Proteomic evaluation of tissues at functionally important regions in the bovine claw

The endemic nature of lameness arising from horn disorder in dairy cows has focused attention on the biology of the bovine claw. The production of lesions causing lameness has been associated with impairments of horn production in the epidermis and connective tissue turnover in the dermis in functionally important regions of the claw.

This paper provides an overview of recent studies which investigated the application of contemporary methodology to the determination of protein expression in tissues of the epidermis and dermis. It provides data derived from a proteomics approach based on 2-dimensional gel electrophoresis of extracts of tissues obtained from different functional sites of the claw. The procedure used separates proteins according to differences in charge and molecular mass with examination of gels effected by application of analytical software.

Images of gels were obtained for extracts of cornified horn and soft (uncornified) tissue and from soft tissue explants obtained from coronary, laminar, solear and heel regions of claws of beef and dairy cattle. Commonalty and certain differences were apparent in profiles of protein spots representative of these anatomical regions particularly in the ranges typical of keratins (40-70kDa) and those of lower molecular mass (< 40kDa). Initial identification of certain protein "spots" by immunoblotting and peptide mass fingerprinting on gels indicated the presence of cytoskeletal and hard keratins, heat shock proteins and proteins involved in energy metabolism and transport of trace minerals and fatty acids. Data were also presented from an immunohistochemical examination of sections of claw tissue for certain intermediate filament and microfilament proteins. The results highlight the additional importance of defining precise cellular or extracellular location of proteins within the tissue. It is concluded that further work will be needed to characterise the individual proteins identified from the protein profiles so that (i) relationships with known differences in amino acid composition and (ii) precise roles in supporting physical function in healthy and pathological states, may be better understood. Attention is also drawn to investigative methodology based on protein identification as a valuable means of advancing research investigating the biology of the bovine claw.