Chlorophyll triplet states in thylakoid membranes of Acaryochloris marina. Evidence for a triplet state sitting on the photosystem I primary donor populated by intersystem crossing.

Photo-induced triplet states in the thylakoid membranes isolated from the cyanobacterium Acaryocholoris marina, that harbours Chlorophyll (Chl) d as its main chromophore, have been investigated by Optically Detected Magnetic Resonance (ODMR) and time-resolved Electron Paramagnetic Resonance (TR-EPR). Thylakoids were subjected to treatments aimed at poising the redox state of the terminal electron transfer acceptors and donors of Photosystem II (PSII) and Photosystem I (PSI), respectively. Under ambient redox conditions, four Chl d triplet populations were detectable, identifiable by their characteristic zero field splitting parameters, after deconvolution of the Fluorescence Detected Magnetic Resonance (FDMR) spectra. Illumination in the presence of the redox mediator N,N,N',N'-Tetramethyl-p-phenylenediamine (TMPD) and sodium ascorbate at room temperature led to a redistribution of the triplet populations, with T3 (|D|= 0.0245 cm-1, |E|= 0.0042 cm-1) becoming dominant and increasing in intensity with respect to untreated samples. A second triplet population (T4, |D|= 0.0248 cm-1, |E|= 0.0040 cm-1) having an intensity ratio of about 1:4 with respect to T3 was also detectable after illumination in the presence of TMPD and ascorbate. The microwave-induced Triplet-minus-Singlet spectrum acquired at the maximum of the |D|-|E| transition (610 MHz) displays a broad minimum at 740 nm, accompanied by a set of complex spectral features that overall resemble, despite showing further fine spectral structure, the previously reported Triplet-minus-Singlet spectrum attributed to the recombination triplet of PSI reaction centre, 3 P 740 [Schenderlein M, Çetin M, Barber J, et al. Spectroscopic studies of the chlorophyll d containing photosystem I from the cyanobacterium Acaryochloris marina. Biochim Biophys Acta 1777:1400-1408]. However, TR-EPR experiments indicate that this triplet displays an eaeaea electron spin polarisation pattern which is characteristic of triplet sublevels populated by intersystem crossing rather than recombination, for which an aeeaae polarisation pattern is expected instead. It is proposed that the observed triplet, which leads to the bleaching of the P740 singlet state, sits on the PSI reaction centre.

Pathogenetic role and clinical significance of interleukin-1ß in cancer.

In recent years, pro-oncogenic mechanisms of the tumour microenvironment (ТМЕ) have been actively discussed. One of the main cytokines of the TМЕ is interleukin-1 beta (IL-1ß), which exhibits proinflammatory properties. Some studies have shown an association between an increase in IL-1ß levels and tumour progression. The purpose of this review is to analyse the pathogenic mechanisms induced by IL-1ß in the TМЕ, as well as the diagnostic significance of the presence of IL-1ß in patients with cancer and the efficacy of treatment with IL-1ß inhibitors. According to the literature, IL-1ß can induce an increase in tumour angiogenesis due to its effects on the differentiation of epithelial cells, pro-angiogenic molecule secretion and expression of adhesion molecules, thus increasing tumour growth and metastasis. IL-1ß is also involved in the suppression of anti-tumour immune responses. The expression and secretion of IL-1ß has been noted in various types of tumours. In some clinical studies, an elevated level of IL-1ß was found to be associated with low efficacy of anti-cancer therapy and a poor prognosis. In most experimental and clinical studies, the use of IL-1ß inhibitors contributed to a decrease in tumour mass and an increase in the response to anti-tumour drugs.

Phylloquinone is the principal Mehler reaction site within photosystem I in high light.

