A novel form of oxytocin in New World monkeys

Abstract

Oxytocin is widely believed to be present and structurally identical in all placental mammals. Here, we report that multiple species of New World monkeys possess a novel form of oxytocin, [P8] oxytocin. This mutation arises from a substitution of a leucine to a proline in amino acid position 8. Further analysis of this mutation in Saimiri sciureus (squirrel monkey) indicates that [P8] oxytocin is transcribed and translated properly. This mutation is specific to oxytocin, as the peptide sequence for arginine vasopressin, a structurally related nonapeptide, is unaltered. These findings dispel the notion that all placental mammals possess a 'universal' oxytocin sequence, and highlight the need for research on the functional significance of this novel nonapeptide in New World monkeys.

Figure 1.

Genomic DNA, amino acid alignment for multiple species with and without the [P8] oxytocin mutation and representative mass spectrometry analysis of [P8] oxytocin (OXT) and arginine vasopressin (AVP) peptide from squirrel monkey pituitary tissue. Asterisks indicate nucleotides or amino acids that are identical to the corresponding residue in the human oxytocin sequence. All squirrel monkey [P8] OXT and AVP were compared with synthetic controls based on the cDNA sequence. Ion peaks represent positive detection of the corresponding peptide. (a) An alignment of genomic DNA for multiple species. A total of 27 nucleotides are depicted in the diagram. This region represents the DNA portion necessary to encode the final oxytocin nonapeptide. (b) Domain organization and amino acid alignment of the pre-oxytocin hormone for multiple species. Numbers below the region marked ‘oxytocin’ represent the amino acid residues corresponding to each of the nine amino acids that comprise the oxytocin peptide. (c) Ion peaks generated from squirrel monkey pituitary tissue. (d) Ion peaks generated from synthetic peptide based on the mutated squirrel monkey cDNA sequence, [P8] OXT (CYIQNCPPG) and AVP (CYFQNCPRG).

Figure 2.

Oxytocin and orthologous peptides. Asterisks represent amino acid residues that are identical to the corresponding residues in the human oxytocin sequence.