Genetic analysis of the nephrogenic diabetes insipidus defect in SWV mice

Females of the SWV mouse strain had an age-dependent nephrogenic diabetes insipidus. The distribution of water intakes in the F1, F2 and backcross to each parental strain indicated that at least the polydipsia was determined by a few major dominant genes; rather than by a polygenic system. The Smirnof and chi square analyses revealed more than one major gene was involved. A hypothesis was presented that there are two dominant genes (one fully dominant and one codominant) which may be linked. The expression of these major genes was influenced multiplicatively by environmental factors and the water intakes approached a continuous distribution. The defect was sex influenced: SWV males had only a very mild urine concentrating defect but the reciprocal crosses showed no X-linkage. The kidney weight of the SWV females correlated significantly (P less than 0.05) with the polydipsia in the F1, BC SWV and F2 progeny and the use of both traits provided a qualitative measure for classification. The polydipsia and enlarged kidneys probably represent pleiotropy.