Nrx-IV⁴³⁰⁴ mutant embryos display malformations of midline glia and of the ventral nerve cord axonal scaffold (revealed by immunolabelling with specific markers).

Embryos have a leaky blood-brain barrier.

Embryos show defects in blood-brain barrier function in the central nervous system in a dextran injection assay.

Mutant embryos lack a functional blood-brain barrier; 10kDa dextran injected into the hemolymph of stage 17 mutant embryos penetrates the central nervous system (CNS) within 15 minutes, whereas no penetration of the dye into the CNS is seen in wild-type embryos.

Homozygous stage 16-17 embryos lack a functional transepithelial barrier in the salivary glands (as analysed using a dye exclusion assay).

10, 70, and 500 kDa labeled dextran molecules can easily penetrate into the CNS in Nrx-IV⁴³⁰⁴ mutant embryos.

Stage 17 homozygous embryos show loss of the blood brain barrier (assayed by studying dextran uptake in living embryos).

In Nrx-IV⁴³⁰⁴ homozygotes lateral pentascolopidial chordotonal organs have a disorganised morphology and rounded, rather than fusiform scolopales. Unlike in wild-type embryos, lateral pentascolopidial chordotonal organs in these embryos fail to exclude a 10kDa dextran dye. Ultrastructural analyses of peripheral nerves in these mutants at late stages of embryogenesis show that, while glial membranes are present and normally spaced around these nerves, the associated septate junctions linking inner and outer glial sheath cells are missing and the boundary between the inner glial membrane and axolemma is abnormally fuzzy.

The tracheal systems of lates stage Nrx-IV⁴³⁰⁴ homozygous embryos have overgrown tubes with unusual expansions, defects in the accumulation of lumen antigens and lumen breaks.

Homozygous embryos have dorsal closure defects; dorsal holes are seen in the cuticle. Necrosis is seen in the salivary glands.

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. Absence of Nrx-IV causes neuronal connectivity defects, affects the septate junctions between scolopale and cap cells resulting in abnormal morphology of scolopales (smooth septate junctions are unaffected, pleated septate junctions lose their characteristic ladder-like septae), 10% embryonic neuromuscular junctions fail to respond to nerve stimulation and the mean amplitude of evoked synaptic transmission of the remaining junctions is 40%-45% of wild type levels. Embryos exhibit a reduced ability to propogate action potentials.