NRX positive cells in the CNS and along the peripheral nerves express glial-specific markers and not neuronal markers. All tissues that express NRX in the embryo are characterized by the presence of pleated synaptic junctions. In the chordotonal organs , NRX is expressed in cells surrounding the scolopales where synaptic junctions have been localized. Effects of mutation or deletion Mutants produce no adult survivors, and most alleles are embryonic lethal. Nrx mutants exhibit behavioral defects.
Mutants exhibit a severe reduction of coordinate muscle propagation waves.
In addition, tracheae do not fill with air. Thus there is no absolute requirement for NRX in axonal pathfinding, but its absence results in a higher propensity for neuronal connectivity defects. Thus NRX function appears to be required presynaptically to facilitate transmission. Bursts of activity at NMJs, which correlate with muscle contractions that permit first-instar larvae to hatch from the egg case, are reduced in mutants, suggesting a suppression of endogenous activity in motoneurons. Interesting, some muscle contractions are observed in Nrx mutant embryos upon dissection in low potassium ion recording solutions.