Figure 7

XSTIM1 is required for midline axon guidance of commissural interneurons in the developing Xenopus spinal cord. (A-E) Sample images of the sagittal view of commissural interneurons and their axonal projections in the Xenopus spinal cord from stage 25-26 embryos. Shown are schematic diagrams and confocal z-stack projection images of 3A10 staining of commissural interneuron axons from uninjected embryos, or embryos injected with mRNAs for GFP (B), YFP-XSTIM1-DN (C), YFP-XSTIM1-CA (D), or YFP-XSTIM1-WT (E), at the two to four cell-stage to manipulate a sub-population of neurons. Dotted line represents ventral midline; arrows point to mis-targeted axons. Scale bars: 20 μm. (F) Quantification of the percentage of 3A10⁺ commissural interneurons with normal midline crossing under different experimental conditions. The number associated with the bar graph indicates the number of embryos examined under each condition. Values represent mean ± s.e.m. (* indicates P < 0.01; Bootstrap-test). (G) Summary of the density of 3A10⁺ commissural neurons under each condition. The same embryos as in (F) were examined. Values represent mean ± s.e.m. (^# indicates P > 0.1; Bootstrap-test).