P14 THE LANC RAT: A CYCLING ALOPECIC MUTANT WHOSE PHENOTYPE RESEMBLES THE LANCEOLATE MOUSE

¹Crossley N., ²Robinson M., ²Reynolds, A.J., ³Porter R.M., ⁴Demarchez M., ²Jahoda C. ¹Department of Clinical Sciences, University of Leeds, UK, ²Department of Biological Sciences, University of Durham, UK:, ³Department of Anatomy and Physiology, University of Dundee, UK, ⁴Research Department, Galderma R & D, Sophia Antipolis, France.

We describe a spontaneous rat mutant which loses hair progressively over successive hair cycles, with a phenotype similar to the lanceolate hair mutation in mice. This line was derived from a single individual originally observed in a BDIX breeding colony. Affected animals grow a first coat of hair. Patchy alopecia is first observed in the head/shoulder region around 17 days, and spreads in a wave towards the tail. By four weeks, animals have lost their hair. Regrowth occurs four days later but fibres abnormalities. Microscopically, a substantial enlargement towards the tip of the hair shaft is observed with a much thinner distal section that is often broken off. In pigmented follicles, this distal element is unpigmented, while the enlargement appears hyperpigmented. Histology shows follicles with a number of unusual features including acute angling or twisting of shafts, root sheath hyperplasia and shaft malformations. In older animals a few follicles remain in a thickened dermis.