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Human skin contains a population of memory T cells that supports tissue homeostasis and provides protective immunity. The study of human memory T cells is often restricted to in vitro studies and to human PBMC serving as primary cell source. Because the tissue environment impacts the phenotype and function of memory T cells, it is crucial to study these cells within their tissue. Here we utilized immunodeficient NOD-scid IL2rγnull (NSG) mice that carried in vivo-generated engineered human skin (ES). ES was generated from human keratinocytes and fibroblasts and was initially devoid of skin-resident immune cells. Upon adoptive transfer of human PBMC, this reductionist system allowed us to study human T cell recruitment from a circulating pool of T cells into non-inflamed human skin in vivo. Circulating human memory T cells preferentially infiltrated ES and showed diverse functional profiles of T cells found in fresh human skin. The chemokine and cytokine microenvironment of ES closely resembled that of non-inflamed human skin. Upon entering the ES T cells assumed a resident memory T cell-like phenotype in the absence of infection, and a proportion of these cutaneous T cells can be locally activated upon injection of monocyte derived dendritic cells (moDCs) that presented Candida albicans. Interestingly, we found that CD69+ memory T cells produced higher levels of effector cytokines in response to Candida albicans, compared to CD69- T cells. Overall, this model has broad utility in many areas of human skin immunology research, including the study of immune-mediated skin diseases.

International audience; The Duchenne muscular dystrophy (DMD) gene has a complex expression pattern regulated by multiple tissue-specific promoters and by alternative splicing (AS) of the resulting transcripts. Here, we used an RNAi-based approach coupled with DMD-targeted RNA-seq to identify RNA-binding proteins (RBPs) that regulate splicing of its skeletal muscle isoform (Dp427m) in a human muscular cell line. A total of 16 RBPs comprising the major regulators of muscle-specific splicing events were tested. We show that distinct combinations of RBPs maintain the correct inclusion in the Dp427m of exons that undergo spatio-temporal AS in other dystrophin isoforms. In particular, our findings revealed the complex networks of RBPs contributing to the splicing of the two short DMD exons 71 and 78, the inclusion of exon 78 in the adult Dp427m isoform being crucial for muscle function. Among the RBPs tested, QKI and DDX5/DDX17 proteins are important determinants of DMD exon inclusion. This is the first large-scale study to determine which RBP proteins act on the physiological splicing of the DMD gene. Our data shed light on molecular mechanisms contributing to the expression of the different dystrophin isoforms, which could be influenced by a change in the function or expression level of the identified RBPs.

Background Cutaneous squamous cell carcinomas (cSCC) are the primary cause of premature deaths in patients suffering from the rare skin-fragility disorder recessive dystrophic epidermolysis bullosa (RDEB), which is in marked contrast to the rarely metastasizing nature of these carcinomas in the general population. This remarkable difference is attributed to the frequent development of chronic wounds caused by impaired skin integrity. However, the specific molecular and cellular changes to malignancy, and whether there are common players in different types of aggressive cSCCs, remain relatively undefined. Methods MiRNA expression profiling was performed across various cell types isolated from skin and cSCCs. Microarray results were confirmed by qPCR and by an optimized in situ hybridization protocol. Functional impact of overexpression or knock-out of a dysregulated miRNA was assessed in migration and 3D-spheroid assays. Sample-matched transcriptome data was generated to support the identification of disease relevant miRNA targets. Results Several miRNAs were identified as dysregulated in cSCCs compared to control skin. These included the metastasis-linked miR-10b, which was significantly upregulated in primary cell cultures and in archival biopsies. At the functional level, overexpression of miR-10b conferred the stem cell-characteristic of 3D-spheroid formation capacity to keratinocytes. Analysis of miR-10b downstream effects identified a novel putative target of miR-10b, the actin- and tubulin cytoskeleton-associated protein DIAPH2. Conclusion The discovery that miR-10b mediates an aspect of cancer stemness – that of enhanced tumor cell adhesion, known to facilitate metastatic colonization – provides an important avenue for future development of novel therapies targeting this metastasis-linked miRNA.