Photosynthesis is a vital process, responsible for fixing carbon dioxide, and producing most of the organic matter on the planet. However, photosynthesis has some inherent limitations in utilizing solar energy, and a part of the energy absorbed is lost in the reduction of O2 to produce the superoxide radical (O2•-) via the Mehler reaction, which occurs principally within photosystem I (PSI). For decades, O2 reduction within PSI was assumed to take place solely in the distal iron-sulfur clusters rather than within the two asymmetrical cofactor branches. Here, we demonstrate that under high irradiance, O2 photoreduction by PSI primarily takes place at the phylloquinone of one of the branches (the A-branch). This conclusion derives from the light dependency of the O2 photoreduction rate constant in fully mature wild-type PSI from Chlamydomonas reinhardtii, complexes lacking iron-sulfur clusters, and a mutant PSI, in which phyllosemiquinone at the A-branch has a significantly longer lifetime. We suggest that the Mehler reaction at the phylloquinone site serves as a release valve under conditions where both the iron-sulfur clusters of PSI and the mobile ferredoxin pool are highly reduced.

Comparative Absorption Dynamics of the Singlet Excited States of Chlorophylls a and d.

Transient absorption dynamics of chlorophylls a and d dissolved in tetrahydrofuran was measured by the broadband femtosecond laser pump-probe spectroscopy in a spectral range from 400 to 870 nm. The absorption spectra of the excited S1 singlet states of chlorophylls a and d were recorded, and the dynamics of the of the Qy band shift of the stimulated emission (Stokes shift of fluorescence) was determined in a time range from 60 fs to 4 ps. The kinetics of the intramolecular conversion Qx→Qy (electronic transition S2→S1) was measured; the characteristic relaxation time was 54 ± 3 and 45 ± 9 fs for chlorophylls a and d, respectively.

Cellular therapy options for genetic skin disorders with a focus on recessive dystrophic epidermolysis bullosa.

INTRODUCTION: Combinatorial cell and gene therapies for life-threatening inherited skin disorders have shown tremendous potential for preclinical and clinical implementation with significant progress made for recessive dystrophic epidermolysis bullosa (RDEB). To date, various cell lineages including resident skin cells and adult stem cells have been investigated for gene and cell therapy for RDEB reaching the clinical trial stage. SOURCES OF DATA: Sources of data are key recent literature, ClinicalTrials.gov, Clinicaltrialsregister.eu and pharma press releases. AREAS OF AGREEMENT: Cell-based gene transfer using autologous patients' cells has demonstrated positive outcomes in preclinical and clinical trials and highlighted the importance of targeting resident skin stem cells to achieve a meaningful long-term effect. Additionally, adult stem cells, such as mesenchymal stromal cells, have the potential to ameliorate systemic manifestations of the disease. AREAS OF CONTROVERSY: While proven safe, the clinical trials of localized treatment have reported only modest and transient improvements. On the other hand, the risks associated with systemic therapies remain high and should be carefully weighed against the potential benefits. It is unclear to what extent adult stem cells can contribute to skin regeneration/wound healing. GROWING POINTS: Further research is warranted in order to fulfil the potential of cellular therapies for RDEB. The development of combinatorial gene and cell-based approaches is required to achieve long-term clinical benefits. AREAS TIMELY FOR DEVELOPING RESEARCH: Induced pluripotent stem cells can potentially provide a valuable source of autologous patient material for cellular therapies. In addition, recent advances in the field of gene editing can overcome hurdles associated with conventional gene addition approaches. DATA AVAILABILITY STATEMENT: No new data were generated or analysed in support of this review.

Long Terminal Repeat CRISPR-CAR-Coupled "Universal" T Cells Mediate Potent Anti-leukemic Effects.

