Df(3L)H99 strongly suppresses the axon scaffold phenotypes seen in Df(1)NetAB^Δ mutant stage 16 embryos. The defects in negative geotaxis behaviour are further enhanced compared to Df(1)NetAB^Δ alone, but the mechanical startle-induced locomotor reactivity phenotype is significantly rescued.

Df(1)NetAB^Δ mutant males carrying either Dp(1;2)51b or Dp(1;2)w⁺70h display courtship defects; unlike in wild type males, Df(1)NetAB^Δ mutants vibrate both wings simultaneously.

Df(3L)H99 has no effect on the reduced viability seen in Df(1)NetAB^Δ.

Df(1)NetAB^Δ mutant embryos exhibit ventral nerve cord defects, including disrupted commissure formation, with the posterior commissure more severely affected.

Df(1)NetAB^Δ homozygous embryonic heart cardioblasts show a rounded morphology, show significant decreases in migration velocity, as well as in filopodial and lamellopodial extensions and activities, as compared to controls; these are associated with gaps in the leading edge, cell clumping, and improper linear alignment of the cardioblasts, as compared to controls.

Df(1)NetAB^Δ mutant stage 16 embryos display reduction of commissural axons and longitudinal axons. CNS apoptosis is increased compared to wild type from stage 14 until the end of embryogenesis. Defects are seen in the number, position and axons path-finding of the eg expressing commissural neurons; the midline crossing of EW neurons is strongly disrupted, while EG neurons are affected to a lesser extent. Df(1)NetAB^Δ mutants display a significant number of missing or reduced EW clusters, whereas EG clusters are statistically unaffected.

Df(1)NetAB^Δ mutant flies have an uncoordinated phenotype and show defects in negative geotaxis assays. Locomotor activity following mechanical startle is significantly reduced compared to wild type.

Df(1)NetAB^Δ mutants display thorax morphology defects; the thorax appears split into two halves with an invagination of varying depth separating the two sides. The area of normal cuticle (darker in colour with bristles present) is frequently reduced leaving plain lighter colored cuticle present. The reduction of cuticle with bristles, as well as the overall volume of the thorax is usually asymmetric and occasionally the wing is also absent. Flies with thorax defects are entirely sterile.

The Df(1)NetAB^Δ mutant stock in which the second site mutations have been recombined (referred to as NetAB[ΔGN]) has some viability defects. Df(1)NetAB^Δ mutant females mated to males of the same genotype lay significantly fewer eggs than controls and a smaller proportion of eggs hatch into larvae within 24 hours. The presence of a wild type X chromosome from the father increases the number of hatching offspring to levels statistically indistinguishable from wild type. Ovaries from Df(1)NetAB^Δ mutant flies display subtle defects in the boundary with nurse cell nuclei found outside the follicle cells or protruding through the squamous follicular cells. This phenotype is only seen in stage 10-11 eggs. Egg laying defects are also seen when Df(1)NetAB^Δ mutant males are mated with wild type females.

Embryos derived from Df(1)NetAB^Δ mutant mothers display axonal phenotypes.

Df(1)NetAB^Δ mutant males display courtship defects; unlike in wild type males, Df(1)NetAB^Δ mutants vibrate both wings simultaneously. Time of courtship initiation and the proportion of time spent on courtship are unaffected.

Df(1)NetAB^Δ mutant flies are unable to fly. Wings are frequently held out at an angle and droop slightly.

Stage 15 Df(1)NetAB^Δ mutant embryos exhibit EW axon midline crossing defects in approximately 40% of segments.

Df(1)NetAB^Δ double mutant escapers display R8 axon stalling at the medulla neuropil border.

Stage 16-17 mutant embryos have defects in the anterior commissures (13.8% thin, 5.8% absent) and in the posterior commissures (26.8% thin, 17.4% absent).

The number of embryonic peripheral glia (ePG) on the intersegmental nerve distal to the SNc nerve branch is reduced compared to wild type in 94% of mutant hemisegments. Sometimes, more than three ePG are detected in the exit area of the affected hemisegment, suggesting that ePG cells have stalled in this area.

29% of hemisegments have ectopic glial cell clusters in the dorsal periphery in close proximity to ePG11. These ectopic clusters correspond to misplaced interface glia which are missing in the central nervous system in these hemisegments. Longitudinal axons display fasciculation defects, especially in hemisegments in which interface glia are missing in the central nervous system.

A small number of Df(1)NetAB^Δ males eclose. The placement of motoneuron dendrites within the medio-lateral axis is not affected in these animals. However, Scer\GAL4^E49-labelled midline-projecting motoneuron dendrites are missing, as well as more medially projecting dendrites in the anterior regions of the neuropil.

In Df(1)NetAB^Δ mutants MN-VO4-6 and MN-VO4/5 dendrites fail to target the midline neuropile. Similarly, MN-LL1 has a clearly reduced innervation of the intermediate neuropile in 63-64% of cases.

96.2% of Df(1)NetAB^Δ/Y embryos show defects in axon guidance in the Bolwig's nerve.

Df(1)NetAB^Δ embryos show defects in the commissures of the central nervous system; 2% of anterior commissures are absent, 12% of anterior commissures are thin, 2% of posterior commissures are absent and 15% of posterior commissures are thin. 36% of segments fail to separate the anterior and posterior commissures correctly.

EW axons fail to cross the midline in many segments of homozygous Df(1)NetAB^Δ mutant embryos.

Both the anterior and posterior commissures are disrupted in homozygous Df(1)NetAB^Δ mutant embryos, with the posterior commissure affected in about 43% of segments and the anterior commissure in 26%.

In homozygous Df(1)NetAB^Δ mutant embryos, the EW axons fail to cross the posterior commissure in about 55% and EG axons fail to to cross the anterior commissure in about 8% of segments.

There is no significant difference in the distribution of axon orientations in homozygous Df(1)NetAB^Δ mutant embryos compared to wild-type embryos. In particular, the percentage of axons oriented toward the midline is similar in both mutant and wild-type embryos.

In contrast to other classes of axons, only the intersegmental posterior commissure axons are significantly under-represented in homozygous Df(1)NetAB^Δ mutant embryos, with a corresponding over-representation of intrasegmental ipsilateral axons compared with wild-type.

The measurement of distance from the axon tip to the center of the central nervous system (CNS) for intrasegmental ipsilateral axons indicates that these axons do not terminate any further from the midline in homozygous Df(1)NetAB^Δ mutants than in wild-type embryos.

Homozygous Df(1)NetAB^Δ is lethal.