Pachyonychia Congenita: A Research Agenda Leading to New Therapeutic Approaches.

Pachyonychia congenita (PC) is a dominantly inherited genetic disorder of cornification. PC stands out among other genodermatoses because despite its rarity, it has been the focus of a very large number of pioneering translational research efforts over the past 2 decades, mostly driven by a patient support organization, the Pachyonychia Congenita Project. These efforts have laid the ground for innovative strategies that may broadly impact approaches to the management of other inherited cutaneous and noncutaneous diseases. This article outlines current avenues of research in PC, expected outcomes, and potential hurdles.

Highly efficient ex-vivo correction of COL7A1 through RNP-based CRISPR/Cas9 and Homology-Directed Repair to treat recessive dystrophic epidermolysis bullosa.

Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a rare and severe genetic skin disease responsible for blistering of the skin and mucosa after minor trauma. RDEB is caused by a wide variety of mutations in COL7A1 encoding C7, the major component of anchoring fibrils (AFs) which form key attachment structures for dermal-epidermal adherence. Here, we achieved highly efficient COL7A1 editing in primary RDEB keratinocytes (RDEB-K) and fibroblasts (RDEB-F) from two patients homozygous for the c.6508C>T (p.Gln2170*) mutation through CRISPR/Cas9-mediated Homology-Directed Repair. Three gRNAs targeting the c.6508C>T mutation or harboring sequences, were delivered together with hfCas9 as a ribonucleoprotein complex (RNP). Among them, one achieved 73% cleavage activity in primary RDEB-K and RDEB-F. Then, we treated RDEB-K and RDEB-F with this specific RNP and the corresponding donor template delivered as ssODN and achieved up to 58% of genetic correction as well as C7 rescue. Finally, grafting of corrected 3D skin onto nude mice induced re-expression and normal localization of C7 as well as AFs formation at the DEJ at five and ten weeks post-grafting. With this promising non-viral approach, we achieved therapeutically relevant specific gene editing which could be applicable to all mutations in exon 80 of COL7A1 in primary RDEB cells.

Transient mTOR inhibition rescues 4-1BB CAR-Tregs from tonic signal-induced dysfunction.

The use of chimeric antigen receptor (CAR)-engineered regulatory T cells (Tregs) has emerged as a promising strategy to promote immune tolerance. However, in conventional T cells (Tconvs), CAR expression is often associated with tonic signaling, which can induce CAR-T cell dysfunction. The extent and effects of CAR tonic signaling vary greatly according to the expression intensity and intrinsic properties of the CAR. Here, we show that the 4-1BB CSD-associated tonic signal yields a more dramatic effect in CAR-Tregs than in CAR-Tconvs with respect to activation and proliferation. Compared to CD28 CAR-Tregs, 4-1BB CAR-Tregs exhibit decreased lineage stability and reduced in vivo suppressive capacities. Transient exposure of 4-1BB CAR-Tregs to a Treg stabilizing cocktail, including an mTOR inhibitor and vitamin C, during ex vivo expansion sharply improves their in vivo function and expansion after adoptive transfer. This study demonstrates that the negative effects of 4-1BB tonic signaling in Tregs can be mitigated by transient mTOR inhibition.

Humans with inherited T cell CD28 deficiency are susceptible to skin papillomaviruses but are otherwise healthy.

We study a patient with the human papilloma virus (HPV)-2-driven "tree-man" phenotype and two relatives with unusually severe HPV4-driven warts. The giant horns form an HPV-2-driven multifocal benign epithelial tumor overexpressing viral oncogenes in the epidermis basal layer. The patients are unexpectedly homozygous for a private CD28 variant. They have no detectable CD28 on their T cells, with the exception of a small contingent of revertant memory CD4+ T cells. T cell development is barely affected, and T cells respond to CD3 and CD2, but not CD28, costimulation. Although the patients do not display HPV-2- and HPV-4-reactive CD4+ T cells in vitro, they make antibodies specific for both viruses in vivo. CD28-deficient mice are susceptible to cutaneous infections with the mouse papillomavirus MmuPV1. The control of HPV-2 and HPV-4 in keratinocytes is dependent on the T cell CD28 co-activation pathway. Surprisingly, human CD28-dependent T cell responses are largely redundant for protective immunity.

Diagnosis of Epidermolysis Bullosa Acquisita: Multicentre Comparison of Different Assays for Serum Anti-type VII Collagen Reactivity.

