A two-locus model for experience-conditioned direction of paw usage in the mouse is suggested by dominant and recessive constitutive paw usage behaviours.
Left-right direction of paw usage in the mouse depends on the genotype and the directional nature of the test. There are two phenotypic classes; in some strains, direction of paw usage is learned or conditioned by the direction of the initial test chamber and the experience of reaching and, in other strains, paw usage is a constitutive behaviour not affected by previous experience. We report the evidence for locus heterogeneity in the cause of constitutive versus experience-conditioned paw usage from a phenotypic analysis of F1 hybrid generations from the experience-conditioned C57BL/6J, C3H/HeHa, and SWV strains and the constitutive CDS/Lay and DBA/2J strains. The F1 hybrids between strains of different phenotypic classes provide evidence of locus heterogeneity. Constitutive paw usage in CDS/Lay is phenotypically dominant to experience-conditioned behaviour in both C57BL/6J and SWV. However, constitutive paw usage in DBA/2J is phenotypically recessive to experience-conditioned behaviour in C57BL/6J and dominant to experience-conditioned behaviour in SWV. Among the experience-conditioned strains, C57BL/6J is highly lateralized but SWV is only weakly lateralized. Our data suggest a model in which C57BL/6J may have a "strong" allele that identifies a functional difference between the constitutive paw usage of CDS/Lay and DBA/2J. DBA/2J may have a loss-of-function mutation at the same locus that is recessive to the strong C57BL/6J allele. SWV may have a "weak" allele and the (SWV x D2)F1 compound heterozygote may be below a threshold for detectability of experience-conditioned behaviour, making the constitutive behaviour of DBA/2J appear to be dominant to the experience-conditioned behaviour of SWV. CDS/Lay may have a dominant allele at a second locus that suppresses experience-conditioned behaviour in all F1 hybrids.
Biddle
F G
FG
Department of Medical Genetics, The University of Calgary, AB, Canada.
Jones
D A
DA
Eales
B A
BA
D000818:Animals; D003213:Conditioning, Psychological; D005247:Feeding Behavior; D005260:Female; D007839:Functional Laterality / Q000235:genetics*; D005799:Genes, Dominant; D005808:Genes, Recessive; D018740:Genetic Heterogeneity; D006824:Hybridization, Genetic; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008957:Models, Genetic