The autosomal recessive mutation sandy (sdy) takes its name from the lightened coat color first identified on the DBA/2J background. As early as 7-8 days of age the pinnae, feet, tail and fur are lighter in color than those of wildtype littermates and the lack of eye pigment is a defining trait at birth. The eye color does not darken with age unlike muted (mu) homozygotes. On the agouti C3H background, sandy homozygotes look like muted homozygotes, but on the non-agouti C57BL/6J or DBA/2J backgrounds, sandy homozygotes look like pallid (Bloc1s6pa) homozygotes. The reduced pigmentation is linked to a storage pool deficiency. Sandy homozygotes have a prolonged bleeding time, in excess of 15 minutes, yet have normal platelet counts and normal sized platelets. Electron microscopy detects very few, if any, dense granules present in individual platelets of sandy homozygotes. Those that are detected are of normal size. Platelet serotonin levels are 7% that of normal mice and aggregation assays show that induced platelet aggregation is reduced at low collagen levels but normal at high collagen levels relative to heterozygous controls although Dtnbp1sdy/Dtnbp1sdy platelets fail to secrete ATP at either concentration. Abnormal secretion of serotonin from dense granules is found such that constitutive secretion is high relative to that of wild type platelets and thrombin stimulation does not further increase this secretion from Dtnbp1sdy/Dtnbp1sdy platelets to anywhere near normal induced levels. Thrombin stimulated release of beta-galactosidase and beta-glucuronidase from platelet granules is also greatly reduced in sandy homozygotes. Kidney lysosomal secretion of beta-galactosidase and beta-glucuronidase into urine is 50% that of wildtype but the concentration of these enzymes in kidneys is twice normal. Fewer intact lysosomes are found in extracts from sandy homozygotes than wild type controls. Ceroid-like pigments characteristic of Hermansky-Pudlack syndrome are found in the kidney proximal tubules of sandy homozygotes, but griant granules in retinal pigment epithelial cells, characteristic of Chediak-Higashi syndrome, were not. Sandy is one of the most severe mouse models of storage pool deficiency. (Sweet, 1990; Swank et al., 1991.)
The Dtnbp1sdy mutation arose spontaneously in 1983 in the DBA/2J colony at The Jackson Laboratory which was then at F143. It was maintained by sibling breeding, primarily heterozyote x homozygote and vice versa. It was frozen after 1990 by breeding homozygous males with DBA/2J females to generate heterozygous embryos that are generation F32N1. The GpnmbR150X mutation arose in DBA/2J subsequent to the separation of this mutant subline.
|Allele Synonym(s)||Bloc1s8sdy; Dys KO; Dys-; sdy; sdy-|
|Gene Symbol and Name||Dtnbp1, dystrobrevin binding protein 1|
|Strain of Origin||DBA/2J|
|Molecular Note||The mutation in the sandy mouse has been attributed to a deletion in the Dtnbp1 gene from intron 5 nucleotide 3701 to intron 7 nucleotide 12377. The deletion results in the loss of 52 amino acids from position 119-172 and abolishes expression of the protein. Western analysis did not detect protein in hippocampus tissue from homozygous mutant mice.|
When using the sandy mouse strain in a publication, please cite the originating article(s) and include JAX stock #001594 in your Materials and Methods section.