Epidermolysis bullosa acquisita is a pemphigoid disease characterized by autoantibodies against type VII collagen. This study compared the sensitivity and specificity of 6 diagnostic assays: type VII collagen non-collagenous domains enzyme-linked immunoassay (NC1/2 ELISA) (MBL, Nagoya, Japan); type VII collagen NC1 ELISA (Euroimmun, Lübeck, Germany); indirect immunofluorescence (IF) microscopy test based on the expression of recombinant NC1 in a human cell line (NC1 BIOCHIP®; Euroimmun); full-length recombinant type VII collagen ELISA; immunoblotting with full-length type VII collagen in the extract of human dermis; and immunoblotting with recombinant NC1. Immunoblotting with recombinant NC1 showed a sensitivity of 93.1% and specificity of 100%, follow-ed by NC1 BIOCHIP® (sensitivity, 89.1%; specificity, 100%), immunoblotting with human dermis (sensitivity, 87.1%; specificity 100%), NC1-ELISA (sensitivity 82.2%; specificity 98.6%), NC1/NC2 ELISA (sensitivity 88.1%; specificity 93.3%), and full-length type VII collagen ELISA (sensitivity 80.2%; specificity 93.8%).

Emerging drugs for the treatment of epidermolysis bullosa.

INTRODUCTION: Epidermolysis Bullosa (EB) form a heterogeneous group of rare, sometimes life-threatening inherited skin diseases characterized by skin and mucosal blistering after mild trauma from birth. They display a wide range of disease severity, with multiple local and systemic complications with no satisfactory treatment. AREAS COVERED: Approaches aiming to restore the functional expression of the defective protein such as ex vivo and in vivo gene therapy, cell therapies, protein replacement and pharmacological approaches have shown promising results. In addition, improved knowledge of EB pathogenesis has open the way to symptom-relief therapies using repurposed drugs in some forms of EB. EXPERT OPINION: A cure for all forms of EB will remain challenging, but it is anticipated that treatments for EB will rely on precision medicine, involving a combination of complementary approaches. Treatments aiming to restore the function of the defective genes will be combined with symptom-relief therapies to address the specific features of the different forms of EB and each patient complications. A growing number of biotech and pharmaceutical companies have shown an increasing interest in the treatment of EB and as a result, have implemented numerous clinical trials. Therefore, we anticipate the emergence of effective treatments in the near future.

Safety and early efficacy outcomes for lentiviral fibroblast gene therapy in recessive dystrophic epidermolysis bullosa.

BACKGROUNDRecessive dystrophic epidermolysis bullosa (RDEB) is a severe form of skin fragility disorder due to mutations in COL7A1 encoding basement membrane type VII collagen (C7), the main constituent of anchoring fibrils (AFs) in skin. We developed a self-inactivating lentiviral platform encoding a codon-optimized COL7A1 cDNA under the control of a human phosphoglycerate kinase promoter for phase I evaluation.METHODSIn this single-center, open-label phase I trial, 4 adults with RDEB each received 3 intradermal injections (~1 × 106 cells/cm2 of intact skin) of COL7A1-modified autologous fibroblasts and were followed up for 12 months. The primary outcome was safety, including autoimmune reactions against recombinant C7. Secondary outcomes included C7 expression, AF morphology, and presence of transgene in the injected skin.RESULTSGene-modified fibroblasts were well tolerated, without serious adverse reactions or autoimmune reactions against recombinant C7. Regarding efficacy, there was a significant (P < 0.05) 1.26-fold to 26.10-fold increase in C7 mean fluorescence intensity in the injected skin compared with noninjected skin in 3 of 4 subjects, with a sustained increase up to 12 months in 2 of 4 subjects. The presence of transgene (codon-optimized COL7A1 cDNA) was demonstrated in the injected skin at month 12 in 1 subject, but no new mature AFs were detected.CONCLUSIONTo our knowledge, this is the first human study demonstrating safety and potential efficacy of lentiviral fibroblast gene therapy with the presence of COL7A1 transgene and subsequent C7 restoration in vivo in treated skin at 1 year after gene therapy. These data provide a rationale for phase II studies for further clinical evaluation.TRIAL REGISTRATIONClincalTrials.gov NCT02493816.FUNDINGCure EB, Dystrophic Epidermolysis Bullosa Research Association (UK), UK NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, and Fondation René Touraine Short-Exchange Award.

Epidermolysis bullosa simplex-generalized severe type due to keratin 5 p.Glu477Lys mutation: Genotype-phenotype correlation and in silico modeling analysis.

