Strain Detail: HR mice

This HR strain was established by the introduction of hairless allele (hr) to BALB/c from hairless mice derived from USA at IMSUT. Then the mice were introduced into National Institute of Health/National Institute of Infectious Diseases in 1981.

HR mice are normal until the first hair cycle started in the embryonic stage, but they don't have the second hair cycle normally started in 2-3 weeks old. Therefore, it's characteristic that they have their hairs until 2-3 weeks, but later they will lose their hairs from the back of their heads to tails.

Genetic analysis in our bank revealed that the HR mice share the same hairless mutation as HRS/J, Skh:HR-1 and Hos:HR-1. Based on the analysis, we estalisheda genotyping PCR for hairless alleles(Ref. 4).

Generally, the homozygous females can't take care of her pups because of mammary gland anomaly. Therefore, this strain should be maintained by mating between homozygous (hairless) males and heterozygous (normal hair) females. These mice are useful for studies related skins because skin tumors are induced easily by chemical mutagens.

About hair cycle

The hair cycle goes through three stages called anagen, catagen and telogen (1). Hair matrix cells divide and make hairs in the stage of anagen. In the catagen stage, hair matrix cells disappear by apoptosis. This apoptosis event is related with TGF-β1 (2). Through the process of telogen after a period of fixed time, hair matrix cells divide again and make new hairs in the next stage of anagen after old hairs fall out.

1. Alonso L, and Fuchs E. (2006) The hair cycle. J. Cell. Sci. 119(Pt 3):391-3. Review [PMID:16443746]
2. Foitzik K, Lindner G, Mueller-Roever S, Maurer M, Botchkareva N, Botchkarev V, Handjiski B, Metz M, Hibino T, Soma T, Dotto GP, and Paus R. (2000) Control of murine hair follicle regression (catagen) by TGF-β1 in vivo. FASEB J. 14(5):752-60. [PMID:10744631]
3. Fukui M, Ito K, Kawamura S, Sudo K, and Suzuki K. (1975) Glomerular changes in hairless mice: a light, immunofluorescent and electron microscopic study. Jpn. J. Exp. Med. 45(6):535-40. [PMID:1232469]
4. Suzuki O, Koura M, Noguchi Y, Uchio-Yamada K, and Matsuda J. (2013) Zygosity determination in hairless mice by PCR based on Hr^hr gene analysis. Exp. Anim. 62(3):267-73. [PMID:23903062]