Junctional Epidermolysis Bullosa Research Articles

Junctional Epidermolysis Bullosa Linked to Homozygous Mutation in LAMC2 Gene: A Case Report With Eosinophil-Rich Inflammatory Infiltrate.

Junctional epidermolysis bullosa (JEB) is a rare, incurable, devastating, and mostly fatal congenital genetic disorder characterized by painful blistering of the skin and mucous membranes in response to minor trauma or pressure. JEB is classified roughly into 2 subtypes: JEB-Herlitz is caused by mutations on genes encoding laminin-332. The authors present a patient consulted with a suspicion of primary immunodeficiency due to skin sores that started at the age of 1 month and a history of 3 siblings who died with similar sores, who was diagnosed with JEB-Herlitz after detecting a homozygous LAMC2 gene mutation in WES analysis. Microscopic evaluation of hematoxylin and eosin-stained sections showed vesicle formation with subepidermal separation, which is accompanied by striking neutrophil and eosinophil leukocyte infiltration both in the vesicle and papillary dermis (eosinophil-rich inflammatory infiltrate). Such a histopathological finding has been rarely reported in this condition.

Abstract 7666: Type XVII collagen as potential biomarker of epithelial damage in patients with atopic dermatitis and patients with metastatic colorectal cancer

Abstract Background Type XVII collagen is a membrane-associated collagen with interrupted triple-helices (MACIT) facilitating adhesion between the basement membrane (BS) and epithelial cells. Mutations in COL17A1 lead to junctional epidermolysis bullosa (JEB), while autoimmunity against type collagen XVII ectodomain can cause bullous pemphigoid (BP). In multiple epithelial cancers, both type XVII collagen and its shed ectodomain are associated with cancer development and invasiveness. This study aims to assess the potential of type XVII collagen as an epithelial damage biomarker in patients with metastatic colorectal cancer (mCRC) and in patients with skin diseases like atopic dermatitis (AD) and psoriasis. Methodology Type XVII collagen ectodomain levels were measured in serum using a competitive ELISA (nordicPRO-C17). The study included two cohorts: cohort 1 comprised 212 patients with mCRC and 28 healthy controls and cohort 2 included patients with AD (n=8) or psoriasis (n=3). PRO-C17 levels in mCRC patients were compared to 28 healthy controls using a t-test. The association between PRO-C17 levels and overall survival (OS) was evaluated by categorizing patients into low PRO-C17 levels (tertiles 1+2) and high PRO-C17 levels (tertile 3). Kaplan-Meier curves and the log-rank test were used to assess differences in survival between the two groups. The independent predictive value of PRO-C17 was evaluated using multivariate Cox analysis. PRO-C17 levels in AD and psoriasis patients were compared to 15 healthy controls using one-way ANOVA, followed by multiple comparisons with Dunn's test. Results PRO-C17 levels were elevated (p<0.05) in mCRC patients treated with bevacizumab compared to healthy controls. Patients with high PRO-C17 levels had a shorter overall survival (390 days) compared to those with low levels (539 days) (p=0.007). High levels of the biomarker were associated with an increased risk of mortality and PRO-C17 levels were independent of other risk factors, such as the number of drugs in the treatment regimen, tumor location, synchronous metastatic disease, primary tumor resection, performance status, and the number of metastatic sites (HR=1.43, 95% CI 1.01-2.01, p=0.044). Further, patients with AD had increased PRO-C17 levels (p=0.0057), while patients with psoriasis showed no significant differences in biomarker levels compared to healthy controls (p=0.58). Conclusions This study demonstrated that high PRO-C17 levels were independently associated with shorter OS and an increased risk of mortality in patients with mCRC. Additionally, elevated levels of PRO-C17 were observed in patients with AD. These findings suggest that type XVII collagen may serve as a reflection of epithelial damage in the invasive front during tumor metastasis. The role of this biomarker in other cancer types and skin diseases warrants further exploration. Citation Format: Marina Crespo-Bravo, Neel Nissen, Rasmus Pedersen, Mogens Boisen, Maria Liljefors, Astrid Johansen, Julia Johansen, Morten Karsdal, Nicholas Willumsen. Type XVII collagen as potential biomarker of epithelial damage in patients with atopic dermatitis and patients with metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7666.

