Fig. 5.

Fence function of SJs is required for establishment of polarized membrane compartments in SPG. (Aa) Immunohistochemistry against Moody and moody>ncGFP. Moody is enriched on the apical (i.e. nervous-system facing) side of SPG in third instar larva. (Ab-d) Live imaging of GFP-tagged Moody using MZ1251>moodyGFP, nuclearCherry. Moody is not polarized in stage 16 embryos, but localizes exclusively to the apical surface by stage 17. (Ad) In Nrg¹⁴ mutants, Moody fails to polarize. Lateral views of the CNS/hemolymph border with the CNS facing up in all images. (B) Quantification of MoodyGFP localization in WT. Polarization of MoodyGFP (magenta), computed as basal/apical ratio of fluorescence intensities, coincides with CNS insulation (green). Insulation was quantified by measuring the levels of fluorescent Dextran-TR diffusion into the CNS. (C) In Nrg¹⁴ mutants, the SPG epithelium forms largely normally (arrowheads), although small gaps in the epithelium remain visible (arrow). 17 h old embryos; glia are labeled by repo>gapGFP; top panels, ventral view; bottom panels, orthogonal view of areas indicated by black box; stack of 15 µm. (D) Both Moody and gapGFP are observed immediately adjacent to but not coincident with SJ components (Nrg::GFP or Contactin). Immunohistochemistry; ventral view of CNS; stacks of 10 µm; graphs show intensity profiles along the line marked by an arrow in the merged panels.