Dystrophic epidermolysis bullosa (DEB) is a blistering skin disease caused by mutations in the gene COL7A1 encoding collagen VII. DEB can be inherited as recessive DEB (RDEB) or dominant DEB (DDEB) and is associated with a high wound burden. Perpetual cycles of wounding and healing drive fibrosis in DDEB and RDEB, as well as the formation of a tumor-permissive microenvironment. Prolonging wound-free episodes by improving the quality of wound healing would therefore confer substantial benefit for individuals with DEB. The collagenous domain of collagen VII is encoded by 82 in-frame exons, which makes splice-modulation therapies attractive for DEB. Indeed, antisense oligonucleotide–based exon skipping has shown promise for RDEB. However, the suitability of antisense oligonucleotides for treatment of DDEB remains unexplored. Here, we developed QR-313, a clinically applicable, potent antisense oligonucleotide specifically targeting exon 73. We show the feasibility of topical delivery of QR-313 in a carbomer-composed gel for treatment of wounds to restore collagen VII abundance in human RDEB skin. Our data reveal that QR-313 also shows direct benefit for DDEB caused by exon 73 mutations. Thus, the same topically applied therapeutic could be used to improve the wound healing quality in RDEB and DDEB.

Human skin contains a population of memory T cells that support tissue homeostasis and provide protective immunity. The study of human memory T cells is often restricted to in vitro studies and to human PBMC serving as primary cell source. Because the tisse environment impacts the phenotype and function of memory T cells, it is crucial to study these cells within their tissue. Here we utilized immunodeficient NOD-scid IL2rγnull (NSG) mice that carried in vivo-generated engineered human skin (ES). ES were generated from human keratinocytes and fibroblasts and is initially devoid of skin-resident immune cells. Upon adoptive transfer of human PBMC this reductionist system allowed to study human T cell recruitment from a circulating pool of T cells into non-inflamed human skin in vivo. Circulating human memory T cells preferentially infiltrated ES and showed diverse functional profiles of T cells found in fresh human skin. The chemokine and cytokine microenvironment of ES closely resembled that of non-inflamed human skin. Upon entering the ES T cells assumed a resident memory T cell-like phenotype in the absence of infection, and a proportion of these cutaneous T cells can be locally activated upon injection of monocyte derived dendritic cells (moDCs) that presented Candida albicans. Interestingly, we found that CD69+ memory T cells produced higher levels of effector cytokines in response to Candida albicans, compared to CD69- T cells. Overall, this model has broad utility in many areas of human skin immunology research, including the study of immune-mediated skin diseases.

In the treatment of genetic disorders, repairing defective pre-mRNAs by RNA trans-splicing has become an emerging alternative to conventional gene therapy. Previous studies have made clear that the design of the binding domains of the corrective RNA trans-splicing molecules (RTMs) is crucial for their optimal functionality. We established a reporter-based screening method that allows for selection of highly functional RTMs from a large pool of variants. The efficiency and functionality of the screen were validated in the COL7A1 gene, in which mutations are the cause of the skin disease dystrophic epidermolysis bullosa. Comparison of RTMs containing different binding domains hybridizing to COL7A1 intron 64/exon 65 revealed highly different trans-splicing efficiencies. Isolated RTMs were then adapted for endogenous trans-splicing in a recessive dystrophic epidermolysis bullosa (RDEB) keratinocyte cell line expressing reduced levels of COL7A1 mRNA. Our results confirm the applicability and relevance of prescreening reporter RTMs, as significant levels of endogenous COL7A1 mRNA repair were seen with RTMs identified as being highly efficient in our screening system.

Spliceosome-mediated RNA trans-splicing (SMaRT) is an RNA-based technology to reprogram genes for diagnostic and therapeutic purposes. For the correction of genetic diseases, SMaRT offers several advantages over traditional gene-replacement strategies. SMaRT protocols have recently been used for in vitro phenotypic correction of a variety of genetic disorders, ranging from epidermolysis bullosa to neurodegenerative diseases. In vivo studies are currently bringing trans-splicing RNA therapy toward clinical application. In this review, we summarize the progress made toward the medical use of SMaRT and provide an outlook on its upcoming applications.

