Short Communications Revised nomenclature for strain 129 mice Michael F.W. Festing, 1 Elizabeth M. Simpson, 2 Muriel T. Davisson, 3 Larry E. Mobraaten 3 1 MRC Toxicology Unit, University of Leicester, P.O. Box 138, Leicester LE1 9HN, UK 2 Centre for Molecular Medicine and Therapeutics, 3018-950 West 28th Avenue, University of British Columbia, Vancouver, B.C. V52 4H4, Canada 3 The Jackson Laboratory, Bar Harbor, Maine, USA Received: 27 January 1999 / Accepted: 23 March 1999 Need for revised nomenclature Two recent papers (Simpson et al. 1997; Threadgill et al. 1997) have shown that there is substantial genetic variation among substrains of this important inbred strain. Some of this has apparently arisen as a result of genetic contamination, and the rest appears to be due to residual heterozygosity and/or “contaminant” alleles introduced dur- ing various backcrossing programs such as in the production of con- genic strains carrying Steel and susceptibility to teratomas. Correct identification and designation of substrains is essential if the genotype of the mouse strain is to be matched accurately with an appropriate embryonic stem cell line in the development of “knockout” strains. Unfortunately, current nomenclature makes this difficult. Thus, substrains 129/SvJ and 129/SvJae are very different, but this is not immediately obvious even to someone with a good understanding of nomenclature rules. Moreover, some substrains can be accurately identified only by use of nomenclature involving quite complex gene symbols. Thus, in view of the wide- spread use of these strains by people with little understanding of genetic nomenclature, it seems sensible to introduce new, simpler nomenclature that will minimize future misunderstandings particu- larly because investigators have sometimes referred to different substrains as simply “129,” adding further confusion. The new nomenclature The following new nomenclature has been approved by the Com- mittee on Standardized Genetic Nomenclature for Mice. The aim is to provide short symbols that distinguish different substrains when they are abbreviated from the frequently long and complicated sub- strain symbols, either in common usage or in manuscripts. The new nomenclature is based on the substrains identified and defined in terms of microsatellite markers by Simpson et al. (1997). A letter and a number have been introduced in front of the slash that will un- equivocally identify each of the substrains. The letter is either P, S, T, or X indicating whether it is a “Parental,” “Steel” “Ter” (that is, susceptible to teratomas), or a genetically contaminated “X” sub- strain, respectively. A number will be used to differentiate between substrains within each grouping, working from left to right in Fig. 2 of Simpson et al. (1997). All existing substrain symbols and gene symbols will be retained. The only change is the introduction of a letter and a number in front of the slash. A genuine congenic strain such as 129/ReJ-Lama2 dy will take the strain designation of its part- ner, that is, it will be designated 129P1/ReJ-Lama2 dy . This nomen- clature change is equivalent to that used to distinguish between RIII and RIIIS, where the latter differs substantially from the former. Table 1 shows the proposed new nomenclature for each sub- strain. Note that the strain that was frozen as embryos in 1978 as 129/Sv (JR000094) has been discovered to be heterozygous at many loci and has not been included on this list because it is clearly not the inbred 129/Sv strain that it was thought to be. 129/SvEms-+ Ter? /J (002065) and 129/SvEmsJ-+ Ter? (JR000094) are presumed to be genetically identical. Implementation These new nomenclature rules should be put into effect as soon as possible, although it is recognized that this may take some time if it involves printing new literature, price lists etc. References Simpson EM, Linder CC, Sargent EE, Davisson MT, Mobraaten LE, Sharp JJ (1997) Genetic variation among 129 substrains and its importance for targeted mutagenesis in mice. Nat Genet 16, 19–27 Threadgill DW, Yee D, Matin A, Nadeau JH, Magnuson T (1997) Genealogy of the 129 inbred strains: 129/SvJ is a contaminated inbred strain. Mamm Genome 8, 390–393 Correspondence to: M.F.W. Festing Table 1. New nomenclature for strain 129 mice. a Abbreviated designation Full designation Former designation Jackson Laboratory stock number 129P1-Lama2 dy 129P1/ReJ-Lama2 dy 129/ReJ-Lama2 dy 000641 129P1 129P1/ReJ 129/ReJ 001137 129P2 129P2/OlaHsd 129/OlaHsd na 129P3 129P3/J 129/J 000690 129P4 129P4/RrRk 129/RrRk na 129X1 129X1/SvJ 129/SvJ 000691 129S1 129S1/Sv-+ p + Tyr-c Mgf Sl-J /+ 129/Sv-+ p + Tyr-c Mgf Sl-J /+ RJ0090 129S2 129S2/SvPas 129/SvPas na 129S3 129S3/SvImJ-+ p + Tyr-c + Mgf-S1J /J 129/SvlmJ (formerly 129/Sv-+ p + Tyr-c + Mgf-S1J /J) 002448 129S4 129S4/SvJae 129/SvJae na 129S5 129S5/SvEvBrd 129/SvEvBrd na 129S6 129S6/SvEvTac 129/SvEvTac na 129S7 129S7/SvEvBrd-Hprt b-m2 129/SvEvBrd-Hprt b-m2 na 129S8 129S8/SvEv-Gpi1 c Hprt b-m2 @J 129/SvEv-Gpi1 c Hprt b-m2 @J (formerly 129/SvEv-Hprt b-m2 ) 002027 129T1 129T1/Sv-+ p Tyr c-ch Ter/+@Na 129/Sv-+ p Tyr c-ch Ter/+@Na na 129T2 129T2/SvEms 129/SvEms (formerly 129/SvEms-+ Ter ? / ) 002064 129T2 129T2/SvEmsJ 129/SvEmsJ (formerly 129/SvEms-+ Ter ?/J) 002065 a Substrains of unknown origin and the original “grandfather” strain will continue to be designated 129/substrain, where “substrain” is a current substrain designation. However, people should make every effort to identify the substrains that they maintain and change the nomenclature accordingly. © Springer-Verlag New York Inc. 1999 Mammalian Genome 10, 836 (1999). Incorporating Mouse Genome