The tracheal dorsal trunk is long and tortuous in mutant embryos compared to wild type.
variMD109/vari03953b embryos die at the end of embryogenesis with convoluted tracheal tubes. Pleated septate junctions are missing between epidermal and between tracheal cells in stage 16 homozygous embryos, while adherens junctions are well developed.
Trachea are longer than normal in mutant embryos.
Mutants show defects in septate junction barrier function (as tested using a dye exclusion assay). The defects show variable penetrance and expressivity depending on the genetic background.
Unlike wild-type, post stage 15 trachea in vari03953b homozygotes are unable to exclude from their lumens, a fluorescently labelled 10kDa dextran injected into the body cavity. This is consistent with these trachea lacking a functioning septate junction barrier.
Mutation has no obvious effect on the morphology of the salivary gland or hindgut. Early tracheal development, including primary branch budding and outgrowth and lumen formation and morphology occur normally during stages 11-14. Stage 16 embryos show a number of tracheal defects. These include an increased length of the dorsal trunk compared to wild type (with no accompanying increase in cell number), mild defects in the diameter of the dorsal trunk and moderate defects in the diameter of other primary branches. Irregular and variable tracheal tube morphologies, with local constrictions and/or dilations are seen in all major branches. The defects are first seen at stage 15.