Introduction of Rhino (hr) into Jackson Laboratory Production Colonies
JAX® NOTES Issue 435, October 1988
Increase Availability
Rhino is a recessive allele of the hairless gene, located on Chromosome 14. It is maintained as an inbred strain (RHJ/LeJ) with forced heterozygosity. Rhino mutants could previously be obtained from a small resource colony at The Jackson Laboratory. Their introduction into the production facility means that these mutants will be more readily available to the scientific community. Rhino homozygotes are phenotypically similar to hairless homozygotes, but no hair regeneration occurs in rhino mutants. The name rhino was derived from the extremely thickened and wrinkled skin of this mutant. Rhino displays extensive hyperkeratosis and subepidermal cysts. Rhino skin contains an unusual triester wax.
Origin of RHJ/LeJ
The origin of the RHJ/LeJ inbred strain is as follows: The mutation to rhino (hrrh) occurred in a Carworth Farms stock of undetermined genetic background. It was sent to The Jackson Laboratory in 1951 and maintained by M. Dickie. In 1960 P.W. Lane (Jackson Laboratory) began maintaining the hrrh mutation. It was crossed to BALB/cHu six times and then once to the Hk/+ stock which was then at F13. Thereafter, the RHJ/Le strain was brother x sister mated. It is now at generation F89. [Note Hk originated from Holman's piebald shaker stock received in 1951; then was crossed to Rex once, to C57BL/6J three times, to AKR/J once, to A/Sn once, and then brother x sister mated].
Breeding
Although hr and hrrh are alleles, there is not much relationship between The Jackson Laboratory inbred strains that carry these alleles. Hairless (hr) is maintained in HRS/J, an inbred strain developed from mice of an unknown background that were mated to BALB/cGn once and then brother x sister mated (current generation F83). Rhino (hrrh) is maintained in RHJ/LeJ, whose origin is described above.
Because each of these alleles is maintained in a unique inbred strain, the best controls for the hairless or rhino mutants are the heterozygous haired sibs of the same inbred strain. Both RHJ/LeJ and HRS/J are bred brother x sister with a heterozygous (haired) female crossed to her homozygous (rhino/hairless) brother at each generation.
In RHJ/LeJ: female +/hrrh x hrrh/hrrh male
In HRS/J: female +/hr x hr/hr male
Results
This mating scheme produces 50% mutant homozygotes (rhino or hairless) and 50% normal heterozygotes (haired). These strains are maintained in this manner because, although mutant females (rhino and hairless) are fertile, they do not raise their young. They may have rudimentary mammary glands, but this has not been thoroughly studied.
