Mutants show loss of expression of P{FMRFa-EGFP.Tv}, a marker for the six Ap4 neurons in the developing ventral nerve cord, and extra expression of eya, which identifies the four Ap cluster neurons.
svp1/svp11C115 mutants exhibit Eya-positive Ap neuron loss in 30% thoracic hemisegments. In the hemisegments in which Ap neurons are generated an increase in Ap neuron number is observed, from 4 to approximately 6 cells. Extra Ap1/Nplp1 neurons are seen and there is loss of the Ap4/FMRFa cell fate.