164 CRISPR/Cas9-mediated gene repair in the COL7A1 gene S Hainzl, T Kocher, EM Murauer, F Larcher, M Steiner, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria, 2 Department of Dermatology, Paracelsus Medical University, Salzburg, Austria, 3 Epithelial Biomedicine Division, CIEMAT, Madrid, Spain and 4 3rd Medical Department, Paracelsus Medical University Salzburg, Austria, Laboratory for Immunological and Molecular Cancer Research, Salzburg, Austria The CRISPR/Cas9 system turned out to be a powerful tool for genome editing and is therefore a promising option for the specific repair of gene mutations causing the blistering skin disease epidermolysis bullosa (EB). We have exploited the CRISPR/Cas9-mediated homologydirected repair (HDR) approach for the correction of a homozygous mutation in COL7A1 exon 80, leading to a complete loss of type VII collagen within the basement membrane zone of the skin. We have predicted a guide RNA (gRNA) specific for intron 80 of COL7A1, which was then cloned either into a wild-type Cas9 dual vector system, inducing double strand breaks, or a D10A Cas9 dual vector system, causing single strand breaks within the target intron. Homology COL7A1 arms for HDR were cloned into a donor vector, including a selection cassette. Transfected patient keratinocytes were selected either via antibiotic selection or fluorescent-activated cell sorting (FACS). RT-PCR on genomic DNA of treated cells and subsequent restriction enzyme digest analysis of the resulting PCR products showed the genetic correction of the COL7A1 mutation. The mutation-specific enzymatic digest revealed the presence of 26% reverted alleles. Additionally, type VII collagen restoration was confirmed via Western blot analysis and immunofluorescence staining. Our data indicate that genome editing using the CRISPR/Cas9 system can be an elegant tool for the repair of genes involved in the severe skin disease epidermolysis bullosa. 165 Combining antisense molecules with splicing modulation for KRT14 repair in epidermolysis bullosa B Liemberger, C Arzt, S Hainzl, J Pinon Hofbauer, V Wally, EM Murauer, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria and 2 Department of Dermatology, Paracelsus Medical University Salzburg, Austria, Salzburg, Austria Epidermolysis bullosa (EB) is an inherited skin disease characterized by severe blistering of the skin and mucous membranes after minor mechanical trauma. In EB simplex (EBS) dominant mutations within KRT14 encoding keratin 14 lead to loss of integrity of the intermediate filament network within basal keratinocytes. In order to correct a dominant mutation in an EBS patient cell line, we exploited the RNA trans-splicing technology which utilizes the cell’s endogenous splicing machinery to facilitate a trans-splicing reaction between two RNAs, generating a new chimeric product at the pre-mRNA level. The designed RNA transsplicing molecule (RTM), containing a binding domain, splicing elements, and the wild-type KRT14 region to be introduced, has already been shown to be able to partially revert the EBS phenotype at the cellular level. In order to increase the repair efficiency mediated by RNA trans-splicing, antisense RNAs (asRNAs) specific for splice sites or splicing enhancer sequences within the KRT14 target pre-mRNA region were randomly generated with the aim of blocking these cis-splicing elements thereby increasing the trans-splicing rate. We analysed the functionality of 76 individual asRNAs by exploiting our fluorescence-based screening system, in which reconstitution of a GFP signal acts as a readout for accurate trans-splicing between a generated KRT14 minigene (KRT14-MG) and the RTM. Triple transfection experiments in HEK293 cells of the KRT14-MG, the RTM, and the most functional asRNA revealed an increase in trans-splicing efficiency of up to 7 fold as monitored by flow cytometry. Our data suggest that the inclusion of asRNAs can increase the trans-splicing efficiency to levels needed to overcome the EBS phenotype.