Strategy for the Optimization of Read-Through Therapy for Junctional Epidermolysis Bullosa with COL17A1 Nonsense Mutation

The read-through therapy suppresses premature termination codons and induces read-through activity consequently restoring missing proteins. Aminoglycosides are widely studied as read-through drugs in different human genetic disorders including hereditary skin diseases. Our previous work revealed that aminoglycosides have effect on COL17A1 nonsense mutations and represent a therapeutic option to alleviate disease severity. However, the amount of restored type XVII collagen (C17) in C17 deficient junctional epidermolysis bullosa (JEB-C17) keratinocytes was less than 1% relative to normal keratinocytes and was achieved only after high dose gentamicin treatment, which induced deep transcriptional changes. Therefore, in this study, we designed a strategy for the read-through therapy to challenge with aminoglycosides limitation factors in clinical use and the chronic inflammation in JEB-C17 patients. We developed TRID-C5 containing low dosage of aminoglycosides, CC-90009, NMDI-14, melatonin and apocynin that was able to induce about 20% of missing C17 without cell toxicity and effect on in vitro wound closure. TRID-C5 significantly induced COL17A1 expression and reverted the proinflammatory phenotype of JEB-C17 keratinocytes. Evaluation of this drug cocktail regarding its stability, penetration and efficacy as a topical treatment remains to be determined. TRID-C5 might represent an improved therapeutic strategy for JEB and for other genetic skin disorders.

Totally endoscopic concomitant aortic and mitral valve surgery in junctional epidermolysis bullosa: a case report

BackgroundJunctional epidermolysis bullosa is a rare skin and mucosal disorder characterized by blister formation in response to minor trauma and extracutaneous manifestations. There have been no reports of cardiac surgery and prognostication in patients with epidermolysis bullosa due to skin and mucosal fragility.Case presentationA 55-year-old man presented with congenital junctional epidermolysis bullosa, hypertension, and vasospastic angina. He complained of dyspnea on exertion, and transthoracic echocardiography revealed severe aortic valve regurgitation, moderate aortic valve stenosis (tricuspid valve), and severe mitral valve regurgitation. Considering that the skin condition in the right chest wall was relatively healthy, the right thoracotomy approach was preferred and totally endoscopic concomitant mitral valve repair and aortic valve replacement were performed using a sutureless bioprosthetic valve (Perceval™ (Corcym, Group, Milan, Italy)). Polyurethane and silicon dressing foams were used to protect the skin at the site of contact with the bag valve mask, arterial pressure catheter, intravenous catheter, and the tracheal intubation tube. Vertical mattress sutures were used for the skin sutures. The postoperative course was uneventful, and the patient was discharged nine days after the operation. There was no indication for reoperation until three years follow-up period.ConclusionsThe totally endoscopic concomitant aortic and mitral valve surgery using Perceval™ prosthesis can be performed safely in patients with junctional epidermolysis bullosa by adequate protection of the skin and mucosa.

IL-6 levels dominate the serum cytokine signature of severe epidermolysis bullosa: A prospective cohort study.

Systemic inflammation is considered a major player in the pathogenesis of epidermolysis bullosa (EB), but its pattern has only been described in small heterogeneous cohorts. There is controversy if and how systemic inflammation should be therapeutically targeted. We examined serum proinflammatory, anti-inflammatory, and itch related cytokines in a paediatric cohort of 29 patients with junctional and dystrophic EB. The cytokine that emerged as the most relevant was measured in a validation cohort of 42 patients during follow-up visits over 2 years. IL-6 showed the most consistent and highest aberration dominating systemic inflammation. IL-6 correlated with wound body surface area (BSA) in both, finding and validation cohorts. Patients with less than 3% wound BSA had normal IL-6, while IL-6 levels significantly increased at more than 5% and 10% of wound BSA. TGF-β was only marginally elevated in patients with severe recessive dystrophic EB, while TNF-α, IFN-γ and IL-1β varied inconsistently. Patients reporting itch showed elevations in type 2 immunity (IgE, TSLP, IL4 and/or IL-31, respectively). Our data suggest a dominant skin barrier and wound healing inflammatory pattern in junctional and dystrophic EB that depends on the wound area and not on the EB type. In EB, itch mediators may be similar to other pruritic disorders.

Patients suffering from dystrophic epidermolysis bullosa are prone to developing autoantibodies against skin proteins: A longitudinal confirmational study.

