A missense mutation in melanocortin 1 receptor is associated with the red coat colour in donkeys.

The research paper discusses a particular genetic mutation in donkeys that significantly affects their coat color, specifically leading to red coats. The researchers identified a recessive genetic variant in the melanocortin 1 receptor gene (MC1R) and proposed a scientific designation for this variant.

The Study and Findings

• The researchers began with observing seven different breeds of donkeys penned in the French studbook. They noted that these breeds primarily exhibited three coat colors: black, bay, and grey. However, an unusual exception was noted in the Normand bay donkeys which sometimes bear red foals. This red coat color, similar to the equine chestnut color, was more common in American miniature donkeys.
• The red coat color was previously linked to a mutation in the MC1R gene. To investigate this further, the authors of the study used 124 donkeys as their research sample.
• They discovered a recessive missense c.629T>C variant in the MC1R gene that was perfectly associated with the red coat color. This variant leads to a substitution in the protein structure, changing methionine to threonine at position 210.
• In addition, it was observed that methionine 210 is highly conserved among vertebrate melanocortin receptors, indicating its importance to the functional structure of the protein.

Implications and Conclusion

• The researchers carried out in silico and in vitro analyses which predicted a functional role for the methionine residue 210 in the MC1R protein structure.
• Experiments and results in vivo further confirmed the crucial role of this methionine residue, where a change led to the red coat phenotype, indicating a loss of function of MC1R.
• The c.629T>C allele found in donkeys was proposed to be named the e allele. With this, they recognized an enlarged pool of recessive MC1R loss-of-function alleles existing in animals and humans. This particular study on donkeys, therefore, adds to the understanding of how genetic variations can affect physical traits in animals and potentially, in humans.