129 Nomenclature Update

JAX® NOTES Issue 483, Fall 2001

Targeted mutagenesis is most often carried out using embryonic stem (ES) cell lines derived from 129 mice. Efficiency of gene targeting is highly dependent upon using the same 129 substrain as the source of the ES cells. Creation of a truly coisogenic strain carrying the targeted mutation also requires that the host 129 substrain be matched to that of the ES cell line.

In 1999, the names of the substrains of 129 were modified to reflect their relationships to one another. Each substrain is now identified by a unique combination of one of four letters and a number preceding the slash in its name. The letter indicates the 129 subtype to which the strain belongs: P for "Parental"; S for "Steel"; and T for "Ter" (teratoma susceptible). X designates a substrain that was genetically contaminated early in its history and differs significantly from other 129 strains; this substrain, 129X1/SvJ, was the source of the RW-4 ES cell line (See "129X1/SvJ Genetically Contaminated. What Does That Really Mean?" JAX Notes No. 481, February 2001).

Frequently, a targeted mutation generated in 129 ES cells is transferred onto another inbred strain background by repeated backcrossing to the host strain. The correct name of such a congenic strain begins with the abbreviated name of the host strain, followed by a period (.) and the abbreviated name of the strain that donated the chromosome segment containing the gene of interest. For example, a strain congenic for a DNA segment from DBA/2J on the C57BL/6J background would be called B6.D2-. The full names of the 129 substrains, some of which are long and complicated, can be abbreviated by "129" followed by the strains? unique letter-number pairs (i.e., 129X1). This makes congenic nomenclature both clear and simple. It also permits easy distinction among 129 substrains in publications, once the abbreviations have been defined.

When the new 129 substrain nomenclature became effective, the name 129S3/SvImJ was assigned to the strain formerly known as 129/SvImJ (Stock Number 002448). This strain was originally developed as a control strain for mice generated from many of the 129-steel derived ES cell lines (e.g., W9.5 and CJ7). In 1995, Stock Number 002448 was made by breeding the steel Jackson mutation out of a population of 129S1/Sv-+p +Tyr-c KitlSl-J/+ (Stock Number 000090), then at F26. The resulting strain was initially named 129/Sv-+p +Tyr-c +Kitl-Sl/J (Stock Number 002448; see Simpson et al, 1997), which was later shortened to 129/SvImJ. Designated 129S3/SvImJ in 1999 (Festing et al, 1999), this strain was renamed 129S1/SvImJ in February, 2001 to emphasize its relationship to Stock Number 000090. SSLP marker analysis indicates that 129S1/SvImJ is identical to 129S1/Sv+p +Tyr-c KitlSl-J/+ at all markers tested throughout the genome except for the region surrounding the Kitl gene on Chr 10. (Kitl, kit ligand, was formerly called Mgf, mast cell growth factor. For more information about this nomenclature change, please see "Mgf gene name changes to Kitl." JAX Notes No. 481, February 2001.)

For more information about the revised nomenclature of 129 mice please refer to JAX Bulletin No. 1 (June 30, 1999--revised June 2001).

References

Authors in bold are Jackson Laboratory scientists.

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.

Festing MF, Simpson EM, Davisson MT, Mobraaten LE. 1999. Revised nomenclature for strain 129 mice. Mamm Genome 10:836.