Molecular cloning of equine transforming growth factor-beta1 reveals equine-specific amino acid substitutions in the mature peptide sequence

Abstract

This study cloned and sequenced equine transforming growth factor (TGF)-1, yielding a unique nucleotide structure which predicted amino acid substitutions not seen in other mammalian species. The nucleotide sequence homology was 89% to bovine, 91% to man, 90% to ovine, and 86% to rat. Derived amino acid sequence comparison showed that the equine protein was unique, differing by two residues from man, cow, sheep, pig, and dog, and by three residues in the rat. Subsequent use of the cDNA clones to examine the expression of the TGF-1 gene in various tissues indicated predominant expression in adult spleen and kidney, with an age-related peak in cartilage expression at 12 months, followed by a decline as the animals matured. Northern blots showed that the predominant transcript sizes were 2·5 and 1·9 kb. More sensitive mRNA detection using PCR reaction showed peak cartilage TGF-mRNA levels in horses 0·7 and 1 year of age, with declining expression in older animals (2·5 and 5·5 years of age).In conclusion, although the primary nucleotide sequence of equine TGF-was relatively homologous to that of other species, the resulting amino acid sequence was unique to the horse, differing by two residues from the majority of mammalian sequences, where the peptide structure is identical. Expression of TGF-was particularly evident in spleen and kidney, and showed an age-related increase in expression in cartilage as the animals approached maturity and then a decline with progressive aging.

Age-Related Effects of TGF-β on Proteoglycan Synthesis in Equine Articular Cartilage

“…It is likely, therefore, that maintenance of the homeostasis of the extracellular matrix of normal articular cartilage depends on the relative amounts of the three isoforms that are present and that changes in their concentration will dictate the extent to which the tissue can repair itself following injury. These results are in accordance with the findings of Nixon et al (17), who has also reported that the expression of TGF-␤1 RNA is increased in young adult equine cartilage and that it then declines as the cartilage ages. In their study, RNA levels were at a maximum in horses aged 0.7 to 1 year of age with declining expression in older animals (2.5 and 5.5 years of age).…”

Effects of growth factors (EGF, PDGF‐BB and TGF‐β1) on cultured equine epithelial cells and keratocytes: implications for wound healing

“…With other researchers finding similarity in growth factor homology among species we felt justified in testing commercially available growth factors of nonequine origin. Equine TGF‐β nucleotide sequencing ranges from 86% to 99% similar in identity to human, bovine and rat TGF‐β 17,18 . While EGF has not been sequenced in the horse, EGF has been reported to be similar between humans and mice 19 .…”

Animal Models for Cartilage Regeneration and Repair

“…This can be attributed in part to the clinical need for cartilage regeneration in horses, to allow animals involved in racing to maintain their athletic performance. 58,77,78,82,[84][85][86][87][88] The horse is the largest of the animal models commonly available for cartilage research (400-500 kg). Due to their weight and physiology, equine jointloading conditions and the consequent hardness of equine subchondral bone are of some concern.…”