During a routine search for wool fibre genes, Dr Simon Bawden, Research Fellow, has found a new gene that turns out to be one for a protein that forms filaments, never before described, and which occurs exclusively in the inner root sheath cells of the follicle and not the fibre. Wool follicle cells that produce the wool fibre are truly remarkable in that they manufacture about 70 different types of proteins that end up forming the fibre structure and they do so at a rate that is faster than most other tissues. There are at least eight different kinds of proteins that make the filaments of the fibre’s fibrous backbone and convey strength and elasticity.
The wool follicle cells also produce the inner root sheath, a rather complex sheath of cells that surrounds the wool fibre as it grows in its follicle and it becomes hard, acting rather like a rolling pin compressing the surface of the fibre to give the flattened shape to the fibre cuticle (Figure 1). It is lost when the fibre leaves the follicle above the skin. Although it has been known that the sheath contains filaments, they have not, to date, been identified.
The research on this new filament gene has shown that it is turned on (Figure 2) at a vital time during the formation of the fibre in the follicle and the protein it produces contributes to the hardness of the sheath. What is particularly interesting is that this protein is markedly different from any other so far described. It clearly plays a distinctive role in the formation of wool. The results have been submitted for publication.
The last transgenes that have been inserted into a sheep and expressed in its follicles were designed to express two proteins in the follicles that should give rise to a higher content of intermediate filaments in the wool fibre cortex. Of several transgenic lambs born, one is expressing both genes and potentially it should be making more filaments. Preliminary examination of the wool of the lamb indicates that there is no ‘dumping’ of the proteins in the fibre cells so it is possible that more filaments are present. More experiments are planned including collaboration with the CRC’s Program 3 (‘Fibre formation, fibre properties and processing performance’) to complete the analysis.
At the same time progress has been made by our SARDI collaborators in the production of pregnancies from nuclear transfers. This work will continue beyond the end of the Wool CRC as will the transgenic studies. The intention is to evaluate the application of nuclear transfer instead of microinjection as the preferred route to increasing the efficiency of transgenesis.
In this issue of The Wool Press: