Harlequin colour pattern

The harlequin coat refers to a type of coat coloration pattern characterized by a white background with darker shaded spots.

Definition

The harlequin trait refers to a characteristic coat pattern corresponding to a white background with darker colored spots. The variant is found in the PSMB7 gene (also known as the H locus), which encodes one of the subunits that are part of the proteasome.

Genetic basis

The harlequin trait presents a dominant form of inheritance, therefore, the presence of a single copy of the c.146T>G variant increases the probability of presenting the trait. Even so, at least one copy of the variant encoding the merle trait at the M locus (not analyzed in our test) is required for the trait to be expressed. Presenting two copies of the c.146T>G variant poses a risk, as it causes death in early stages of embryogenesis. For this reason, crossing two dogs carrying one or two copies of the c.146T>G variant is not recommended.

Other relevant information

The trait arises as a consequence of the interaction of the PMEL gene (M locus) and the PSMB7 gene (H locus). The presence of one copy of the variant at the M locus and one copy of the variant at the H locus is sufficient to express the "harlequin" colouring pattern. In addition to this gene interaction, the A locus can also interfere with the final expression of the phenotype. This type of characteristic colouring pattern is present only in the Great Dane breed.

Bibliography

Clark LA, Tsai KL, Starr AN,et al. A missense mutation in the 20S proteasome β2 subunit of Great Danes having harlequin coat patterning. Genomics. 2011 Apr;97(4):244-8.