Cross-linked features of mouse pelage hair resistant to detergent extraction

Cross-linking defects in hair cuticle have been observed in certain rare hu man disorders (trichothiodystrophy, transglutaminase-deficient lamellar ich thyosis). The hypothesis being investigated is that defective cross-linking in the cuticle or other parts of the fiber is a feature of some mouse muta nts in which the hair is sparse or appears structurally unsound. Pelage hai r samples from 13 mouse mutants displaying defective hair were extracted wi th sodium dodecyl sulfate and dithiothreitol at neutral pH and examined by transmission electron microscopy. All samples were indistinguishable after extraction from normal hair fibers in appearance of the medulla and cortex. In the cortex, keratins were completely extractable, but material remainin g at the cell boundaries was clearly evident. Cells of the medulla were lar gely unextracted, containing distinct nuclei and amorphous material in the cytoplasm. In two samples (from mice with the matted/flaky tail and naked m utations) cells of the cuticle, which readily detached from the fiber when incubated at 100 degrees C, were more extensively extracted than normal. De fective cross-linking is thus observable in a minority of mouse hair mutant s. The observed perturbation of cross-linking in the cuticle was not accomp anied by visible perturbation in the cortex or medulla, indicating that dif ferent proteins participate in cross-linking in the different cell types. A nat Rec 254:231-237, 1999. (C) 1999 Wiley-Liss, Inc.