Insertion in the promoter region.
Hemizygous embryos show multiple phenotypic effects in conjunction with embryonic or larval lethality. The embryos have segmentation defects (represented by fused segments) and strong abnormalities in the muscle pattern and in the peripheral and central nervous systems. The nervous system shows severe loss of neurons, disrupted axon tracks and misguided axons.
P{lacW} not verified as causing the lethality.
Precise excision of the insertion reverts the mutant embryonic phenotype.