The central nervous system of stage 15 vnd^Scer\UAS.cMa; Scer\GAL4^elav.PLu embryos lacks HGTX expressing neurons.

Overexpression of vnd using vnd^Scer\UAS.cMa under the control of Scer\GAL4^sca-109-68 and Scer\GAL4^Kr.PM generates CNS phenotypes that are more subtle than that seen in vnd^hs.PM embryos, yet similarly leads to embryonic lethality. The longitudinal connectives are discontinuous and positioned farther from the midline in embryos overexpressing vnd^Scer\UAS.cMa under the control of Scer\GAL4^sca-109-68 and Scer\GAL4^Kr.PM compared to wild-type. In addition, commissural formation is also affected. Overexpression of vnd^Scer\UAS.cMa in the Kr domain by Scer\GAL4^Kr.PM leads to a more variable phenotype than in vnd^hs.PM or vnd^Scer\UAS.cMa driven by Scer\GAL4^sca-109-68 embryos. The distribution of eve expressing neurons in embryos mutant for vnd^Scer\UAS.cMa driven by Scer\GAL4^sca-109-68 parallels that seen in vnd^hs.PM embryos (clumps of neurons are detected in an antero-midline proximal position-these may be over-specified aCC, pCC, CQ, and/or U neurons. The RP2 neurons are generally missing), although the eve-positive EL neurons are generally present. In embryos where vnd^Scer\UAS.cMa is driven by Scer\GAL4^sca-109-68, the aCC neurons are clearly duplicated. The number of Fas2-positive neurons at the posterior of the hemisegment is also generally reduced. These include RP2, vMP2, and dMP2. In embryos where vnd^Scer\UAS.cMa is driven by Scer\GAL4^sca-109-68, the number of Fas3-expressing neurons is generally greater than that seen in vnd^hs.PM embryos. Some Fas3-positive fascicles do extend contralaterally as seen in wild-type embryos. However, their position is often highly irregular. In addition, some neurons that express Fas3 extend their axons posterolaterally, instead of across the ventral midline. Overexpression of vnd^Scer\UAS.cMa by Scer\GAL4^Kr.PM results in an overabundance of sim-expressing 'midline glia' that are aberrantly positioned and dispersed throughout the expanded mesectoderm. In embryos in which vnd^Scer\UAS.cMa is under the control of Scer\GAL4^Kr.PM, the pattern of fascicles in the postero-abdominal segments is wild-type. However, in the thoracic segments the three longitudinal tracts are often highly disrupted. In embryos where vnd^Scer\UAS.cMa is driven by Scer\GAL4^sca-109-68, the number of repo-positive longitudinal glia is often reduced compared to that in wild-type. In contrast to the migration of wild-type longitudinal glia to a mediolateral position, the longitudinal glia assume a more lateral position. In embryos in which vnd^Scer\UAS.cMa is under the control of Scer\GAL4^Kr.PM, repo expression (indicating glial cell fate) is affected from stage 12 onwards. At stage 14, repo expression is almost completely absent in the domain of the CNS where vnd overexpression is targeted.