Knockdown of fog in somatic muscle cells, through expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^Mhc.PU results in multiple mitochondrial morphologies. Most frequently, the mitochondria appear predominantly long and filamentous or small and fragmented, and 'donut' shaped (suggesting that they could be autofused forms of mitochondria). A relatively less common phenotype is the formation of large amorphous aggregates especially around nuclei. In about 27% of the muscles, mitochondria show mixed morphologies consisting of elongated as well donut-shaped forms.

Down-regulation of fog in neurons, through expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^elav.PLu generates numerous defects in motorneuron projection.

Expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^htl.POS or Scer\GAL4^repo results in distinct changes in the positioning and shape of the longitudinal glia. Gaps are observed in the two rows of glia on either side of the CNS midline. Glial cells appear smaller and rounder than normal, and their outlines irregular, often bearing tiny finger-like projections. The distance between the inner glial rows is also greater than in wild-type. The glial processes fail to extend ventrally in these mutants and do not ensheath the axons.

Neuronal down-regulation of fog, through expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^elav.PLu, in all post-mitotic neurons, leads to defects in SNa motor axon guidance. In most segments that display a phenotype, either the posterior or the anterior SNa branch is missing. Occasionally, extra anterior branches are observed. In rare cases, the entire SNa appears to stall at the bifurcation point. Expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^repo does not affect motor axon guidance.

Expression of fog^{dsRNA.Scer\UAS} under the control of Scer\GAL4^repo does not affect motor axon guidance.