A New Recessive Hair Mutation on Chromosome 9
Authors: Louise Dionne, Richard Samples, and Kenneth R. Johnson
Source of Support: This research was supported by NIH/NCRR grant RR01183 to the Mouse Mutant Resource (M.T.Davisson, PI) and Cancer Center Core Grant CA34196.
Mutation (allele) symbol: thnh
Mutation (allele) name: thin hair
Gene symbol: thnh
Strain of origin: NOD/ShiLtJ
Current strain name: NOD.Cg-H2<b> thnh/J
Stock #:006935 (view JAX® Mice Data Sheet for additional information including Price and Supply Information)
Phenotype categories: hair and skin
Origin and description
A new mutation that causes mice to have a sparse coat has been discovered in a production colony of NOD/ShiLtJ Stock#001976 mice at the Jackson Laboratory, and has been mapped to Chromosome 9.
At two weeks of age, mice homozygous for this recessive mutation are recognized by sparse hair growth (see photo). The colony is maintained by mating homozygous mutant mice to +/+ mice of strain NOD.B10Sn-H2<b> Stock# 002591, a diabetes-resistant strain, and then intercrossing the heterozygous progeny.
Genetic Analysis
Using our standard mapping protocol NOD.Cg-H2<b> thnh/J homozygous mutant mice were mated to CAST/EiJ mice. The F1 progeny from these matings were then intercrossed and 21 affected F2's were used for linkage analysis. This mutation was mapped distal to D9Mit111 (86.4 Mb) and proximal to D9Mit36 (100.3Mb). A search of MGI did not indicate any obvious gene candidates in this region, and no mutations with similar phenotype have been mapped to this region.
Pathology
A pathological screen of one homozygous mouse was performed at 4 weeks of age. The results indicate follicles in the skin are somewhat dilated, and the deepest portions of anagen hair follicles in the subcutaneous adipose layer are degenerating. Pieces of hair from broken down follicles are free in the connective tissue and appear to induce a severe foreign body granulomatous inflammation within giant cells. (See photo)
A pelt pad and hair sample were taken from a homozygous mouse at 3 weeks of age. The results showed crowded follicles and inflamation of the skin. Analysis of the hair, from a mutant and a control revealed all 4 hair types, but fewer zigzags are present in the mutant than in the control.
The eyes of three homozygous mutants at 5 weeks of age were examined by opthalamoscopy and electroretinogram tests (ERG), which revealed no gross abnormalities.
Acknowledgements
The authors wish to thank Vicki Hutchinson for discovering the mouse, Bo Chang for the eye examination, and Coleen Kane for her technical assistance.
