number of mesenchymal stem cells or mesenchymal stromal cells are circulating in the peripheral blood, which enables us to detect COL7A1 mRNA in PBMCs. Taken together, our novel method for analyzing mutation consequences using mRNA obtained from PBMCs in DEB will significantly contribute to genetic diagnoses and novel therapies for DEB.

Otological complications in inversa type recessive dystrophic epidermolysis bullosa

BACKGROUND

The rare inversa subtype of recessive dystrophic epidermolysis bullosa (RDEB-I) is characterized by predominant intertriginous skin blistering and marked mucosal involvement. Specific recessive missense mutations in the collagen VII triple helix are implicated. To date, otological complications have infrequently been reported in this patient group.

METHODS

We conducted an observational, retrospective, double institution case record review of RDEB-I patients who presented with otological complications between January 2000 and June 2020. Diagnosis was established on the basis of clinical features, family history and mutation analysis of COL7A1.

RESULTS

Forty-four percent (11/25) of RDEB-I patients in our database (2 paediatric, 9 adult; mean age 40.9 years, range 8-72 years) experienced otological complications. Ten of 11 individuals (90.9%) had recurrent otitis externa, 7/11 (63.6%) had meatal stenosis and 7/11 (63.6%) had recurrent blistering of external auditory canals. All 11 patients reported hearing difficulties, with conductive hearing loss confirmed by audiology testing in 6/11 (54.5%). Three of 11 (27.3%) patients had implantable hearing aids fitted with favourable outcome; 2 bone-anchored hearing aids (BAHA) and 1 middle ear implant (MEI). One paediatric patient presented with a cholesteatoma that was surgically managed.

DISCUSSION

We observed a higher prevalence of otological morbidity in RDEB-I than previously reported and present the first case of cholesteatoma in EB. Our data indicate that BAHA and MEI are safe and effective treatment options for hearing loss in EB. Clinicians should be vigilant in screening for ear symptoms in RDEB-I and consider early referral to an ENT specialist.

Dystrophic Epidermolysis Bullosa: Secondary Disease Mechanisms and Disease Modifiers

The phenotypic presentation of monogenetic diseases is determined not only by the nature of the causative mutations but also is influenced by manifold cellular, microenvironmental, and external factors. Here, heritable extracellular matrix diseases, including dystrophic epidermolysis bullosa (DEB), are no exceptions. Dystrophic epidermolysis bullosa is caused by mutations in the COL7A1 gene encoding collagen VII. Deficiency of collagen VII leads to skin and mucosal fragility, which progresses from skin blistering to severe fibrosis and cancer. Clinical and pre-clinical studies suggest that targeting of secondary disease mechanisms or employment of natural disease modifiers can alleviate DEB severity and progression. However, since many of these mechanisms are needed for tissue homeostasis, informed, selective targeting is essential for safe and efficacious treatment. Here, we discuss a selection of key disease modifiers and modifying processes active in DEB, summarize the still scattered knowledge of them, and reflect on ways forward toward their utilization for symptom-relief or enhancement of curative therapies.

Epigenetic and metabolic regulation of epidermal homeostasis

Continuous exposure of the skin to environmental, mechanical and chemical stress necessitates constant self‐renewal of the epidermis to maintain its barrier function. This self‐renewal ability is attributed to epidermal stem cells (EPSCs), which are long‐lived, multipotent cells located in the basal layer of the epidermis. Epidermal homeostasis – coordinated proliferation and differentiation of EPSCs – relies on fine‐tuned adaptations in gene expression which in turn are tightly associated with specific epigenetic signatures and metabolic requirements. In this review, we will briefly summarize basic concepts of EPSC biology and epigenetic regulation with relevance to epidermal homeostasis. We will highlight the intricate interplay between mitochondrial energy metabolism and epigenetic events – including miRNA‐mediated mechanisms – and discuss how the loss of epigenetic regulation and epidermal homeostasis manifests in skin disease. Discussion of inherited epidermolysis bullosa (EB) and disorders of cornification will focus on evidence for epigenetic deregulation and failure in epidermal homeostasis, including stem cell exhaustion and signs of premature ageing. We reason that the epigenetic and metabolic component of epidermal homeostasis is significant and warrants close attention. Charting epigenetic and metabolic complexities also represents an important step in the development of future systemic interventions aimed at restoring epidermal homeostasis and ameliorating disease burden in severe skin conditions.

