Fig. 2. Genetic interactions alter CNS midline cell development. Whole-mount embryos stained with anti-SIM (A-C,F-I) and anti-SLI (D,E,J,K). (A-E,H,I) Sagittal section with anterior towards the left and (F,G,J,K) frontal views with anterior upwards. (A) In stage 13 wild-type embryos, SIM-positive cells are distributed ventrally to dorsally (arrow) and are only occasionally outside the nerve cord (arrowhead). (B) In stage 13 jing⁰¹⁰⁹⁴, tgo¹ sim^H9 triple heterozygotes, the midline cells are displaced dorsally (arrowhead) and ventrally (arrow). (C) In stage 14 jing⁰¹⁰⁹⁴, sim^H9 double heterozygotes, midline cells are displaced ventrally. Arrow denotes absence of dorsal midline cells. (D) In stage 13 wild-type embryos, SLI-positive glia are present dorsally. (E) In stage 13 jing⁰¹⁰⁹⁴, tgo¹ sim^H9 triple heterozygotes, SLI immunoreactivity is displaced to segment boundaries (arrow) and ventrally. (F) Stage 15 wild-type embryo showing SIM⁺ cells. (G) Absence of SIM immunoreactivity in stage 15 jing⁰¹⁰⁹⁴, tgo¹ sim^H9 triple heterozygotes. (H) SIM⁺ midline cells are displaced ventrally in stage 14 sim^H9/sli¹ double heterozygotes. (I) Midline cells are displaced ventrally (arrow) in jing⁰¹⁰⁹⁴/sli¹ double heterozygotes. Arrowhead denotes absence of cells. (J) Wild-type midline SLI immunoreactivity. Stage 14. (K) Reduced SLI immunoreactivity in stage 14 jing⁰¹⁰⁹⁴/sli¹ double heterozygotes. Arrows in J,K indicate SLI immunoreactivity.

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