Abstract
A retrotransposon insertion in the SILV gene is associated with a peculiar phenotype of dog, known as a merle. It is characterised by various areas of their coat colour becoming diluted due to a malfunction in the eumelanin-producing pigment cells. Recent studies have shown that the exact size of the short interspersed element (SINE) insertion is in correlation with specific phenotypic attributes, but was not able to absolutely confine dogs to a certain colour pattern. Our study focused on the merle variations occurring in the Mudi breed. Altogether, 123 dog samples from 11 countries were tested and genotyped. The exact length of the merle alleles were determined by automated fluorescent capillary fragment analysis. The most frequent merle genotype in this Mudi sample collection was the 'classic' merle (m/M: 61.8%), whereas other variants, such as atypical (m/Ma and m/Ma+: 5.7%), harlequin (m/Mh: 13.8%), double merle (M/M: 0.8%) and mosaic profiles (17.9%) were also observed. The practical significance of testing this mutation is that, phenotypically, not only merle dogs are carriers of this insertion, but also the so-called hidden merle individuals (where the merle phenotype is fully covered by the pheomelanin-dominated colouration) are potentially capable of producing unintentionally homozygous 'double merle' progeny with ophthalmologic, viability and auditory impairments.
Highlights
The first description of this Hungarian herding breed, designated as ‘Mudi’, is from 1936 (Fényes, 1936)
This study involved a total of 123 Mudis which either showed a merle pattern or previous genetic testing verified the presence of the elongated merle allele with short interspersed element (SINE) insertion (Pelles et al, 2018)
Before the molecular identification of the SINE insertion into the PMEL gene and elaboration of the appropriate direct genetic test, the merle genotype was assessed on the basis of the phenotype alone
Summary
The first description of this Hungarian herding breed, designated as ‘Mudi’, is from 1936 (Fényes, 1936). The merle colour was reintroduced into the breed in 1994 by a blue merle female from a shepherd’s stock. It is assumed by some dog breeders that the original merle variation still survived. The causative mutation is a short interspersed element (SINE) in the premelanosome protein (PMEL, formerly designated SILV – silver) gene. With this breakthrough, genetic testing of the merle mutation became a routine procedure in dog breeds carrying this mutation, as well as in Mudis in Hungary (Hédan et al, 2006; Miluchová et al, 2015; Pelles et al, 2018). The aim of this study was to survey the different merle varieties in the Mudi breed and detect their effects on the phenotype, in order to assist in the preparation of well-founded breeding and mating decisions
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