Signatures of Dermal Fibroblasts from RDEB Pediatric Patients

The recessive form of dystrophic epidermolysis bullosa (RDEB) is a debilitating disease caused by impairments in the junctions of the dermis and the basement membrane of the epidermis. Mutations in the COL7A1 gene induce multiple abnormalities, including chronic inflammation and profibrotic changes in the skin. However, the correlations between the specific mutations in COL7A1 and their phenotypic output remain largely unexplored. The mutations in the COL7A1 gene, described here, were found in the DEB register. Among them, two homozygous mutations and two cases of compound heterozygous mutations were identified. We created the panel of primary patient-specific RDEB fibroblast lines (FEB) and compared it with control fibroblasts from healthy donors (FHC). The set of morphological features and the contraction capacity of the cells distinguished FEB from FHC. We also report the relationships between the mutations and several phenotypic traits of the FEB. Based on the analysis of the available RNA-seq data of RDEB fibroblasts, we performed an RT-qPCR gene expression analysis of our cell lines, confirming the differential status of multiple genes while uncovering the new ones. We anticipate that our panels of cell lines will be useful not only for studying RDEB signatures but also for investigating the overall mechanisms involved in disease progression.

Next-generation sequencing through multigene panel testing for the diagnosis of hereditary epidermolysis bullosa in Chinese population

Epidermolysis bullosa (EB) is a heritable blistering disorder. We performed a next-generation sequencing-based multigene panel test and successfully predicted 100% of the EB types, including, 36 EB simplex (EBS), 13 junctional EB (JEB), 86 dystrophic EB (DEB), and 3 Kindler EB. Chinese JEB and recessive DEB (RDEB) patients have relatively mild phenotypes; for severe type separately accounts for 45.5% and 23.8%, respectively. We identified 96 novel and 49 recurrent pathogenic variants in 11 genes, although we failed to detect the second mutation in one JEB and five RDEB patients. We identified one novel p.E475K mosaic mutation in the clinically normal mother of one out of 13 EBS patients with KRT5 mutations, one recurrent p.G2034R mosaic mutation, and one novel p.G2043R mosaic mutation in the clinically normal relatives of two out of 19 dominant DEB patients. This study shows that next-generation technology could be an effective tool in diagnosing EB.

Natural history of growth and anaemia in children with epidermolysis bullosa: a retrospective cohort study

BACKGROUND

Impaired growth and anaemia are major extracutaneous complications of epidermolysis bullosa (EB), but data on their development are lacking.

OBJECTIVES

To determine the clinical course of growth and anaemia in children with EB and clarify the impact of nutritional compromise, inflammation and genetic factors.

METHODS

A retrospective study was conducted of 200 children, 157 with recessive dystrophic EB (RDEB) and 43 with junctional EB (JEB)-generalized intermediate, followed at the main referral centre in Germany. Growth charts were calculated using the modified LMS method and were correlated with parameters of anaemia, nutrition, inflammation and the molecular defect in a linear model.

RESULTS

In our cohort of patients with RDEB, weight impairment started at 12-18 months old; by the age of 10 years, 50% showed wasting. The predicted median weight at age 20 years was 35·2 kg for men and 40·1 kg for women. In JEB, growth resembled that of healthy children. Anaemia was present from the second year of life onwards in RDEB and JEB. Low levels of haemoglobin, iron, vitamin D, zinc and albumin, high levels of C-reactive protein, and absence of collagen VII correlated significantly with low weight in RDEB. No correlation was observed in JEB.

CONCLUSIONS

The results highlight that nutritional compromise occurs early in children with RDEB and therefore may require interventions as of the first year or two of life. What's already known about this topic? Children with epidermolysis bullosa (EB) suffer from failure to thrive and anaemia as major extracutaneous complications. The course of growth and the development of anaemia in EB are poorly characterized. What does this study add? A molecularly well characterized cohort of 200 children with EB was followed with regard to anthropometrics, anaemia and inflammation. We demonstrate early onset of growth failure and anaemia, most pronounced in the subset of recessive dystrophic EB. Awareness of early growth delay and nutritional deficiencies will improve EB care in daily practice.

