Grey depigmentation, Melanoma

Sample

• 5 mL - blood - K3 EDTA tube

Turnaround time

• 2 to 5  working days

Why test?

• This genetic test can help breeders that are interested in specifically breeding grey foals. Homozygous grey specimens are ideal as they will always transmit the grey gene when bred, thus guaranteeing eventual grey progeny.
• For the breeder that wants to  “breed-out” the grey modifier to gain non-fading foals may hope for heterozygous grey horses.
• Some breed-types have a large percentage of grey stock which through historical lineage may harbour colours and dilutions that are ‘hidden’ by the masking effect of the grey.
• Insight into a foal’s potential to fade: since grey may cause slow de-pigmentation, it may not be visually apparent whether or not a newborn foal will eventually fade to grey. The de-pigmentation process may take many years and therefore DNA testing is useful in the cases whereby a foal is born of one or more grey parents and verification of the presence of grey is necessary.

Results description

The DNA test verifies the presence of the grey mutation and presents results as one of the following:

• N/ – Non-grey horse. Negative for grey. Horse will not turn grey.
• G/N - Grey horse. Positive for dominant grey gene, carrying a single inherited copy. Carrier’s coat modified and will eventually become de-pigmented. Heterozygous grey horses are statistically likely to pass the gene to 50% off their progeny when bred.
• G/ - Grey horse. Positive for dominant grey gene, carrying two inherited copies. Carrier’s coat modified and will eventually become de-pigmented. Homozygous grey horses are genetically bound to pass the gene to 100% of their progeny when bred, so all foals will receive grey and fade-out.

Additional information

Grey is the dominant gene responsible for the gradual and progressive de-pigmentation (fading) of the carrying horse. Grey cannot be considered a base-color, or a dilution, but rather a gene which slowly removes pigment from the coat. 

This gene is considered to be the ‘strongest’ of all coat modifiers, and acts upon any base-color regardless of the carrying horse’s phenotype. The fading process itself may last for years, but once hair is de-pigmented, the horse’s original colouring will never return.

Since grey is a dominant gene, where it is present it is expressed. However, the final phenotype of the carrier will vary from horse to horse.

Some grey horses fade to full de-pigmentation (almost pure white) whereas others may be ‘fleabitten’. Fleabitten refers to grey horses with tiny non-faded spots or ‘fleabites.’ The grey carrying horse may also experience de-pigmentation of the skin itself, and before skin is fully faded may display ‘mottling’.

Equine melanomas occur most often in grey horses, and it is expected that at least 80% of grey horses will develop melanoma.