015 Genetic and pathological analysis on a novel mouse hair mutation, Hague

Atsushi Yoshiki1, Christophe Poirier1, Kyoko Fujiwara1, Chikako Yoshida-Noro1, Yasuaki Ichikawa2, Jean-Louis Guenet3, Moriaki Kusakabe4 Experimental Animal Research Division, RIKEN Tsukuba Institute1, Dept. 1 st Anatomy, Nihon Medical University2, Unite de Genetique des Mammiferes, Institut Pasteur3, Dept Anatomy, The Jikei University School of Medicine4

Mouse hair mutations are useful model to study molecular mechanism of hair development. A spontaneous mouse hair mutation was recovered in our C3H/HeN mice colony. The purpose of this study is to clarify pathological characteristics of the developing hair follicle and to finely map the causative gene. For light microscopy dorsal skin tissues were fixed with 4% paraformaldehyde and embedded in polyester or Technovit resin. For transmission electron microscopy tissues were fixed with Ito-Karnovsky fixative. A high-resolution linkage map was constructed by crossing the mutant mice with wild-derived strains, M. m. castaneus and PWK. The original mutation was recovered as wavy-hair mouse. Cross experiment indicated that the mode of transmission of the mutation was semi-dominant with incomplete penetrance at the heterozygous state. In homozygote mice lost most hairs around 1 month of age. Linkage analysis indicated that this trait was controlled by a single locus Hague (Hag) which was mapped to telomeric region of mouse Chromosome 15. This mutation was shown to be unstable since its transmission could be switched from semi-dominant to recessive. Moreover, Hag can interact with Caracul mutation, another dominant hair mutation on Chr 15. Interestingly, double heterozygotes of Hag and Ca showed patch pattern of hairy and bald regions. Histopathological analyses of homozygotes by light and transmission electron microscopy clearly demonstrated that the significant cell degeneration was detected especially in the Henele’s and Huxley’s layers of inner root sheath. To identify the causative gene and the nature of the mutation, Hague was introduced into a high resolution and high density molecular genetic map. Over 1000 meiosis were analyzed and the mutation was mapped to the keratin 2 complex genes. A YAC and BAC physical map of the critical region was then constructed and the gene involved was located in a 600-800 kb long segment. From this region several candidate genes including 3 epidermic cytokeratin and four hard keratin genes were analyzed but none were mutated in the Hague mice. In conclusion the Hague mutation occurred within keratin 2 complex region will be a unique model to study the molecular mechanism of hair follicle development.