Natural Exon Skipping Sets the Stage for Exon Skipping as Therapy for Dystrophic Epidermolysis Bullosa

Dystrophic epidermolysis bullosa (DEB) is a devastating blistering disease affecting skin and mucous membranes. It is caused by pathogenic variants in the COL7A1 gene encoding type VII collagen, and can be inherited dominantly or recessively. Recently, promising proof-of-principle has been shown for antisense oligonucleotide (AON)-mediated exon skipping as a therapeutic approach for DEB. However, the precise phenotypic effect to be anticipated from exon skipping, and which patient groups could benefit, is not yet clear. To answer these questions, we studied new clinical and molecular data on seven patients from the Dutch EB registry and reviewed the literature on COL7A1 exon skipping variants. We found that phenotypes associated with dominant exon skipping cannot be distinguished from phenotypes caused by other dominant DEB variants. Recessive exon skipping phenotypes are generally relatively mild in the spectrum of recessive DEB. Therefore, for dominant DEB, AON-mediated exon skipping is unlikely to ameliorate the phenotype. In contrast, the overall severity of phenotypes associated with recessive natural exon skipping pivots toward the milder end of the spectrum. Consequently, we anticipate AON-mediated exon skipping for recessive DEB caused by bi-allelic null variants should lead to a clinically relevant improvement of this devastating phenotype.

Basement membrane collagens and disease mechanisms

Basement membranes (BMs) are specialised extracellular matrix (ECM) structures and collagens are a key component required for BM function. While collagen IV is the major BM collagen, collagens VI, VII, XV, XVII and XVIII are also present. Mutations in these collagens cause rare multi-systemic diseases but these collagens have also been associated with major common diseases including stroke. Developing treatments for these conditions will require a collective effort to increase our fundamental understanding of the biology of these collagens and the mechanisms by which mutations therein cause disease. Novel insights into pathomolecular disease mechanisms and cellular responses to these mutations has been exploited to develop proof-of-concept treatment strategies in animal models. Combined, these studies have also highlighted the complexity of the disease mechanisms and the need to obtain a more complete understanding of these mechanisms. The identification of pathomolecular mechanisms of collagen mutations shared between different disorders represent an attractive prospect for treatments that may be effective across phenotypically distinct disorders.

An overview of the genetic basis of epidermolysis bullosa in Brazil: discovery of novel and recurrent disease-causing variants

Epidermolysis bullosa (EB) is a genodermatosis that encompasses a group of clinically and genetically heterogeneous disorders classified in four major types: EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB) and Kindler syndrome. Our aim was to characterize recurrent and novel mutations associated to EB in a sample of Brazilian patients. Eighty-seven patients (25 EBS, 4 JEB and 58 DEB) were studied. We performed a next-generation sequencing-based multigene panel through ion torrent technology including 11 genes: KRT5, KRT14, PLEC, TGM5, LAMA3, LAMB3, LAMC2, COL17A1, ITGB4, COL7A1, and FERMT1. A total of 72 different pathogenic or likely pathogenic variants were identified, 32 of them are novel. The causal variant was detected in 82 patients (efficiency of 94.3%). Pathogenic variants in the residue 125 of KRT14 were identified in 32% of all EBS patients. In DEB patients, four COL7A1 variants were quite frequent, some of them clustered in specific Brazilian regions. Our study extends the spectrum of known mutations in EB and describes, for the first time, the genetic profile of EB patients from Brazil.

Neonatal epidermolysis bullosa: lessons to learn about genetic counseling

BACKGROUND

Epidermolysis Bullosa (EB) is a heterogeneous group of congenital blistering diseases that usually presents in the neonatal period. EB is classified into three major categories, each with many subtypes based on the precise location at which separation or blistering occurs, namely epidermolysis bullosa simplex (EBS), junctional epidermolysis bullosa (JEB) and dystrophic epidermolysis bullosa (DEB).

METHODS

We describe genetics of neonatal EB in Hong Kong.

RESULTS

Two neonates of consanguineous Pakistani parents had the EB-Pyloric Atresia (EB-PA) variant. One had a 4 kb homozygous deletion of exon 19-25 of the ITGB4 gene, and the other with only a histopathological diagnosis. Both died of sepsis in infancy. Aberrant COL7A1 mutations in the dominant and recessive EB were described. Genetic analysis, together with histopathological classification is important to aid prognosis and counseling. JEB and EB-PA are associated with consanguinity and mortality during infancy. Morbidity and prognosis of the autosomal dominant DEB are optimistic. The autosomal recessive DEB is more severe, with neonatal onset and recurrent blistering. It is also associated with chronicity and malignant changes when the child reaches adulthood.

CONCLUSION

Exact genetic diagnosis aids in counseling of the family concerning the prognosis in the affected child and the risk of affected children in future pregnancies.

Recent advances in understanding and managing epidermolysis bullosa

Epidermolysis bullosa (EB) is a clinically and genetically heterogeneous skin fragility disorder characterized by trauma-induced skin dissociation and the development of painful wounds. So far, mutations in 20 genes have been described as being associated with more than 30 clinical EB subtypes. The era of whole-exome sequencing has revolutionized EB diagnostics with gene panels being developed in several EB centers and allowing quicker diagnosis and prognostication. With the advances of gene editing, more focus has been placed on gene editing-based therapies for targeted treatment. However, their implementation in daily care will still take time. Thus, a significant focus is currently being placed on achieving a better understanding of the pathogenetic mechanisms of each subtype and using this knowledge for the design of symptom-relief therapies, i.e. treatment options aimed at ameliorating and not curing the disease.

