AXB/BXA Recombinant Inbred Strains

JAX® NOTES Issue 465, Spring 1996

The following article, published in Mouse Genome 1995 93(4) by Dr. Benjamin Taylor, Senior Staff Scientist at The Jackson Laboratory, discusses nonindependence of the AXB/BXA recombinant inbred strains. The Jackson Laboratory distributes the following strains. Strains affected are indicated in bold lettering.

Strain Stock Number Strain Stock Number
AXB-1/Pgn JR1673 BXA-1/Pgn JR1692
AXB-2/Pgn JR1674 BXA-2/Pgn JR1693
AXB-4/Pgn JR1676 BXA-4/Pgn JR1694
AXB-5/Pgn JR1677 BXA-7/Pgn JR1696
AXB-6/Pgn JR1678 BXA-8/Pgn JR1697
AXB-8/Pgn JR1679 BXA-11/Pgn JR1699
AXB-10/Pgn JR1681 BXA-12/Pgn JR1700
AXB-11/Pgn JR1682 BXA-13/Pgn JR1701
 AXB-12/Pgn JR1683  BXA-14/Pgn  JR1702 
 AXB-13/Pgn JR1826  BXA-16/Pgn  JR1703 
 AXB-14/Pgn JR1684  BXA-17/Pgn  JR1704 
 AXB-15/Pgn JR1685  BXA-24/Pgn  JR1710 
AXB-18/Pgn  JR1686  BXA-25/Pgn  JR1711 
AXB-19/Pgn  JR1687  BXA-26/Pgn  JR1999 
AXB-20/Pgn  JR1688  AXB-23/Pgn  JR1690 
AXB-24/Pgn JR1691
 

Nonindependence of AXB RI Strains

The AXB/BXA recombinant inbred (RI) strains were derived from crossing A/J and C57BL/6J (Nesbitt and Skamene, J. Leukocyte Biol. 36:357-364, 1984). While reviewing a listing of AXB/BXA RI strain distribution patterns, I noticed an unusual degree of similarity among three strains (AXB 18, AXB 19 and AXB20). Tabulation of the number of typings at which these strains were identical and different supported this impression. AXB18 and AXB19 were identical at 162 of 180 loci (90%), AXB19 and AXB20 were identical at 153 of 178 loci (86%), and AXB18 AXB20 were identical at 171 of 193 loci (89%). (I used the data I had summarized for the revised version of GVSLM (Taylor, Genetic Variants and Strains of the Laboratory Mouse, Oxford University Press, 1995). The high degree of identity is strikingly different from the 50% expected for independently derived RI strains, suggesting that at some point during their inbreeding, one strain contaminated the others, or that all three are actually separate sublines of the same strain which were separated after partial inbreeding. Simple crossing of one RI strain with another, followed by brother-sister mating, would predict only 75% identity. Comparisons among other AXB/BXA RI strains revealed that AXB13 and AXB14 were identical at 159 of 180 loci (88%), and that BXA8 and BXA17 were identical at 149 of 168 (89%) of loci. Marshall et al. (Mammal. Genome 3:669-680, 1992) found that multiple typings for the AXB13, AXB20, BXA8, and BXA17 RI strains (among others) differed from their previously published genotypes, a result consistent with genetic contamination. They also found examples of RI strains which were segregating for multiple loci, also suggesting the possibility of genetic contamination. Thus, there is other evidence that inbreeding did not always proceed in the standard way.

Given the high degree of similarity within these three groups of related strains, they should not be considered independent when analyzing AXB/BXA data. Thus, linkage statistics and associations of phenotypic traits and genotypes should not include more than one representative of each of these three groups. Inclusion of such nonindependent data could result in declaration of false linkages and in spuriously high and low recombination frequency estimates. Users of the AXB/BXA RI strains might consider limiting their studies to a single member of each of the nonindependent groups. - B. A. Taylor

If you have any questions regarding this information, please contact Carol Cutler Linder, Technical Services Advisor, at 800-422-MICE ext 6230, Fax 207-288-8982, email ccl@jax.org.