Role of CtBP2 in the Apoptosis of Retinal Ganglion Cells

Stage-specific dynamic reorganization of genome topology shapes transcriptional neighborhoods in developing human retinal organoids

We have generated a high-resolution Hi-C map of developing human retinal organoids to elucidate spatiotemporal dynamics of genomic architecture and its relationship with gene expression patterns. We demonstrate progressive stage-specific alterations in DNA topology and correlate these changes with transcription of cell-type-restricted gene markers during retinal differentiation. Temporal Hi-C reveals a shift toward A compartment for protein-coding genes and B compartment for non-coding RNAs, displaying high and low expression, respectively. Notably, retina-enriched genes are clustered near lost boundaries of topologically associated domains (TADs), and higher-order assemblages (i.e., TAD cliques) localize in active chromatin regions with binding sites for eye-field transcription factors. These genes gain chromatin contacts at their transcription start site as organoid differentiation proceeds. Our study provides a global view of chromatin architecture dynamics associated with diversification of cell types during retinal development and serves as a foundational resource for in-depth functional investigations of retinal developmental traits.

C-terminal binding protein 2 promotes high-glucose-triggered cell proliferation, angiogenesis and cellular adhesion of human retinal endothelial cell line

PURPOSE

The proliferation and angiogenesis of human retinal endothelial cells (HRECs) are critical for the pathophysiology of diabetic retinopathy (DR). C-terminal binding protein 2 (CtBP2) has multiple biologic functions, but its effect on HRECs under high-glucose (HG) conditions is unclear.

METHODS

The cell viability, angiogenesis, cellular adhesion and CtBP2 expression levels of HRECs were measured following treatment with different concentrations of glucose. Small interfering CtBP2-targeting RNA, wide-type and function mutant plasmid of CtBP2 were constructed and then were transfected into HRECs to evaluate the effects of CtBP2 on cell functions of HRECs.

RESULTS

The expression of CtBP2 in HRECs was increased after HG treatment. HG treatment significantly increased cell proliferation, angiogenesis, and decreased relative gene expressions in gap junctions, tight junctions and adherens junctions. After CtBP2 was inhibited via siRNA, the changes induced by HG were partially restored. Conversely, only wild-type CtBP2 could increase cell proliferation and angiogenesis under HG condition. Mechanistically, we also found that CtBP2 exerted its functions to effect HG-induced changes via Akt signaling pathway.

CONCLUSION

This study implicates that CtBP2 promotes HG-induced cell proliferation, angiogenesis and cellular adhesion, and CtBP2 might be a potential target in the prevention of DR.

Glaucoma Pathogenesis and Neurotrophins: Focus on the Molecular and Genetic Basis for Therapeutic Prospects

BACKGROUND

Retinal ganglion cell (RGC) degeneration is a major feature of glaucoma pathology. Neuroprotective approaches that delay or halt the progression of RGC loss are needed to prevent vision loss which can occur even after conventional medical or surgical treatments to lower intraocular pressure.

OBJECTIVE

The aim of this review was to examine the progress in genetics and cellular mechanisms associated with endoplasmic reticulum (ER) stress, RGC dysfunction and cell death pathways in glaucoma.

MATERIALS AND METHODS

Here, we review the involvement of neurotrophins like brain derived neurotrophic factor (BDNF) and its high affinity receptor tropomyosin receptor kinase (TrkB) in glaucoma. The role of ER stress markers in human and animal retinas in health and disease conditions is also discussed. Further, we analysed the literature highlighting genetic linkage in the context of primary open angle glaucoma and suggested mechanistic insights into potential therapeutic options relevant to glaucoma management.

RESULTS

The literature review of the neurobiology underlying neurotrophin pathways, ER stress and gene associations provide critical insights into association of RGCs death in glaucoma. Alteration in signalling pathway is associated with increased risk of misfolded protein aggregation in ER promoting RGC apoptosis. Several genes that are linked with neurotrophin signalling pathways have been reported to be associated with glaucoma pathology.

CONCLUSION

Understanding genetic heterogeneity and involvement of neurotrophin biology in glaucoma could help to understand the complex pathophysiology of glaucoma. Identification of novel molecular targets will be critical for drug development and provide neuroprotection to the RGCs and optic nerve.

CtBP2 ameliorates palmitate-induced insulin resistance in HepG2 cells through ROS mediated JNK pathway

Oxidative stress plays a significant role in the development of hepatic insulin resistance, but the underlying molecular mechanisms remain poorly understood. In this study, we discovered that C-terminal-binding protein 2 (CtBP2) level was decreased in insulin resistance. Taking into account the relationship between CtBP family protein (ANGUSTIFOLIA) and reactive oxygen species (ROS) accumulation, we conjectured CtBP2 was involved in insulin resistance through ROS induced stress. In order to verify this hypothesis, we over-expressed CtBP2 in palmitate (PA) treated HepG2 cells. Here, we found that over-expression of CtBP2 ameliorated insulin sensitivity by increasing phosphorylation of glycogen synthase kinase 3β (GSK3β) and protein kinase B (AKT). These data suggest that CtBP2 plays a critical role in the development of insulin resistance. Moreover, CtBP2 reversed the effects of PA on ROS level, lipid accumulation, hepatic glucose uptake and gluconeogenesis. We also found that over-expression of CtBP2 could suppress PA induced c-jun NH2 terminal kinase (JNK) activation. Furthermore, JNK inhibitor SP600125 was shown to promote the effect of CtBP2 on insulin signaling. Thus, we demonstrated that CtBP2 ameliorated PA-induced insulin resistance via ROS-dependent JNK pathway.

MicroRNA-212 Regulates the Expression of Olfactomedin 1 and C-Terminal Binding Protein 1 in Human Endometrial Epithelial Cells to Enhance Spheroid Attachment In Vitro

Successful embryo implantation requires a synchronized dialogue between a competent blastocyst and the receptive endometrium, which occurs in a limited time period known as the "window of implantation." Recent studies suggested that down-regulation of olfactomedin 1 (OLFM1) in the endometrium and fallopian tube is associated with receptive endometrium and tubal ectopic pregnancy in humans. Interestingly, the human chorionic gonadotropin (hCG) induces miR-212 expression, which modulates OLFM1 and C-terminal binding protein 1 (CTBP1) expressions in mouse granulosa cells. Therefore, we hypothesized that embryo-derived hCG would increase miR-212 expression and down-regulate OLFM1 and CTBP1 expressions to favor embryo attachment onto the female reproductive tract. We found that hCG stimulated the expression of miR-212 and down-regulated OLFM1 but not CTBP1 mRNA in both human endometrial (Ishikawa) and fallopian (OE-E6/E7) epithelial cells. However, hCG suppressed the expression of OLFM1 and CTBP1 proteins in both cell lines. The 3'UTR of both OLFM1 and CTBP1 contained binding sites for miR-212. The miR-212 precursor suppressed luciferase expression, whereas the miR-212 inhibitor stimulated luciferase expression of the wild-type (WT)-OLFM1 and WT-CTBP1 reporter constructs. Furthermore, hCG (25 IU/ml) treatments stimulated trophoblastic (Jeg-3) spheroid (blastocyst surrogate) attachment onto Ishikawa and OE-E6/E7 cells. Transfection of miR-212 precursor increased Jeg-3 spheroid attachment onto Ishikawa cells and decreased OLFM1 and CTBP1 protein expressions, whereas the opposite occurred with miR-212 inhibitor. Taken together, hCG stimulated miR-212, which in turn down-regulated OLFM1 and CTBP1 expression in fallopian and endometrial epithelial cells to favor spheroid attachment.