cer9 is a CRISPR-generated 462 bp deletion at the beginning of the ikb-1 coding sequence, including the start codon (no transcript should be synthesized). Low penetrance of developmental defects such as abnormal L1 morphology, aberrant gonad migration, and an abnormal number of distal tip cells. Reference: Brena D, et al. Sci Rep. 2020 Sep 30;10(1):16153.