Molecular cloning of equine chromogranin A and its expression in endocrine and exocrine tissues.

The research article discusses the molecular cloning of Equine Chromogranin A (CGA), a protein found in adrenal medullary cells, neurons and paraneurons. Comparisons among different species have been made, and the distribution of CGA in various horse tissues was examined.

Molecular Cloning of Equine CGA

• The researchers cloned the gene responsible for encoding the Chromogranin A protein in horses. This was achieved using RT-PCR (Reverse transcription polymerase chain reaction) and RACE (Rapid Amplification of complementary DNA Ends) techniques, which are common in molecular biology for copying and amplifying small sections of DNA.
• Through these techniques, they found that the sequence encoding this protein is 1,828 base pairs long in horses. This genetic code produces a protein made up of 448 amino-acid residues, which includes an 18-residue signal peptide, essential for directing the protein to its specific location in the cell.

Comparison of Equine CGA with Other Species

• The amino-acid sequence of the horse CGA protein was compared to the corresponding CGA in humans, pigs, cows, mice, rats, and frogs. There was a high degree of similarity observed in the NH2-terminal and COOH-terminal regions of these proteins, indicating that these regions are highly conserved and likely perform vital functions in different species.
• The middle portion of the protein showed significant variation across species, suggesting that this region may have divergent functions depending on the species, or could be subject to fewer constraints of evolutionary selection.

Expression of CGA in Various Horse Tissues

• The researchers used Northern blot analysis and RT-PCR to investigate which tissues expressed the CGA protein in horses. This was important to understand where this protein functions within the horse’s body.
• The study found that CGA mRNA is present in many different tissues throughout the horse’s body, including the cerebrum, cerebellum, pituitary gland, spinal cord, liver, thyroid gland, striated muscle, lung, spleen, kidney, parotid gland and sublingual gland. This wide distribution suggests that CGA plays a role in these tissues’ functionality.
• The presence of CGA mRNA was confirmed in adrenal chromaffin cells and cells of the anterior-intermediate lobe of the pituitary gland by using in situ hybridization with anti-sense CGA cRNA probe.