MAPPING QUANTITATIVE TRAIT LOCI FOR OPEN-FIELD BEHAVIOR IN MICE

By performing a whole genome screen in an F-2 intercross of two strain s of mice (A/J and C57BL/6J), which differ markedly in their behaviora l response to a brightly lit open field (O-F), we have mapped several quantitative trait loci (QTL) for this complex behavioral phenotype. Q TL on chromosomes 1 and 10 were identified that affect both initial am bulation in the O-F (initial ''response to novelty'' ambulation) (lod of 7.1 and 8.8, respectively) and vertical rearings (lod of 4.5 and 8. 5, respectively). For habituated O-F behavior, QTL were identified on chromosomes 3 and 10 for ambulation (lod of 4.1 and 14.7, respectively ) and on chromosomes 1, 10, and 19 for vertical rearings (lod of 5.8, 6.0, and 4.7, respectively). The QTL on chromosome 1 (near D1Mit116; 1 01 cM) was specific for initial O-F ambulation behavior, whereas the Q TL on chromosome 10 (near D10Mit237; 74 cM) affected both initial and habituated rearing behavior. Additional suggestive QTL (lod, >2.8) wer e mapped to chromosomes 1, 8, 11, 15, and 19. The QTL on chromosomes 1 , 10, and 19 individually explain from 3.2 to 12.7%. Collectively, the multiple independent QTL explain from 16.3 to 24.1% of the F-2 popula tion's phenotypic variance, depending on the trait. These identified Q TL should prove useful for dissecting the genetic and behavioral dimen sions of O-F behavior, fostering an understanding of individual differ ences.