Epidermolysis bullosa (EB) is a heritable skin blistering disease caused by variants in genes coding for proteins that secure cell-cell adhesion and attachment of the epidermis to the dermis. Interestingly, several proteins involved in inherited EB are also associated with autoimmune blistering diseases (AIBD). In this study, we present a long-term follow-up of 15 patients suffering from recessive dystrophic or junctional EB. From these patients, 62 sera were analysed for the presence of autoantibodies associated with AIBD. We show that patients suffering from recessive dystrophic EB (RDEB) are more susceptible to developing autoantibodies against skin proteins than patients suffering from junctional EB (70% vs. 20%, respectively). Interestingly, no correlation with age was observed. Most patients showed reactivity to Type XVII collagen/linear IgA bullous dermatosis autoantigen (n = 5; 33%), followed by BP230 (n = 4; 27%), Type VII collagen (n = 4; 27%) and laminin-332 (n = 1; 7%). The pathogenicity of these autoantibodies remains a subject for future experiments.

Efficacy of human living skin equivalent in the treatment of inherited epidermolysis bullosa

Background: inherited epidermolysis bullosa is a group of genetic skin disorders caused by mutations in genes encoding structural proteins of epidermis and dermo-epidermal junction. Clinical manifestations are characterized by spontaneous or trauma-induced skin and/or mucosal blistering, and extensive wounds. Cell therapy is considered to be a perspective therapeutic approach in improving wound healing process.
 Aims: to assess safety and efficacy of human skin equivalent in the treatment of inherited epidermolysis bullosa patients
 Materials and methods: 7 patients (5 female and 2 male subjects from the age of 20 to 55) with inherited epidermolysis bullosa with different clinical subtypes were enrolled in the study: 3 patients with intermediate recessive dystrophic epidermolysis bullosa, 2 patients with severe recessive dystrophic epidermolysis bullosa, 1 patient with dominant dystrophic epidermolysis bullosa and 1 patient with junctional epidermolysis bullosa. Transplantation of composite allogeneic living skin equivalent comprising allogeneic keratinocytes and fibroblasts in low concentration (5 mg/ml) embedded within a type I collagen gel matrix was performed. The living skin equivalent was developed at N.K. Koltsov Institute of Developmental Biology. 19 erosions and ulcers with a surface area between 0,4 cm2 and 120 cm2 were evaluated. At day 14 clinical assessment was performed. To assess level of expression immunofluorescence antigen mapping was used.
 Results: at day 14 complete erosion closure was achieved in 10 (53%) erosions. 4 (21%) erosions reduced in size 75%. Size reduction between 25% and 75% was shown in a single (5%) case. No clinical efficacy was demonstrated in 4 (21%) cases. Collagen VII expression increased comparing to baseline level and accompanied clinical improvement.
 Conclusions: the obtained data showed clinical efficacy of topical treatment with living skin equivalent, although no statistically significant difference was seen between living skin equivalent and atraumatic non-adhesive dressings.
 Keywords: inherited epidermolysis bullosa, junctional epidermolysis bullosa, recessive dystrophic epidermolysis bullosa, erosions, healing, topical treatment.

Gross motor development in children with epidermolysis bullosa.

Epidermolysis bullosa (EB) is a group of rare, congenital skin disorders, characterized by skin fragility and formation of blisters. The gross motor outcomes of children with EB are not known. The primary objective of the study was to measure the proportion of gross motor delay in children with EB. The secondary objectives were to measure the difference in gross motor outcomes between EB sub-types and change in gross motor outcomes over time. Children with EB, aged between one month and five and a half years of age, attending the Sydney Children's Hospital, Epidermolysis Bullosa Clinic, were eligible. Carers completed Ages and Stages Questionnaires, Third Edition, on behalf of their children. Questionnaires were scored, and outcomes were compared to age-expected norms. There were 24 participants to complete a questionnaire. Eleven participants completed additional questionnaires over the 24 month study duration. The proportion of children with EB with gross motor delay was greater than age-expected norms (29.17% vs. 2.5%). The delay occurred in children with recessive dystrophic (80%) and epidermolysis bullosa simplex (33.33%) sub-types, but not dominant dystrophic (0%). No children with Junctional EB or Kindler EB joined this study. This study demonstrates a difference in gross motor outcomes in children with EB. Children with recessive dystrophic and epidermolysis bullosa simplex should be prioritized for monitoring of, and intervention for, gross motor outcomes through multidisciplinary care. Further research investigating long-term outcomes for children with EB and the effectiveness of interventions would be beneficial.

