The number of cells expressing particular neuropeptide markers in the ap cell cluster of the NB5-6T lineage is changed relative to controls (number of eya expressing cells is increased, no. of FMRFa or Nplp1 positive cells is decreased) in both Ctr9^12P023 homozygote and Ctr9^12P023/Df(3L)BSC250 embryos. Ctr9^12P023/Df(3L)BSC250 mutant embryos display increased general proliferation rate of both neuroblasts (NBs) and daughter cells in the thoracic segments of embryonic ventral nerve cord and small but significant increase in the total number of NBs is observed. The divisions of neuroblast in both the NB5-6T and NB3-3A lineages are also aberrantly extended: up to stage 17 or 16, respectively; there is a minor increase in the proliferation of daughter cells in the NB5-6T lineage but none in the NB3-3A.

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.