Mice homozygous for the muted spontaneous mutation (Bloc1s5mu) have light eyes at birth and their fur is a muted brown shade, often with white underfur. Some have a balance defect, similar to that of pallid (Bloc1s6pa). Homozygous mutant mice show head-tilting and loss of postural reflexes, due to absence of otoliths from the sacculus and utriculus of one or both ears. The bony labyrinth is normal; the mice are not deaf and do not circle. Mutant mice have prolonged bleeding times and a platelet storage pool deficiency (SPD) associated with abnormalities of the dense granules of the blood platelets. The combination of pigment, otolith, and SPD abnormalities also occurs in two other mouse mutants, pallid and mocha (Ap3d1mh), and is also seen in human Hermansky-Pudlak syndrome.
|Allele Type||Spontaneous (Hypomorph)|
|Gene Symbol and Name||Bloc1s5, biogenesis of lysosomal organelles complex-1, subunit 5, muted|
|Strain of Origin||STOCK t|
|Molecular Note||An early transposon (Etn) insertion has been identified as the mutation underlying the phenotype in muted mice. Analysis of genomic DNA revealed an insertion into the third intron. 183 bp of Etn sequence has been incorporated into the mRNA , likely by the activation of cryptic splice sites within the Etn. This results in an in-frame insertion into the translated protein at position 106, predicting a 246 amino acid protein. A significant reduction in mRNA levels is observed.|