A comprehensive next-generation sequencing assay for the diagnosis of epidermolysis bullosa

BACKGROUND

Historically, diagnosis of epidermolysis bullosa has required skin biopsies for electron microscopy, direct immunofluorescence to determine which gene(s) to choose for genetic testing, or both.

METHODS

To avoid these invasive tests, we developed a high-throughput next-generation sequencing (NGS)-based diagnostic assay called EBSEQ that allows simultaneous detection of mutations in 21 genes with known roles in epidermolysis bullosa pathogenicity. Mutations are confirmed with traditional Sanger sequencing.

RESULTS

We present our EBSEQ assay and preliminary studies on the first 43 subjects tested. We identified 11 cases of epidermolysis bullosa simplex, five cases of junctional epidermolysis bullosa, 11 cases of dominant dystrophic epidermolysis bullosa, 15 cases of recessive dystrophic epidermolysis bullosa, and one case that remains without diagnosis. We also found an additional 52 variants of uncertain clinical significance in 17 of the 21 epidermolysis bullosa-associated genes tested. Three of the variants of uncertain clinical significance were also found in three other patients, for a total of 49 unique variants of uncertain clinical significance. We found the clinical sensitivity of the assay to be 75% to 98% and the analytical sensitivity to be 99% in identifying base substitutions and small deletions and duplications. Turnaround time was 3 to 6 weeks.

CONCLUSIONS

EBSEQ is a sensitive, relatively rapid, minimally invasive, comprehensive genetic assay for the diagnosis of epidermolysis bullosa.

Combinatorial Omics Analysis Reveals Perturbed Lysosomal Homeostasis in Collagen VII-deficient Keratinocytes

The extracellular matrix protein collagen VII is part of the microenvironment of stratified epithelia and critical in organismal homeostasis. Mutations in the encoding gene COL7A1 lead to the skin disorder dystrophic epidermolysis bullosa (DEB), are linked to skin fragility and progressive inflammation-driven fibrosis that facilitates aggressive skin cancer. So far, these changes have been linked to mesenchymal alterations, the epithelial consequences of collagen VII loss remaining under-addressed. As epithelial dysfunction is a principal initiator of fibrosis, we performed a comprehensive transcriptome and proteome profiling of primary human keratinocytes from DEB and control subjects to generate global and detailed images of dysregulated epidermal molecular pathways linked to loss of collagen VII. These revealed downregulation of interaction partners of collagen VII on mRNA and protein level, but also increased abundance of S100 pro-inflammatory proteins in primary DEB keratinocytes. Increased TGF-β signaling because of loss of collagen VII was associated with enhanced activity of lysosomal proteases in both keratinocytes and skin of collagen VII-deficient individuals. Thus, loss of a single structural protein, collagen VII, has extra- and intracellular consequences, resulting in inflammatory processes that enable tissue destabilization and promote keratinocyte-driven, progressive fibrosis.

miR-29 Regulates Type VII Collagen in Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a complex inherited skin disorder caused by loss-of-function mutations in the COL7A1 gene. For an effective treatment of this disorder to be realized, both a thorough understanding of the regulation of COL7A1 and an understanding of the underlying nature of the complications of RDEB are needed. Currently, both posttranscriptional regulation of COL7A1 and the underlying causes of fibrosis in RDEB patients are poorly understood. Here, we describe a mechanism of regulation, to our knowledge previously unknown, by which micro RNA-29 (miR-29) regulates COL7A1 in a complex network: both directly through targeting its 3' untranslated region at two distinct seed regions and indirectly through targeting an essential transcription factor required for basal COL7A1 expression, SP1. In turn, miR-29 itself is regulated by SP1 activity and transforming growth factor-β signaling. RDEB mice express high levels of transforming growth factor-β and significantly lower miR-29 compared with wild-type cohorts. The sustained decrease in miR-29 in RDEB skin leads to an increase of miR-29 target genes expressed in the skin, including profibrotic extracellular matrix collagens. Collectively, we identify miR-29 as an important factor in both regulating COL7A1 and inhibiting transforming growth factor-β-mediated fibrosis.