Genotype–Phenotype Correlation in Junctional Epidermolysis Bullosa: Signposts to Severity

Junctional epidermolysis bullosa (JEB) is a rare autosomal recessive genodermatosis with a broad spectrum of phenotypes. Current genotype-phenotype paradigms are insufficient to accurately predict JEB subtype and characteristics from genotype, particularly for splice site mutations, which account for over a fifth of disease-causing mutations in JEB. This study evaluated genetic and clinical findings from a JEB cohort, investigating genotype-phenotype correlations through bioinformatic analyses and comparison with previously reported mutations.Eighteen unique mutations in LAMB3, LAMA3, LAMC2 or COL17A1 were identified from seventeen individuals. Seven had severe JEB, nine intermediate JEB and one laryngo-onycho-cutaneous syndrome. Seven mutations were previously unreported. Deep phenotyping was completed for all intermediate JEB cases and demonstrated substantial variation between individuals. Splice site mutations underwent analysis with SpliceAI, a state-of-the-art artificial intelligence tool, in order to predict resultant transcripts. Predicted functional effects included exon skipping and cryptic splice site activation, which provided potential explanations for disease severity and in most cases correlated with lamimin-332 immunofluorescence. RT-PCR was performed for one case to investigate resultant transcripts produced from the splice site mutation.This study expands the JEB genomic and phenotypic landscape. AI tools show potential for predicting functional effects of splice site mutations and may identify candidates for confirmatory laboratory investigation. Investigation of RNA transcripts will help to further elucidate genotype-phenotype correlations for novel mutations.

Inheritance of the Epidermolysis Bullosa Subtypes

Epidermolysis bullosa (EB) is a group of inherited disorders that cause skin to blister and tear easily. The disease is caused by mutations in structural proteins that are key for maintaining the integrity of the skin’s basement membrane zone or dermoepidermal junction. EB can be inherited in two ways: autosomal dominant and autosomal recessive. The most common form of EB, epidermolysis bullosa simplex (EBS), as well as some forms of dystrophic epidermolysis bullosa (DEB) are inherited in an autosomal dominant pattern. This means they are passed down from an affected parent to half of his or her children. Other forms of EB, such as junctional epidermolysis bullosa (JEB) and some forms of DEB, are inherited in an autosomal recessive pattern. This means that two copies of the mutated gene, one from each parent, are required to develop the condition.

Hypermobility in patients with epidermolysis bullosa—A retrospective observational study from a national referral center

AbstractBackgroundEpidermolysis bullosa (EB) is an inherited genodermatosis of variable severity characterised by skin and mucosal fragility commonly associated with altered gait patterns and hypermobility.ObjectivesTo define the altered gait pattern and identify possible causes in patients with EB.MethodsRetrospective review of the EB database to identify children with EB with at least one physiotherapy assessment between 2009 and 2022.ResultsForty‐eight children out of 59 referrals to physiotherapy with an altered gait pattern were identified (81.3%); 23 (48%) had recessive dystrophic EB (RDEB), 17 (36%) EB simplex, five (10%) Junctional EB (JEB) and three (6%) dominant dystrophic EB (DDEB). The patho‐mechanical altered gait patterns were characterised by altered load‐bearing surface in contact with the floor (63%), short shuffling pattern with high cadence and decreased single support (42%) and equinovarus (toe walking) (6%). Hypermobility (as defined by the Beighton score) was present in 67% of patients: 43% in RDEB, 88% in EBS, 100% in JEB and 67% in DDEB.ConclusionsIn this study, we provide the first accurate data for the causes of altered gait patterns in children with EB. Healthcare professionals should be aware of joint hypermobility and its effect on gait in this patient cohort.

Heterozygous COL17A1 variants are a frequent cause of amelogenesis imperfecta

BackgroundCollagen XVII is most typically associated with human disease when biallelic COL17A1 variants (>230) cause junctional epidermolysis bullosa (JEB), a rare, genetically heterogeneous, mucocutaneous blistering disease with amelogenesis imperfecta (AI),...

