Heterozygous shaven mice have a greasy coat and some waviness of the vibrissae. Homozygotes do not grow a first coat during the pre-weaning period and thereafter show cyclic growth and loss of very short sparse furry hairs. The vibrissae are short and wavy at birth and throughout life. Hairs are of normal size in heterozygotes, but the air spaces in the medulla are smaller than normal and filled with sudanophilic fluid. In homozygotes the hairs are thin and uneven in diameter, and the air spaces are very small, irregular and filled with sudanophilic fluid. Keratinization of the hairs is defective, and they fail to penetrate the epidermis.
Shaven (Sha) arose in a stock in the Endocrinology Department at Edinburgh, Scotland. It was imported to the Jackson Laboratory from Welcome Research Animal Laboratories at the University of Dublin, Ireland in 1988. Welcome Research had received it as an inbred line from Edinburgh in the mid 1970¿s. It was inbred until the early 1980¿s and was then random bred within stock. At the Jackson Laboratory it was inbred homozygote x homozygote. It was cryopreserved in 1990 by mating homozygous males at F5 or F6 to C57BL/6J females.
|Gene Symbol and Name||Tyr, tyrosinase|
|Site of Expression||Melanocytes.|
|Strain of Origin||old mutant of the mouse fancy|
|General Note||Tyrc, albino. This very old mutant was already known in Greek and Roman times. Hair and eyes are completely devoid of pigment (J:5436, J:5001, J:30725). The albino mutation affects the amount of tyrosinase, and thus of melanin, in pigment cells, but does not interfere with the production of pigment cells themselves (J:12173, J:13092). Melanocytes with melanosomes showing normal fine structure occur in the retina and hair follicles. Pigment granules are smaller and fewer than normal and completely lack melanin (J:5346, J:5001, J:30725). Tyrosinase is almost absent (J:12173).Although Tyr is the structural gene for tyrosinase, some albino mutations may affect tyrosinase enzyme regulation rather than structure (J:6611), suggesting that these mutations affect tyrosinase inhibition (J:5346), presumably via control regions of the gene. All the mutant alleles are recessive to wild-type in phenotype, but heterozygotes with wild-type produce intermediate amounts of tyrosinase (J:12173).Albino-locus mutants with lightly pigmented eyes have a reduced number of fibers of the optic nerve going to the ipsilateral lateral geniculate nucleus of the brain. This is probably a secondary effect of reduced tyrosinase activity or amount of pigment in the pigment epithelium, since genes at other loci that reduce eye pigmentation also cause the same anomaly (J:5436, J:6064).Abnormal retinal pathways disrupted at the optic chiasm that occur in albinism can be corrected with a Tyr normal transgene (J:22320).Lipofuscin is a terminal oxidation product pigment that accumulates with age. In a cross of C57BL/6J and BALB/cJ, which differ in cardiac deposition of the pigment, this trait segregated with albinism, and is controlled by the Tyr locus (J:15460).Tyrc homozygotes do not perform as well as normal in a number of behavioral tests. It is likely that this effect is mediated, at least in part, by defective vision resulting from lack of retinal pigment (J:5470, J:5360, J:5378).|
|Molecular Note||The specific mutation in the albino allele is a G-to-C transversion causing an amino acid change from cysteine to serine at position 103 or 85 (p.C103S for pre-protein, p.C85S for mature protein). This mutation introduces a DdeI enzyme restriction site.|
|Allele Name||wild-type agouti|
|Allele Synonym(s)||dark-bellied agouti|
|Gene Symbol and Name||a, nonagouti|
|Strain of Origin||various|
|General Note||The A allele is usually regarded as a wild-type allele. For example,the C3H and CBA mouse sublines are homozygous for agouti. Hairs are black with a subapical yellow band. This black-yellow-black pattern is referred to as agouti. The general appearance is yellowish brown, slightly lighter on the belly than on the back.|
|Molecular Note||This allele, often referred to as wild-type, comprises a novel 131 amino acid protein encoded in a gene comprising four exons, three coding, spanning 18kb. Unique changes in this gene account for all other alleles that have been molecularly characterized. The expression of this allele is almost always dominant to other alleles of this gene.|