Evaluation of photoreceptor-directed fibroblasts derived from retinitis pigmentosa patients with defects in the EYS gene: a possible cost-effective cellular model for mechanism-oriented drug.

BACKGROUND: The most common gene responsible for autosomal recessive retinitis pigmentosa (RP) is EYS. The manner of decay of genetically defective EYS gene transcripts varies depending on the type of mutation using our cellular model, which consists of induced photoreceptor-directed fibroblasts from EYS-RP patients (EYS-RP cells). However, disease-specific profiles have not been clarified in EYS-RP cells. Herein we investigated comprehensive gene expression patterns and restoration of altered expression by low molecular weight molecules in EYS-RP cells. METHODS: Using induced photoreceptor-like cells by CRX, RAX, NeuroD, and OTX2, we employed qRT-PCR and DNA microarray analysis to compare expression levels of disease-related genes in EYS-RP cells. We investigated the effect of antiapoptotic or anti-endoplasmic reticulum (ER) stress/antioxidant reagents on the restoration of altered gene expression. RESULTS: Expression levels of phototransduction-related genes (blue opsin, rhodopsin, S-antigen, GNAT1, GNAT2) were lower in EYS-RP cells. CRYGD was extracted by global gene expression analysis, as a downregulated, retina-related and apoptosis-, endoplasmic reticulum (ER) stress- or aging-related gene. Pathway enrichment analysis suggested that "complement and coagulation cascades," "ECM-receptor interaction" and "PI3K-Akt signaling pathway" could be involved in EYS-RP-associated pathogenesis. Among the matching/overlapping genes involved in those pathways, F2R was suggested as an EYS-RP-associated gene. The downregulation of CRYGD and F2R was completely restored by additional 4-PBA, an inhibitor of ER stress, and partially restored by metformin or NAC. In addition, 4-PBA normalized the expression level of cleaved caspase-3. CONCLUSIONS: Our cellular model may reflect the ER stress-mediated degenerative retina and serve as a pathogenesis-oriented cost-effective rescue strategy for RP patients.

eys +/- ; lrp5 +/- Zebrafish Reveals Lrp5 Can Be the Receptor of Retinol in the Visual Cycle.

Vision is essential for vertebrates including humans. Sustained vision is accomplished by retinoid metabolism, the "visual cycle," where all-trans retinol (atROL) is incorporated into the retinal pigment epithelium (RPE) from photoreceptors presumably through decade-long missing receptor(s). Here, we show that the LDL-related receptor-5 (Lrp5) protein is linked to the retinol binding protein 1a (Rbp1a), the transporter of atROL in the visual cycle, by generating and analyzing the digenic eyes shut homolog +/- ; lrp5 +/- zebrafish, the same form of gene defect detected in a human case of inherited retinal degeneration. Global gene expression analysis followed by genetic study clarified that rbp1a played a role downstream of lrp5. Rbp1a protein was colocalized with Lrp5 protein at microvilli of RPE cells. Furthermore, Rbp1a directly bound to the C-terminal intracellular region of Lrp5 in vitro. Collectively, these results strongly suggest that Lrp5 is a potent candidate of the receptor of atROL in the visual cycle.

Five major sequence variants and copy number variants in the EYS gene account for one-third of Japanese patients with autosomal recessive and simplex retinitis pigmentosa.