Gene editing can be used to overcome allo-recognition, which otherwise limits allogeneic T cell therapies. Initial proof-of-concept applications have included generation of such "universal" T cells expressing chimeric antigen receptors (CARs) against CD19 target antigens combined with transient expression of DNA-targeting nucleases to disrupt the T cell receptor alpha constant chain (TRAC). Although relatively efficient, transgene expression and editing effects were unlinked, yields variable, and resulting T cell populations heterogeneous, complicating dosing strategies. We describe a self-inactivating lentiviral "terminal" vector platform coupling CAR expression with CRISPR/Cas9 effects through incorporation of an sgRNA element into the ΔU3 3' long terminal repeat (LTR). Following reverse transcription and duplication of the hybrid ΔU3-sgRNA, delivery of Cas9 mRNA resulted in targeted TRAC locus cleavage and allowed the enrichment of highly homogeneous (>96%) CAR+ (>99%) TCR- populations by automated magnetic separation. Molecular analyses, including NGS, WGS, and Digenome-seq, verified on-target specificity with no evidence of predicted off-target events. Robust anti-leukemic effects were demonstrated in humanized immunodeficient mice and were sustained longer than by conventional CAR+TCR+ T cells. Terminal-TRAC (TT) CAR T cells offer the possibility of a pre-manufactured, non-HLA-matched CAR cell therapy and will be evaluated in phase 1 trials against B cell malignancies shortly.

Effect of artificial redox mediators on the photoinduced oxygen reduction by photosystem I complexes.

The peculiarities of interaction of cyanobacterial photosystem I with redox mediators 2,6-dichlorophenolindophenol (DCPIP) and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) were investigated. The higher donor efficiency of the reduced DCPIP form was demonstrated. The oxidized form of DCPIP was shown to be an efficient electron acceptor for terminal iron-sulfur cluster of photosystem I. Likewise methyl viologen, after one-electron reduction, DCPIP transfers an electron to the molecular oxygen. These results were discussed in terms of influence of these interactions on photosystem I reactions with the molecular oxygen and natural electron acceptors.

Mechanism of adiabatic primary electron transfer in photosystem I: Femtosecond spectroscopy upon excitation of reaction center in the far-red edge of the QY band.

The ultrafast primary charge separation in Photosystem I (PS I) excited by femtosecond pulses centered at 720 and 760nm was studied by pump-to-probe laser spectroscopy. The absorbance in the red edge of PS I absorption spectrum has an unusual exponential dependence on wavelength. The cutoff of short wavelength components of 760nm pulse allows direct excitation of reaction center chlorophyll molecules without involvement of light-harvesting antenna. The transient spectrum manifests the features of the primary ion-radical pair P700+A0- at time delay <180fs, followed by formation of the secondary pair P700+A1- with a characteristic time of 26ps. The obtained data are rationalized in the framework of adiabatic three-state model that includes the chlorophyll dimer P700 and two symmetrically arranged nearest chlorophyll molecules of A0. The arrangement of chlorophylls results in strong electronic coupling between P700 and A0. Excitation in the maximum of P700 absorption generates electronic states with the highest contribution from P700*, whereas excitation in the far-red edge predominantly generates charge transfer state P700+A0- in both branches of redox-cofactors. The three-level model accounts for a flat-bottomed potential surface of the excited state and adiabatic character of electron transfer between P700 and A0, providing a microscopic explanation of the ultrafast formation of P700+A0- and exponential decline of PS I absorption.

Kinetic modeling of electron transfer reactions in photosystem I complexes of various structures with substituted quinone acceptors.

The reduction kinetics of the photo-oxidized primary electron donor P700 in photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 were analyzed within the kinetic model, which considers electron transfer (ET) reactions between P700, secondary quinone acceptor A1, iron-sulfur clusters and external electron donor and acceptors - methylviologen (MV), 2,3-dichloro-naphthoquinone (Cl2NQ) and oxygen. PS I complexes containing various quinones in the A1-binding site (phylloquinone PhQ, plastoquinone-9 PQ and Cl2NQ) as well as F X-core complexes, depleted of terminal iron-sulfur F A/F B clusters, were studied. The acceleration of charge recombination in F X-core complexes by PhQ/PQ substitution indicates that backward ET from the iron-sulfur clusters involves quinone in the A1-binding site. The kinetic parameters of ET reactions were obtained by global fitting of the P700+ reduction with the kinetic model. The free energy gap ΔG 0 between F X and F A/F B clusters was estimated as -130 meV. The driving force of ET from A1 to F X was determined as -50 and -220 meV for PhQ in the A and B cofactor branches, respectively. For PQ in A1A-site, this reaction was found to be endergonic (ΔG 0 = +75 meV). The interaction of PS I with external acceptors was quantitatively described in terms of Michaelis-Menten kinetics. The second-order rate constants of ET from F A/F B, F X and Cl2NQ in the A1-site of PS I to external acceptors were estimated. The side production of superoxide radical in the A1-site by oxygen reduction via the Mehler reaction might comprise ≥0.3% of the total electron flow in PS I.