164 CRISPR/Cas9-mediated gene repair in the COL7A1 gene S Hainzl, T Kocher, EM Murauer, F Larcher, M Steiner, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria, 2 Department of Dermatology, Paracelsus Medical University, Salzburg, Austria, 3 Epithelial Biomedicine Division, CIEMAT, Madrid, Spain and 4 3rd Medical Department, Paracelsus Medical University Salzburg, Austria, Laboratory for Immunological and Molecular Cancer Research, Salzburg, Austria The CRISPR/Cas9 system turned out to be a powerful tool for genome editing and is therefore a promising option for the specific repair of gene mutations causing the blistering skin disease epidermolysis bullosa (EB). We have exploited the CRISPR/Cas9-mediated homologydirected repair (HDR) approach for the correction of a homozygous mutation in COL7A1 exon 80, leading to a complete loss of type VII collagen within the basement membrane zone of the skin. We have predicted a guide RNA (gRNA) specific for intron 80 of COL7A1, which was then cloned either into a wild-type Cas9 dual vector system, inducing double strand breaks, or a D10A Cas9 dual vector system, causing single strand breaks within the target intron. Homology COL7A1 arms for HDR were cloned into a donor vector, including a selection cassette. Transfected patient keratinocytes were selected either via antibiotic selection or fluorescent-activated cell sorting (FACS). RT-PCR on genomic DNA of treated cells and subsequent restriction enzyme digest analysis of the resulting PCR products showed the genetic correction of the COL7A1 mutation. The mutation-specific enzymatic digest revealed the presence of 26% reverted alleles. Additionally, type VII collagen restoration was confirmed via Western blot analysis and immunofluorescence staining. Our data indicate that genome editing using the CRISPR/Cas9 system can be an elegant tool for the repair of genes involved in the severe skin disease epidermolysis bullosa. 165 Combining antisense molecules with splicing modulation for KRT14 repair in epidermolysis bullosa B Liemberger, C Arzt, S Hainzl, J Pinon Hofbauer, V Wally, EM Murauer, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria and 2 Department of Dermatology, Paracelsus Medical University Salzburg, Austria, Salzburg, Austria Epidermolysis bullosa (EB) is an inherited skin disease characterized by severe blistering of the skin and mucous membranes after minor mechanical trauma. In EB simplex (EBS) dominant mutations within KRT14 encoding keratin 14 lead to loss of integrity of the intermediate filament network within basal keratinocytes. In order to correct a dominant mutation in an EBS patient cell line, we exploited the RNA trans-splicing technology which utilizes the cell’s endogenous splicing machinery to facilitate a trans-splicing reaction between two RNAs, generating a new chimeric product at the pre-mRNA level. The designed RNA transsplicing molecule (RTM), containing a binding domain, splicing elements, and the wild-type KRT14 region to be introduced, has already been shown to be able to partially revert the EBS phenotype at the cellular level. In order to increase the repair efficiency mediated by RNA trans-splicing, antisense RNAs (asRNAs) specific for splice sites or splicing enhancer sequences within the KRT14 target pre-mRNA region were randomly generated with the aim of blocking these cis-splicing elements thereby increasing the trans-splicing rate. We analysed the functionality of 76 individual asRNAs by exploiting our fluorescence-based screening system, in which reconstitution of a GFP signal acts as a readout for accurate trans-splicing between a generated KRT14 minigene (KRT14-MG) and the RTM. Triple transfection experiments in HEK293 cells of the KRT14-MG, the RTM, and the most functional asRNA revealed an increase in trans-splicing efficiency of up to 7 fold as monitored by flow cytometry. Our data suggest that the inclusion of asRNAs can increase the trans-splicing efficiency to levels needed to overcome the EBS phenotype.

