Within the next decade, we will see many gene therapy clinical trials for eye diseases, which may lead to treatments for thousands of visually impaired people around the world. To target retinal diseases that affect specific cell types, several recombinant adeno-associated virus (AAV) serotypes have been generated and used successfully in preclinical mouse studies. Because there are numerous anatomic and physiologic differences between the eyes of mice and "men" and because surgical delivery approaches and immunologic responses also differ between these species, this study evaluated the transduction characteristics of two promising new serotypes, AAV7m8 and AAV8BP2, in the retinas of animals that are most similar to those of humans: non-human primates (NHPs). We report that while AAV7m8 efficiently targets a variety of cell types by subretinal injection in NHPs, transduction after intravitreal delivery was mostly restricted to the inner retina at lower doses that did not induce an immune response. AAV8BP2 targets the cone photoreceptors efficiently but bipolar cells inefficiently by subretinal injection. Additionally, transduction by both serotypes in the anterior chamber of the eye and the optic pathway of the brain was observed post-intravitreal delivery. Finally, we assessed immunogenicity, keeping in mind that these AAV capsids may be used in future clinical trials. We found that AAV8BP2 had a better safety profile compared with AAV7m8, even at the highest doses administered. These studies underscore the differences in AAV transduction between mice and primates, highlighting the importance of careful evaluation of therapeutic vectors in NHPs prior to moving to clinical trials.
Mutation of the polarity gene Crumbs homolog 1 (CRB1) is responsible for >10% of Leber congenital amaurosis (LCA) cases worldwide; LCA is characterized by early-onset degenerative retinal dystrophy. The role of CRB1 in LCA8 pathogenesis remains elusive since Crb1 mouse mutants, including a null allele, have failed to mimic the early-onset of LCA, most likely due to functional compensation by closely related genes encoding Crb2 and Crb3. Crb proteins form an evolutionarily conserved, apical polarity complex with the scaffolding protein associated with lin-seven 1 (Pals1), also known as MAGUK p55 subfamily member 5 (MPP5). Pals1 and Crbs are functionally inter-dependent in establishing and maintaining epithelial polarity. Pals1 is a single gene in the mouse and human genomes; therefore, we ablated Pals1 to establish a mouse genetic model mimicking human LCA. In our study, the deletion of Pals1 leads to the disruption of the apical localization of Crb proteins in retinal progenitors and the adult retina, validating their mutual interaction. Remarkably, the Pals1 mutant mouse exhibits the critical features of LCA such as early visual impairment as assessed by electroretinogram, disorganization of lamination and apical junctions and retinal degeneration. Our data uncover the indispensible role of Pals1 in retinal development, likely involving the maintenance of retinal polarity and survival of retinal neurons, thus providing the basis for the pathologic mechanisms of LCA8.
Hippo-Yap signaling has been implicated in organ size determination via its regulation of cell proliferation, growth and apoptosis (Pan, 2007). The vertebrate lens comprises only two major cell types, lens progenitors and differentiated fiber cells, thereby providing a relatively simple system for studying size-controlling mechanisms. In order to investigate the role of Hippo-Yap signaling in lens size regulation, we conditionally ablated Yap in the developing mouse lens. Lens progenitor specific deletion of Yap led to near obliteration of the lens primarily due to hypocellularity in the lens epithelium (LE) and accompanying lens fiber (LF) defects. A significantly reduced LE progenitor pool resulted mainly from failed self-renewal and increased apoptosis. Additionally, Yap-deficient lens progenitor cells precociously exited the cell cycle and expressed the LF marker, β-Crystallin. The mutant progenitor cells also exhibited multiple cellular and subcellular alterations including cell and nuclear shape change, organellar polarity disruption, and disorganized apical polarity complex and junction proteins such as Crumbs, Pals1, Par3 and ZO-1. Yap-deficient LF cells failed to anchor to the overlying LE layer, impairing their normal elongation and packaging. Furthermore, our localization study results suggest that, in the developing LE, Yap participates in the cell context-dependent transition from the proliferative to differentiation-competent state by integrating cell density information. Taken together, our results shed new light on Yap’s indispensable and novel organizing role in mammalian organ size control by coordinating multiple events including cell proliferation, differentiation, and polarity.
