The intracellular DNA sensor, cGAS, initiates the host immune response by recognizing pathogen‐ or endogenous‐derived cytoplasmic DNA. After binding to DNA, activated cGAS‐STING pathway induces the transcription of the Type I interferon and other pro‐inflammatory genes. Mitochondrial dysfunction is known to be involved in various retinal degenerative and angiogenic diseases, including age‐related macular degeneration and diabetic retinopathy. As a consequence of mitochondrial stress, cytosolic escape of mitochondrial DNA has been reported to induce cGAS‐STING pathway activation. In this study, we characterized the expression of cGAS‐STING pathway in murine retina.

The expression of cGAS and STING in murine retina, microglia cells (BV2), primary RPE and B6‐RPE07, primary Müller glial and photoreceptor cells (661W) was examined by RT‐PCR and immunohistochemistry. The cells were transfected with exogenous dsDNA poly(dA:dT) (5ug/mL) for 8 hours. The expression of cGAS, STING, phosphorylated TBK1 (pTBK1) and IRF3 (pIRF3), type‐1 interferon, IL‐6 and TNFa was analysed by RT‐PCR and immunocytochemistry.

Both cGAS and STING were detected in the murine retina, microglia, Müller glial, photoreceptor and RPE cells. Following poly(dA:dT) treatment, the expression of cGAS and pTBK1 was increased in these cells. In addition, intranuclear translocation of pIRF3 was observed in poly(dA:dT)‐treated microglia, RPE, Müller glial and photoreceptor cells. In line with these observations, the mRNA expression of IFNa, IFNb, IL6 and TNFa was significantly increased (p < 0.05) in poly(dA:dT)‐treated cells.

The cGAS‐STING pathway is expressed in many cells within the retina, including microglia, Muller cells, photoreceptor and RPE cells. This pathway may play an important role in retinal innate immunity against endogenous or exogenous cytosolic DNA. Uncontrolled cGAS‐STING pathway may be involved in retinal degenerative diseases.