Genetic basis of voluntary water consumption in two divergently selected strains of inbred mice

BACKGROUND: Inbred mouse strains with normal renal function show a substantial difference in daily water consumption across strains. This study uses two strains of inbred mice C57BR/CDJ (BR), which are high consumers, and C57BL/10J (BL), which are low consumers, their reciprocal F (1) crosses, inter se bred F (2)s and backcrosses produced by breeding high consuming F (2) animals to the low consumer parent strain and low consuming F (2) animals to the high consuming parent strain. Consumption was corrected for body weight prior to analysis. METHODS: The effective number of genes controlling water consumption was estimated using the Castle–Wright estimator. Additive and dominance genotypic values as well as the degree of dominance were calculated using estimated strain means. RESULTS: According to Castle–Wright, a minimum of 10 factors were estimated to affect the difference in consumption across the two strains. Between seven and eight are expected to be high effect factors. Using the Zeng adjustment, it was determined that 30–40 factors potentially affect the difference in consumption. CONCLUSIONS: These numbers were surprising but may be related to several sources of variation present in the BR strain. A negative degree of dominance indicated the BL strain has more dominant factors.