Most genetically distinct inherited retinal degenerations are primary photoreceptor degenerations. We selected a severe early onset form of Leber congenital amaurosis (LCA), caused by mutations in the gene LCA5, in order to test the efficacy of gene augmentation therapy for a ciliopathy. The LCA5-encoded protein, Lebercilin, is essential for the trafficking of proteins and vesicles to the photoreceptor outer segment. Using the AAV serotype AAV7m8 to deliver a human LCA5 cDNA into an Lca5 null mouse model of LCA5, we show partial rescue of retinal structure and visual function. Specifically, we observed restoration of rod-and-cone-driven electroretinograms in about 25% of injected eyes, restoration of pupillary light responses in the majority of treated eyes, an ∼20-fold decrease in target luminance necessary for visually guided behavior, and improved retinal architecture following gene transfer. Using LCA5 patient-derived iPSC-RPEs, we show that delivery of the LCA5 cDNA restores lebercilin protein and rescues cilia quantity. The results presented in this study support a path forward aiming to develop safety and efficacy trials for gene augmentation therapy in human subjects with LCA5 mutations. They also provide the framework for measuring the effects of intervention in ciliopathies and other severe, early-onset blinding conditions.
RASSF2 belongs to the Ras-association domain family (RASSF) of proteins, which may be involved in the Hippo signalling pathway. However, the role of RASSF2 in vivo is unknown. Here, we show that Rassf2 knockout mice manifest a multisystemic phenotype including haematopoietic anomalies and defects in bone remodelling. Bone marrow (BM) transplantation showed that Rassf2 À/À BM cells had a normal haematopoietic reconstitution activity, indicating no intrinsic haematopoietic defects. Notably, in vitro differentiation studies revealed that ablation of Rassf2 suppressed osteoblastogenesis but promoted osteoclastogenesis. Co-culture experiments showed that an intrinsic defect in osteoblast differentiation from Rassf2 À/À osteoblast precursors likely leads to both haematopoiesis and osteoclast defects in Rassf2 À/À mice.Moreover, Rassf2 deficiency resulted in hyperactivation of nuclear factor (NF)-jB during both osteoclast and osteoblast differentiation. RASSF2 associated with IjB kinase (IKK) a and b forms, and suppressed IKK activity. Introduction of either RASSF2 or a dominant-negative form of IKK into Rassf2 À/À osteoclast or osteoblast precursors inhibited NF-jB hyperactivation and normalized osteoclast and osteoblast differentiation. These observations indicate that RASSF2 regulates osteoblast and osteoclast differentiation by inhibiting NF-jB signalling.
METHODS. Thirty-three Korean FEVR patients, who previously screened negative for TSPAN12 mutations, mutations in other FEVR-associated genes such as NDP, FZD4, LRP5, and large deletions and duplications of NDP, FZD4, and LRP5, were selected for TSPAN12 large deletion and duplication analyses. Semiquantitative multiplex PCR for TSPAN12 gene dosage analyses were performed, followed by droplet digital PCR (ddPCR) for validation. RESULTS.Among the 33 patients, three patients were confirmed to carry large TSPAN12 deletions. Two of them had whole-gene deletions of TSPAN12, and the other patient possessed a deletion of TSPAN12 in exon 4. FEVR severity detected in these patients was not more severe than in a patient with TSPAN12 point mutation.CONCLUSIONS. Regarding previously reported proportions of FEVR-associated genes contributing to the disorder's autosomal dominant inheritance pattern in Korea, we determined that patients with TSPAN12 large deletions were more common than patients with single nucleotide variants in TSPAN12. Evaluating TSPAN12 large deletions and duplications should be considered in FEVR screening and diagnosis as well as in routine genetic workups for FEVR patients.Keywords: familial exudative vitreoretinopathy, TSPAN12, large deletions, droplet digital PCR F amilial exudative vitreoretinopathy (FEVR) is a rare, genetically heterogeneous disorder that impairs vision and causes retinal detachment. Autosomal dominant inheritance is the most common form of FEVR and is known to be associated with the FZD4, LRP5, and TSPAN12 genes. Recently, the ZNF408 and KIF11 genes were also implicated in FEVR. 1,2 In a previous report by our group, mutational studies regarding FZD4, LRP5, and TSPAN12 were carried out in 51 unrelated FEVR patients lacking NDP mutations. Among them, mutations with high probabilities of being pathogenic were detected in 18 patients. 