Colleagues and I previously performed quantitative trait locus (QTL) analysis on plasma total-cholesterol (T-CHO) levels in C57BL/6J (B6) × RR F
2 mice. We identified only one significant QTL (
Cq6) on chromosome 1 in a region containing the
Apoa2 gene locus, a convincing candidate gene for
Cq6. Because
Cq6 was a highly significant QTL, we considered that the detection of other potential QTLs might be hindered. In the present study, QTL analysis was performed in B6.KK-
Apoa2b N(8) × RR F
2 mice [B6.KK-
Apoa2b N(8) is a partial congenic strain carrying the
Apoa2b allele from the KK strain, and RR also has the
Apoa2b allele] by controlling of the effects of the
Apoa2 allele, for identifying additional QTLs. Although no significant QTLs were identified, 2 suggestive QTLs were found on chromosomes 2 and 3 in place of the effects of the
Apoa2 allele. A significant body weight QTL was identified on chromosome 3 (
Bwq7, peak LOD score 5.2); its effect on body weight was not significant in previously analyzed B6 × RR F
2 mice. Suggestive body weight QTL that had been identified in B6 × RR F
2 mice on chromosome 4 (LOD score 3.8) was not identified in B6.KK-
Apoa2b N(8) × RR F
2 mice. Thus, contrary to expectation, the genetic control of body weight was also altered significantly by controlling of the effects of the
Apoa2 allele. The QTL mapping strategy by controlling of the effects of a major QTL facilitated the identification of additional QTLs.
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