BACKGROUND/OBJECTIVES: Epidermolysis bullosa is a group of diseases caused by mutations in skin structural proteins. Availability of genetic sequencing makes identification of causative mutations easier, and genotype-phenotype description and correlation are important. We describe six patients with a keratin 5 mutation resulting in a glutamic acid to lysine substitution at position 477 (p.Glu477Lys) who have a distinctive, severe and sometimes fatal phenotype. We also perform in silico modeling to show protein structural changes resulting in instability. METHODS: In this case series, we collected clinical data from six patients with this mutation identified from their national or local epidermolysis bullosa databases. We performed in silico modeling of the keratin 5-keratin 14 coil 2B complex using CCBuilder and rendered with Pymol (Schrodinger, LLC, New York, NY). RESULTS: Features include aplasia cutis congenita, generalized blistering, palmoplantar keratoderma, onychodystrophy, airway and developmental abnormalities, and a distinctive reticulated skin pattern. Our in silico model of the keratin 5 p.Glu477Lys mutation predicts conformational change and modification of the surface charge of the keratin heterodimer, severely impairing filament stability. CONCLUSIONS: Early recognition of the features of this genotype will improve care. In silico analysis of mutated keratin structures provides useful insights into structural instability.

Correction to: Antisense-Mediated Splice Modulation to Reframe Transcripts.

The original version of this book was published with the following errors: "2'MOE" have been corrected into "2'MOEPS" in figure.6 - Chapter 35, multiple typo errors in page numbers: 532, 533, 534, 537, 542, 548 and 549. These errors has been updated.

Antisense-Mediated Splice Modulation to Reframe Transcripts.

Numerous genetic disorders are caused by loss-of-function mutations that disrupt the open reading frame of the gene either by nonsense or by frameshift (insertion, deletion, indel, or splicing) mutations. Most of the time, the result is the absence of functional protein synthesis due to mRNA degradation by nonsense-mediated mRNA decay, or rapid degradation of a truncated protein. Antisense-based splicing modulation is a powerful tool that has the potential to treat genetic disorders by restoring the open reading frame through selective removal of the mutated exon, or by restoring correct splicing.We have developed this approach for a severe skin genetic disorder, recessive dystrophic epidermolysis bullosa, caused by mutations in the COL7A1 gene encoding type VII collagen. This gene is particularly suited for exon skipping approaches due to its unique genomic structure. It is composed of 118 exons, 83 of which are in frame. Moreover, these exons encode a single repetitive collagenous domain.Using this gene as an example, we describe general methods that demonstrate the feasibility and efficacy of the antisense-mediated exon skipping strategy to reframe transcripts.

APOBEC mutation drives early-onset squamous cell carcinomas in recessive dystrophic epidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare inherited skin and mucous membrane fragility disorder complicated by early-onset, highly malignant cutaneous squamous cell carcinomas (SCCs). The molecular etiology of RDEB SCC, which arises at sites of sustained tissue damage, is unknown. We performed detailed molecular analysis using whole-exome, whole-genome, and RNA sequencing of 27 RDEB SCC tumors, including multiple tumors from the same patient and multiple regions from five individual tumors. We report that driver mutations were shared with spontaneous, ultraviolet (UV) light-induced cutaneous SCC (UV SCC) and head and neck SCC (HNSCC) and did not explain the early presentation or aggressive nature of RDEB SCC. Instead, endogenous mutation processes associated with apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) deaminases dominated RDEB SCC. APOBEC mutation signatures were enhanced throughout RDEB SCC tumor evolution, relative to spontaneous UV SCC and HNSCC mutation profiles. Sixty-seven percent of RDEB SCC driver mutations was found to emerge as a result of APOBEC and other endogenous mutational processes previously associated with age, potentially explaining a >1000-fold increased incidence and the early onset of these SCCs. Human papillomavirus-negative basal and mesenchymal subtypes of HNSCC harbored enhanced APOBEC mutational signatures and transcriptomes similar to those of RDEB SCC, suggesting that APOBEC deaminases drive other subtypes of SCC. Collectively, these data establish specific mutagenic mechanisms associated with chronic tissue damage. Our findings reveal a cause for cancers arising at sites of persistent inflammation and identify potential therapeutic avenues to treat RDEB SCC.

A recessive form of hyper-IgE syndrome by disruption of ZNF341-dependent STAT3 transcription and activity.

