Fig. S3

Fig. S3

Anatomical and Electrophysiological Properties of Radial Astrocytes Projecting to the L-MO, Related to Figure 3

(A) Distinct expression patterns of CoChR-eGFP driven by the gfappromoter and jRGECO1b driven by the elavl3 promoter suggests that the gfap-driven expression was largely restricted to radial astrocytes. Three columns represent three sections arranged from dorsal to ventral across the brain, indicated by the horizontal dashed lines in the schematic at the top of each column. Row 1, separated channels for CoChR-eGFP and jRGECO1b (the green channel was overexposed in order to visualize the low-level fluorescence in the tectum); Row 2, merged view of those two channels; Row 3, zoomed-in view of the region outlined by dashed lines in Row 2. Arrowheads indicate microscopy software stitching artifacts. Scale bars, 100 μm.

(B) Distinct expression patterns of jRGECO1b driven by the gfappromoter and GCaMP6f driven by the elavl3 promoter, the combination being used for simultaneous imaging of radial astrocytes and neurons. Scale bars, 20 μm.

(C) Schematic side view of the fish brain showing the position of the panel (D) and the cross sections in (E) and (F).

(D) Side view of a section of the hindbrain showing astrocytic cell bodies and processes (white arrow) and the lateral hindbrain neuropil (yellow arrow). Scale bars, 100 μm.

(E) Cross section from a level of the hindbrain that contains the lateral hindbrain (L-MO) (the cyan box inset contains the L-MO). Scale bars, 100 μm.

(F) Cross section at the level of the cerebellum showing the midbrain-hindbrain border (MHB) (arrow). Top-Left, Astrocytic cells are shown in green; DAPI staining labels nuclei of all cells (neurons and radial astrocytes). Bottom-Left, astrocytic cells only. Purple box inset, astrocytic cell bodies (white arrow) can be seen along the dorsal midline and the MHB. Neurons are dark without the GFAP label (yellow arrow). Cyan box inset, long astrocytic processes extend dorso-ventrally and terminate in the lateral and ventral gliopil. Scale bars, 100 μm.

(G) Patch-clamp recording of a GCaMP6f-positive cell from a Tg(gfap:GCaMP6f) fish shows electrophysiological properties of radial astrocytes: (1) a linear voltage change in response to injected current, (2) more negative resting membrane potential than typical neuronal membrane (−84 mV), consistent with known recordings of radial astrocytes in zebrafish (Li et al., 2015). Error bars, SEM.