The gene hairless (Hr) encodes a protein with a zinc finger domain, LXXLL protein interaction motif, and a jumonji domain. Lui et al. (PMID:34493660) determined that HR regulates H3K9 demethylation and in so doing is essential in maintaining heterochromatin structure in muscle stem cells. They found that Hr is expressed in quiescent muscle stem cells, downregulated when muscle stem cells exit quiescence, and that muscle-specific loss of Hr leads to decreased H3K9 trimethylation. Hr has also been classified as a tumor suppressor, found to interact with the tumor suppressor CELF2, and found mutated in a significant subset of breast cancers as well as cancer of the prostate, lung, uterus, and melanoma and glioma. Given their susceptibility to carcinogen- or UV-induced skin cancer, Hr mutants are often used for research into skin cancer. Although rhino homozygotes do grow a normal first coat of hair, this is lost at the first hair cycle beginning around 12 days of age and completing around 14 days of age. The hair does not grow back, which is unlike the cycles of sparse hair that grow back in hairless (Hrhr) homozygotes. Around 14 days of age there is significant epidermal hyperplasia, thickened stratum corneum, and follicular dysplasia with extensive hyperkeratosis, which later develops into cystic follicles and subsequent sebaceous cysts. The hairless skin of rhino homozygotes becomes thickened and severely wrinkled, with reports of overgrown skin folds so severe that they interfere with walking and vision. The toenails overgrow, longer than those of hairless (Hrhr) homozygotes, becoming evident by 5 weeks of age and continuing to grow potentially to 1 cM by 8 months of age. As they continue to overgrow the initial description of the rhino mutation describes the two outer nails of the hindfeet curving into spirals and the central nails and nails of the front feet curving mostly ventrally. Left untreated, this impediment of the overgrown, curved toenails has been reported to force the homozygote to walk on the backs of the feet. 
 HR is important in white adipogenesis through a pathway involving PPARG and rhino homozygotes on an FVB background were found to have diminished subcutaneous white adipose tissue, but normal brown adipose tissue. Beyond the skin, the retinas were found to have thinner than normal areas of the inner plexiform and ganglion cell layers, and cochlear degeneration occurs, with the cochlear ganglion significantly reduced in both size and cell density and severe loss of inner and outer hair cells with the surviving hair cells lacking stereocilia, but the supporting cells appearing normal. The Meibomian glands show follicular hyperkeratosis with clogged ducts and acinar cell atrophy by 3 months of age and after a year they can degrade into large cysts in the dermis. The colon was found to have epithelial hyperproliferation, increased villi and increased diameter of the muscularis mucosae, while the villi of the ileum were found to be shorter and more fragile than those of controls. (Fraser, 1946; Jester et al., 1988; Cachon-Gonzalez et al., 1999; Kumpf et al., 2012). Thymic atrophy, decreased T cell responses and increased anti-nuclear antibodies were also reported in past literature for rhino homozygotes on a BALB/c background.

This strain is currently unavailable due to replenishing of cryopreserved stocks.&nbsp; Interested customers can register interest.Mice homozygous for the rhino mutation in the Hr nuclear receptor have a dermatological phenotype consistent with papular atrichia, and additional defects in the eye, inner ear, intestines, immune system, along with a paucity of white adipose tissue and other defects have also been reported. The rhino allele (Hrrh) is more severe than the hairless allele (Hrhr).

Not available for ordering yet; register interest to be informed of changes in availability or <a target="_blank" href="https://www.jax.org/jax-mice-and-services/customer-support/technical-support/contact-technical-support-form">Contact Technical Support</a> for more information.