Fig. 2: In vivo conversion of striatal astrocytes into GABAergic neurons in WT mouse brain.

a Coexpression of NeuroD1 (green) and Dlx2 (blue) together with mCherry (red, NeuroD1-p2A-mCherry and Dlx2-P2A-mCherry) in AAV-infected striatal astrocytes (GFAP, cyan) at 7 dpi. b At 30 dpi, NeuroD1 (green) and Dlx2 (blue) coexpressed cells became NeuN⁺ neurons (cyan). Scale bar for (a) and (b): 20 µm. c Summarized data showing coexpression of NeuroD1 and Dlx2 in striatal astrocytes at 7 dpi, which mostly converted into NeuN⁺ neurons by 30 dpi (n = 8 mice for 7 dpi, n = 9 mice for 30 dpi), data are shown as mean ± SEM. d Diagram illustrating the astrocyte-to-neuron conversion process induced by NeuroD1 and Dlx2 coexpression. e Representative images illustrating the gradual morphological change from astrocytes to neurons over a time window of 1 month. Note that most mCherry⁺ cells were co-labeled with GFAP (cyan) at early time points post AAV injection, but later lost GFAP signal and acquired NeuN signal (green). Arrowheads indicate mCherry⁺ cells that are co-labeled with NeuN. Scale bar: 50 µm. f Time course showing the cell identity (astrocyte vs neuron) among viral infected cells (mCherry⁺ cells) in the control group (mCherry⁺ alone, top graph, n = 5 for 7 dpi, n = 8 for 11 dpi, n = 9 for 15 dpi, n = 9 for 21 dpi, and n = 8 for 30 dpi) or NeuroD1 + Dlx2 group (bottom graph, n = 11 for 7 dpi, n = 8 for 11 dpi, n = 7 for 15 dpi, n = 6 for 21 dpi, and n = 10 for 30 dpi). Most of the viral infected cells in the control group were astrocytes, whereas the NeuroD1 + Dlx2-infected cells gradually shifted from mainly astrocytic population to a mixed population of astrocytes and neurons, and then to mostly neuronal population, data are shown as mean ± SD. g Confocal images showing converted neurons co-stained with GAD67, GABA, DARPP32, and parvalbumin (PV) after ectopic expression of NeuroD1 and Dlx2 in striatal astrocytes (30 dpi). Arrowheads indicate co-labeled cells. Scale bar: 20 µm. h Quantified data showing the composition of the astrocyte-converted neurons induced by NeuroD1 and Dlx2 in the striatum. Most of the converted neurons were GABAergic neurons (>80%) and a significant proportion were immunopositive for DARPP32 (55.7%), data are shown as mean ± SEM.