164 CRISPR/Cas9-mediated gene repair in the COL7A1 gene S Hainzl, T Kocher, EM Murauer, F Larcher, M Steiner, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria, 2 Department of Dermatology, Paracelsus Medical University, Salzburg, Austria, 3 Epithelial Biomedicine Division, CIEMAT, Madrid, Spain and 4 3rd Medical Department, Paracelsus Medical University Salzburg, Austria, Laboratory for Immunological and Molecular Cancer Research, Salzburg, Austria The CRISPR/Cas9 system turned out to be a powerful tool for genome editing and is therefore a promising option for the specific repair of gene mutations causing the blistering skin disease epidermolysis bullosa (EB). We have exploited the CRISPR/Cas9-mediated homologydirected repair (HDR) approach for the correction of a homozygous mutation in COL7A1 exon 80, leading to a complete loss of type VII collagen within the basement membrane zone of the skin. We have predicted a guide RNA (gRNA) specific for intron 80 of COL7A1, which was then cloned either into a wild-type Cas9 dual vector system, inducing double strand breaks, or a D10A Cas9 dual vector system, causing single strand breaks within the target intron. Homology COL7A1 arms for HDR were cloned into a donor vector, including a selection cassette. Transfected patient keratinocytes were selected either via antibiotic selection or fluorescent-activated cell sorting (FACS). RT-PCR on genomic DNA of treated cells and subsequent restriction enzyme digest analysis of the resulting PCR products showed the genetic correction of the COL7A1 mutation. The mutation-specific enzymatic digest revealed the presence of 26% reverted alleles. Additionally, type VII collagen restoration was confirmed via Western blot analysis and immunofluorescence staining. Our data indicate that genome editing using the CRISPR/Cas9 system can be an elegant tool for the repair of genes involved in the severe skin disease epidermolysis bullosa. 165 Combining antisense molecules with splicing modulation for KRT14 repair in epidermolysis bullosa B Liemberger, C Arzt, S Hainzl, J Pinon Hofbauer, V Wally, EM Murauer, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria and 2 Department of Dermatology, Paracelsus Medical University Salzburg, Austria, Salzburg, Austria Epidermolysis bullosa (EB) is an inherited skin disease characterized by severe blistering of the skin and mucous membranes after minor mechanical trauma. In EB simplex (EBS) dominant mutations within KRT14 encoding keratin 14 lead to loss of integrity of the intermediate filament network within basal keratinocytes. In order to correct a dominant mutation in an EBS patient cell line, we exploited the RNA trans-splicing technology which utilizes the cell’s endogenous splicing machinery to facilitate a trans-splicing reaction between two RNAs, generating a new chimeric product at the pre-mRNA level. The designed RNA transsplicing molecule (RTM), containing a binding domain, splicing elements, and the wild-type KRT14 region to be introduced, has already been shown to be able to partially revert the EBS phenotype at the cellular level. In order to increase the repair efficiency mediated by RNA trans-splicing, antisense RNAs (asRNAs) specific for splice sites or splicing enhancer sequences within the KRT14 target pre-mRNA region were randomly generated with the aim of blocking these cis-splicing elements thereby increasing the trans-splicing rate. We analysed the functionality of 76 individual asRNAs by exploiting our fluorescence-based screening system, in which reconstitution of a GFP signal acts as a readout for accurate trans-splicing between a generated KRT14 minigene (KRT14-MG) and the RTM. Triple transfection experiments in HEK293 cells of the KRT14-MG, the RTM, and the most functional asRNA revealed an increase in trans-splicing efficiency of up to 7 fold as monitored by flow cytometry. Our data suggest that the inclusion of asRNAs can increase the trans-splicing efficiency to levels needed to overcome the EBS phenotype.

