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

This research delves into the molecular cloning of the equine transforming growth factor (TGF)-beta1, suggesting the presence of distinct amino acid substitutions in horses that aren’t observed in other mammalian species, basing this on the uniqueness of the derived nucleotide sequence and amino acid sequence. Also, the study reveals how the gene’s expression varies across different tissues and changes with age.

Equine-Specific Sequence of TGF-beta1

• The study successfully cloned and sequenced the equine (horse) transforming growth factor-beta1. Transforming growth factor-beta1 (TGF-beta1) is a protein that regulates a range of biological processes such as cell growth, proliferation, differentiation, and apoptosis. It plays a major role in tissue homeostasis and the immune response.
• The identified nucleotide sequence of the equine TGF-beta1 revealed uniquely predicted amino acid substitutions, not seen in other mammalian species. This implies that the structural sequence of TGF-beta1 in horses differs somewhat from that in other animals.
• The research compared the nucleotide sequence homology (similarity) across species and found that equine TGF-beta1 showed a sequence homology of 89% to bovine (cow), 91% to human, 90% to ovine (sheep), and 86% to rat.
• A closer look at the derived amino acid sequence showed that the equine protein was different from the proteins in man, cow, sheep, pig, and dog by two residues, and by three residues from rats.

Tissue specific and Age-related Gene Expression

• Following the genetic profiling, the authors made use of the cloned cDNA to analyze the genes’ expression in various tissues. They observed that the TGF-beta1 gene was predominantly expressed in the adult spleen and kidney of the equine subjects.
• The expression of the gene showed an age-related peak in cartilage at 12 months, followed by a decrease as the horses aged.
• More sensitive mRNA detection techniques using polymerase chain reaction (PCR) confirmed these age-related changes in TGF-beta expression.
• They noted peak levels of TGF-beta mRNA in the cartilage of horses aged 0.7 and 1 year, with reducing expression as the subjects aged (2.5 and 5.5 years).

Conclusion

• Although the primary nucleotide sequence of equine TGF-beta was relatively similar to other species, the resulting amino acid sequence was unique to horses, implying a possible equine-specific function of this protein.
• The gene’s expression was high in the spleen and kidney, and it also showed an age-dependent change in expression in cartilage – increasing as the horses approached maturity and subsequently declining with progressive aging.