A small deletion derived from imprecise excision of a P-element removes part of the second exon including the initiator codon for translation and creates an additional exon from the P-element. An upstream portion of the second exon is spliced out upstream of codon 69. The ATG at position 145 is the first possible initiator resulting in an N-terminally truncated protein lacking the first 144 amino acids.
The melanotic tumour penetrance is reduced in lwr4-3 cactE8/lwr5 cactE10 double mutants compared to lwr4-3/lwr5 single mutants and by day 8, the amount of circulating hemocytes is reduced in the double mutants. In contrast, the amount of lamellocytes remains as high as in the single mutants.
Embryos laid by cactE10/+, dl1/+ females are weakly dorsalized, 90% of embryos produced by cactE10/+, spz4/+ are weakly dorsalized and 50% of embryos produced by cactE10/+, ea1/+ are weakly dorsalized. More than 80% of embryos produced by cactE10/+, fus1/+ are distinctly dorsalized, and the Egfrfus,fus2 chromosome has a similar but stronger effect. Fewer than 10% of embryos produced by cactE10/+, fus1/+ females hatch and 80-90% show the twisted body and head defects characteristic of a loss of mesoderm. Mesodermal cell types are lost.