The merling gene is not only beautiful, but important to understand, since just like in all breeds, two copies of this gene (homozygous merle) can produce serious health issues. Although there is some misinformation about this within the Pyrenean Shepherd community, the gene for merling in the Pyrenean Shepherd is that same gene as in other breeds, so it does cause the same health defects. (See research article below.)
Merle – UC Davis (Listed for Pyrenean Shepherds)
RESEARCH & ARTICLES
Merle – SINE Insertion from Mc – Mh (Mary Langevin)
An important resource concerning the merling genes.
Merle phenotypes in dogs – SILV SINE insertions from Mc to Mh (Mary Langevin, Helena Synkova, Tereza Jancuskova, Sona Pekova)
It has been recognized that the Merle coat pattern in dogs is not only a visually interesting feature, but it also exerts an important biological role, in terms of hearing and vision impairments.
Unraveling the Mysteries of Merle (Mary Langevin)
Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog (Leigh Anne Clark, Jacquelyn M. Wahl, Christine A. Rees, and Keith E. Murphy)
Intro – Merle is a pattern of coloring observed in the coat of the domestic dog and is characterized by patches of diluted pigment. This trait is inherited in an autosomal, incompletely dominant fashion. Dogs heterozygous or homozygous for the merle locus exhibit a wide range of auditory and ophthalmologic abnormalities… (NOTE: The Pyrenean Shepherd is referenced in this article.)