Purpose: To elucidate the variant spectrum of the EYS gene in a large cohort of Japanese patients with autosomal recessive and simplex retinitis pigmentosa (arRP and sRP). Methods: We performed a direct sequencing analysis of 44 exons of the EYS gene in 469 patients with RP (including 144 arRP, 288 sRP, and 17 autosomal dominant RP (adRP) cases) in eastern and western regions of Japan and a multiplex ligation-dependent probe amplification (MLPA) of patients who had a single heterozygous pathogenic variant. Results: We identified six pathogenic and 16 likely pathogenic variants from a total of 186 nucleotide sequence variants, of which five variants, c.2528G>A (p.(Gly843Glu)), c.4957dupA (p.(Ser1653Lysfs*2)), c.6557G>A (p.(Gly2186Glu)), c.6563T>C (p.(Ile2188Thr)), and c.8868C>A (p.(Tyr2956*)), were prevalent in patients with arRP and sRP. The homozygous and heterozygous combinations of these five variants accounted for 32.4% (140/432) of Japanese patients with arRP and sRP. Five patients with adRP also had these variants. These five variants segregated with the phenotype in 15 families with RP. MLPA revealed seven copy number variations (CNVs) of the EYS exon(s). Conclusions: This study showed that five major sequence variants and CNVs in the EYS gene account for one-third of Japanese patients with arRP and sRP, and these variants are also responsible for RP showing an autosomal dominant inheritance pattern. This is the first report showing the pathogenicity of three missense variants (p.(Gly843Glu), p.(Gly2186Glu), and p.(Ile2188Thr)) and the presence of CNVs in the EYS gene of Japanese patients with arRP and sRP.

Intra- and interspecies comparison of EYS transcripts highlights its characteristics in the eye.

Inherited mutations in the eyes shut homolog (EYS) gene cause retinitis pigmentosa. Although knock out of eys in zebrafish is pathogenic, the molecular function of EYS in vertebrate photoreceptors is poorly understood. Here, we show that the 5' portion of EYS is eye-specific across vertebrates. We previously determined that a 3' fragment of EYS with an unknown transcription start site is expressed in human dermal fibroblasts (HDF). To obtain insights into the molecular function of EYS in vertebrate photoreceptors, we extensively analyzed EYS (eys) expression in the human fibroblast cell line HDF-adult (HDF-a), the Y79 retinoblastoma cell line, and in zebrafish eyes using rapid amplification of cDNA end, cap analysis of gene expression, RNA sequencing, and RT-PCR. In HDF-a cells, we identified a novel transcript variant (tv), tv5, transcribed from exon 37. In Y79 cells and zebrafish eyes, EYS (eys) was predominantly transcribed from exon 1 or 2, whereas it was transcribed exclusively from exon 37 in HDF-a cells. In the zebrafish eye, there were splice variants that introduced stop codons, resulting in complete loss of the 3' portion of the RNA. These comparative approaches indicate that the 5' portion of the EYS (eys) mRNA appears to be photoreceptor-specific and that the compositions of the deduced EYS proteins in the eye are well-conserved across vertebrates.-Takita, S., Miyamoto-Matsui, K., Seko, Y. Intra- and interspecies comparison of EYS transcripts highlights its characteristics in the eye.

The manner of decay of genetically defective EYS gene transcripts in photoreceptor-directed fibroblasts derived from retinitis pigmentosa patients depends on the type of mutation.

BACKGROUND: Generation of induced photoreceptors holds promise for in vitro modeling of intractable retinal diseases. Retinitis pigmentosa is an inherited retinal dystrophy that leads to visual impairment. The EYS gene was reported to be the most common gene responsible for autosomal recessive retinitis pigmentosa (arRP). arRP with defects in the EYS gene is denoted by "EYS-RP". We previously established a "redirect differentiation" method to generate photosensitive photoreceptor-like cells from commercially available human dermal fibroblasts. In this study, we produced photoreceptor-like cells from dermal fibroblasts of EYS-RP patients as a replacement for the degenerative retinas using "redirect differentiation". We analyzed defective transcripts of the EYS gene in these cells to elucidate phenotypes of EYS-RP patients because decay of transcripts was previously suggested to be involved in phenotypic variation associated with diseases. METHODS: Using "redirect differentiation" by CRX, RAX, NeuroD and OTX2, we made photoreceptor-directed fibroblasts derived from three normal volunteers and three EYS-RP patients with homozygous or heterozygous mutations. We tested inducible expression of the photoreceptor-specific genes (blue opsin, rhodopsin, recoverin, S-antigen, PDE6C) in these cells. We then analyzed transcripts derived from three different types of the defective EYS gene, c.1211dupA, c.4957dupA and c.8805C > A, expressed in these cells by RT-PCR and sequencing. RESULTS: Photoreceptor-specific genes including the EYS gene were up-regulated in all the photoreceptor-directed fibroblasts tested. However, expression levels of defective transcripts were markedly different depending on the type of mutation. Transcripts derived from these three defective genes were scarcely detected, expressed at a lower level, and expressed at almost the same level as in normal volunteers, respectively. CONCLUSIONS: Expression levels of genetically defective EYS gene transcripts in photoreceptor-directed fibroblasts of EYS-RP patients vary depending on the type of mutation. Variation in expression levels in transcripts having c.1211dupA, c.4957dupA and c.8805C > A suggests that almost complete nonsense-mediated mRNA decay (NMD), partial NMD and escape from NMD occurred for these transcripts, respectively. To determine the relationship with phenotypic variations in EYS-RP patients, more samples are needed. The present study also suggests that the redirect differentiation method could be a valuable tool for disease modeling despite some limitations.

