Development and characterization of congenic strains for new body weight QTLs derived from wild mice

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We have previously mapped several quantitative trait foci (QTLs) affecting body weight at 10 weeks after birth in the backcross population from a cross between Philippine wild mice and the common inbred strain C57BL/6J, the difference in adult body weight was 1.7 fold. In this study, we tried to develop congenic strains for QTLs on chromosomes 2,6,10 and 12 and examined characteristics of the congenic strains with the uniform genetic background of C57BL/6J by evaluating growth related traits such as body weights at 1-10 weeks of age, body length, organ weights and white fat pad weights. We were finally successful in establishing three congenic strains for the QTLs on chromosomes 2,10 and 12 by using a standard, marker-assisted selection method. Genotyping mouse microsatellite marker indicated that these strains had wild-derived genomic regions of about 27.0,33.0 and 26.0 cM, respectively. Comparison of the strains with C57BL/6J confirmed the QTL effects expected in the previous study, except for the chromosome 2 congenic strain. In this study, it was newly revealed that fat pad weights in all three congenic strains established were significantly lower than those of C57BL/6J. Some candidates were found in the introduced genomic regions by searching public data bases. In the near future, it will be needed to conduct a more detailed investigation into the QTL effects using a F2 segregation population of the congenic strains and C57BL/6J in order to minimize growth differences due to environmental factors such as litter sizes and litters.