ksrS-638 embryos (as well as ksrS-638/ksrS-627 that show a stronger phenotype) derived from mothers bearing ksrS-638 mutant germline clones and thus lacking both maternal and zygotic ksr do not show any loss of muscle founder cells at late embryonic stages and only display rather mild visceral muscle phenotypes such as myotube stretching defects at stage 13/14 and incomplete midgut constriction at the end of embryogenesis.
Clonal analysis fails to produce clones of ksrS-638 suggesting ksr is required for cell proliferation or survival. Embryos derived from germline clones reveal severe terminal defects. They are missing posterior structures beyond the seventh abdominal segment and have collapsed head skeleton. Embryos derived from germline clones of ksrS-638 reveal severe terminal defects.