The mutation in kuzR1-4 arises from a splice-donor-site mutation in the 4th intron (the point mutation is five base pairs downstream of the 4th exon). This results in a failure to splice a 68 bp intron, which finally causes a truncation within the prodomain of kuz due to a frameshift. The predicted protein lacks any recognizable domains.
G13609992A
G?A
G to A mutation in the 5th base of the intron prevents splicing of the 68 bp intron.
kuzR1-4 mutant embryos display an approximately twofold excess of cardioblasts along the whole anterior-posterior axis of the dorsal vessel, although the phenotype is more prominent in the posterior segments. Mef2 and svp labellings show that all types of cardioblasts in an abdominal hemisegment are increased in number, although to different extent.
The number of zfh1 and odd expressing pericardial cells is reduced in kuzR1-4 mutant embryos. In contrast, the number of eve expressing pericardial cells is not affected.
kuzR1-4 mutant embryos show an increased number of wg-positive cardioblasts that fail to form the typically double pairs and exhibit an abnormal morphology.
The number of lymph gland precursor cells is reduced in kuz[R1-4] embryos.
Homozygous kuzR1-4 embryos display muscle contraction but fail to hatch and die approximately 2 days after egg deposition.