There are no phenotypes associated with vestigial mutation, either in segmentation or neural development, but mutant flies manifest a complete lack of balance organs of the third thoracic segment, as well as a lack of development of wings and halteres. Cells lacking vestigial undergo extensive cell death in the presumptive wing region of the third-larval instar imaginal discs. This results in the complete elimination of wing structures in adults.
Several observations link vestigial function with cell survival and proliferation.
The effect of these drugs is to reduce the level of vestigial transcription, suggesting that the level of vestigial transcription is regulated by metabolites of dihydrofolate reductase. Specific mutations in the vestigial locus result in a diminished response to these foliate inhibitors, restoring normal development. The nicking phenomenon induced by drug treatment and its reversal by genetic modifications in vestigial , suggest a role for vestigial in cell proliferation. Thus future research in vestigial biology may reveal an interesting interaction with genes involved in regulation of cell cycle . An intronic enhancer, located between the first and second exons of vestigial , is responsible for vestigial transcription at the wing margin, assuring the presence of vestigial at the margin.