ABSTRACT
The matted mutation was discovered in 1952 in a colony of CBA/Gr mice at the University College of London. Some mice in this colony developed bald patches on their backs. Mice homozygous for the matted mutation (ma/ma) have hairs that stand up and stick together to form matted clumps rather than lying flat against the body as does normal mouse hair. The matted appearance of the hair can be more easily seen when the fur is stroked in the wrong direction. There is also a tendency for hair of affected black mice to turn brown with age. Mice with an agouti coat color have hairs that appear darker, since the proximal portion of the hair is darker than the tip. Bald patches develop at friction points because of breakage of the hair shaft. Hair follicle density is equivalent to normal, even in areas of alopecia. By scanning electron microscopy, all hairs examined had a variety of prominent abnormalities.
