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It’s been at least a year since I started talking about the different types of the merle gene and its alleles. I called them “variants” that justified how the merle gene influenced the various subjects with this particular color differently. I’ve been studying the topic for a while and I admit that it is not a simple topic at all, but rather, extremely complex. During my studies I came across several articles. From here I then got in touch with the various authors who all showed great willingness to answer my many doubts. On the one hand, these doubts were justified because in our breed probably less than 10 dogs in Italy will have taken a test for the Merle gene and very probably 9 of these have taken it with the old classifications, when it was simply specified whether the subject was m/m (i.e. a solid) or M/m (i.e. a merle). In recent years, genetics has made great strides on the topic and since 2016 things have changed, I would say radically. In Germany they are already talking about it and are aware of it. In the United States, Australian Shepherd breeders are just starting to take an interest in the subject. In Italy, we are really at the beginning, but perhaps, thanks also to this article, we will not be the last. What you will read below is only intended to be a starting point to give all Australian Shepherd breeders and owners the opportunity to delve deeper into these new concepts and, above all, to test their dogs that they believe have “particular” colors. From here, we will then have the opportunity, over time, to find much more data that will be able to give us a great hand in improving the selection of the breed. Furthermore, understanding these new studies as best as possible will allow us to avoid unwanted mating that could give birth to dogs with non-standard colors or, even worse, dogs with serious handicaps. The hope is that this article will be read and shared by as many people as possible, both to spread these new and important concepts, and to integrate them, but also to correct them in case I have written inaccuracies. I don’t think I’ve made any huge mistakes, because as I wrote above I’ve always consulted other scholars and experts on the subject, but unfortunately I’ve also received or read incorrect answers from people I thought could give me correct answers, so I’ve always asked more people to be sure I’ve written the right things, but, in fact, it cannot be ruled out that I’ve reported some inaccuracies that I’ll be happy to correct if they’re reported to me. Personally, I remain available to anyone who wants to ask questions about any doubts. Happy reading.

What is the Merle gene?

The Merle gene is an incomplete dominant gene, what does this mean? That it will always manifest itself, but not completely. At the phenotypic level (therefore the set of characteristics that the individual manifests and that are visible to the naked eye) we will have a mixture of the characteristics involved that depend on the genotype (that is, the interactions of the genes that cause it). A heterozygous subject, that is, that will inherit only one Merle gene, will show a greyish coat with black or red spots depending on the base color that it has inherited. Even a single hair can have different shades of color. Furthermore, heterozygous merle subjects often show light-colored eyes, as well as areas of depigmentation on the nose, eyelids and lips. This is the standard definition, that is, the one we have always read until recently. In reality, as we will see later, at the phenotypic level the merle gene will not always manifest itself in a clear and evident way and not infrequently it will manifest itself with unusual colorations conditioned by the alleles that compose it.

What does the Merle gene mean?

The merle gene is defined as sub-lethal. If a subject inherits the merle gene from both parents (and for this to happen both parents must be merle colored, but as we will see only with certain specific alleles of the merle gene, which are still the most common), we will find ourselves faced with a homozygous subject with a double merle gene, better known as “double merle”. Why sub-lethal? Because unlike the lethal genes, which if combined cause the reabsorption of the fetus, in the case of the merle gene, this does not always happen, favoring the birth of subjects with potential problems. To understand the reason for these problems and where they mostly occur, we must go back to the embryonic state. The first cells that form in the embryo are found in the neural crest, these will then move and differentiate into the various types of cells that form the various organs and tissues as well as the pigment cells. The Merle gene intervenes already at this stage on the pigment cells, altering them to the point that they do not reach the places where they should go. And it is established that both the cells that give rise to the ear and the cells that give rise to the eyes are directly linked to the pigment cells. From this we understand why, in the case of Double Merles, we can see subjects born not only blind, but often also without eyes or eyes only partially formed and evidently wall-shaped and often also deaf. In terms of hair color, we will witness a massive depigmentation of the same with very large white areas that can vary from subject to subject. And finally, these subjects will almost always have a nose, depigmented eyelids and lips and therefore pink in color. Until recently it was also claimed that double merle led to sterility, but these were only suppositions and no study has ever been done on the matter. Furthermore, as we will see later, in some breeds DM are regularly used in breeding programs, so the question of sterility remains very unlikely. Most of these degenerative effects also occur in heterozygous subjects, therefore normal merles, but absolutely within the limits of normal survival without causing any deficits such as those listed above. Here too it must be specified that even in homozygous subjects for some types of alleles, the degeneration is not such as to create disabling deficits, we will see which ones later.

