Help & Documentation

How are alleles named?

IMPC uses standard rules to name alleles.

The gene symbol is followed by a superscript that indicates the serial number and the laboratory code.

As part of the superscript, “tm” indicates targeted mutation, and “em” an endonuclease-mediated allele. IMPC alleles carry KOMP, EUCOMM or IMPC as part of the laboratory name.


  • Cib2tm1a(EUCOMM)Wtsi : targeted, KO first allele (reporter-tagged insertion with conditional potential).
  • Nxntm1b(EUCOMM)Wtsi : targeted, reporter-tagged deletion allele (post-Cre).
  • Nxnem1(IMPC)J : endonuclease-mediated allele; indel.

More information on IMPC allele design can be found here.