Deletion of 5' noncoding exon I but not exon II.
htlΔ30/htlLH14 transheterozygous embryos show defects in the migration and organisation of the mesodermal cells. htlΔ30/htlLH14 transheterozygous embryos have only small patches of visceral mesoderm. htlΔ30/htlLH14 transheterozygous embryos have few muscles that show irregular organisation and attachment. Scer\GAL4hs.2sev and Scer\GAL4twi.PG mediated expression of dppScer\UAS.cSa allows full rescue of defects, Scer\GAL4ptc-559.1 expression allows only partial rescue.