164 CRISPR/Cas9-mediated gene repair in the COL7A1 gene S Hainzl, T Kocher, EM Murauer, F Larcher, M Steiner, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria, 2 Department of Dermatology, Paracelsus Medical University, Salzburg, Austria, 3 Epithelial Biomedicine Division, CIEMAT, Madrid, Spain and 4 3rd Medical Department, Paracelsus Medical University Salzburg, Austria, Laboratory for Immunological and Molecular Cancer Research, Salzburg, Austria The CRISPR/Cas9 system turned out to be a powerful tool for genome editing and is therefore a promising option for the specific repair of gene mutations causing the blistering skin disease epidermolysis bullosa (EB). We have exploited the CRISPR/Cas9-mediated homologydirected repair (HDR) approach for the correction of a homozygous mutation in COL7A1 exon 80, leading to a complete loss of type VII collagen within the basement membrane zone of the skin. We have predicted a guide RNA (gRNA) specific for intron 80 of COL7A1, which was then cloned either into a wild-type Cas9 dual vector system, inducing double strand breaks, or a D10A Cas9 dual vector system, causing single strand breaks within the target intron. Homology COL7A1 arms for HDR were cloned into a donor vector, including a selection cassette. Transfected patient keratinocytes were selected either via antibiotic selection or fluorescent-activated cell sorting (FACS). RT-PCR on genomic DNA of treated cells and subsequent restriction enzyme digest analysis of the resulting PCR products showed the genetic correction of the COL7A1 mutation. The mutation-specific enzymatic digest revealed the presence of 26% reverted alleles. Additionally, type VII collagen restoration was confirmed via Western blot analysis and immunofluorescence staining. Our data indicate that genome editing using the CRISPR/Cas9 system can be an elegant tool for the repair of genes involved in the severe skin disease epidermolysis bullosa. 165 Combining antisense molecules with splicing modulation for KRT14 repair in epidermolysis bullosa B Liemberger, C Arzt, S Hainzl, J Pinon Hofbauer, V Wally, EM Murauer, JW Bauer, J Reichelt and U Koller 1 EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology, University Hospital of the Paracelsus Medical University, Salzburg, Austria and 2 Department of Dermatology, Paracelsus Medical University Salzburg, Austria, Salzburg, Austria Epidermolysis bullosa (EB) is an inherited skin disease characterized by severe blistering of the skin and mucous membranes after minor mechanical trauma. In EB simplex (EBS) dominant mutations within KRT14 encoding keratin 14 lead to loss of integrity of the intermediate filament network within basal keratinocytes. In order to correct a dominant mutation in an EBS patient cell line, we exploited the RNA trans-splicing technology which utilizes the cell’s endogenous splicing machinery to facilitate a trans-splicing reaction between two RNAs, generating a new chimeric product at the pre-mRNA level. The designed RNA transsplicing molecule (RTM), containing a binding domain, splicing elements, and the wild-type KRT14 region to be introduced, has already been shown to be able to partially revert the EBS phenotype at the cellular level. In order to increase the repair efficiency mediated by RNA trans-splicing, antisense RNAs (asRNAs) specific for splice sites or splicing enhancer sequences within the KRT14 target pre-mRNA region were randomly generated with the aim of blocking these cis-splicing elements thereby increasing the trans-splicing rate. We analysed the functionality of 76 individual asRNAs by exploiting our fluorescence-based screening system, in which reconstitution of a GFP signal acts as a readout for accurate trans-splicing between a generated KRT14 minigene (KRT14-MG) and the RTM. Triple transfection experiments in HEK293 cells of the KRT14-MG, the RTM, and the most functional asRNA revealed an increase in trans-splicing efficiency of up to 7 fold as monitored by flow cytometry. Our data suggest that the inclusion of asRNAs can increase the trans-splicing efficiency to levels needed to overcome the EBS phenotype.

Functional defects in type VII collagen, caused by premature termination codons on both alleles of the COL7A1 gene, are responsible for the severe autosomal recessive types of the skin blistering disease, recessive dystrophic epidermolysis bullosa (RDEB). The full-length COL7A1 complementary DNA (cDNA) is about 9kb, a size that is hardly accommodated by therapeutically used retroviral vectors. Although there have been successful attempts to produce functional type VII collagen protein in model systems of RDEB, the risk of genetic rearrangements of the large repetitive cDNA sequence may hamper the clinical application of full-length COL7A1 cDNA in the human system. Therefore, we used trans -splicing to reduce the size of the COL7A1 transcript. Retroviral transduction of RDEB keratinocytes with a 3′ pre- trans -splicing molecule resulted in correction of full-length type VII collagen expression. Unlike parental RDEB keratinocytes, transduced cells displayed normal morphology and reduced invasive capacity. Moreover, transduced cells showed normal localization of type VII collagen at the basement membrane zone in skin equivalents, where it assembled into anchoring fibril-like structures. Thus, using trans -splicing we achieved correction of an RDEB phenotype in vitro , which marks an important step toward its application in gene therapy in vivo .JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://www.nature.com/jid/journalclub