What Color Is the Skin of a Mouse?

Abstract

Laboratory mice naturally come in a large variety of colors ranging from black to white, brown to yellow, and spotted. 10,11 However, as obvious as this feature is, it refers to the color of the mouse's hair, not of its skin. Investigators are perpetually confused when they shave, clip, or chemically depilate mice to see black mice with pink skin or with patches of pink, grey, or black skin. Knowledge of basic physiological differences between mice and humans provides an obvious answer to this extremely commonly asked question. By examining the skin carefully in several inbred strains or the same inbred strain with various coat color mutations, the answer becomes obvious, as do many other peculiarities of the skin commonly overlooked by most investigators ''phenotyping'' mutant mice. One must understand normal anatomy and biology in order to correctly interpret both normal and abnormal features (phenotypes). 8 We present here an evaluation of adults from several different strains with different coat colors to illustrate these important features.Wild-type (normal, þ/þ) retired female breeders from the following inbred strains were used: BALB/cJ (JR#651, albino, white); C3H/HeJ (JR#659, agouti); C57BL/6J (JR#664, black); B6.Cg-Tyr c-J /J (JR#35, white); and DBA/1J (JR#670, dilute brown). All mice were obtained from The Jackson Laboratory (Bar Harbor, ME). Mice were euthanized by CO 2 asphyxiation, shaved with electric clippers (Oster #78005-010, Niles, IL), and photographed on a copy stand with a digital camera. 14 This work was done with our Institutional Animal Care and Use Committee's approval. Skin was removed with a scalpel and cut in a longitudinal, head-to-tail strip, laid flat on aluminum foil, fixed by immersion in Fekete's acid-alcohol-formalin solution overnight, stored in 70% ethanol, trimmed, processed routinely, embedded in paraffin, sectioned at 6 mm, and stained with hematoxylin and eosin. 9,15 Gross photographs of each of these mice illustrate various shades of pink skin with pigmented areas for the colored mice (Figs. 1-5). Next to each gross image is a scanned image of the skin section to correlate histology with the marked anatomic site. Note that hair follicles vary in size, especially in length, which corresponds to the thickness of the hypodermal fat layer. This is the normal hair cycle in the

Identification of Genes Important for Cutaneous Function Revealed by a Large Scale Reverse Genetic Screen in the Mouse

“…Regulators of this process include developmentally important proteins such as members of the bone morphogenetic protein (BMP), hedgehog (HH) and wingless-related MMTV integration site (WNT) signalling pathways, as well as a variety of cytokines, transcription factors, and adhesion molecules (reviewed in [20] ). A simple way to examine the stage of hair follicle cycle at a gross level is to assess skin color in shaved animals; as follicles in anagen darken the skin due to melanocyte activity [21] . This process is non-invasive and requires minimal expertise, making it highly suitable for application to high throughput screens.…”

Lack of Response to Laser Comb in Spontaneous and Graft-Induced Alopecia Areata in C3H/HeJ Mice

“…Rather, their sham treated mice (laser turned off) show normal mouse skin in telogen, the common, persistent stage found in adult mouse skin. The representative mouse treated with the laser on had normal hair follicles in late anagen (lacking clear evidence of inflammation in and around the follicles) ( Wikramanayake et al , 2012 ) which is found although infrequently in adult mice ( Sundberg and Silva, 2012 ). Alopecia in small foci in C3H/HeJ mice can be due to AA but also is not less commonly due to grooming behavior abnormalities (barbering, a form of trichotilomania).…”

Photosensitivity of murine skin greatly depends on the genetic background: clinically relevant dose as a new measure to replace minimal erythema dose in mouse studies

“…In contrast, rodents live an elusive lifestyle, so their pigments are mainly responsible for their hair colour and camouflage. This theory is supported by the fact that pigment in mice is produced in growing hair follicles and there is no to little pigmentation in interfollicular epidermis (19). Additionally, it has been described before that melanin, particularly pheomelanin, besides its protecting role could also serve as an effective photosensitize (41) and recent publication demonstrate its role in the formation of dark-CPDs (20).…”