3 FZD4 mutations accounted for the largest proportion of autosomal dominant FEVR cases (13/18 patients, 72.2%), followed by LRP5 (4/18 patients, 22.2%), and TSPAN12 (1/18 patients, 5.6%) mutations. In rest of the 33 patients, no FZD4, LRP5, and TSPAN12 mutations were detected.In our previous report, large deletions/duplications in NDP, FZD4, and LRP5 had been screened via multiplex ligationdependent probe amplification (MLPA) using the SALSA P285-C1 LRP5-NDP-FZD4 (MRC-Holland, Amsterdam, Netherlands).Because TSPAN12 was not included, we looked for large deletions/duplications of TSPAN12 in the patients with no mutation detected to determine the genetic cause of FEVR. Gene dosage analysis by semiquantitative multiplex PCR and droplet digital PCR (ddPCR) were performed. In this study, we discovered and confirmed three cases of FEVR due to TSPAN12 large deletions. METHODS SubjectsAmong the 51 FEVR patients from our previous study, 33 patients were selected for large deletion/duplication analyses of TSPAN12. These patients were diagnosed with FEVR between
Patients with Zellweger spectrum disorder (ZSD) commonly present with vision loss due to mutations in PEX genes required for peroxisome assembly and function. Here, we evaluate PEX1 retinal gene augmentation therapy in a mouse model of mild ZSD bearing the murine equivalent (PEX1-p[Gly844Asp]) of the most common human mutation. Experimental adeno-associated virus 8.cytomegalovirus.human PEX1.hemagglutinin (AAV8.CMV. HsPEX1.HA ) and control AAV8.CMV. EGFP vectors were administered by subretinal injection in contralateral eyes of early (5-week-old)- or later (9-week-old)-stage retinopathy cohorts. HsPEX1.HA protein was expressed in the retina with no gross histologic side effects. Peroxisomal metabolic functions, assessed by retinal C26:0 lysophosphatidylcholine (lyso-PC) levels, were partially normalized after therapeutic vector treatment. Full-field flash electroretinogram (ffERG) analyses at 8 weeks post-injection showed a 2-fold improved retinal response in the therapeutic relative to control vector-injected eyes. ffERG improved by 1.6- to 2.5-fold in the therapeutic vector-injected eyes when each cohort reached 25 weeks of age. At 32 weeks of age, the average ffERG response was double in the therapeutic relative to control vector-injected eyes in both cohorts. Optomotor reflex analyses trended toward improvement. These proof-of-concept studies represent the first application of gene augmentation therapy to treat peroxisome biogenesis disorders and support the potential for retinal gene delivery to improve vision in these patients.
Crumbs polarity complex proteins are essential for cellular and tissue polarity, and for adhesion of epithelial cells. In epithelial tissues deletion of any of three core proteins disrupts localization of the other proteins, indicating structural and functional interdependence among core components. Despite previous studies of function and co-localization that illustrated the properties that these proteins share, it is not known whether an individual component of the complex plays a distinct role in a unique cellular and developmental context. In order to investigate this question, we primarily used confocal imaging to determine the expression and subcellular localization of the core Crumbs polarity complex proteins during ocular development. Here we show that in developing ocular tissues core Crumbs polarity complex proteins, Crb, Pals1 and Patj, generally appear in an overlapping pattern with some exceptions. All three core complex proteins localize to the apical junction of the retinal and lens epithelia. Pals1 is also localized in the Golgi of the retinal cells and Patj localizes to the nuclei of the apically located subset of progenitor cells. These findings suggest that core Crumbs polarity complex proteins exert common and independent functions depending on cellular context.
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