Pan et al. (2019) have found that circRNA-filip1L is notably increased in the ipsilateral SDH of mice with IP and that miRNA-1224 knockdown or Ago2 overexpression induces nociceptive behaviors in naive mice. Functional evidence has suggested that circRNA-Filip1l regulates IP by targeting Ubr5 in an Ago2-dependent manner (Pan et al., 2019). This evidence concerns the gene AGO2 and incontinentia pigmenti.