En Route to Targeted Ribosome Editing to Replenish Skin Anchor Protein LAMB3 in Junctional Epidermolysis Bullosa

Severe junctional epidermolysis bullosa is a rare genetic, postpartum lethal skin disease, predominantly caused by nonsense/premature termination codon (PTC) sequence variants in LAMB3 gene. LAMB3 encodes LAMB3, the β subunit of epidermal-dermal skin anchor laminin 332. Most translational reads of a PTC mRNA deliver truncated, nonfunctional proteins, whereas an endogenous PTC readthrough mechanism produces full-length protein at minimal and insufficient levels. Conventional translational readthrough-inducing drugs amplify endogenous PTC readthrough; however, translational readthrough-inducing drugs are either proteotoxic or nonselective. Ribosome editing is a more selective and less toxic strategy. This technique identified ribosomal protein L35/uL29 (ie, RpL35) and RpL35-ligands repurposable drugs artesunate and atazanavir as molecular tools to increase production levels of full-length LAMB3. To evaluate ligand activity in living cells, we monitored artesunate and atazanavir treatment by dual luciferase reporter assays. Production levels of full-length LAMB3 increased up to 200% upon artesunate treatment, up to 150% upon atazanavir treatment, and up to 170% upon combinatorial treatment of RpL35 ligands at reduced drug dosage, with an unrelated PTC reporter being nonresponsive. Proof of bioactivity of RpL35 ligands in selective increase of full-length LAMB3 provides the basis for an alternative, targeted therapeutic route to replenish LAMB3 in severe junctional epidermolysis bullosa.

METTL14-mediated N6-methyladenosine modification of Col17a1/Itgα6/Itgβ4 governs epidermal homeostasis

BackgroundN6-methyladenosine (m6A) is the most abundant and reversible modification occurring in eukaryotic mRNAs, however, its functions in mammalian epidermal development are still not fully elucidated. ObjectiveTo explore the role of METTL14 (Methyltransferase like 14), one of the m6A methyltransferases, in maintaining epidermal homeostasis. MethodsWe constructed mice with Mettl14-inactivation in the epidermal basal cells. The phenotype was explored by H&E staining and immunofluorescence staining. To explore the underlying mechanisms, we performed RNA-seq, Ribosome profiling and MeRIP-seq on wild-type and Mettl14-inactivation epidermal keratinocytes. Moreover, HaCaT cells were used for in vitro validation. ResultsInactivation of Mettl14 in murine epidermis led to transient thicker epidermis and exhaustion of the epidermal stem cell pool. Interestingly, we found that the mRNA of type XVII collagen (Col17a1), integrin β4 (Itgβ4) and α6 (Itgα6) had m6A modifications, and the proteins expression were decreased in Mettl14-inactivated epidermis. Furthermore, in epidermis-specific Mettl4-inactivated mice, the epidermis was detached from the dermis and presented a phenotype similar to junctional epidermolysis bullosa (JEB), which may result from hemidesmosomes damage (decrease of COL17A1, ITGB4 and ITGA6). Knockdown of Mettl14 in HaCaT cells impaired the self-renewal and decreased the protein level of COL17A1, ITGB4 and ITGA6 and Itgβ4 knockdown inhibited colony formation. ConclusionOur study highlighted the role of METTL14 in the maintenance of epidermal homeostasis and identified its critical role through m6A-mediated translational inhibition of Col17a1, Itgβ4 and Itgα6. Our study suggested that METTL14 may be a potential therapeutic target for the treatment of hemidesmosomes-deficient diseases, such as JEB.

Full-thickness Skin Grafts for Hand Contractures in an Adult Patient with Junctional Epidermolysis Bullosa: A Case Report

Epidermolysis bullosa is a group of inherited skin fragility disorders with blister formation in the basement membrane zone. Chronic scarring after repeated blistering of the hands causes narrowing of the first web, flexion contractures of the digits, and pseudosyndactyly. Junctional epidermolysis bullosa is a type of epidermolysis bullosa that is characterized by blister formation in the lamina lucida. This condition is associated with survival into adulthood. In adult survivors, hand function might be required in order to participate in normal social activities. However, there is a lack of literature on the management of hand surgery for adult patients with junctional epidermolysis bullosa. We herein describe an adult patient with junctional epidermolysis bullosa who had pseudosyndactyly and flexion contractures in both hands. Five surgeries were performed. Contractures were released and reconstructed using split- or full-thickness skin grafts. Delayed wound healing was always observed due to epidermal necrosis in the graft. After epithelialization, a satisfactory functional outcome was obtained.

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 molecular features in a cohort of Middle Eastern patients with epidermolysis bullosa.

