SPRAGUE DAWLEY® Hairless Rat

R. W. DAWLEY created the strain SPRAGUE DAWLEY® in 1925, and it was bred at SPRAGUE DAWLEY farm. The hairless mutation appeared in a SPRAGUE DAWLEY® colony in 2004; Bazzi et al. studied the development of the hair follicle in individuals that displayed the hairless phenotype. “Hairless” rats have hair shafts shaped like a lance head (“lanceolate”). This characteristic which presents similarities with other rodents’ hair, led Bazzi et al. to study the gene responsible for this phenotype. During their research, they identified the desmoglein-4 gene (Dsg-4) in chromosome 18.
The nature of the mutation has been shown to be a deletion of 9 exons. The desmogleins (Dsgs), cadherin-type cell adhesion proteins, are involved in the cell’s adhesion process and in the mechanisms of epithelial cell stability and integrity. The mutation may disturb the extracellular interactions of the protein by a defect of fixation of calcium on its calcic reception sites.

There is no observable abnormality in the first stages of hair follicle morphogenesis. There are however, severe impairments of next steps of internal epithelial sheath and of the formation of the hair shaft. These are due to a bad proliferation of the hair matrix and to an abnormal differentiation in the pre-cortex region. This leads to a decrease in size of hair bulbs and to the formation of dysmorphic hair shafts.

Animals with the hairless phenotype show abnormalities in hair and vibrissae growth, and a thickened epidermis, while having a functional immune system (they are immunocompetent). This phenotype appears at the age of 4 weeks and becomes permanent at about 8 – 9 weeks.
Homozygous females have a deficient lactation that prevents them from nursing their young.

Main application and research fields