Oral epigallocatechin-3-gallate for treatment of dystrophic epidermolysis bullosa: a multicentre, randomized, crossover, double-blind, placebo-controlled clinical trial

Abstract

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare genodermatosis with severe blistering. No curative treatment is available. Scientific data indicated that epigallocatechin-3-gallate (EGCG), a green tea extract, might improve the phenotype of RDEB patients. In a multicentre, randomized, crossover, double-blind, placebo-controlled clinical trial, we evaluated a 4-month oral EGCG treatment regimen in 17 RDEB patients. We found that EGCG treatment was not more effective than placebo in modified intention to treat and per protocol analysis (n = 16; p = 0.78 and n = 10; p = 1 respectively). Tolerance was good. Specific organizational and technical difficulties of controlled randomized double-blind trials in EB patients are discussed.

Trial registration

US National Institutes of Health Clinical Trial Register (NCT00951964).

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0411-5) contains supplementary material, which is available to authorized users.

Ptbp1 and Exosc9 knockdowns trigger skin stability defects through different pathways

In humans, genetic diseases affecting skin integrity (genodermatoses) are generally caused by mutations in a small number of genes that encode structural components of the dermal-epidermal junctions. In this article, we first show that inactivation of both exosc9, which encodes a component of the RNA exosome, and ptbp1, which encodes an RNA-binding protein abundant in Xenopus embryonic skin, impairs embryonic Xenopus skin development, with the appearance of dorsal blisters along the anterior part of the fin. However, histological and electron microscopy analyses revealed that the two phenotypes are distinct. Exosc9 morphants are characterized by an increase in the apical surface of the goblet cells, loss of adhesion between the sensorial and peridermal layers, and a decrease in the number of ciliated cells within the blisters. Ptbp1 morphants are characterized by an altered goblet cell morphology. Gene expression profiling by deep RNA sequencing showed that the expression of epidermal and genodermatosis-related genes is also differentially affected in the two morphants, indicating that alterations in post-transcriptional regulations can lead to skin developmental defects through different routes. Therefore, the developing larval epidermis of Xenopus will prove to be a useful model for dissecting the post-transcriptional regulatory network involved in skin development and stability with significant implications for human diseases.

Lysyl Hydroxylase 3 Localizes to Epidermal Basement Membrane and Is Reduced in Patients with Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is caused by mutations in COL7A1 resulting in reduced or absent type VII collagen, aberrant anchoring fibril formation and subsequent dermal-epidermal fragility. Here, we identify a significant decrease in PLOD3 expression and its encoded protein, the collagen modifying enzyme lysyl hydroxylase 3 (LH3), in RDEB. We show abundant LH3 localising to the basement membrane in normal skin which is severely depleted in RDEB patient skin. We demonstrate expression is in-part regulated by endogenous type VII collagen and that, in agreement with previous studies, even small reductions in LH3 expression lead to significantly less secreted LH3 protein. Exogenous type VII collagen did not alter LH3 expression in cultured RDEB keratinocytes and we show that RDEB patients receiving bone marrow transplantation who demonstrate significant increase in type VII collagen do not show increased levels of LH3 at the basement membrane. Our data report a direct link between LH3 and endogenous type VII collagen expression concluding that reduction of LH3 at the basement membrane in patients with RDEB will likely have significant implications for disease progression and therapeutic intervention.

Amplicon-based next-generation sequencing: an effective approach for the molecular diagnosis of epidermolysis bullosa

BACKGROUND

Epidermolysis bullosa (EB) is caused by mutations in genes that encode proteins belonging to the epidermal-dermal junction assembly. Due to the extreme clinical/genetic heterogeneity of the disease, the current methods available for diagnosing EB involve immunohistochemistry of biopsy samples and transmission electron microscopy followed by single-candidate gene Sanger sequencing (SS), which are labour-intensive and expensive clinical pathways.

OBJECTIVES

According to the recently published recommendations for the diagnosis and treatment of EB, the assessment of the mutational landscape is now a fundamental step for developing a comprehensive diagnostic path. We aimed to develop a customized, cost-effective amplicon panel for the complete and accurate sequencing of all the pathogenic genes already identified in EB, and to minimize the processing time required for the execution of the test and to refine the analysis pipeline to achieve cost-effective results from the perspective of a routine laboratory set-up. Next-generation sequencing (NGS) via the parallel ultra-deep sequencing of many genes represents a proper method for reducing the processing time and costs of EB diagnostics.

MATERIALS AND METHODS

We developed an EB disease-comprehensive AmpliSeq panel to accomplish the NGS on an Ion Torrent Personal Genome Machine platform. The panel was performed on 10 patients with known genetic diagnoses and was then employed in eight family trios with unknown molecular footprints.

