OK sit down with a cuppa because this is heavy, and until I rewrite it with some pictures, will stay that way.
Alleles at the E locus have been identified in some sighthound breeds (Eg) and cocker spaniels. (Eh). The sighthound Eg allele was identified first in saluki, (Dreger, Schmutz, 2010) . The saluki domino allele Eg is described in the study as being DOMINANT to the usual E allele, and affecting only at/at black and tan dogs. It is caused by a single nucleotide substitution 233G>T, resulting in p.Gly78Va in the ASIP protein.
As there is a lot of interest in canine coat colour, this study has been widely quoted, repeated and paraphrased on the internet, usually with no references to the original paper, and no qualifications as to the size of the research population, or whether the findings should be generalized to other dog populations.
Lapphunds do not often tepositive for 'saluki domino'. But they do posess a distinctive phenotype which shares similarities with the saluki domino pattern. Husky dogs also have a distinctive pale faced phenotye which is very like the Lapphund equivalent.
The pale faced phenotype is distinctive and pretty in these breeds. Hold that thought. Would you notice domino if it didnt cause spitz dogs to have an attractively marked face?
Because of the similarity to other 'domino' phenotypes, the lapphund coat phenotype has been known as domino for over a decade.
The causative allele for the lappie version has not been described or published. Informal communication has led me to believe that one research lab HAS elicited it, and that it MAY be the same as the 'husky' domino but that work is not yet published.
For the time being I am going to avoid using an abbreviation for the allele and call it 'lappie domino'
The "lappie domino" allele behaves experimentally in ways that differ from the published research for Saluki Domino Eg
It appears to be recessive to "non Domino" . Dogs that are phenotypically non-Domino may have domino puppies.
It affects Aw Wolfsable dogs as well as At black and tan dogs. In general, an Aw Domino can be seen to have a lighter phenotype than an At Domino, but it may be very difficult, if not impossible to determine the underlying agouti phenotype just by looking at a domino lapphund. A very dark domino is unlikely to be wolfsable. A lighter domino may be either wolfsable or black and tan.
I will suggest that Domino is an overall MODIFIER of eumelanin production, and is not just a 'pretty face pattern'. I suspect that Domino may also affect Ay sable/soopeli lapphunds and cause them to have a very light, almost cream phenotype in adulthood. I find this empirically observable in certain Lappie matings where photos exist on the lappalaiskoirat galleria. The lapphund community generally does not 'breed for colour' which is a very good thing. Ay sable/soopeli is a less common allele in the lapphund population, as is domino, and so the combination of Sable and domino together is infrequently seen.
I haven't found a reference on the internet for the mechanism of the 'faulty' recessive black ASIP ligand. Does it bind permanently to and block the MDR1 receptor? Does it leave eumelanin production permanently 'switched on' ?
An Ay domino epistatic relationship is also biologically plausible. A sable ASIP ligand binds to the domino MD1R receptor and alters the melanocortin switching within the cell. This view of mine does not have widespread acceptance at this time, and we may need to wait for the lapphund domino colour allele testing to be commercially available before it can be confirmed or dismissed.
I've recently found that Dr Schmutz' own page does display an Ay/_ Eg/Eg saluki named Bertha who has a cream, with comments that the mechanism is unknown. I personally find that the existence of Bertha supports my observations of an Ay Domino epistasis in Finnish Lapphunds.
https://www.ncbi.nlm.nih.gov/pubmed/20525767