Merle Mc-Mh

Von Mary Langevin

To Whom It May Concern

Merle has always been the most misunderstood pattern in canine coat genetics with a great extent of detrimental misinformation. Even after the mutation was identified in 2006 there were still so many unanswered questions as the test could only offer a result of “yes” or “no” as to the presence of the SINE insertion. Advances in technology have led us to more advanced testing and the ability to accurately report the length of merle’s poly-A tail along with any mosaic results and offer those base pair numbers to breeders. The allele bins (base pair length of each allele) have been set specifically for breeders, to help them produce the healthiest merle offspring while protecting the important genetic diversity in their breed’s population. https://doi.org/10.1371/journal.pone.0198536

There have been long held misconceptions that “double merle” can cause more health issues then just vision and hearing impairments. Issues such as; sterility, cardio problems, skeletal defects, missing limbs, skin conditions, aggression, behavioral issues, embryonic death, neurological issues, compromised kidney function, digestive disorders, allergies and early death anywhere from a few months to a few years old. None of these myths have any science to backup these claims. Auditory and ocular are the only two known impairments that can be caused by “double merle”. Using the 7 M locus alleles as set out in the “langevin et al” paper there are 28 possible merle allele combinations, 14 of which are considered “double merle” as they come with the ability to delete pigment to white and therefore come with a low, moderator or high risk of hearing and/or vision impairments. As well there has been the idea that dogs who have a single merle allele - m/M* also have a risk for these same impairments. This belief has been based on outdated science well before proper Merle testing was available. There is no risk to any dog of any breed who is heterozygous for merle with the single alleles of Mc, Mc+, Ma, Ma+ and M. The Mh - Harlequin Merle allele does fall into a category of its own, as even when heterozygous it does have the ability to delete pigment to white and therefore does come with some level of risk. The risk for hearing impairments from Mh is extremely low and to date we have seen no examples of any type of eye impairment. In my opinion the risk is so low as to be inconsequential. In the United States the Mh allele is more prevalent than the M allele in the Australian Shepherd population and following hundreds of litters produced by an Mh parent have shown only a few examples of a hearing impairment.

https://journals.plos.org/plosone/article?id=10.1371/journal. pone.0198536 https://www.researchgate.net/profile/Mary-Langevin https://www.merle-sine-insertion-from-mc-mh.com/