RESULTS

The panel was successful in finding the causative mutations in all 10 patients with known mutations, fully confirming the SS data and providing proof of concept of the sensitivity, specificity and accuracy of this procedure. In addition to being consistent with the clinical diagnosis, it was also effective in the trios, identifying all of the variants, including ones that the SS missed or de novo mutations.

CONCLUSIONS

The NGS and AmpliSeq were shown to be an effective approach for the diagnosis of EB, resulting in a cost- and time-effective 72-h procedure.

Medical cell technologies for treatment of patients suffering from recessive dystrophic epidermolysis bullosa. Method of intracutaneous administration of fibroblasts

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe inherited disease developing due to genetic abnormalities in the synthesis of Type VII collagen by fibroblasts. A low production rate of Type VII collagen and abnormalities related to the formation of anchoring fibrils weaken the epidermis and derma adhesion strength, which results in the formation of blisters or erosions in case of any mechanical injury. Fibroblasts and keratinocytes belong to the key sources of Type VII collagen in the skin. Application of allogeneic fibroblasts is a promising cell technique for treating RDEB patients. The therapeutic effect of fibroblasts intradermal administration is stipulated by high stability of newly synthesized Type VII collagen and its ability to form anchoring fibrils in the area of the dermoepidermal junction. According to experimental and clinical studies, it is possible to boost the content of Type VII collagen in the dermoepidermal junction area and heal long-term skin defects in RDEB patients by means of intradermal administration of allogeneic fibroblasts.

High Local Concentrations of Intradermal MSCs Restore Skin Integrity and Facilitate Wound Healing in Dystrophic Epidermolysis Bullosa

Dystrophic epidermolysis bullosa (DEB) is an incurable skin fragility disorder caused by mutations in the COL7A1 gene, coding for the anchoring fibril protein collagen VII (C7). Life-long mechanosensitivity of skin and mucosal surfaces is associated with large body surface erosions, chronic wounds, and secondary fibrosis that severely impede functionality. Here, we present the first systematic long-term evaluation of the therapeutic potential of a mesenchymal stromal cell (MSC)-based therapy for DEB. Intradermal administration of MSCs in a DEB mouse model resulted in production and deposition of C7 at the dermal-epidermal junction, the physiological site of function. The effect was dose-dependent with MSCs being up to 10-fold more potent than dermal fibroblasts. MSCs promoted regeneration of DEB wounds via normalization of dermal and epidermal healing and improved skin integrity through de novo formation of functional immature anchoring fibrils. Additional benefits were gained by MSCs' anti-inflammatory effects, which led to decreased immune cell infiltration into injured DEB skin. In our setting, the clinical benefit of MSC injections lasted for more than 3 months. We conclude that MSCs are viable options for localized DEB therapy. Importantly, however, the cell number needed to achieve therapeutic efficacy excludes the use of systemic administration.

Recessive bullous dermolysis of the newborn in preterm siblings with a missense mutation in type VII collagen

Bullous dermolysis of the newborn is a dominant or recessive inherited subtype of dystrophic epidermolysis bullosa characterized by the tendency to spontaneously stop blistering within the first months of life. Here we report two siblings with bullous dermolysis of the newborn who were born prematurely and have a novel recessive mutation, p.Pro2259Leu, in the triple helix domain of type VII collagen. We discuss the possible relationship between genotype and prematurity and clinical manifestations in these patients.

New intragenic and promoter region deletion mutations in FERMT1 underscore genetic homogeneity in Kindler syndrome

BACKGROUND

Kindler syndrome (KS) is a rare autosomal recessive skin disorder, which was recently reclassified as a subtype of epidermolysis bullosa. Despite the fact that loss-of-function mutations in the FERMT1 gene, encoding kindlin-1, have been shown to cause the syndrome in numerous patients, a small number of typical cases of KS in which FERMT1 mutations could not be identified has raised the possibility that the disorder may be genetically heterogeneous.

AIM

To assess two highly consanguineous families with clinical characteristics of KS.

RESULTS

In the first family, a hitherto unreported deletion (c.137-140delTAGT) in FERMT1 was detected, which is predicted to lead to premature termination of translation. However, direct sequencing of the coding region of FERMT1 failed to disclose any pathogenic change in the second family. To confirm the possibility that the disease in this family may be due to a mutation in another gene, we used homozygosity mapping, and found that all affected family members share a segment of homozygosity on 20p12.3, spanning the FERMT1 gene. Accordingly, a large and highly unusual deletion (g.-711-1241del) spanning the putative FERMT1 promoter sequence and the first noncoding exon of the gene was found to cosegregate with the disease phenotype in this family, and to prevent transcription of the gene, as attested by the lack of FERMT1 message in the skin of a patient.

