Abstract
We characterised wool traits, and skin gene expression profiles of fine wool Super Merino (SM) and coarse wool Small Tail Han (STH) sheep. SM sheep had a significantly higher total density of wool follicles, heavier fleeces, finer fibre diameter, and increased crimp frequency, staple length and wool grease (lanolin) production. We found 435 genes were expressed at significantly different levels in the skin of the two breeds (127 genes more highly in SM and 308 genes more highly in STH sheep). Classification of the genes more highly expressed in SM sheep revealed numerous lipid metabolic genes as well as genes encoding keratins, keratin-associated proteins, and wool follicle stem cell markers. In contrast, mammalian epidermal development complex genes and other genes associated with skin cornification and muscle function were more highly expressed in STH sheep. Genes identified in this study may be further evaluated for inclusion in breeding programs, or as targets for therapeutic or genetic interventions, aimed at altering wool quality or yield. Expression of the lipid metabolic genes in the skin of sheep may be used as a novel trait with the potential to alter the content or properties of lanolin or the fleece.
Highlights
Sheep (Ovis aries) are renowned for their ability to produce the natural fibre wool which is an important agricultural commodity used in clothing and textiles
In comparison to Small Tail Han (STH) sheep, we found that the wool of Super Merino (SM) sheep was of higher quality, having finer diameter, increased crimp frequency and staple length, as well as being produced from fleeces of increased weight and skin with a greater density of wool follicles
The wool follicles from the two breeds had similar morphological characteristics indicative of the anagen phase, with the follicle passageway extending from the dermal papilla to the skin, and the dermal papilla and inner root sheath visible and active (Fig. 1)
Summary
Sheep (Ovis aries) are renowned for their ability to produce the natural fibre wool which is an important agricultural commodity used in clothing and textiles. The wool follicle is a regenerating mini-organ comprised of the dermal papilla, sebaceous gland, sweat gland and arrector pili muscle[9] that undergoes a variable cycle of growth (anagen), apoptosis-mediated regression (catagen) and relative quiescence (telogen)[10]. In sheep, this cycle lasts up to two years but this varies greatly between breeds of sheep, and is affected by hormones[11]. Transcript profiling revealed that genes associated with skin development, lipid/fatty acid metabolism, hair follicle stem cells, such as FOXI3, CD200, CD24, and fibre shaft structural genes, including KRTAP1-1 and KRTAP6-1, were expressed at higher levels in SM sheep. Mammalian epidermal development complex (EDC) family genes and other genes associated with skin cornification and muscle function were more highly expressed in STH sheep, consistent with the thickened epidermis and significantly larger primary follicles and increased density of primary follicles, with associated arrector pili muscles, observed in the skin of STH sheep
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