Interaction of various types of photosystem I complexes with exogenous electron acceptors.

Interaction of photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 containing various quinones in the A1-site (phylloquinone PhQ in the wild-type strain (WT), and plastoquinone PQ or 2,3-dichloronaphthoquinone Cl 2 NQ in the menB deletion strain) and different numbers of Fe4S4 clusters (intact WT and FX-core complexes depleted of FA/FB centers) with external acceptors has been studied. The efficiency of interaction was estimated by measuring the light-induced absorption changes at 820 nm due to the reduction of the special pair of chlorophylls (P700+) by an external acceptor(s). It was shown that externally added Cl 2 NQ is able to effectively accept electrons from the terminal iron-sulfur clusters of PS I. Moreover, the efficiency of Cl 2 NQ as external acceptor was higher than the efficiency of the commonly used artificial electron acceptor, methylviologen (MV) for both the intact WT PS I and for the FX-core complexes. The comparison of the efficiency of MV interaction with different types of PS I complexes revealed gradual decrease in the following order: intact WT > menB > FX-core. The effect of MV on the recombination kinetics in menB complexes of PS I with Cl 2 NQ in the A1-site differed significantly from all other PS I samples. The obtained effects are considered in terms of kinetic efficiency of electron acceptors in relation to thermodynamic and structural characteristics of PS I complexes.

Ultrasound Diagnosis and Near-Infrared Spectroscopy in the Study of Encephalopathy in Neonates Born under Asphyxia: Narrative Review.

Brain injury resulting from adverse events during pregnancy and delivery is the leading cause of neonatal morbidity and disability. Surviving neonates often suffer long-term motor, sensory, and cognitive impairments. Birth asphyxia is among the most common causes of neonatal encephalopathy. The integration of ultrasound, including Doppler ultrasound, and near-infrared spectroscopy (NIRS) offers a promising approach to understanding the pathology and diagnosis of encephalopathy in this special patient population. Ultrasound diagnosis can be very helpful for the assessment of structural abnormalities associated with neonatal encephalopathy such as alterations in brain structures (intraventricular hemorrhage, infarcts, hydrocephalus, white matter injury) and evaluation of morphologic changes. Doppler sonography is the most valuable method as it provides information about blood flow patterns and outcome prediction. NIRS provides valuable insight into the functional aspects of brain activity by measuring tissue oxygenation and blood flow. The combination of ultrasonography and NIRS may produce complementary information on structural and functional aspects of the brain. This review summarizes the current state of research, discusses advantages and limitations, and explores future directions to improve applicability and efficacy.

Role of pheophytin a in the primary charge separation of photosystem I from Acaryochloris marina: Femtosecond optical studies of excitation energy and electron transfer reactions.