CONCLUSION

The present data provide evidence in support of genetic homogeneity in KS.

Whole-exome sequencing improves mutation detection in a diagnostic epidermolysis bullosa laboratory

BACKGROUND

Subtypes of inherited epidermolysis bullosa (EB) vary significantly in their clinical presentation and prognosis. Establishing an accurate diagnosis is important for genetic counselling and patient management. Current approaches in EB diagnostics involve skin biopsy for immunohistochemistry and transmission electron microscopy, and Sanger sequencing of candidate genes. Although informative in most cases, this approach can be expensive and laborious and may fail to identify pathogenic mutations in ~15% of cases.

OBJECTIVES

Next-generation DNA sequencing (NGS) technologies offer a fast and efficient complementary diagnostic strategy, but the value of NGS in EB diagnostics has yet to be explored. The aim of this study was to undertake whole-exome sequencing (WES) in nine cases of EB in which established diagnostic methods failed to make a genetic diagnosis.

METHODS

Whole-exome capture was performed using genomic DNA from each case of EB, followed by massively parallel sequencing. Resulting reads were mapped to the human genome reference hg19. Potentially pathogenic mutations were subsequently confirmed by Sanger sequencing.

RESULTS

Analysis of WES data disclosed biallelic pathogenic mutations in each case, with all mutations occurring in known EB genes (LAMB3, PLEC, FERMT1 and COL7A1). This study demonstrates that NGS can improve diagnostic sensitivity in EB compared with current laboratory practice.

CONCLUSIONS

With appropriate diagnostic platforms and bioinformatics support, WES is likely to increase mutation detection in cases of EB and improve EB diagnostic services, although skin biopsy remains an important diagnostic investigation in current clinical practice.

The genetics of skin fragility

Genetic skin fragility manifests with diminished resistance of the skin and mucous membranes to external mechanical forces and with skin blistering, erosions, and painful wounds as clinical features. Skin fragility disorders, collectively called epidermolysis bullosa, are caused by mutations in 18 distinct genes that encode proteins involved in epidermal integrity and dermal-epidermal adhesion. The genetic spectrum, along with environmental and genetic modifiers, creates a large number of clinical phenotypes, spanning from minor localized lesions to severe generalized blistering, secondary skin cancer, or early demise resulting from extensive loss of the epidermis. Laboratory investigations of skin fragility have greatly augmented our understanding of genotype-phenotype correlations in epidermolysis bullosa and have also advanced skin biology in general. Current translational research concentrates on the development of biologically valid treatments with therapeutic genes, cells, proteins, or small-molecule compounds in preclinical settings or human pilot trials.

Advances in understanding and treating dystrophic epidermolysis bullosa

Epidermolysis bullosa is a group of inherited disorders that can be both systemic and life-threatening. Standard treatments for the most severe forms of this disorder, typically limited to palliative care, are ineffective in reducing the morbidity and mortality due to complications of the disease. Emerging therapies—such as the use of allogeneic cellular therapy, gene therapy, and protein therapy—have all shown promise, but it is likely that several approaches will need to be combined to realize a cure. For recessive dystrophic epidermolysis bullosa, each particular therapeutic approach has added to our understanding of type VII collagen (C7) function and the basic biology surrounding the disease. The efficacy of these therapies and the mechanisms by which they function also give us insight into developing future strategies for treating this and other extracellular matrix disorders.

Loss of collagen VII is associated with reduced transglutaminase 2 abundance and activity

Absence of collagen VII leads to widespread cellular and tissue phenotypes. However, the underlying molecular mechanisms are not well understood. To gain insights into cellular responses to loss of collagen VII, we undertook a quantitative disease proteomics approach. By using recessive dystrophic epidermolysis bullosa (RDEB), a skin blistering disease caused by collagen VII deficiency, as a genetic model, collagen VII-dependent differences in cellular protein abundances and protein-protein interactions were analyzed. Absence of collagen VII led to alterations of intracellular protein compositions and to perturbations in cell adhesion, protein trafficking, and the turnover pathway autophagy. A potential linker of the different cellular phenotypes is transglutaminase 2 (TGM2), a multifunctional enzyme important for protein cross-linking. TGM2 was identified as a stable interaction partner of collagen VII. In RDEB, both abundance and activity of TGM2 were reduced, accounting not only for diminished adhesion and perturbed autophagy but also for reduced cross-linking of the extracellular matrix and for decreased epidermal-dermal integrity in RDEB.

