Hydronephrosis in the mouse: the effects of the short-ear gene, sex and ureteral vascular system.

The short-ear gene in the mouse, se, affects a number of soft tissues; skeletal effects result in reduced body cavities. A high incidence of hydronephrosis in short-ear genotypes has been ascribed to pressure on the lower ureter resulting from crowding of organs in the body cavity. This study concerns the ureteral vascular system as observed in 861 autopsies of mice of varying age, of the three short-ear genotypes, drawn from ten stocks. Incidence and expression of hydronephrosis is greater in short-ear males than in females, and the ratio between the two varies from one stock to another. This study seeks an explanation. Short-ear genotypes have an abnormally high incidence of unusual ureteral veins, hydronephrosis being strongly associated with the more posterior ones. Ureteraonadal and iliac veins. The spermatic vein's more posterior position, compared with the ovarian, is strongly correlated with the sex difference in posterior ureteral venation and thus with the sex difference in incidence of hydronephrosis. Stocks are compared according to the amount of selection for fitness of short-ear genotypes; there is a reduced incidence of hydronephrosis with selection, accompanied by fewer posterior ureteral veins. Age also affects hydronephrosis; its expression increases slightly with age, and the male sese progeny of young mothers appear to be particularly prone to hydronephrosis. Three skeletal mutants segregate; of these fidget, fi, causes a type of hydronephrosis differing somewhat from that caused by se.