Photosystem I (PSI) of the cyanobacterium Acaryochloris marina is capable of performing an efficient photoelectrochemical conversion of far-red light due to its unique suite of cofactors. Chlorophyll d (Chl-d) has been long known as the major antenna pigment in the PSI from A. marina, while the exact cofactor composition of the reaction centre (RC) was established only recently by cryo-electron microscopy. The RC consists of four Chl-d molecules, and, surprisingly, two molecules of pheophytin a (Pheo-a), which provide a unique opportunity to resolve, spectrally and kinetically, the primary electron transfer reactions. Femtosecond transient absorption spectroscopy was here employed to observe absorption changes in the 400-860 nm spectral window occurring in the 0.1-500 ps timescale upon unselective antenna excitation and selective excitation of the Chl-d special pair P740 in the RC. A numerical decomposition of the absorption changes, including principal component analysis, allowed the identification of P740(+)Chld2(-) as the primary charge separated state and P740(+)Pheoa3(-) as the successive, secondary, radical pair. A remarkable feature of the electron transfer reaction between Chld2 and Pheoa3 is the fast, kinetically unresolved, equilibrium with an estimated ratio of 1:3. The energy level of the stabilised ion-radical state P740(+)Pheoa3(-) was determined to be ~60 meV below that of the RC excited state. In this regard, the energetics and the structural implications of the presence of Pheo-a in the electron transfer chain of PSI from A. marina are discussed, also in comparison with those of the most diffused Chl-a binding RC.

Cytosine Deaminase Base Editing to Restore COL7A1 in Dystrophic Epidermolysis Bullosa Human: Murine Skin Model.

Recessive dystrophic epidermolysis bullosa is a debilitating blistering skin disorder caused by loss-of-function mutations in COL7A1, which encodes type VII collagen, the main component of anchoring fibrils at the dermal-epidermal junction. Although conventional gene therapy approaches through viral vectors have been tested in preclinical and clinical trials, they are limited by transgene size constraints and only support unregulated gene expression. Genome editing could potentially overcome some of these limitations, and CRISPR/Cas9 has already been applied in research studies to restore COL7A1 expression. The delivery of suitable repair templates for the repair of DNA cleaved by Cas9 is still a major challenge, and alternative base editing strategies may offer corrective solutions for certain mutations. We show highly targeted and efficient cytidine deamination and molecular correction of a defined recessive dystrophic epidermolysis bullosa mutation (c.425A>G), leading to restoration of full-length type VII collagen protein expression in primary human fibroblasts and induced pluripotent stem cells. Type VII collagen basement membrane expression and skin architecture were restored with de novo anchoring fibrils identified by electron microscopy in base-edited human recessive dystrophic epidermolysis bullosa grafts recovered from immunodeficient mice. The results show the potential and promise of emerging base editing technologies in tackling inherited disorders with well-defined single nucleotide mutations.

Derivation and feeder-free propagation of human embryonic stem cells under xeno-free conditions.

BACKGROUND AIMS: Human embryonic stem (hES) cells hold great potential for cell therapy and regenerative medicine because of their pluripotency and capacity for self-renewal. The conditions used to derive and culture hES cells vary between and within laboratories depending on the desired use of the cells. Until recently, stem cell culture has been carried out using feeder cells, and culture media, that contain animal products. Recent advances in technology have opened up the possibility of both xeno-free and feeder-free culture of stem cells, essential conditions for the use of stem cells for clinical purposes. To date, however, there has been limited success in achieving this aim. METHODS, RESULTS AND CONCLUSIONS: Protocols were developed for the successful derivation of two normal and three specific mutation-carrying (SMC) (Huntington's disease and myotonic dystrophy 1) genomically stable hES cell lines, and their adaptation to feeder-free culture, all under xeno-free conditions.

ABE8e adenine base editor precisely and efficiently corrects a recurrent COL7A1 nonsense mutation.