How many alleles of the Merle gene do we know?

What are alleles first of all? To avoid making too complicated discussions, it is enough to know that the allele is a sort of variable of the gene in question. There can be different alleles for each gene that combine with each other. In the specific case of the merle gene, which is still under study, 6 alleles have been discovered (7 if we also consider the non-merle). Only the Vemodia laboratory (http://www.vemodia.cz) has been able to identify all the alleles discovered since 2016 at the time of this article, which are classified as follows:

• m

not-merle

• Mc

Cryptic merle

• Mc+

Cryptic merle

• Ma

Atypical merle

• Ma+

Atypical merle

• Mh

Merle Herding Harlequin

To avoid complicating our lives too much, we will base ourselves on the classification made by Biofocus (www.biofocus.de) which classifies 4 alleles (5 with the non-merle one) which is sufficient for us at the moment to understand how they interact with each other. To help with understanding, I will use drawings later. It is important to point out that the drawings shown are only for example purposes, since phenotypically speaking it is not at all certain that the dog has a coat as shown in the drawing and only the specific genetic test can give certainty of the type of merle that the dog carries. Furthermore, the different types of merle coloring can also vary with the growth of the dog, as well as due to environmental factors, so the matter is really very complex. If we then take into account that the Vemodia laboratory has classified several dogs with 3 or even more alleles of the merle gene (this type of combination is defined in genetics as “mosaic” which does not refer to a type of color, but rather to the presence of more than two alleles of a single gene), if we were to consider the combinations in matings even between subjects that have more than two alleles of the merle gene, we would probably risk going crazy. In the following table we learn about the various alleles that we will use later:

ALLELE SYMBOLDEFINITIONPOSSIBLE CHARACTERISTICS
mnot merleno merle in the phenotype.
McCryptic merleno merle in the phenotype and perhaps a less intense base color in the puppy that darkens over time and becomes indistinguishable from a non-merle subject.
Maatypical merledepending on the combination of alleles we can have no merle, harlequin, a very marked merle or on the contrary a very faded merle.
MFull merlenormal merle or double merle
Mhmerle herding harlequin (not to be confused with the harlequin coat of Australian Shepherds)merle in phenotype, with the body featuring white spots and dilution spots of various colors

Let’s now look specifically at the various types of merles with the help of drawings, always remembering that to be sure of their genotype it is absolutely necessary to carry out the genetic test. Paradoxically, we will understand later why, even for subjects that we consider “not merles” only the genetic test can give us certainty. The drawings are, therefore, only a rough indication to better understand the various types of merles, also because, as we have already written, from tests carried out by the Vemodia laboratory, combinations of even 3 or 4 alleles result, here below is the result of a test of a subject who was M/Ma/Mc.

Below we can see a comparison of the classifications made by the two laboratories Biofocus and Vemodia where it is immediately evident that the latter has a more complete and detailed classification and this does not mean that the tests of Biofocus or other laboratories that use the same method as Biofocus are less valid, they are simply less detailed.

I wrote above that I didn’t want to make the discussion too complicated, but to better understand the graph just inserted, we must explain or rather try to imagine what a merle gene is like. This is made up of a head, a body and a tail. A spermatozoon comes to mind, but I don’t think it’s very far from this vision. When the first tests on the merle gene began, they were based only on the presence or absence of the same, therefore only of the body, without taking into consideration the length of the tail. As we will see later, the presence of the merle gene was instead ascertained even in subjects that at a visual level seemed solid. From here we began to take into consideration also the length of the tail (Poly-A-Tail) which allowed us to identify the different alleles that we will now analyze specifically. The graph above also allows us to understand how the Cryptic Merle allele is less aggressive, pardon the term, at the level of genetic mutation and therefore also phenotypic, unlike a Merle Herding Harlequin where the mutation will instead be very evident to the naked eye.

