Gene therapy in patient-specific stem cell lines and a preclinical model of retinitis pigmentosa with membrane frizzled-related protein defects

Defects in Membrane Frizzled-related Protein (MFRP) cause autosomal recessive retinitis pigmentosa (RP). MFRP codes for a retinal pigment epithelium (RPE)-specific membrane receptor of unknown function. In patient-specific induced pluripotent stem (iPS)-derived RPE cells, precise levels of MFRP, and its dicistronic partner CTRP5, are critical to the regulation of actin organization. Overexpression of CTRP5 in naive human RPE cells phenocopied behavior of MFRP-deficient patient RPE (iPS-RPE) cells. AAV8 (Y733F) vector expressing human MFRP rescued the actin disorganization phenotype and restored apical microvilli in patient-specific iPS-RPE cell lines. As a result, AAV-treated MFRP mutant iPS-RPE recovered pigmentation and transepithelial resistance. The efficacy of AAV-mediated gene therapy was also evaluated in Mfrp(rd6)/Mfrp(rd6) mice--an established preclinical model of RP--and long-term improvement in visual function was observed in AAV-Mfrp-treated mice. This report is the first to indicate the successful use of human iPS-RPE cells as a recipient for gene therapy. The observed favorable response to gene therapy in both patient-specific cell lines, and the Mfrp(rd6)/Mfrp(rd6) preclinical model suggests that this form of degeneration caused by MFRP mutations is a potential target for interventional trials

Clinical and Therapeutic Evaluation of the Ten Most Prevalent <i>CRB1</i> Mutations

Mutations in the Crumbs homolog 1 (CRB1) gene lead to severe inherited retinal dystrophies (IRDs), accounting for nearly 80,000 cases worldwide. To date, there is no therapeutic option for patients suffering from CRB1-IRDs. Therefore, it is of great interest to evaluate gene editing strategies capable of correcting CRB1 mutations. A retrospective chart review was conducted on ten patients demonstrating one or two of the top ten most prevalent CRB1 mutations and receiving care at Columbia University Irving Medical Center, New York, NY, USA. Patient phenotypes were consistent with previously published data for individual CRB1 mutations. To identify the optimal gene editing strategy for these ten mutations, base and prime editing designs were evaluated. For base editing, we adopted the use of a near-PAMless Cas9 (SpRY Cas9), whereas for prime editing, we evaluated the canonical NGG and NGA prime editors. We demonstrate that for the correction of c.2843G>A, p.(Cys948Tyr), the most prevalent CRB1 mutation, base editing has the potential to generate harmful bystanders. Prime editing, however, avoids these bystanders, highlighting its future potential to halt CRB1-mediated disease progression. Additional studies investigating prime editing for CRB1-IRDs are needed, as well as a thorough analysis of prime editing’s application, efficiency, and safety in the retina

Missense mutation in SLIT2 associated with congenital myopia, anisometropia, connective tissue abnormalities, and obesity.

BACKGROUND: SLIT2 is a protein ligand for the Roundabout (ROBO) receptor and was found to play a major role in repulsive midline axon guidance in central nervous system development. Based on studies utilizing knockout models, it has been postulated that SLIT2 is important for preventing inappropriate axonal routing during mammalian optic chiasm development. METHODS: Case report. RESULTS: Here, we report a case of congenital myopia, anisometropia, and obesity in a patient with a SLIT2 point mutation. Examination of the patient\u27s skin biopsy revealed abnormalities in elastin and collagen fibrils that suggest an underlying connective tissue disorder. Structural modeling placed the novel mutation (p.D1407G) in the EGF-like domain 8 and was predicted to affect interactions with SLIT2 binding partners. CONCLUSIONS: To the authors\u27 knowledge, this is the first report of a SLIT2 variant in the context of these ocular findings

Bestrophin Gene Mutations in Patients with Best Vitelliform Macular Dystrophy

Best vitelliform macular dystrophy (VMD2) is an autosomal dominant dystrophy with a juvenile age of onset. Mutations in the Bestrophin gene were shown in patients affected with VMD2. In a mutation study, we made three new and interesting observations. First, we identified possible mutation hotspots within the gene, suggesting that particular regions of the protein have greater functional significance than others. Second, we described a 2-bp deletion in a part of the gene where mutations have not previously been reported; this mutation causes a frameshift and subsequent premature termination of the protein. Finally, we have evidence that some mutations are associated with variable expression of the disease, suggesting the involvement of other factors or genes in the disease phenotype

Compound heterozygous inheritance of two novel COQ2 variants results in familial coenzyme Q deficiency

Background Primary coenzyme Q10 deficiency is a rare disease that results in diverse and variable clinical manifestations. Nephropathy, myopathy and neurologic involvement are commonly associated, however retinopathy has also been observed with certain pathogenic variants of genes in the coenzyme Q biosynthesis pathway. In this report, we describe a novel presentation of the disease that includes nephropathy and retinopathy without neurological involvement, and which is the result of a compound heterozygous state arising from the inheritance of two recessive potentially pathogenic variants, previously not described. Materials and methods Retrospective report, with complete ophthalmic examination, multimodal imaging, electroretinography, and whole exome sequencing performed on a family with three affected siblings. Results We show that affected individuals in the described family inherited two heterozygous variants of the COQ2 gene, resulting in a frameshift variant in one allele, and a predicted deleterious missense variant in the second allele (c.288dupC,p.(Ala97Argfs*56) and c.376C > G,p.(Arg126Gly) respectively). Electroretinography results were consistent with rod-cone dystrophy in the affected individuals. All affected individuals in the family exhibited the characteristic retinopathy as well as end-stage nephropathy, without evidence of any neurological involvement. Conclusions We identified two novel compound heterozygous variants of the COQ2 gene that result in primary coenzyme Q deficiency. Targeted sequencing of coenzyme Q biosynthetic pathway genes may be useful in diagnosing oculorenal clinical presentations syndromes not explained by more well known syndromes (e.g., Senior-Loken and Bardet-Biedl syndromes)