Inhibition of the MAPK/c-Jun-EGR1 Pathway Decreases Photoreceptor Cell Death in the rd1 Mouse Model for Inherited Retinal Degeneration

by Selleckchem | Aug 06 2023

Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies that typically results in photoreceptor cell death and vision loss. Here, we explored the effect of early growth response-1 (EGR1) expression on photoreceptor cell death in Pde6brd1 (rd1) mice and its mechanism of action. To this end, single-cell RNA-seq (scRNA-seq) was used to identify differentially expressed genes in rd1 and congenic wild-type (WT) mice. Chromatin immunoprecipitation (ChIP), the dual-luciferase reporter gene assay, and western blotting were used to verify the relationship between EGR1 and poly (ADP-ribose) polymerase-1 (PARP1). Immunofluorescence staining was used to assess PARP1 expression after silencing or overexpression of EGR1. Photoreceptor cell death was assessed using the TUNEL assay following silencing/overexpression of EGR1 or administration of MAPK/c-Jun pathway inhibitors tanzisertib and PD98059. Our results showed differential expression of ERG1 in rd1 and WT mice via scRNA-seq analysis. The ChIP assay demonstrated EGR1 binding to the PARP1 promoter region. The dual-luciferase reporter gene assay and western blotting results revealed that EGR1 upregulated PARP1 expression. Additionally, the TUNEL assay showed that silencing EGR1 effectively reduced photoreceptor cell death. Similarly, the addition of tanzisertib and PD98059 reduced the expression of c-Jun and EGR1 and decreased photoreceptor cell death. Our study revealed that inhibition of the MAPK/c-Jun pathway reduced the expression of EGR1 and PARP1 and prevented photoreceptor cell death. These results highlight the importance of EGR1 for photoreceptor cell death and identify a new avenue for therapeutic interventions in RP.

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In this study, the researchers investigated the role of early growth response-1 (EGR1) expression in photoreceptor cell death in Pde6brd1 (rd1) mice, a commonly used model for retinitis pigmentosa (RP). RP is a group of inherited retinal dystrophies characterized by the death of photoreceptor cells and subsequent vision loss. The researchers aimed to understand the mechanism underlying photoreceptor cell death and identify potential therapeutic targets.

To begin, the researchers used single-cell RNA sequencing (scRNA-seq) to compare gene expression patterns between rd1 mice and congenic wild-type (WT) mice. This analysis revealed differential expression of EGR1 between the two groups, suggesting its potential involvement in photoreceptor cell death.

To further investigate the relationship between EGR1 and photoreceptor cell death, the researchers conducted several experiments. They performed chromatin immunoprecipitation (ChIP) assays, which demonstrated that EGR1 binds to the promoter region of poly (ADP-ribose) polymerase-1 (PARP1), indicating a potential regulatory interaction between the two.

To validate the regulatory relationship between EGR1 and PARP1, the researchers employed dual-luciferase reporter gene assays and western blotting. These experiments confirmed that EGR1 positively regulates PARP1 expression, suggesting that EGR1 may contribute to photoreceptor cell death through PARP1-mediated pathways.

Immunofluorescence staining was employed to assess PARP1 expression after manipulating EGR1 levels. Silencing or overexpression of EGR1 led to corresponding changes in PARP1 expression, further supporting the regulatory relationship observed between the two.

To evaluate the functional consequences of EGR1 modulation on photoreceptor cell death, the researchers performed TUNEL assays, which detect DNA fragmentation indicative of cell death. Silencing EGR1 effectively reduced photoreceptor cell death, suggesting that EGR1 plays a crucial role in promoting cell death in the context of RP.

Moreover, the researchers investigated the potential involvement of the MAPK/c-Jun pathway in EGR1-mediated photoreceptor cell death. They administered inhibitors of this pathway, namely tanzisertib and PD98059, and observed a decrease in c-Jun and EGR1 expression, as well as a reduction in photoreceptor cell death.

Overall, this study elucidated the involvement of EGR1 in photoreceptor cell death in rd1 mice, providing insights into the underlying molecular mechanisms. The findings suggest that targeting EGR1 or the MAPK/c-Jun pathway could be potential therapeutic strategies for intervening in RP and preventing photoreceptor cell death.