Epidermolysis bullosa (EB) features skin and mucosal fragility due to pathogenic variants in genes encoding components of the cutaneous basement membrane. Based on the level of separation within the dermal-epidermal junction, EB is sub-classified into four major types including EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler EB (KEB) with 16 EB-associated genes reported to date. We ascertained a cohort of 151 EB patients of various Middle Eastern ethnic backgrounds. The cohort was comprised of EBS (64%, 97/151), DEB (21%, 31/151), JEB (12%, 18/151), and KEB (3%, 5/151). KRT14 and KRT5 variants were most common among EBS patients with 43% (42/97) and 46% (45/97) of EBS patients carrying mutations in either of these two genes, respectively. Truncal involvement was more common in KRT14-associated EBS as compared to EBS due to KRT5 mutations (p < .05). Mutations in COL17A1 and laminin 332-encoding genes were identified in 55% (10/18) and 45% (8/18) of JEB patients. Scarring alopecia, caries, and EB nevi were most common among JEB patients carrying COL17A1 mutations as compared to laminin 332-associated JEB (p < .05). Abnormal nails were evident in most DEB and JEB patients while poikiloderma was exclusively observed in KEB (p < .001). EB patients of Middle Eastern origin were found to feature specific phenotype-genotype correlations of relevance to the diagnosis and genetic counseling of patients in this region.

Functional analysis of Collagen 17a1: A genetic modifier of junctional epidermolysis bullosa in mice.

Previous work strongly implicated Collagen 17a1 (Col17a1) as a potent genetic modifier of junctional epidermolysis bullosa (JEB) caused by a hypomorphic mutation (Lamc2jeb) in mice. The importance of the noncollagenous domain (NC4) of COLXVII was suggested by use of a congenic reduction approach that restricted the modifier effect to 2-3 neighboring amino acid changes in that domain. The current study utilizes TALEN and CRISPR/Cas9 induced amino acid replacements and in-frame indels nested to NC4 to further investigate the role of this and adjoining COLXVII domains both as modifiers and primary risk effectors. We confirm the importance of COLXVI AA 1275 S/G and 1277 N/S substitutions and utilize small nested indels to show that subtle changes in this microdomain attenuate JEB. We further show that large in-frame indels removing up to 1482 bp and 169 AA of NC6 through NC1 domains are surprisingly disease free on their own but can be very potent modifiers of Lamc2jeb/jeb JEB. Together these studies exploiting gene editing to functionally dissect the Col17a1 modifier demonstrate the importance of epistatic interactions between a primary disease-causing mutation in one gene and innocuous 'healthy' alleles in other genes.

Independent COL17A1 Variants in Cats with Junctional Epidermolysis Bullosa.

Epidermolysis bullosa (EB), characterized by defective adhesion of the epidermis to the dermis, is a heterogeneous disease with many subtypes in human patients and domestic animals. We investigated two unrelated cats with recurring erosions and ulcers on ear pinnae, oral mucosa, and paw pads that were suggestive of EB. Histopathology confirmed the diagnosis of EB in both cats. Case 1 was severe and had to be euthanized at 5 months of age. Case 2 had a milder course and was alive at 11 years of age at the time of writing. Whole genome sequencing of both affected cats revealed independent homozygous variants in COL17A1 encoding the collagen type XVII alpha 1 chain. Loss of function variants in COL17A1 lead to junctional epidermolysis bullosa (JEB) in human patients. The identified splice site variant in case 1, c.3019+1del, was predicted to lead to a complete deficiency in collagen type XVII. Case 2 had a splice region variant, c.769+5G>A. Assessment of the functional impact of this variant on the transcript level demonstrated partial aberrant splicing with residual expression of wildtype transcript. Thus, the molecular analyses provided a plausible explanation of the difference in clinical severity between the two cases and allowed the refinement of the diagnosis in the affected cats to JEB. This study highlights the complexity of EB in animals and contributes to a better understanding of the genotype-phenotype correlation in COL17A1-related JEB.

PRIMA-1MET/APR-246 Can Partially Rescue In Vitro Cell Adhesion of Patient-Derived Junctional Epidermolysis Bullosa Epidermal Cells

PRIMA-1MET/APR-246 Can Partially Rescue In Vitro Cell Adhesion of Patient-Derived Junctional Epidermolysis Bullosa Epidermal Cells