Variation in the Phenotype of Photosensitive Cells Produced from Human Fibroblast Cell Lines.

BACKGROUND: Photoreceptors differentiated from somatic cells are a useful tool for transplantation and drug screening. We previously showed that photosensitive cells are differentiated from human fibroblasts by direct reprogramming. In induced pluripotent stem (iPS) cells or embryonic stem (ES) cells, the properties of differentiated cells differ among the source of cell lines. However, whether or not the properties of the photosensitive cells produced by direct reprogramming are controlled by the origin of the cell line remains unknown. METHODS: We compared the morphological and physiological properties of photosensitive cells induced by two fibroblast cell lines. RESULTS: The differentiated cells had larger somas and more primary processes than the non-infected cells in both cell lines. The degree of morphological change was statistically different between the two cell lines. In addition, physiological responses to light differed between the two cell lines. An outward current (photoreceptor-like response) was observed in both cell lines, while an inward current (intrinsically photosensitive retinal ganglion cell-like response) was observed only in one cell line under light stimulation. CONCLUSIONS: These results suggest that photosensitive cells produced from different cell lines by direct reprogramming might express different phenotypes.

Violet Light Exposure Can Be a Preventive Strategy Against Myopia Progression.

Prevalence of myopia is increasing worldwide. Outdoor activity is one of the most important environmental factors for myopia control. Here we show that violet light (VL, 360-400nm wavelength) suppresses myopia progression. First, we confirmed that VL suppressed the axial length (AL) elongation in the chick myopia model. Expression microarray analyses revealed that myopia suppressive gene EGR1 was upregulated by VL exposure. VL exposure induced significantly higher upregulation of EGR1 in chick chorioretinal tissues than blue light under the same conditions. Next, we conducted clinical research retrospectively to compare the AL elongation among myopic children who wore eyeglasses (VL blocked) and two types of contact lenses (partially VL blocked and VL transmitting). The data showed the VL transmitting contact lenses suppressed myopia progression most. These results suggest that VL is one of the important outdoor environmental factors for myopia control. Since VL is apt to be excluded from our modern society due to the excessive UV protection, VL exposure can be a preventive strategy against myopia progression.

Anteroposterior Patterning of Gene Expression in the Human Infant Sclera: Chondrogenic Potential and Wnt Signaling.

Purpose/Aim: We sought to identify the anteroposterior spatial gene expression hierarchy in the human sclera to develop a hypothesis for axial elongation and deformity of the eyeball. MATERIALS AND METHODS: We analyzed the global gene expression of human scleral cells derived from distinct parts of the human infant sclera obtained from surgically enucleated eyes with retinoblastoma, using Affymetrix GeneChip oligonucleotide arrays, and compared, in particular, gene expression levels between the anterior and posterior parts of the sclera. The ages of three donors were 10M, 4M, and 1Y9M. RESULTS: K-means clustering analysis of gene expression revealed that expression levels of cartilage-associated genes such as COLXIA and ACAN increased from the anterior to the posterior part of the sclera. Microarray analyses and RT-PCR data showed that the expression levels of MGP, COLXIA, BMP4, and RARB were significantly higher in the posterior than in the anterior sclera of two independent infant eyes. Conversely, expression levels of WNT2, DKK2, GREM1, and HOXB2 were significantly higher in the anterior sclera. Among several Wnt-family genes examined, WNT2B was found to be expressed at a significantly higher level in the posterior sclera, and the reverse order was observed for WNT2. The results of luciferase reporter assays suggested that a GSK-3ß inhibitor stimulated Wnt/ß-catenin signaling particularly strongly in the posterior sclera. The expression pattern of RARB, a myopia-related gene, was similar in three independent eyes. CONCLUSIONS: Chondrogenic potential was higher and Wnt/ß-catenin signaling was more potently activated by a GSK-3ß inhibitor in the posterior than in the anterior part of the human infant sclera. Although the differences in the gene expression profiles between the anterior and posterior sclera might be involved only in normal growth processes, this anteroposterior hierarchy in the sclera might contribute to disorders involving abnormal elongation and deformity of the eyeball, including myopia.

