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Wool fibre crimp is determined by mitotic asymmetry and position of final keratinisation and not ortho- and para-cortical cell segmentation

Published online by Cambridge University Press:  01 June 2009

P. I. Hynd ,
N. M. Edwards ,
M. Hebart ,
M. McDowall  and
S. Clark
P. I. Hynd*
Affiliation:
Discipline of Agricultural and Animal Science, Faculty of Sciences, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia
N. M. Edwards
Affiliation:
Discipline of Agricultural and Animal Science, Faculty of Sciences, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia
M. Hebart
Affiliation:
Discipline of Agricultural and Animal Science, Faculty of Sciences, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia
M. McDowall
Affiliation:
Discipline of Agricultural and Animal Science, Faculty of Sciences, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia
S. Clark
Affiliation:
Discipline of Agricultural and Animal Science, Faculty of Sciences, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia
*
E-mail: philip.hynd@adelaide.edu.au
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Abstract

Crimp, a distinguishing feature of sheep fibres, significantly affects wool value, processing and final fabric attributes. Several explanations for fibre bending have been proposed. Most concentrate on relative differences in the physicochemical properties of the cortical cells, which comprise the bulk of the fibre. However, the associations between cortical properties and fibre crimp are not consistent and may not reflect the underlying causation of fibre curvature (FC). We have formulated a mechanistic model in which fibre shape is dictated primarily by the degree of asymmetry in cell supply from the follicle bulb, and the point at which keratinisation is completed within the follicle. If this hypothesis is correct, one would anticipate that most variations in fibre crimp would be accounted for by quantitative differences in both the degree of mitotic asymmetry in follicle bulbs and the distance from the bulb to the point at which keratinisation is completed. To test this hypothesis, we took skin biopsies from Merino sheep from sites producing wool differing widely in fibre crimp frequency and FC. Mitotic asymmetry in follicle bulbs was measured using a DNA-labelling technique and the site of final keratinisation was defined by picric acid staining of the fibre. The proportion of para- to ortho-cortical cell area was determined in the cross-sections of fibres within biopsy samples. Mitotic asymmetry in the follicle bulb accounted for 0.64 (P < 0.0001) of the total variance in objectively measured FC, while the point of final keratinisation of the fibre accounted for an additional 0.05 (P < 0.05) of the variance. There was no association between ortho- to para-cortical cell ratio and FC. FC was positively associated with a subjective follicle curvature score (P < 0.01). We conclude that fibre crimp is caused predominantly by asymmetric cell division in follicles that are highly curved. Differential pressures exerted by the subsequent asymmetric cell supply and cell hardening in the lower follicle cause fibre bending. The extent of bending is then modulated by the point at which keratinisation is completed; later hardening means the fibre remains pliable for longer, thereby reducing the pressure differential and reducing fibre bending. This means that even highly asymmetric follicles may produce a straight fibre if keratinisation is sufficiently delayed, as is the case in deficiencies of zinc and copper, or when keratinisation is perturbed by transgenesis. The model presented here can account for the many variations in fibre shape found in mammals.

Keywords

crimpcurlfolliclehairwool
Type
Full Paper
Information
animal , Volume 3 , Issue 6 , June 2009 , pp. 838 - 843
Copyright
Copyright © The Animal Consortium 2009

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References

Auber, L 1950. The anatomy of follicles producing wool fibres, with special reference to keratinization. Transactions of the Royal Society of Edinburgh 62, 191–254.Google Scholar
Bawden, CS, Powell, BC, Walker, SK, Rogers, GE 1998. Expression of a wool intermediate filament keratin transgene in sheep fibre alters structure. Transgenic Research 7, 273–287.Google Scholar
Caldwell, JP, Mastronade, DN, Woods, J, Bryson, WG 2005. The three dimensional arrangement of intermediate filaments in Romney wool cortical cells. Journal of Structural Biology 151, 298–305.Google Scholar
Campbell, M, Whiteley, KJ, Gillespie, JM 1972. Compositional studies of high- and low-crimp wools. Australian Journal of Biological Science 25, 977–987.Google Scholar
Clarke, WH, Maddocks, IG 1965. Wool fibres: sectioning and staining, differentiation of ortho and paracortex. Stain Technology 40, 339–342.Google Scholar
Fraser, RDB, Rogers, GE 1954. The origin of segmentation in wool cortex. Biochemical and Biophysical Research Communications 13, 297–298.CrossRefGoogle ScholarPubMed
Horio, M, Kondo, T 1953. Crimping of wool fibres. Textile Research Journal 23, 373–386.CrossRefGoogle Scholar
Hynd, PI, Everett, BK 1990. Estimation of cell birth rate in the wool follicle bulb using colchicine metaphase arrest or DNA labelling with bromodeoxyuridine. Australian Journal of Agricultural Research 41, 741–749.Google Scholar
Kajiura, Y, Watanabe, S, Itou, T, Nakamura, K, Iida, A, Inoue, K, Yagi, N, Shinohara, Y, Amemiya, Y 2006. Structural analysis of human hair single fibres by scanning microbeam SAXS. Journal of Structural Biology 155, 438–444.Google Scholar
Marston, H, Lee, HJ 1948. Nutritional factors involved in wool production by Merino sheep II. The influence of copper deficiency on the rate of wool growth and on the nature of the fleece. Australian Journal of Scientific Research Series B 1, 376–387.Google Scholar
Nagorcka, BN 1981. Theoretical basis for crimp. Australian Journal of biological science 34, 189–209.Google Scholar
Nay, T, Johnson, H 1967. Follicle curvature and crimp size in some selected Australian Merino groups. Australian Journal of Agricultural Research 18, 833–840.Google Scholar
Philpott, MP, Sanders, DA, Kealey, T 1994. Effects of insulin and insulin-like growth factors on cultured human hair follicles: IGF-I at physiologic concentrations is an important regulator of hair follicle growth in vitro. Journal of Investigative Dermatology 102, 857–861.Google Scholar
Plowman, JE, Bryson, WG, Jordan, TW 2000. Application of proteomics for determining protein markers for wool quality traits. Electrophoresis 21, 1899–1906.Google Scholar
Schlake, T 2005. Segmental IGFbp5 expression is specifically associated with the bent structure of zigzag hairs. Mechanisms of Development 122, 988–997.CrossRefGoogle ScholarPubMed
Short, BF 1958. A dominant felting lustre mutant fleece-type in the Australian Merino sheep. Nature 181, 1414–1415.Google Scholar
Smith, J 2002. Crimp frequency in fine wool Merino sheep: a study of genetic variation and wool processing performance. PhD, University of New England Armidale New South Wales, Australia.Google Scholar
Thibaut, S, Gaillard, O, Bouhanna, P, Cannell, DW, Bernard, BA 2005. Human hair shape is programmed from the bulb. British Journal of Dermatology 152, 632–638.Google Scholar
White, CL, Martin, GB, Hynd, PI, Chapman, RE 1994. The effect of zinc deficiency on wool growth and skin and wool follicle histology of male Merino lambs. British Journal of Nutrition 71, 425–435.CrossRefGoogle ScholarPubMed