The non-merle

Non-merle subjects, that is, subjects that we normally define as solid color always have a combination of m/m alleles (lowercase m which actually means non-merle) and visually do not show any merle coloration. Two examples of the classic solid colors that we most commonly see, on the left a black tricolor and on the right a red tricolor.m/m

m/m

The Cryptic Merle

Let’s immediately tackle an interesting topic that concerns Cryptic Merle. As we saw in the summary table above, where the various alleles are explained, we read that in the case of the Mc allele, that is, a cryptic Merle at a phenotypic level, we will not have any merle coloration in heterozygosis with the “m” allele and perhaps, because it is not yet certain, only in young subjects will we be able to notice a slightly lighter coat coloration tending towards gray that will normalize with growth, especially in homozygous subjects, that is, Mc/Mc. For this reason, I previously wrote that paradoxically, even for subjects that we consider non-merle, only the genetic test can give us certainty, especially if “particular” colorations have appeared in the litter. Furthermore, we will always see later at a genetic level that the apparently solid Cryptic merle behaves in exactly the same way as a non-merle. From here we learn a further concept and that is that it is wrong to call those subjects that are almost totally solid and show only small merle spots with the name of Cryptic Merle. It is correct to call these subjects Phantom Merle and such subjects are normal merles in all respects. This concept must be very clear because by mating a phantom merle with a merle we will have a 25% chance of giving birth to double merles, that is dogs with serious handicaps, unlike a Cryptic Merle. Let’s see through the drawings the various possible types of Cryptic Merle.Mc/m

Mc/Mc

Mc/M

Mc/Ma

From the drawings above it is clear that the first three combinations are practically identical to normal solids or merles. Since very few Australians have been tested after the latest discoveries on the merle gene, it is not yet clear, as already mentioned, whether subjects born with the Mc allele have a lighter color at birth, tending towards gray (or light brown) or faded spots in the case of apparently normal merle subjects, which within a few months tend to become a normal solid color. From the few dogs tested it would seem so, but the interesting thing is that this sort of “mutation” is not present in other breeds such as the Catahoula, where Mc/Mc subjects, for example, are born with a dark color like a normal solid. The combination of the Mc/Ma alleles, however, introduces the additional type of allele which is the Atypical Merle which we will explore in more detail shortly. In the specific case from the drawing you will notice how the Mc/Ma subject has spots with a lighter pigmentation which represent a very dark merle. In these subjects, it is not to be excluded that in adulthood they may have a lighter color, as well as appear perfectly solid in color. They may also have a lighter eye color. I also remind you that only the genetic test can give certainty on the type of merle of the subject to be analyzed and that with the naked eye it is only possible to make assumptions.

The Atypical merle

Let us now introduce the Atypical Merle (Ma) allele which until a few years ago was completely unknown and which then paved the way to define in more detail also the other types of alleles until finding as many as 6 distinct ones (I remember that only the Czech laboratory Vemodia http://www.vemodia.cz is able at the time this article is written to identify all the discovered alleles and that we, to avoid complicating the matter too much, will base the mating combinations that we will see later only on the 4 alleles classified by the German laboratory Biofocus). How was this allele discovered? To avoid going on too long, it all started with the Catahoula breeders, an American breed, where the merle color is the master in all its variations. The breeders of this breed saw merle subjects born from two subjects that apparently seemed solid without understanding the reason and from the tests carried out later these subjects were classified as double merle, that is M/M by the old tests. In 2012, if I am not mistaken, a breeder, Dr. Helena Synková from the Czech Republic, where there are several Catahoula breeders, decides to look into the matter further and in collaboration with Biofocus they manage to define in 2015 what had already emerged in 2006 from a study done by Dr. Clark where he highlighted the different types of alleles of the merle gene. Hence the discovery of the atypical Merle allele which in combination with the other alleles gives different types of color that are often confused with dilute coats, but which in reality have not been found to be such after being tested. Small aside: there is a discussion about changing the definition of Atypical Merle with Dilute Merle, but given that not all subjects of the various breeds affected by the merle gene, having this allele show dilutions, the term Atypical Merle will most likely remain. Let’s look in detail at the possible colorations.Ma/m

