Mice homozygous for the recessive buff (Vps33abf) mutation on a non-agouti (a/a) background have a lightened coat color that has been described as khaki. On an agouti background, Vps33bf homozygotes have dark ears, opaque eyes, and the belly is lighter in color than is the rest of the coat. Although no change in eye color is outwardly evident, electron microscopy shows fewer and smaller melanosomes than normal in the retinal pigment epithelium and choroid. These mutants have a platelet-storage pool defect evidenced by an increased bleeding time of 9.7 minutes on average, a reduction in the number of platelet dense granules, and slightly decreased collagen-mediated platelet aggregation, secretion of dense-granule ATP and secretion of seratonin. Hakansson and Lundin found increased activity of the lysosomal glycosidases beta- galactosidase, beta-glucuronidase, and N-acetyl-beta-hexosaminidase in kidney cell lysates. Suzuki et al. found no significant difference in kidney beta- galactosidase and beta-glucuronidase activity, no significant decrease in beta-glucuronidase secretion into the urine, but a 53% reduction in the secretion of beta-galactosidase into the urine. (Dickie, 1964; Davisson, 1977; Hakansson and Lundin, 1977; Suzuki et al., 2003.)
The recessive buff (Vps33abf) mutation arose spontaneously in 1962 on the C57BL/6J background at The Jackson Laboratory. It was maintained primarily by sibling breeding heterozygote x homozygote and in later years the strain was also intermittently backcrossed homozygote to C57BL/6J. In 1975 this strain was at generation N7F24 then N8, in 1977 it reached generation N9F3, in 1979 N9F7 then N10, and in 1981 heterozygous embryos were frozen from C57BL/6J females bred to homozygous males at N10F4 or N10F5.
|Gene Symbol and Name||Vps33a, VPS33A CORVET/HOPS core subunit|
|Strain of Origin||C57BL/6J|
|Molecular Note||This allele comprises a T-to-G transversion that causes a missense substitution of aspartic acid to glutamic acid at codon 251 (p.D251E).|