Coat colour H locus / Harlequin (PSMB7-related) - Great Dane

What does this test examine?

This genetic test analyses the PSMB7 variant c.146T>G at the H locus in Great Danes. The trait is known as harlequin, Harlequin, H locus and harlequin coat pattern. The H locus acts as a modifier of merle and changes dark merle patches into a typical pattern with a light or white base and irregular black or dark patches.

What does the harlequin pattern mean?

The harlequin pattern becomes visible when the H variant is combined with a suitable merle background and enough dark pigment. Without merle, the H variant can remain visually hidden. Other coat-colour genes, such as E locus, B locus, D locus, S locus and A locus, also influence how clearly the pattern is expressed.

Inheritance and result

The H variant acts as an autosomal dominant pattern modifier, but two copies are described as embryonic lethal. A dog with N/N does not carry the H variant, N/H carries one copy and can show harlequin when the right merle and pigment context is present, while H/H is normally not expected in living puppies.

Practical value of this test

• Helps breeders combine harlequin, merle and hidden H carriers more deliberately in colour planning.
• Makes the risk of H x H matings clearer, which is important for litter size and responsible breeding management.
• Gives buyers and breeders a clearer explanation of why a dog does or does not show a harlequin pattern.
• Supports interpretation together with M locus, E locus and other coat-colour tests for realistic colour expectations.