Some cells of the central nervous system of homozygous mid^GA174 embryos exhibit abnormal neuronal cell fate specification.

mid^GA174 and mid^GA174/Df(2L)x528 mutant embryos show a significant loss of NB1-1 in the odd-numbered abdominal segments (68.7 % and 70.8% loss, respectively) while the loss of NB1-1 in the even-numbered abdominal segments is minimal (5 and 9.7%). Likewise, loss of NB2-5 and NB2-4 neuroblasts is higher in odd-numbered than in even-numbered abdominal segments, although the loss is less extreme than for NB1-1 neuroblasts (NB2-5 odd loss: 32% in mid^GA174 embryos and 29% in mid^GA174/Df(2L)x528 embryos; even loss is 7% and 8.3%; NB2-4 loss is 19% for mid^GA174 embryos and 17.8% for mid^GA174/Df(2L)x528 embryos; even loss is 3.6% and 4.1%). There is no evidence that row 1/2 neuroblasts adopt row 3/4 identities in these embryos. In contrast, formation of early row 7 neuroblasts is unaffected in mid^GA174 embryos. Similarly to the situation with neuroblasts, GMC7-1a forms correctly in these embryos but GMC1-1a is frequently absent in odd-numbered segments.

Stage 16 mid^GA174 embryos show no ectopic EL neuron clusters, suggesting that NB3-3 identity is correctly specified.

In 46% of hemisegments, mid^GA174 embryos show a one eve-positive extra neuron per hemisegment at a position similar to the RP2 neuron. This extra neuron projects its axon toward the ventral midline, indicating that it is not, in fact, an RP2 neuron. The ectopic neuron occurs in similar amounts in odd-numbered and even-numbered segments.

The mature ventral nerve cord of mid^GA174 embryos shows a frequent loss of the lateral-most en-positive cell clusters. The medio-lateral cluster contains 3-4 instead of 5-6 cells and these cells are spatially disarranged. At the ventral midline, the number of mid^GA174 cells is reduced to 4-5 in most segments and mid^GA174 cells are completely absent in 12% of segments.

Mutant larvae show loss of denticles in the ventral most part of the abdominal denticle belts.