In this section:
Wool Biology and Wool Follicle Initiation
The advent of transgenesis and, more recently, cloning by somatic cell nuclear transfer, have broadened the scope of phenotypic varieties which may be sought by genetic means.
In the past, selection of sheep for improved wool traits by conventional breeding has been limited by the genome and, through each selection round, the genetic profile of the original strains is altered at an indeterminate number of loci. Where wool is comprised of between 50 to 100 different proteins representing some 14 different protein families, the possibility for changes to the expression profile of genes encoding these wool structural proteins alone is considerable. Changes to regulatory genes governing wool follicle initiation, development and structural gene expression profiles could also occur.
In contrast to this, the transgenesis and cloning methodologies allow the valuable genetic background of pre-existing strains to be preserved. Moreover, these methods can now be used to alter single or multiple loci and can add or remove genes. The advantages of this approach are clear, and there seems no limit to the genetic alterations possible.
However, in order to clearly define the experimental options for sheep transgenesis and wool fibre alteration, a better knowledge of the Molecular Biology of the wool follicle and the molecules which control initiation of wool follicle growth is required. In the preceding 15 years, much basic research centred upon the keratin and keratin associated protein (KAP) genes expressed in the sheep wool follicle, has been carried out by members of the Molecular Biology Laboratory.
Genomic and cDNA clones representative of nearly all keratin and KAP gene families expressed in the wool follicle have been isolated and the expression patterns of these genes have been mapped by RNA in situ hybridisation. Transgenesis with many of these clones has enabled functional gene promoter elements to be delineated and the wool of transgenic sheep produced by SARDI, overexpressing specific keratin and KAPs in the fibre cortex, have provided further insights into the biology of assembly of the wool fibre.
Further to this, the Molecular Biology Laboratory has recently obtained funding for two major projects within the Australian Wool Innovation/ Meat & Livestock Association (AWI/MLA) Sheep Genomics Program. Within the Wool Subprogram, these entail characterisation of the development of wool follicles in Merino skin by gene expression profiling, and use of mutant and genetically extreme sheep to elucidate pathways controlling fibre and fleece properties of commercial significance.
For further information, please contact:
Dr C Simon Bawden
Molecular Biology Group
SARDI Livestock and FarmingSystems