Base editing introduces precise single-nucleotide edits in genomic DNA and has the potential to treat genetic diseases such as the blistering skin disease recessive dystrophic epidermolysis bullosa (RDEB), which is characterized by mutations in the COL7A1 gene and type VII collagen (C7) deficiency. Adenine base editors (ABEs) convert A-T base pairs to G-C base pairs without requiring double-stranded DNA breaks or donor DNA templates. Here, we use ABE8e, a recently evolved ABE, to correct primary RDEB patient fibroblasts harboring the recurrent RDEB nonsense mutation c.5047 C > T (p.Arg1683Ter) in exon 54 of COL7A1 and use a next generation sequencing workflow to interrogate post-treatment outcomes. Electroporation of ABE8e mRNA into a bulk population of RDEB patient fibroblasts resulted in remarkably efficient (94.6%) correction of the pathogenic allele, restoring COL7A1 mRNA and expression of C7 protein in western blots and in 3D skin constructs. Off-target DNA analysis did not detect off-target editing in treated patient-derived fibroblasts and there was no detectable increase in A-to-I changes in the RNA. Taken together, we have established a highly efficient pipeline for gene correction in primary fibroblasts with a favorable safety profile. This work lays a foundation for developing therapies for RDEB patients using ex vivo or in vivo base editing strategies.

Primary charge separation within the structurally symmetric tetrameric Chl2APAPBChl2B chlorophyll exciplex in photosystem I.

In Photosystem I (PS I), the role of the accessory chlorophyll (Chl) molecules, Chl2A and Chl2B (also termed A-1A and A-1B), which are directly adjacent to the special pair P700 and fork into the A- and B-branches of electron carriers, is incompletely understood. In this work, the Chl2A and Chl2B transient absorption ΔA0(λ) at a time delay of 100 fs was identified by ultrafast pump-probe spectroscopy in three pairs of PS I complexes from Synechocystis sp. PCC 6803 with residues PsaA-N600 or PsaB-N582 (which ligate Chl2B or Chl2A through a H2O molecule) substituted by Met, His, and Leu. The ΔA0(λ) spectra were quantified using principal component analysis, the main component of which was interpreted as a mutation-induced shift of the equilibrium between the excited state of primary donor P700⁎ and the primary charge-separated state P700+Chl2-. This equilibrium is shifted to the charge-separated state in wild-type PS I and to the excited P700 in the PS I complexes with the substituted ligands to the Chl2A and Chl2B monomers. The results can be rationalized within the framework of an adiabatic model in which the P700 is electronically coupled with the symmetrically arranged monomers Chl2A and Chl2B; such a structure can be considered a symmetric tetrameric exciplex Chl2APAPBChl2B, in which the excited state (Chl2APAPBChl2B)* is mixed with two charge-transfer states P700+Chl2A- and P700+Chl2B-. The electron redistribution between the two branches in favor of the A-branch apparently takes place in the picosecond time scale after reduction of the Chl2A and Chl2B monomers.

Positive and Negative Effects of Metal Oxide Nanoparticles on Antibiotic Resistance Genes Transfer.

Rapid development of antibiotic resistance in bacteria is a critical public health problem in the world. One of the main routes of resistance development is the transfer of genes containing antibiotic resistance cassettes. Gene transfer can be done through horizontal transfer of genes: transduction, conjugation, and transformation. Many factors in the environment influence these processes, and one of them is the action of metal oxide nanoparticles (MONPs), which can appear in the milieu through both biological synthesis and the release of engineered nanomaterial. In this study, the effect of AlOOH, CuO, Fe3O4, TiO2, and ZnO MONPs on the transformation (heat shock transformation) of bacteria Escherichia coli K12, and the conjugation between E. coli cc118 and E. coli Nova Blue were studied. The MONPs were synthesized by one method and fully characterized. ZnO nanoparticles (NPs) have significantly increased the efficiency of transformation (more than 9-fold), while the other NPs have reduced it to 31 times (TiO2 NPs). AlOOH NPs increased the number of transconjugants more than 1.5-fold, while CuO and Fe3O4 NPs did not have a significant effect on transformation and conjugation. Thus, the data shows that different types of MONPs can enhance or inhibit different gene transfer mechanisms, affecting the spread of antibiotic resistance genes.

Human Mesenchymal Stromal Cells Engineered to Express Collagen VII Can Restore Anchoring Fibrils in Recessive Dystrophic Epidermolysis Bullosa Skin Graft Chimeras.

