The International Complex Trait Consortium

Generation and Characterization of Highly Recombinant Inbred Lines from an Advanced Intercross

Jeremy L Peirce1, Lu Lu2, Guomin Zhou2, Lee M. Silver1, Robert W. Williams2

1Department of Molecular Biology, Princeton University, Princeton, NJ 08544
2University of Tennessee Health Science Center, Center of Genomics and Bioinformatics, Memphis, TN 38163 USA

ABSTRACT
 
Ultimately, the number of breakpoints available to researchers defines the lower limit of resolution available for QTL and the other mapping. Advanced Intercross Lines (AILs; Darvasi and Soller, 1995) are an excellent resource for generating recombination in a segregating population, but are extremely time consuming and expensive to generate and are not a stable resource. Here we describe the production of advanced recombinant inbred (ARI) lines starting with an advanced intercross between C57BL/6 and DBA/2.

A total of 20 lines are currently characterized and are inbred between F10 and F16. Ten lines each derive from the advanced intercrosses generated at the University of Tennessee Health Science Center (crossed to G9 before inbreeding) and Princeton University (crossed to G10 before inbreeding). Breakpoints present in the final lines are derived both from the advanced intercross phase and the inbreeding phase.

Theoretically, these lines should have a 4.5-fold (G9) or 5-fold (G10) map expansion during the inbreeding phase, though Darvasi notes that the theoretical n/2 expansion, where n is the number of generations in the advanced intercross, will diminish after G6-G7. Addition to the approximately 3.3-fold expansion gives an expansion of 7.8 (G9) to 8.3-fold (G10). Ignoring the problem of shared origins and allowing for additional breakpoints accruing from the resolution of heterozygous regions, and the observed expansions were 5.8 (G9) and 6.1-fold (G10), suggesting that the AIL phase contributed substantially, but somewhat less than theoretically expected. Of course, shared recombinants will lower these values somewhat. Preliminary analysis suggests no more than 15% shared recombinations in each 10-strain set, though this fraction will increase as additional strains are characterized. Advanced Recombinant Inbred (ARI) lines contain approximately 75% (G9) - 85% (G10) more recombinations per line than average RI lines.

These lines have been genotyped at 500 markers and should be phatogen-free and available for researchers interested in mapping traits in the BXD system after rederivation, likely witin 12-18 months. We will demonstrate preliminary alcohol preference mapping as an application of the currently existing lines.

References

Darvasi A, Soller M (1995) Advanced intercross lines, an experimental population for fine genetic mapping. Genetic 141: 1199-1207

[This work supported by a grant from the National Institute on Alcohol Abuse and Alcoholism to LMS]