M Locus (MERLE)
M Locus (Merle), Merle Coat Color
A mutation in the SILV gene leads to the unique coat pattern known as “Merle” typically seen in breeds such as Australian Shepherds, Border Collies, Dachshunds, Great Danes, Louisiana Leopard dogs, Cardigan Welsh Corgi, and many others. The Merle pattern is typically categorized as mottled patches of color on a solid or piebald coat. The Merle pattern can affect all solid coat colors including black (blue merle) and brown (red merle) coated dogs. The Merle pattern can also be described using different terms in different breeds such as “dapple” in Dachshunds. The Merle mutation can be present in various sizes which can impact expression and lead to various coat patterns including “Cryptic Merle” which does not display the Merle coat pattern even in the presence of the mutation. These dogs can appear as non-Merle but can still pass the Merle mutation to their offspring. The test offered here is intended as an affordable option to screen a dog for the presence or absence of the Merle mutation and does not differentiate between various Merle-size alleles. If a dog is found to carry the Merle mutation, it is recommended that subsequent testing be conducted to determine the allele size of the mutation to make a determination of the effect on coat color and health status.
Reading Your Results
These dogs have two copies of the normal gene and will have no Merle coat pattern nor pass this mutation to their offspring.
These dogs have one copy of the normal gene and one copy of the mutation associated with this coat color. They can develop a Merle coat pattern and will, if bred, pass the mutation to 50% of its offspring, on average. Some dogs that possess one copy of the mutation may not show the Merle coat pattern (i.e., Cryptic Merle). It is recommended that subsequent testing be conducted to determine the allele size of the mutation to make a determination of the effect on coat color and health status.
C. (AT RISK/AFFECTED):
These dogs have two copies of the mutation associated with Merle coat color which can result in coat variation from Merle to light or white coat coloring. These dogs will also typically suffer from serious health issues including deficits in hearing or sight. It is recommended that subsequent testing be conducted to determine the allele size of the mutation to make a determination of the effect on coat color and health status.
G.292837-292838 (CanFam3): ~254 Bp Insertion; G.292838-292852 (CanFam3): 15 Bp Duplication (Dup TAGGCGAAGACTTCT)
Clark LA, Wahl JM, Rees CA, Murphy KE. Retrotransposon insertion in SILV is responsible for the merle patterning of the domestic dog. Proc Natl Acad Sci USA. 2006 Jan 31; 103(5):1376-81. [PubMed: 16407134]