International Mammalian Genome Society

The 16th International Mouse Genome Conference (2002)


L Lu
University of Tennessee

1) Gu J, 2) Threadgill D, 1) Williams R
1) University of Tennessee, 2)University of North Carolina

Recombinant inbred intercross (RIX) mapping is a new gene mapping method that extends the power of existing sets of recombinant inbred strains. Here we used the CXB RIX set to map quantitative trait loci (QTLs) that modulate hippocampus size. Our mapping panel consists of all 13 CXB parental strains, and the full set of 78 non-reciprocal F1 RIX hybrids. The hippocampus was dissected from fixed brain and weighed immediately. The average bilateral hippocampal weight of CXB strains is 27.1 ± 2.55 mg whereas the average of RIX progeny is 28.6 ± 1.85 mg. We corrected for differences in age, sex, body weight, and brain weight by multiple linear regression. The adjusted data—the weight residuals—range from –10.4 to +6.0 mg in CXB strains and from –9.9 to +3.8 mg in RIX F1 mice. Map Manager QTX program was used for QTL analysis. Mapping in CXB parental strains detects only one weak QTL on Chr 11 with LRS of 11.8 between 24 and 33 Mb. Using the large RIX panel, we verified this QTL, but the LRS increased to 32.3. Additional regions with strong linkage (LRS > 18.4) were also detected on Chrs 2, 3, 9, 10, and 19. After controlling for non-syntenic association using the strongest of these intervals, we retained two independent and significant QTLs. In conclusion, this study demonstrate that RIX mapping panel adds additional statistical power to RI mapping panels, and three QTLs modulating mice hippocampal weight have been found by using RIX mapping method.

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