Effects of knockdown or overexpression of PNPLA6 in human retinal pigment epithelial cell line ARPE-19
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ABSTRACT: Although mutations in human patatin-like phospholipase PNPLA6 are associated with hereditary retinal degenerative diseases, its mechanistic action in the retina is poorly understood. Here, we uncover the molecular mechanism by which PNPLA6 dysfunction disturbs retinal homeostasis and visual function. PNPLA6, by acting as a phospholipase B, regulates choline mobilization from phosphatidylcholine and subsequent choline turnover for phosphatidylcholine regeneration in retinal pigment epithelial (RPE) cells. PNPLA6-driven choline is supplied from RPE cells to adjacent photoreceptor cells to support their survival. Inhibition of this pathway results in abnormal morphology, proliferation, metabolism, and functions of RPE and photoreceptor cells, and mice with retina-specific PNPLA6 deletion exhibit retinitis pigmentosa-like retinal degeneration. Notably, these abnormalities are entirely rescued by choline supplementation. Thus, PNPLA6 plays an essential role in retinal homeostasis by controlling choline availability for phospholipid recycling and provide a framework for the development of a novel ophthalmic drug target for retinal degeneration.
Project description:Although mutations in human patatin-like phospholipase PNPLA6 are associated with hereditary retinal degenerative diseases, its mechanistic action in the retina is poorly understood. Here, we uncover the molecular mechanism by which PNPLA6 dysfunction disturbs retinal homeostasis and visual function. PNPLA6, by acting as a phospholipase B, regulates choline mobilization from phosphatidylcholine and subsequent choline turnover for phosphatidylcholine regeneration in retinal pigment epithelial (RPE) cells. PNPLA6-driven choline is supplied from RPE cells to adjacent photoreceptor cells to support their survival. Inhibition of this pathway results in abnormal morphology, proliferation, metabolism, and functions of RPE and photoreceptor cells, and mice with retina-specific PNPLA6 deletion exhibit retinitis pigmentosa-like retinal degeneration. Notably, these abnormalities are entirely rescued by choline supplementation. Thus, PNPLA6 plays an essential role in retinal homeostasis by controlling choline availability for phospholipid recycling and provide a framework for the development of a novel ophthalmic drug target for retinal degeneration.
Project description:Retinitis Pigmentosa is a group of inherited eye disorders characterized by progressive degeneration of photoreceptor cells in the retina, leading to vision loss and eventual blindness. One of the known genetic mutations associated with RP is the c.6926A>C mutation in the RPE (retinal pigment epithelium) cells. The dataset involves multiple experimental approaches and cell types, providing a comprehensive understanding of the disease and potential corrective strategies.
Project description:Due to the high energy demands and characteristic morphology, retinal photoreceptor cells require a specialized lipid metabolism for survival and function. This study focused on the roles of saturated fatty acids and their metabolism. A frameshift mutation of lysophosphatidylcholine acyltransferase 1 (Lpcat1), introducing saturated fatty acids into lysophosphatidylcholine to produce disaturated phosphatidylcholine (PC), has been reported to cause spontaneous retinal degeneration in mice (rd11 mice). In this study, we performed a detailed characterization of Lpcat1 in the retina and found that Lpcat1 deficiency induces light-independent and photoreceptor-specific apoptosis in mice. Lipidomic analyses of the retina and isolated photoreceptor outer segment (OS) suggested that loss of Lpcat1 affects disaturated PC production and the proper cellular fatty acid flux, presumably by altering saturated fatty acyl-CoA availabilities. Furthermore, we demonstrated that Lpcat1 deletion increased mitochondrial reactive oxygen species (ROS) levels in photoreceptor cells, but not in other retinal cells without affecting the OS structure and trafficking of OS-localized proteins. These results suggest that the LPCAT1-dependent production of disaturated PC is critical for metabolic adaptation during photoreceptor maturation. Our findings highlight the therapeutic potential of saturated fatty acid metabolism in photoreceptor cell degeneration-related retinal diseases.
Project description:Due to the high energy demands and characteristic morphology, retinal photoreceptor cells require the specialized lipid metabolism for survival and functions. In this study, we focus on the roles of saturated fatty acids and their metabolism in these processes. Frame-shift mutation of lysophosphatidylcholine acyltransferase 1 (Lpcat1), which introduces saturated fatty acid into lysophosphatidylcholine to produce disaturated phosphatidylcholine (PC), has been reported as a causative for spontaneous retinal degeneration in mice (rd11 mice). However, the molecular basis of retinal degeneration caused by Lpcat1 mutation remains unclear. Here, we report that Lpcat1 deficiency induces light-independent and photoreceptor-specific apoptosis in mice. Lipidomic analyses of retina and isolated photoreceptor outer segment (OS) suggested that loss of Lpcat1 affects not only disaturated PC production, but also the proper cellular fatty acid flux presumably through altering saturated fatty acyl-CoA availabilities. Furthermore, we demonstrated that Lpcat1 deletion increased mitochondrial reactive oxygen species (ROS) levels in photoreceptor cells, but not in other retinal cells, without affecting the OS structure and trafficking of OS localized proteins. These results suggested that LPCAT1-dependent production of disaturated PC is critical for metabolic adaptation during photoreceptor maturation. Our findings highlight the therapeutic potential of saturated fatty acid metabolism in photoreceptor cell degeneration-related retinal diseases.
