Optogenetic control of cell differentiation in channelrhodopsin-2-expressing OS3, a bipotential glial progenitor cell line

- OS3ChR2 cells are Channelrhodopsin-2-expressing clonal glial progenitor cells.
- OS3ChR2 successfully differentiated into GalC-expressing oligodendrocytes by photo-activation.
- OS3ChR2 cells increased intracellular cations, particularly Ca2+, by photo-activation.
- The increase in intracellular cations triggered activation of the PI3K/Akt pathway.
- These signaling resulted in oligodendrocyte differentiation.

Alterations in the intracellular ion environment have been identified as one of the signals playing a critical role in the control of cellular proliferation and differentiation; however, the mechanisms responsible for signal transduction remain unclear. Recent studies have reported that channelrhodopsin-2 (ChR2) is a rapidly gated blue light (BL)-sensitive cation channel suitable for the non-invasive control of ion influx. We herein examined the expression of differentiation-associated markers by photo-activation and its signal transduction in ChR2-expressing OS3 (OS3ChR2) cells, which are clonal bipotential glial progenitor cells. Increases were observed in intracellular Na+ and Ca2+ concentrations in OS3ChR2 cells with BL exposure. Alterations in the intracellular ion environment, particularly in Ca2+, led to increases in the expression of oligodendrocyte markers including galactocerebrosides (GalC) and decreases in that of astrocyte markers such as glial fibrillary acidic protein (GFAP). These alterations also triggered activation of the ERK1/2 signaling pathway, which is involved in cell survival, and PI3K/Akt/mTOR signaling pathway, which is involved in oligodendrocyte differentiation, characterized by GalC expression. Moreover, when photo-activated OS3ChR2 cells were injected into mice with lysophosphatidyl choline (LPC)-induced demyelination, deficits in motor function were reduced. Our results demonstrated that signal transduction by ChR2-expressing glial progenitor cells may be controlled through alterations induced in the intracellular ion environment by photo-activation and results in oligodendrocyte differentiation from glial progenitor cells. Our results also suggest that ChR2-expressing glial progenitor cells have potential as a useful tool for therapeutic approaches to brain and spinal cord disorders associated with oligodendrocyte dysfunctions.