Heterozygosity for human signal transducer and activator of transcription 3 (STAT3) dominant-negative (DN) mutations underlies an autosomal dominant form of hyper-immunoglobulin E syndrome (HIES). We describe patients with an autosomal recessive form of HIES due to loss-of-function mutations of a previously uncharacterized gene, ZNF341 ZNF341 is a transcription factor that resides in the nucleus, where it binds a specific DNA motif present in various genes, including the STAT3 promoter. The patients' cells have low basal levels of STAT3 mRNA and protein. The autoinduction of STAT3 production, activation, and function by STAT3-activating cytokines is strongly impaired. Like patients with STAT3 DN mutations, ZNF341-deficient patients lack T helper 17 (TH17) cells, have an excess of TH2 cells, and have low memory B cells due to the tight dependence of STAT3 activity on ZNF341 in lymphocytes. Their milder extra-hematopoietic manifestations and stronger inflammatory responses reflect the lower ZNF341 dependence of STAT3 activity in other cell types. Human ZNF341 is essential for the STAT3 transcription-dependent autoinduction and sustained activity of STAT3.

The Molecular Revolution in Cutaneous Biology: Emerging Landscape in Genomic Dermatology: New Mechanistic Ideas, Gene Editing, and Therapeutic Breakthroughs.

Stunning technological advances in genomics have led to spectacular breakthroughs in the understanding of the underlying defects, biological pathways and therapeutic targets of skin diseases leading to new therapeutic interventions. Next-generation sequencing has revolutionized the identification of disease-causing genes and has a profound impact in deciphering gene and protein signatures in rare and frequent skin diseases. Gene addition strategies have shown efficacy in junctional EB and in recessive dystrophic EB (RDEB). TALENs and Cripsr/Cas9 have emerged as highly efficient new tools to edit genomic sequences to creat new models and to correct or disrupt mutated genes to treat human diseases. Therapeutic approaches have not been limited to DNA modification and strategies at the mRNA, protein and cellular levels have also emerged, some of which have already proven clinical efficacy in RDEB. Improved understanding of the pathogenesis of skin disorders has led to the development of specific drugs or repurposing of existing medicines as in basal cell nevus syndrome, alopecia areata, melanoma and EB simplex. These discoveries pave the way for improved targeted personalized medicine for rare and frequent diseases. It is likely that a growing number of orphan skin diseases will benefit from combinatory new therapies in a near future.

Targeted Exon Skipping Restores Type VII Collagen Expression and Anchoring Fibril Formation in an In Vivo RDEB Model.

Dystrophic epidermolysis bullosa is a group of orphan genetic skin diseases dominantly or recessively inherited, caused by mutations in COL7A1 encoding type VII collagen, which forms anchoring fibrils. Individuals with recessive dystrophic epidermolysis bullosa develop severe skin and mucosal blistering after mild trauma. The exon skipping strategy consists of modulating splicing of a pre-mRNA to induce skipping of a mutated exon. We have targeted COL7A1 exons 73 and 80, which carry recurrent mutations and whose excision preserves the open reading frame. We first showed the dispensability of these exons for type VII collagen function in vivo. We then showed that transfection of primary recessive dystrophic epidermolysis bullosa keratinocytes and fibroblasts carrying null mutations in exon 73 and/or 80, with 2'-O-methyl antisense oligoribonucleotides, led to efficient ex vivo skipping of these exons (50-95%) and resulted in a significant level (up to 36%) of type VII collagen re-expression. Finally, one or two subcutaneous injections of antisense oligoribonucleotides at doses ranging from 400 µg up to 1 mg restored type VII collagen expression and anchoring fibril formation in vivo in a xenograft model of recessive dystrophic epidermolysis bullosa skin equivalent. This work provides a proof of principle for the treatment of patients with recessive dystrophic epidermolysis bullosa by exon skipping using subcutaneous administration of antisense oligoribonucleotides.

Comparison of 3 type VII collagen (C7) assays for serologic diagnosis of epidermolysis bullosa acquisita (EBA).

BACKGROUND: Serologic diagnosis of epidermolysis bullosa acquisita (EBA) relies on the detection of circulating autoantibodies to type VII collagen (C7). OBJECTIVE: We sought to compare the diagnostic performances of a commercialized enzyme-linked immunosorbent assay (ELISA) using C7 noncollagenous (NC) domains (C7-NC1/NC2 ELISA) and indirect immunofluorescence (IIF) biochip test on NC1-C7-expressing transfected cells (IIFT), with a full-length-C7 ELISA developed in our laboratory. METHODS: C7-NC1/NC2 ELISA, IIFT, and full-length-C7 ELISA were run on 77 nonselected consecutive EBA sera. RESULTS: C7-NC1/NC2 ELISA, IIFT, and full-length-C7 ELISA were positive, respectively, for: 30%, 27%, and 65% of the 77 sera; 43%, 32%, and 80% of 44 sera labeling the salt-split-skin (SSS) floor (F) by IIF (SSS/F(+)); 9%, 22%, and 47% of 32 SSS/F(-) sera; 28%, 28%, and 58% of classic EBA; 41%, 41%, and 82% of inflammatory EBA; and 18%, 0%, and 55% of mucous-membrane-predominant EBA. Significant differences for all sera were found between: the 2 ELISAs for the 77 sera, SSS/F(+) and SSS/F(-) sera, and IIFT versus full-length-C7 ELISA. LIMITATIONS: The retrospective design was a limitation. CONCLUSION: C7-NC1/NC2 ELISA and IIFT sensitivities for serologic diagnoses of EBA were low. Full-length-C7 ELISA was significantly more sensitive and could serve as a reference test.

