In mutant embryos commissures are fused and longitudinal connectives appear thinner than wild-type. The formation of the VUM axons is not affected in mutant embryos. Midline glial cells are specified in their normal number and are able to migrate but finally fail to intercalate in between segmental commissures. The longitudinal glial cells are initially specified in normal number, however during stages 15-16, migration defects are seen. In extreme cases, no or only few glial cells are found in some hemineuromeres, whereas in the directly neighbouring hemineuromeres increased numbers of glial cells are found. In mutant animals, the neuronal components of the peripheral nervous system (PNS) form relatively normally. The peripheral glial cells are born in normal numbers but migrate to ectopic positions. In some cases, migration is not initiated and glial cells accumulate at the CNS-PNS transition zone. When mutant eye discs are allowed to develop, the eye is reduced in size and anterior structures are missing. In addition the formation of head bristles and ocelli are affected. When larval eye discs are made consisting entirely of foi^B1-089 tissue, the progression of the morphogenetic furrow is disturbed; it does not advance as far anterior as seen in wild-type discs. Concurrently, a stream of glial cells migrates across the morphogenetic furrow - not terminating where they do in wild-type. This effect is not seen in small mutant clones. In mutant embryos, the lateral transverse muscles do not migrate normally. They pass the wild-type attachment sites and continue to grow ventrally to ectopic positions. the growth tips of the muscle fibres are not round as in wild-type, but resemble the motile structure found in young muscle fibres. Paternal rescue is observed for the lethality seen in homozygous germ-line clones.

Mutant embryos show a clear fusion of commissures and frequent disruption of longitudinal connectives. Midline glial cells are either reduce in number or fail to properly migrate in between anterior and posterior commissures. General embryonic morphology is relatively normal, though the PNS shows a slight reduction in sensory neurons and defects in the trajectories of motoneurons.