The Mlc1 Promoter Directs Muller Cell-specific Gene Expression in the Retina

Purpose: Because the importance of glia in regulating brain functions has been demonstrated, genetic technologies that manipulate glial cell-specific gene expression in the brain have become essential and have made great progress. However, it is unknown whether the same strategy that is used in the brain can be applied to the retina because retinal glia differs from glia in the brain. Here, we aimed to find a method for selective gene expression in Muller cells (characteristic glial cells in the retina) and identified Mlc1 as a specific promoter of Muller cells. Methods: Mlc1-tTA::Yellow-Cameleon-Nano(tetO/tetO) (YC-Nano) mice were used as a reporter line. YC-Nano, a fluorescent protein, was ectopically expressed in the cell type controlled by the Mlc1 promotor. Immunofluorescence staining was used to identify the cell type expressing YC-Nano protein. Results: YC-Nano-positive (+) signalswere observed as vertical stalks in the sliced retina and spanned from the nerve fiber layer through the outer nuclear layer. The density of YC-Nano+ cells was higher around the optic nerve head and lower in the peripheral retina. The YC-Nano+ signals colocalized with vimentin, a marker of Muller cells, but not with the cell markers for blood vessels, microglia, neurons, or astrocytes. Conclusions: TheMlc1 promoter allows us to manipulate gene expression in Muller cells without affecting astrocytes in the retina. Translational Relevance: Gene manipulation under control of Mlc1 promoter offers novel technique to investigate the role of Muller cells.