Pigmentation and lysosome function in mice homozygous for both pale ear and Beige-J pigment genes

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Abstract
SUMMARY We have examined mice doubly homozygous for both pale ear (ep/ep) and beige (bg J/bg J) mutations in order to detect genetic interactions between these 2 loci affecting pigmentation and lysosome physiology. The doubly homozygous mouse has a new pigmentation phenotype consistent with independent effects ofepandbg. The beige (Brandt, Elliott & Swank, 1975) and pale ear (Novak & Swank, 1979)genes have abnormal kidney lysosomal enzyme accumulation caused by defective secretion into urine. No cumulative effect on these functions was observed in the new double mutant phenotype. The new phenotype has giant lysosomes typical of the beige mutation. Unexpectedly, the beige gene corrects the effect of the pale ear on serum lysosomal enzyme concentration. There is also a gene dosage effect of the beige gene on this serum lysosomal enzyme phenotype. The results suggest that the beige and pale ear genes affect the same pathway(s) of lysosome biosynthesis and/or processing. The action of the beige gene may precede that of the pale ear gene in lysosome physiology.