058 Effect of Increased Expression of High Glycine/Tyrosine Proteins Targeted to the Fibre Cortex in the Follicles of Transgenic Sheep

L. N. Jones1, G. E. Rogers2, S. M. Bawden2, M. G. Huson1 and P. S. Turner1. CSIRO, Textile & Fibre Technology, Belmont, Vic, Australia1 and SARDI, Adelaide, SA, Australia2.

The aim of the research is to determine the relationship of structure and physical properties of hair keratin using the sheep model. A selected keratin gene is constructed with a promoter for targeting to the follicles and transgenic sheep are produced following transfer of single cell embryos microinjected with the transgene to surrogate ewes and subsequent lambing after 5 months. The wool from transgenics that are expressing the inserted gene (or genes) is collected after sufficient growth and submitted to biochemical and structural analysis. The most efficient follicle specific promoter is K2.10 (see Powell & Rogers [1990] EMBO J. 9, 1485-1493) and is both follicle specific and fibre cortex specific. If necessary, sheep are bred to the first generation to overcome chimerism. We report here results from the overexpression of one of the high glycine/tyrosine (HGT) proteins (KAP6) that together with other HGT members and also the cystine-rich family of KAP proteins, constitute the protein matrix between the cortical intermediate filaments. Wool fibres, follicles and control specimens have been examined using techniques of gel electrophoresis, amino acid analysis, scanning and transmission electron microscopy and mechanical testing. Gel electrophoretic studies of protein composition and amino acid content have shown that the wool has significantly increased contents of HGT and markedly reduced amounts of ultrahigh sulphur proteins compared to controls. We have also observed changes in cell ultrastructure of cuticle and particularly the cortex where orthocortical cells were found to predominate. Effects on mechanical properties include a reduction in tensile modulus, intrinsic strength and strain at break. Overall, comparison of transgenic and control wool fibres have indicated changes in structure and formation which support our existing knowledge of the composition and properties of HGT together with their function and location within the fibre. The characteristics of these modified fibres indicate they possess new physical properties that might have application in the fibre industry.