In vitro transdifferentiation of human peripheral blood mononuclear cells to photoreceptor-like cells.

Direct reprogramming is a promising, simple and low-cost approach to generate target cells from somatic cells without using induced pluripotent stem cells. Recently, peripheral blood mononuclear cells (PBMCs) have attracted considerable attention as a somatic cell source for reprogramming. As a cell source, PBMCs have an advantage over dermal fibroblasts with respect to the ease of collecting tissues. Based on our studies involving generation of photosensitive photoreceptor cells from human iris cells and human dermal fibroblasts by transduction of photoreceptor-related transcription factors via retrovirus vectors, we transduced these transcription factors into PBMCs via Sendai virus vectors. We found that retinal disease-related genes were efficiently detected in CRX-transduced cells, most of which are crucial to photoreceptor functions. In functional studies, a light-induced inward current was detected in some CRX-transduced cells. Moreover, by modification of the culture conditions including additional transduction of RAX1 and NEUROD1, we found a greater variety of retinal disease-related genes than that observed in CRX-transduced PBMCs. These data suggest that CRX acts as a master control gene for reprogramming PBMCs into photoreceptor-like cells and that our induced photoreceptor-like cells might contribute to individualized drug screening and disease modeling of inherited retinal degeneration.

Derivation of human differential photoreceptor cells from adult human dermal fibroblasts by defined combinations of CRX, RAX, OTX2 and NEUROD.

Redirecting differentiation of somatic cells by over-expression of transcription factors is a promising approach for regenerative medicine, elucidation of pathogenesis and development of new therapies. We have previously defined a transcription factor combination, that is, CRX, RAX and NEUROD, that can generate photosensitive photoreceptor cells from human iris cells. Here, we show that human dermal fibroblasts are differentiated to photoreceptor cells by the same transcription factor combination as human iris cells. Transduction of a combination of the CRX, RAX and NEUROD genes up-regulated expression of the photoreceptor-specific genes, recoverin, blue opsin and PDE6C, in all three strains of human dermal fibroblasts that were tested. Additional OTX2 gene transduction increased up-regulation of the photoreceptor-specific genes blue opsin, recoverin, S-antigen, CNGB3 and PDE6C. Global gene expression data by microarray analysis further showed that photoreceptor-related functional genes were significantly increased in induced photoreceptor cells. Functional analysis, that is, patch-clamp recordings, clearly revealed that induced photoreceptor cells from fibroblasts responded to light. Both the NRL gene and the NR2E3 gene were endogenously up-regulated in induced photoreceptor cells, implying that exogenous CRX, RAX, OTX2 and NEUROD, but not NRL, are sufficient to generate rod photoreceptor cells.

Derivation of human differential photoreceptor-like cells from the iris by defined combinations of CRX, RX and NEUROD.

