Figure 4D-E) Immunofluorescence against CITRINE (electroporated cells), SOX10 (Schwann cell precursors and Schwann cells) and ISL1 (sensory and sympathetic neurons) on embryos electroporated with either control CRISPR plasmid (D) or a CRISPR plasmid containing a guide-RNA against Sox8 (E). CITRINE+ cells populate the developing dorsal root ganglia (DRG) and peripheral nerves. Examples of CITRINE+/SOX10+ cells shown by arrowheads. Asterisks show ventral boundary cap glia. Scale bar is 50 µm in overviews and 10 µm in insets. F) Quantification of the fate distribution of CITRINE+ cells as a % between glial (SOX10+) cells, sensory neurons (ISL1+) or neither (SOX10-/ISL1-) in the DRG of control and Sox8KD chick embryos. Biological replicates - N=3 embryos per condition (wild type versus Sox8 KD). Data represented as mean±SEM. Statistical significance determined using the Holm-Sidak method (alpha = 0.05) (multiple t-tests, unpaired). SOX10+ cells: p=0.7901, ISL1+ cells: p=0.9206, SOX10-/ISL1- cells: p=0.9206. For statistical significance: non-significant - p-value≥0.05. G) Quantification of (left) the % of SOX10+ cells in the peripheral nerves that are CITRINE+ in control and Sox8KD chick embryos and (right) the % of PH3+ CITRINE+ cells corresponding to proliferative cells. Biological replicates - N=4 embryos per condition for SOX10+ distribution and N=2 for PH3 quantification (wild type versus Sox8 KD). Data represented as mean±SEM. Statistical significance determined unpaired t-test with two-tailed p value. SOX10+ cells: p=0.0044, PH3+ cells: p=0.4929. For statistical significance: non-significant - p-value≥0.05, ** - p-value<0.01. Data information: In total, 6 embryos were analyzed for the control electroporation and 7 embryos were analyzed for the Sox8 knock down electroporation and data depicted in graphs correspond to mean±SEM per embryo (corresponding to biological replicates): 3-4 electroporated embryos were analyzed per condition (control and SOX8 knock down) with 4-5 sections stained and analyzed per embryo per region of interest (DRG, DRG: dorsal root ganglia, sg: sympathetic ganglionI) Immunofluorescence against CITRINE (electroporated cells), SOX10 (Schwann cell precursors and Schwann cells) and TH (sympathetic neurons and chromaffin cells) of the sympathoadrenal domain on control and Sox8KD embryos. CITRINE+/SOX10+ cells shown by empty arrowheads while CITRINE+/TH+ cells are shown by filled arrowheads. Scale bar = 50 µm. J) Quantification of the fate distribution of CITRINE+ cells as a % between glial (SOX10+) cells, chromaffin cells (TH+) or neither (SOX10-/TH-) in the proximity of the dorsal aorta and visceral nerve of wild type and Sox8 KD chick embryos. Biological replicates - N=4 embryos per condition. Data represented as mean±SEM. Statistical significance determined using the Holm-Sidak method (alpha = 0.05) (multiple t-tests, unpaired). SOX10+ cells: p=0.0067, TH+ cells: p=0.0067, SOX10-/TH- cells: p=0.8819. For statistical significance: non-significant - p-value≥0.05, * - p-value<0.05. Data information: In total, 6 embryos were analyzed for the control electroporation and 7 embryos were analyzed for the Sox8 knock down electroporation and data depicted in graphs correspond to mean±SEM per embryo (corresponding to biological replicates): 3-4 electroporated embryos were analyzed per condition (control and SOX8 knock down) with 4-5 sections stained and analyzed per embryo per region of interest Sympathoadrenal domain).