Figure 1.
Morphological Development of Newborn Neurons and Emergence of Neurotransmitter Identity
(A) Top: schematic dorsal view of the zebrafish brain. The electroporated optic tectum (OT) is indicated by the blue square. The DNA injection capillary scheme is depicted in black. The electroporation electrodes are shown in red (cathode) and black (anode) bars. Cb, cerebellum; Hb, habenula; HB, hindbrain; OB, olfactory bulb; Tel, telencephalon. Bottom: Optical section of a Tg(huC:GCaMP5G) zebrafish larva showing pan-neuronal GCaMP5 expression corresponding to the area in the top scheme (blue rectangle). The periventricular zone (PVZ) of the OT left hemisphere is highlighted in red; Np, neuropil, highlighted in blue. The neurogenesis site is circled in green. The scale bar represents 50 μm. L, left; R, right; A, anterior; P, posterior.
(B) Example of a developing newborn-labeled neuron chronically imaged from 1 to 4 dpe. The neuron developed to become a non-stratified peri-ventricular neuron. Bottom: corresponding morphological reconstructions. The scale bar represents 20 μm.
(C) An optical section of the tectum’s caudo-lateral region of an electroporated Tg(EF1:mAG-hGem;huC:GCaMP5G) larva (all neurons express GCaMP5G in the cytoplasm and dividing cells express the nuclear localized GFP mAG in the nucleus; dashed line). Note the non-fluorescence region between the dividing cells and the GCaMP5G-expressing neurons. This dark region corresponds to cells that exited the dividing cycle but are not yet neurons. An electroporated newborn neuron can be observed adjacent to the neurogenesis site (imaged at 1 dpe and expressing dTomatoCAAX; arrowhead). The scale bar represents 20 μm.
(D) Total dendritic length obtained from morphological reconstructions of newborn neurons from 1 to 5 dpe (n = 22, 17, 10, 12, and 3, respectively). Only one neuron was reconstructed per electroporated larva. The red circle represents the average dendritic length of functionally mature neurons at 1 dpe, n = 8. The error bars represent SEM. ∗∗∗p < 10−3.
(E) Fraction of excitatory and inhibitory newborn-labeled neurons in Tg(gad1b:GFP;vglut2a:loxP-DsRed-loxP-GFP) larvae at 1 and 4 dpe. For visualization of the newborn-labeled neurons, a blue fluorescence protein was used for the electroporations (1 dpe: n = 34 neurons from 13 larvae; 4 dpe: n = 62 neurons from 29 larva).
See also Figure S1.