Examples of direct differentiation by defined transcription factors have been provided for beta-cells, cardiomyocytes and neurons. In the human visual system, there are four kinds of photoreceptors in the retina. Neural retina and iris-pigmented epithelium (IPE) share a common developmental origin, leading us to test whether human iris cells could differentiate to retinal neurons. We here define the transcription factor combinations that can determine human photoreceptor cell fate. Expression of rhodopsin, blue opsin and green/red opsin in induced photoreceptor cells were dependent on combinations of transcription factors: A combination of CRX and NEUROD induced rhodopsin and blue opsin, but did not induce green opsin; a combination of CRX and RX induced blue opsin and green/red opsin, but did not induce rhodopsin. Phototransduction-related genes as well as opsin genes were up-regulated in those cells. Functional analysis; i.e. patch clamp recordings, clearly revealed that generated photoreceptor cells, induced by CRX, RX and NEUROD, responded to light. The response was an inward current instead of the typical outward current. These data suggest that photosensitive photoreceptor cells can be generated by combinations of transcription factors. The combination of CRX and RX generate immature photoreceptors: and additional NEUROD promotes maturation. These findings contribute substantially to a major advance toward eventual cell-based therapy for retinal degenerative diseases.

Establishment of functioning human corneal endothelial cell line with high growth potential.

Hexagonal-shaped human corneal endothelial cells (HCEC) form a monolayer by adhering tightly through their intercellular adhesion molecules. Located at the posterior corneal surface, they maintain corneal translucency by dehydrating the corneal stroma, mainly through the Na(+)- and K(+)-dependent ATPase (Na(+)/K(+)-ATPase). Because HCEC proliferative activity is low in vivo, once HCEC are damaged and their numbers decrease, the cornea begins to show opacity due to overhydration, resulting in loss of vision. HCEC cell cycle arrest occurs at the G1 phase and is partly regulated by cyclin-dependent kinase inhibitors (CKIs) in the Rb pathway (p16-CDK4/CyclinD1-pRb). In this study, we tried to activate proliferation of HCEC by inhibiting CKIs. Retroviral transduction was used to generate two new HCEC lines: transduced human corneal endothelial cell by human papillomavirus type E6/E7 (THCEC (E6/E7)) and transduced human corneal endothelial cell by Cdk4R24C/CyclinD1 (THCEH (Cyclin)). Reverse transcriptase polymerase chain reaction analysis of gene expression revealed little difference between THCEC (E6/E7), THCEH (Cyclin) and non-transduced HCEC, but cell cycle-related genes were up-regulated in THCEC (E6/E7) and THCEH (Cyclin). THCEH (Cyclin) expressed intercellular molecules including ZO-1 and N-cadherin and showed similar Na(+)/K(+)-ATPase pump function to HCEC, which was not demonstrated in THCEC (E6/E7). This study shows that HCEC cell cycle activation can be achieved by inhibiting CKIs even while maintaining critical pump function and morphology.

Human sclera maintains common characteristics with cartilage throughout evolution.

BACKGROUND: The sclera maintains and protects the eye ball, which receives visual inputs. Although the sclera does not contribute significantly to visual perception, scleral diseases such as refractory scleritis, scleral perforation and pathological myopia are considered incurable or difficult to cure. The aim of this study is to identify characteristics of the human sclera as one of the connective tissues derived from the neural crest and mesoderm. METHODOLOGY/PRINCIPAL FINDINGS: We have demonstrated microarray data of cultured human infant scleral cells. Hierarchical clustering was performed to group scleral cells and other mesenchymal cells into subcategories. Hierarchical clustering analysis showed similarity between scleral cells and auricular cartilage-derived cells. Cultured micromasses of scleral cells exposed to TGF-betas and BMP2 produced an abundant matrix. The expression of cartilage-associated genes, such as Indian hedge hog, type X collagen, and MMP13, was up-regulated within 3 weeks in vitro. These results suggest that human 'sclera'-derived cells can be considered chondrocytes when cultured ex vivo. CONCLUSIONS/SIGNIFICANCE: Our present study shows a chondrogenic potential of human sclera. Interestingly, the sclera of certain vertebrates, such as birds and fish, is composed of hyaline cartilage. Although the human sclera is not a cartilaginous tissue, the human sclera maintains chondrogenic potential throughout evolution. In addition, our findings directly explain an enigma that the sclera and the joint cartilage are common targets of inflammatory cells in rheumatic arthritis. The present global gene expression database will contribute to the clarification of the pathogenesis of developmental diseases such as high myopia.

The role of cytokine mRNA stability in the pathogenesis of autoimmune disease.