Gene-Corrected Fibroblast Therapy for Recessive Dystrophic Epidermolysis Bullosa using a Self-Inactivating COL7A1 Retroviral Vector.

Patients with recessive dystrophic epidermolysis bullosa (RDEB) lack type VII collagen and therefore have severely impaired dermal-epidermal stability causing recurrent skin and mucosal blistering. There is currently no specific approved treatment for RDEB. We present preclinical data showing that intradermal injections of genetically corrected patient-derived RDEB fibroblasts using a Good Manufacturing Practices grade self-inactivating COL7A1 retroviral vector reverse the disease phenotype in a xenograft model in nude mice. We obtained 50% transduction efficiency in primary human RDEB fibroblasts with an average low copy number (range = 1-2) of integrated provirus. Transduced fibroblasts showed strong type VII collagen re-expression, improved adhesion properties, normal proliferative capabilities, and viability in vitro. We show that a single intradermal injection of 3 × 10(6) genetically corrected RDEB fibroblasts beneath RDEB skin equivalents grafted onto mice allows type VII collagen deposition, anchoring fibril formation at the dermal-epidermal junction, and improved dermal-epidermal adherence 2 months after treatment, supporting functional correction in vivo. Gene-corrected fibroblasts previously showed no tumorigenicity. These data show the efficacy and safety of gene-corrected fibroblast therapy using a self-inactivating vector that has now been good manufacturing grade-certified and pave the way for clinical translation to treat nonhealing wounds in RDEB patients.

HEK293-based production platform for γ-retroviral (self-inactivating) vectors: application for safe and efficient transfer of COL7A1 cDNA.

The clinical application of self-inactivating (SIN) retroviral vectors requires an efficient vector production technology. To enable production of γ-retroviral SIN vectors from stable producer cells, new targetable HEK293-based producer clones were selected, providing amphotropic, GALV, or RD114 pseudotyping. Viral vector expression constructs can reliably be inserted at a predefined genomic locus via Flp-recombinase-mediated cassette exchange. Introduction of a clean-up step, mediated by Cre-recombinase, allows the removal of residual sequences that were required for targeting and selection, but were dispensable for the final producer clones and eliminated homology-driven recombination between the tagging and the therapeutic vector. The system was used to establish GALV and RD114 pseudotyping producer cells (HG- and HR820) for a clinically relevant long terminal repeat-driven therapeutic vector, designed for the transfer of a recombinant TCR that delivered titers in the range of 2×10(7) infectious particles (IP)/ml. Production capacity of the amphotropic producer cell (HA820) was challenged by a therapeutic SIN vector transferring the large COL7A1 cDNA. The final producer clone delivered a titer of 4×10(6) IP/ml and the vector containing supernatant was used directly to functionally restore primary fibroblasts and keratinocytes isolated from recessive dystrophic epidermolysis bullosa patients. Thus, the combinatorial approach (fc-technology) to generate producer cells for therapeutic γ-retroviral (SIN) vectors is feasible, is highly efficient, and allows their safe production and application in clinical trials.

Antisense-mediated exon skipping to reframe transcripts.

Numerous genetic disorders are caused by loss-of-function mutations that disrupt the open reading frame of the gene either by nonsense or by frameshift (insertion, deletion, indel, or splicing) mutations. Most of the time, the result is the absence of functional protein synthesis due to mRNA degradation by nonsense-mediated mRNA decay, or rapid degradation of a truncated protein. Antisense-based splicing modulation is a powerful tool that has the potential to treat genetic disorders by restoring the open reading frame through selective removal of the mutated exon, or by restoring correct splicing.We have developed this approach for a severe genetic skin disorder, recessive dystrophic epidermolysis bullosa, caused by mutations in the COL7A1 gene encoding type VII collagen. This gene is particularly suited for exon-skipping approaches due to its unique genomic structure. It is composed of 118 exons, 83 of which are in frame. Moreover, these exons encode a single repetitive collagenous domain.Using this gene as an example, we describe general methods that demonstrate the feasibility and efficacy of the antisense-mediated exon-skipping strategy to reframe transcripts.