Recessive dystrophic epidermolysis bullosa (RDEB) is a debilitating genodermatosis caused by loss-of-function mutations in COL7A1 encoding type VII collagen (C7), the main component of anchoring fibrils at the dermal-epidermal junction. With no curative treatments presently available, retrovirally transduced autologous epidermal grafts and intradermal lentivirally engineered fibroblast injections are being investigated. Alternative approaches aim to infuse allogeneic mesenchymal stromal cells (MSCs) to provide a more generalized treatment for RDEB. We investigated whether healthy human MSCs could be engineered to overexpress C7 and correct RDEB in a human:murine chimeric model. Initially, engineered MSCs incorporated ex vivo into RDEB grafts, their presence confirmed by fluorescence in situ hybridization, revealed recovery of function of the dermal-epidermal junction with no signs of blister formation. Importantly, the detection of anchoring fibrils by transmission electron microscopy corroborated structural recovery. Next, MSCs cotransduced to express C7 and luciferase were delivered intradermally into grafted RDEB skin, resulting in localized MSC persistence with deposition of de novo C7 at the site. Notably, C7 expression was sufficient to restore anchoring fibril density to normal levels. In contrast, intravenously injected engineered MSCs were undetectable within grafts and lacked anchoring fibril reconstitution. Our data suggest that although localized correction may be achievable using engineered MSCs, strategies for systemic administration require further modeling.

Allele-Specific Small Interfering RNA Corrects Aberrant Cellular Phenotype in Keratitis-Ichthyosis-Deafness Syndrome Keratinocytes.

Keratitis-ichthyosis-deafness (KID) syndrome is a severe, untreatable condition characterized by ocular, auditory, and cutaneous abnormalities, with major complications of infection and skin cancer. Most cases of KID syndrome (86%) are caused by a heterozygous missense mutation (c.148G>A, p.D50N) in the GJB2 gene, encoding gap junction protein Cx26, which alters gating properties of Cx26 channels in a dominant manner. We hypothesized that a mutant allele-specific small interfering RNA could rescue the cellular phenotype in patient keratinocytes (KCs). A KID syndrome cell line (KID-KC) was established from primary patient KCs with a heterozygous p.D50N mutation. This cell line displayed impaired gap junction communication and hyperactive hemichannels, confirmed by dye transfer, patch clamp, and neurobiotin uptake assays. A human-murine chimeric skin graft model constructed with KID-KCs mimicked patient skin in vivo, further confirming the validity of these cells as a model. In vitro treatment with allele-specific small interfering RNA led to robust inhibition of the mutant GJB2 allele without altering expression of the wild-type allele. This corrected both gap junction and hemichannel activity. Notably, allele-specific small interfering RNA treatment caused only low-level off-target effects in KID-KCs, as detected by genome-wide RNA sequencing. Our data provide an important proof-of-concept and model system for the potential use of allele-specific small interfering RNA in treating KID syndrome and other dominant genetic conditions.

CRISPR/Cas9 gene editing for genodermatoses: progress and perspectives.

Genodermatoses constitute a clinically heterogeneous group of devastating genetic skin disorders. Currently, therapy options are largely limited to symptomatic treatments and although significant advances have been made in ex vivo gene therapy strategies, various limitations remain. However, the recent technical transformation of the genome editing field promises to overcome the hurdles associated with conventional gene addition approaches. In this review, we discuss the need for developing novel treatments and describe the current status of gene editing for genodermatoses, focusing on a severe blistering disease called epidermolysis bullosa (EB), for which significant progress has been made. Initial research utilized engineered nucleases such as transcription activator-like effector nucleases and meganucleases. However, over the last few years, clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) have upstaged older generation gene editing tools. We examine different strategies for CRISPR/Cas9 application that can be employed depending on the type and position of the mutation as well as the mode of its inheritance. Promising developments in the field of base editing opens new avenues for precise correction of single base substitutions, common in EB and other genodermatoses. We also address the potential limitations and challenges such as safety concerns and delivery efficiency. This review gives an insight into the future of gene editing technologies for genodermatoses.