While mice carrying the Hk mutation often have a hooked curl at the end of a shortened tail, this mutation may more consistently result in a displaced anus that is positioned posterior to the normal site and is more slit-shaped than circular. In some instances the anus has been located in the beginning of the tail and a depression was found to extend partway down the ventral side of the tail (Holman, 1951). The Hk mutation is semidominant with homozygotes often showing a shorter, more affected tail than heterozygotes (P.W. Lane Personal Communication).
The Hk mutation arose spontaneously. It was identified in 1949 in a piebald shaker stock and was sent from SP Holman to GD Snell in 1951. This was subsequently crossed once to a rex (Re) stock, crossed three times to C57BL/6, crossed once to AKR, crossed twice to A/Sn, and then crossed once to C57BL/6J before PW Lane inbred the line by sibling mating. This resulted in an inbred background homozygous for Tyrc and a and segregating for Hk. In 1978 embryos were generated for cryopreservation by breeding Hk/+ females with Hk/Hk males when the strain was at F59.
|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.|
When using the hook mouse strain in a publication, please cite the originating article(s) and include JAX stock #000006 in your Materials and Methods section.