Inflammatory cytokines such as interferon (IFN)-gamma, interleukin (IL)-2, tumor-necrosis factor (TNF)-alpha and IL-17 play an important role in the pathogenesis of cell-mediated autoimmune diseases. Cytokine gene expression is tightly regulated at the post-transcriptional level. Cytokine mRNA decay is dependent not only upon cis-elements in the RNA but also upon trans-acting factors such as the RNA binding proteins TTP, HuR, AUF-1, Nucleolin and YB-1. Physiologic signals, for instance signaling through the CD28 receptor on T cells, can modulate the half-life of a select subset of cytokine mRNAs, such as IL-2. Distinct cis- and trans-acting elements in human and mouse IL-2 mRNA may account for the different pattern of CD28-mediated mRNA stabilization in these two species. TTP-deficient mice or mice with a deletion of the TNF-alpha mRNA ARE element develop a complex inflammatory syndrome that is associated with a prolonged TNF-alpha mRNA half-life and elevated levels of circulating TNF-alpha. This syndrome can be prevented by treatment with TNF-alpha blocking antibodies. Evidence from mice with altered cytokine mRNA stability, along with human data, suggests that imbalance between the stability and decay of inflammatory cytokine mRNAs could represent a basic mechanism leading to autoimmunity.

Selective cytoplasmic translocation of HuR and site-specific binding to the interleukin-2 mRNA are not sufficient for CD28-mediated stabilization of the mRNA.

The interleukin-2 mRNA is a labile transcript containing AU-rich elements that is transiently stabilized by CD28 receptor signaling. For a number of proto-oncogenes and cytokines, the HuR protein has been shown to avidly bind the AU-rich elements that confer instability upon their mRNAs. HuR was originally thought to participate in mRNA degradation but subsequent studies indicated that it actually functions to stabilize mRNA. Binding of HuR to the mouse interleukin-2 mRNA has not been studied. We tested if HuR binds the interleukin-2 mRNA and whether such binding is related to CD28-mediated stabilization of the mRNA. First, we confirm that T cell receptor signaling, which is sufficient to induce interleukin-2 transcription, also triggers translocation of HuR from the nucleus to the cytoplasm. Interestingly, T cell receptor-triggered translocation is selective as heterogeneous nuclear ribonucleoprotein A1 does not shuttle under the same conditions. Engagement of both the T cell and CD28 receptors, which enhance interleukin-2 transcription and induce stabilization of the mRNA, did not further increase the level of cytoplasmic HuR. Using an in vitro binding assay, we demonstrate that HuR binds the interleukin-2 mRNA and localize binding to a sequence downstream of the single nonameric AU-rich element that is present in its 3'-untranslated region. However, we conclude that HuR binding to the interleukin-2 mRNA, both in vitro and in vivo, is not associated with alterations in mRNA stability.

Involvement of mechanical stretch in the gelatinolytic activity of the fibrous sclera of chicks, in vitro.

PURPOSE: To investigate the role of mechanical stretch in the regulation of matrix metalloproteinase-2 (MMP-2) in scleral fibroblasts of chick embryos. METHODS: Scleral fibroblasts derived from chick embryos were seeded onto flexible bottom culture plates, and subjected to a pulsatile stretch when the cells became subconfluent. After stretching, the cells and the conditioned medium were harvested. One portion of the conditioned medium was activated by reduction, alkylation, and 4-aminophenylmercuric acetate (APMA) treatment. The conditioned medium, with and without the treatment, was subjected to gelatin zymography and quantitative assays. Total cytoplasmic RNA was extracted from the cells, and the expression of MMP-2 and the tissue inhibitor of metalloproteinase-2 (TIMP-2) mRNA was examined by Northern blot analysis. RESULTS: The predominant gelatinolytic enzyme secreted by scleral fibroblasts was MMP-2. The mechanical stretch increased the gelatinolytic activities significantly in the conditioned medium with reduction, alkylation, and APMA treatment. Mechanical stretch also enhanced the expression of MMP-2 and TIMP-2 mRNA in scleral fibroblasts significantly. CONCLUSIONS: These results suggest that mechanical stretch may be involved in the regulation of the extracellular matrix in the fibrous sclera of chicks in vivo.