Mechanisms of natural gene therapy in dystrophic epidermolysis bullosa

Revertant mosaicism has been reported in several inherited diseases, including the genetic skin fragility disorder epidermolysis bullosa (EB). Here, we describe the largest cohort of seven patients with revertant mosaicism and dystrophic EB (DEB), associated with mutations in the COL7A1 gene, and determine the underlying molecular mechanisms. We show that revertant mosaicism occurs both in autosomal dominantly and recessively inherited DEB. We found that null mutations resulting in complete loss of collagen VII and severe disease, as well as missense or splice-site mutations associated with some preserved collagen VII function and a milder phenotype, were corrected by revertant mosaicism. The mutation, subtype, and severity of the disease are thus not decisive for the presence of revertant mosaicism. Although collagen VII is synthesized and secreted by both keratinocytes and fibroblasts, evidence for reversion was only found in keratinocytes. The reversion mechanisms included back mutations/mitotic recombinations in 70% of the cases and second-site mutations affecting splicing in 30%. We conclude that revertant mosaicism is more common than previously assumed in patients with DEB, and our findings will have implications for future therapeutic strategies using the patient's naturally corrected cells as a source for cell-based therapies.

Rat model for dominant dystrophic epidermolysis bullosa: glycine substitution reduces collagen VII stability and shows gene-dosage effect

Dystrophic epidermolysis bullosa, a severely disabling hereditary skin fragility disorder, is caused by mutations in the gene coding for collagen VII, a specialized adhesion component of the dermal-epidermal junction zone. Both recessive and dominant forms are known; the latter account for about 40% of cases. Patients with dominant dystrophic epidermolysis bullosa exhibit a spectrum of symptoms ranging from mild localized to generalized skin manifestations. Individuals with the same mutation can display substantial phenotypic variance, emphasizing the role of modifying genes in this disorder. The etiology of dystrophic epidermolysis bullosa has been known for around two decades; however, important pathogenetic questions such as involvement of modifier genes remain unanswered and a causative therapy has yet to be developed. Much of the failure to make progress in these areas is due to the lack of suitable animal models that capture all aspects of this complex monogenetic disorder. Here, we report the first rat model of dominant dystrophic epidermolysis bullosa. Affected rats carry a spontaneous glycine to aspartic acid substitution, p.G1867D, within the main structural domain of collagen VII. This confers dominant-negative interference of protein folding and decreases the stability of mutant collagen VII molecules and their polymers, the anchoring fibrils. The phenotype comprises fragile and blister-prone skin, scarring and nail dystrophy. The model recapitulates all signs of the human disease with complete penetrance. Homozygous carriers of the mutation are more severely affected than heterozygous ones, demonstrating for the first time a gene-dosage effect of mutated alleles in dystrophic epidermolysis bullosa. This novel viable and workable animal model for dominant dystrophic epidermolysis bullosa will be valuable for addressing molecular disease mechanisms, effects of modifying genes, and development of novel molecular therapies for patients with dominantly transmitted skin disease.

Global remodelling of cellular microenvironment due to loss of collagen VII

Loss of collagen VII causes recessive dystrophic epidermolysis bullosa. Quantitative proteomics analysis of the extracellular matrix and secretome of human fibroblasts derived from pathologically altered skin reveals a global remodelling of the cellular microenvironment.

A global analysis of the microenvironment of human skin fibroblasts was carried out to reveal disease-related alterations in the extracellular proteome.

The loss of collagen VII causes a deregulation of the basement membrane and dermal matrix proteome.

Post-translational modifications of secreted proteins were altered in fibroblasts from recessive dystrophic epidermolysis bullosa samples.

Metalloproteases displayed reduced activity and turnover in collagen VII-deficient cells.

The mammalian cellular microenvironment is shaped by soluble factors and structural components, the extracellular matrix, providing physical support, regulating adhesion and signalling. A global, quantitative mass spectrometry strategy, combined with bioinformatics data processing, was developed to assess proteome differences in the microenvironment of primary human fibroblasts. We studied secreted proteins of fibroblasts from normal and pathologically altered skin and their post-translational modifications. The influence of collagen VII, an important structural component, which is lost in genetic skin fragility, was used as model. Loss of collagen VII had a global impact on the cellular microenvironment and was associated with proteome alterations highly relevant for disease pathogenesis including decrease in basement membrane components, increase in dermal matrix proteins, TGF-β and metalloproteases, but not higher protease activity. The definition of the proteome of fibroblast microenvironment and its plasticity in health and disease identified novel disease mechanisms and potential targets of intervention.