A short conversation with specialized laboratory. Note that:

  1. there are three marked variations of “d” allele, “d1”, “d”2 and “d3”
  2. current names for those alleles have nothing to do with alleged “d1” allele, which was pointed out as the possible cause of Color Dilution Alopecia (CDA) in times when variants of “d” allele had not been yet discovered
  3. none of those variants is responsible for CDA, dog has to be diluted (homozygotes for any d allele)  to develop CDA – which only occurs in “diluted” dogs – but it is not the cause of CDA
  4. the marker for CDA is yet to be discovered, the mutation for CDA is not connected to d1,d2 or d3 allele. 
  5. Any dog (also one “DD” !) can carry the mutation for CDA
  6. testing for D-Locus has no connection with CDA (see point 5 above)




Prior to testing, I wanted to ask a question about D-locus D1 (dilution) test that is available in your laboratory.

Several years ago (as I understood the markers were only able to detect two alleles “D” or “d”) the working thesis was that mutation of d can cause color dilution alopecia. Back then some of the researches were referring that disease-causing variant as “d1”, yet it was not confirmed (marked).

Now, several years later I see that you can test whether the D-Locus variant is d1 ,d2 or d3. The question is if the d1 in your test is the same one that causes CDA? Or as time has go on, you have started to mark the variants with numbers (1,2,3..) and the old “nomenclature” created before that is not longer valid, and present time “d1” does not cause CDA?

Laboklin answer:

Thank you for your request.
The recessive variants for colour dilution on the D-locus are responsible for the change in the distribution of the pigment in the hair.
Different causative variants have been described over the last few years.
The first variant was known as “d” at first, but was changed to “d1” as “d2” was discovered.
The three known variants are now called d1, d2 and d3 correspondingly.
Therefore, your assumption about change in the nomenclature is correct.
Even if all three variants can be the base for a colour dilution alopezia (CDA),
as all three might cause diluted colours by themselves or in combination with one another,
none of the variants does cause CDA directly.
The genetic factor responsible for CDA symptoms in diluted dogs,
that presumably has to exist in combination with d1, d2 and/or d3 to cause CDA,
is not known yet.