Project description:Retinal Pigment Epithelial (RPE) cells are located behind the retina and are critical for photoreceptor survival. Loss of RPE is associated with several pathogenic conditions such as Age Related Macular Degeneration and Retinitis Pigmentosa. RPE derived from human embryonic stem cells (hESC) offer a potential source for producing these cells for therapy. Here we report the molecular and cellular characterization of RPE differentiated from hESC. hESC derived RPE are capable of proliferation and lose their epithelial characteristics before becoming confluent and re-differentiating back into their typical pigmented, cobblestoned appearance. During the proliferative phase, they adopt a mesenchymal morphology and express mesenchymal markers. Our results demonstrate that this apparent Epithelial-Mesenchymal Transition is not regulated by the classical EMT transcription factors SNAIL and SLUG. Furthermore, it is possible to regulate RPE de-differentiation and re-differentiation by modulating the Wnt and BMP pathway respectively. These findings further our understanding of the genesis and expansion of RPE which is essential for their therapeutic use.
Project description:Retinal Pigment Epithelial (RPE) cells are located behind the retina and are critical for photoreceptor survival. Loss of RPE is associated with several pathogenic conditions such as Age Related Macular Degeneration and Retinitis Pigmentosa. RPE derived from human embryonic stem cells (hESC) offer a potential source for producing these cells for therapy. Here we report the molecular and cellular characterization of RPE differentiated from hESC. hESC derived RPE are capable of proliferation and lose their epithelial characteristics before becoming confluent and re-differentiating back into their typical pigmented, cobblestoned appearance. During the proliferative phase, they adopt a mesenchymal morphology and express mesenchymal markers. Our results demonstrate that this apparent Epithelial-Mesenchymal Transition is not regulated by the classical EMT transcription factors SNAIL and SLUG. Furthermore, it is possible to regulate RPE de-differentiation and re-differentiation by modulating the Wnt and BMP pathway respectively. These findings further our understanding of the genesis and expansion of RPE which is essential for their therapeutic use.
Project description:Eye development and photoreceptor maintenance requires the retinal pigment epithelium (RPE), a thin layer of cells that underlies the neural retina. Despite its importance, RPE development has not been studied by a genomic approach. A microarray expression profiling methodology was established in this study for studying RPE development. The intact retina with RPE attached was dissected from developing embryos, and differentially expressed genes in RPE were inferred by comparing the dissected tissues with retinas without RPE using microarray and statistical analyses. We found 8810 probesets to be significantly expressed in RPE at 52 hours post-fertilization (hpf), of which 1443 might have biologically meaningful expression levels. Further, 78 and 988 probesets were found to be significantly over- or under-expressed in RPE respectively compared to retina. Also, 79.2% (38/48) of the known over-expressed probesets have been independently validated as RPE-related transcripts. The results strongly suggest that this methodology can obtain in vivo RPE specific gene expression from the zebrafish embryos and identify novel RPE markers. Experiment Overall Design: The gene expression levels of three independent replicates of retina with RPE attached consisting of ten samples each at 52hpf (WRR52) were compared with three independent pure retinal samples consisting of ten retinas each at 52hpf (WR52). The yield-adjusted WR52 expression values were assumed to be equivalent to the retinal contribution in WRR52 samples and deducted from WRR52 expression values to obtain estimations of RPE gene expression at 52hpf (RPE52). Differential gene expressions between RPE and retina were inferred by comparing the RPE52 estimates and WR52 expression values.
Project description:Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. The extent to which epigenetic changes regulate the progression of AMD is unclear. Here we profiled chromatin accessibility in the retina and retinal pigmented epithelium (RPE) from AMD patients and controls. Global decreases in chromatin accessibility occur in the RPE in early AMD and in the retina with advanced disease. Footprints of photoreceptor and RPE-specific transcription factors are enriched in differentially accessible regions (DARs) and reduced AMD. Genes associated with DARs show altered expression in AMD. Cigarette smoke, an established risk factor for AMD, applied to human iPSC-derived RPE cells recapitulates epigenomic changes seen in AMD. In addition to providing a comprehensive profile of chromatin accessibility in human RPE and retina, this study shows that global decreases in chromatin accessibility may play a critical role in AMD progression.
Project description:Shp2, a critical SH2-domain-containing tyrosine phosphatase, is essential for cellular regulation and implicated in metabolic disruptions, obesity, diabetes, Noonan syndrome, LEOPARD syndrome, and cancers. This study focuses on Shp2 in rod photoreceptor cells, revealing its enrichment, particularly in rods. Deletion of Shp2 in rods leads to age-dependent photoreceptor degeneration. Shp2 targets occludin (OCLN), a tight junction protein, and its deletion reduces OCLN expression in the retina and retinal pigment epithelium (RPE). Isolation of actively translating mRNAs from rods lacking Shp2, followed by RNA sequencing, reveals alterations in cell cycle regulation. Altered retinal metabolism is observed in retinal cells lacking Shp2. Our studies indicate that Shp2 is crucial for maintaining the structure and function of photoreceptors.
Project description:The retinal pigment epithelium (RPE) provides vital support to photoreceptor cells and its dysfunction is associated with the onset and progression of age-related macular degeneration (AMD). Surgical provision of RPE cells may ameliorate AMD and thus it would be valuable to develop sources of patient-matched RPE cells for this application of regenerative medicine. We describe here the generation of functional RPE-like cells from fibroblasts that represent an important step toward that goal. We identified candidate master transcriptional regulators of RPEs using a novel computational method and then used these regulators to guide exploration of the transcriptional regulatory circuitry of RPE cells and to reprogram human fibroblasts into RPE-like cells. The RPE-like cells share key features with RPEs derived from healthy individuals, including morphology, gene expression and function, and thus represent a step toward the goal of generating patient-matched RPE cells for treatment of macular degeneration. Expression analysis was performed on induced retinal pigment epithelium-like cells.