Targeted Mutation Nomenclature Updates
JAX® NOTES Issue 484, Winter 2001
Mutations that are the result of gene targeting by homologous recombination in ES cells are given the symbol of the targeted gene, with a superscript consisting of three parts: the symbol tm to denote a targeted mutation, a serial number from the laboratory of origin, and the Laboratory Code indicating where the mutation was produced. For example, Cftrtm1Unc is the first targeted mutation of the cystic fibrosis transmembrane regulator (Cftr) gene produced at the University of North Carolina (Laboratory Code: Unc).
So-called "knock-in" mutations, in which all or part of the coding region of one gene is replaced by another are given a tm symbol and the particular details of the knock-in associated with the name in publications or databases. Where there has been a replacement of the complete coding region, the replacing gene symbol can be used parenthetically as part of the allele symbol of the replaced gene, along with a Laboratory Code and serial number. For example, En1tm1(Otx2)Wrst is used where the coding region of engrailed 1 (En1) was replaced by the Otx2 gene, originating from the W. Wurst laboratory.
When a targeting vector is used to generate multiple germline transmissible alleles, such as in the Cre-lox system, the original knock-in of loxP would follow the regular tm designation rules. If a second heritable allele were then generated after mating with a Cre transgenic mouse, it would retain the parental designation followed by a decimal point and serial number. For example, Tfamtm1Lrsn designates a targeted mutation where loxP was inserted into the transcription factor A, mitochondria, (Tfam) gene. Tfamtm1.1Lrsn designates another germline transmissible allele generated after mating with a Cre transgenic mouse.
These guidelines do not apply to offspring generated by mating a Tfamtm1Lrsn mutant mouse and a Cre transgenic strain, resulting in the disruption of Tfam in selective tissues, since somatic recombination events are not heritable.
To view the complete list of Mouse Nomenclature Rules and Guidelines, visit the following Web site: www.informatics.jax.org/mgihome/nomen/table.shtml.
