Fluorescent dye injected into the body cavity of Nrx-IV⁴⁰²⁵ embryos penetrates into the nerve cord after the stage at which the nerve cord is sealed in wild-type embryos, showing that formation of the blood-brain barrier if defective.

In Nrx-IV⁴⁸⁶⁵/Nrx-IV⁴⁰²⁵ embryos, tracheal phenotypes are apparent from stage 15. At stage 16 in these embryos the average dorsal trunk length is significantly greater than wild type (P<0.005) (116+/-4% mean+/-s.e.m., n>5, normalized to stage 16 wild-type value). In addition these embryos have moderately severe diameter increases in the dorsal trunk and other primary tracheal branches, and some ganglionic branches exhibit missing lumen.

Transheterozygotes with Df(3L)vin8 or Df(3L)BK9 are lethal, rare adults escapers are occasionally obtained. Transheterozygous embryos with Df(3L)BK9 show a complete absence of muscle-propagation waves, staining reveals smooth septate junctions are unaffected, pleated septate junctions lose their characteristic ladder-like septae.