Mc/Ma

Ma/Ma

Ma/M

Ma/m may be indistinguishable from a normal solid. When young, these subjects may show a dark gray or slate-like coloration of the hair and also of the pigment (see nose and labial and eyelid fissures), therefore with a slight tendency towards red in black subjects, while in red subjects we will have a very light red pigment. As they age, they may take on a coloration indistinguishable from a solid or, on the contrary, lighten or even highlight merle colorations. We discussed Ma/Mc before when we talked about the Cryptic Merle and it could behave more or less in the same way as Ma/m. Ma/Ma may also seem like a normal merle, but in reality it tends to have a much lower presence of black (or red) spots than a normal merle and also a less intense black (or red), in addition to having a lighter and more uniform basic merle color. These subjects can also have a nose, eyelid and lip rims of a washed-out color that can make one think of a dilution that in reality is not at all obvious, on the contrary. Finally, we have the Ma/M combination which is the classic coloration that in our breed is called “harlequin” with patches of different colors, often washed-out and sometimes with white spots on the body. It should be noted that this variant called harlequin is not to be confused with the Mh allele, or “Merle Herding Harlequine”, which is a further allele of merle, the most extreme if you like, and at the same time this allele is not to be confused with the H gene of the harlequin Great Danes’ coats, since dogs with the Mh allele did not have, after being further tested, the H gene. Always regarding the “harlequin” coloration referred to the Australian Shepherd, the example drawing inserted above and which refers to a combination of Ma/M alleles is absolutely indicative. From recent studies that have emerged on other breeds, in particular on Catahoulas, such colorations very often had combinations of multiple alleles, 3 or even 4 with the presence of the Mc and also Mh alleles. To further complicate the matter is the enormous difficulty in even having a phenotypic confirmation to be able to make a clear distinction between this coloration and the tweed one, since they are very similar, superimposable or even interchangeable.

The Merle Herding Harlequine

Here we touch on an even more recent topic, introduced by the Vemodia laboratory in 2016. As already written above, the Mh allele that stands for Merle Herding Harlequine is the most extreme variant of the merle; we can define it as its maximum phenotypic expression of the Merle gene. Searching online for examples to understand the phenotypic typology that this allele produces, we find many photos of Catahoulas tested at the Vemodia laboratory, but not of Australian Shepherds. Or rather, I have seen a couple, but they are not purebred dogs, so I don’t feel like taking them as an absolute reference. However, based on the photos of Catahoulas and these non-pure Australians, the similarities with what we call “tweed” coloring are very evident. In fact, you can see large areas of coat with often faded base colors, interspersed with white spots and merle areas, also sometimes faded in color. We are talking about heterozygous subjects, because logically, in the case in which we were to find ourselves faced with a double merle combination, therefore Mh/M or even Mh/Mh and Mh/Ma, the subject will most likely present large areas of white coat and almost certainly blindness and deafness. And always very probably, it will not undergo particular variations in the coat in the case in which we had Mh/Mc combinations, since the Mc allele, as we wrote at the beginning of the article, is expressed in a less evident way if not even not expressed at all. Let’s see how an Mh could appear:

Mh/m

Here too, the same argument made above for the harlequin color in Australian Shepherds applies. It is very likely that subjects with these colors have more than two alleles that condition their merle coloration and therefore this example should also be taken as a very indicative one.

Let’s clear up the Phantom Merle discussion

As previously explained, the phantom merle should not be confused with the cryptic merle and vice versa. The phantom merle, which means ghost merle, is a normal merle in all respects, but with a coloration that may seem solid at first glance, but which in reality shows small portions of merle-colored hair sometimes hidden by the white hair or even by the tan markings. Paradoxically, these portions of hair could also be found on the tail and if this is amputated, as often happens, we will not have any visual clues to define the color type of the dog. In these cases, if after mating with a merle subject, we see double merle subjects born, without understanding the reason, we must immediately think about this possibility and test the dog. Let’s look at a drawing to better understand the concept, but the possible variations are practically infinite.M/m

The Double Merle

Double merles are those subjects that inherit the normal merle gene (M) or Herding Harlequin (Mh) or the Atypical Merle Ma+ from both parents and will therefore have the following combinations of alleles that almost always cause serious vision and hearing problems.

Mh/Mh

Mh/M

Mh/Ma+

Mh/Ma

M/M

M/Ma+

Why did I also specify the Ma+ allele in this case, since we said that we will not take it into consideration? Because it is certain that this has a high probability of giving birth to blind and deaf subjects if combined with the other alleles mentioned above, while there are still doubts as to whether or not vision and hearing problems can occur in M/Ma subjects and it would seem that this could depend on the amount of white in the reproduced subjects, but it is still not clear how the s locus (which regulates white) interacts specifically. The M/Ma could be those subjects in our breed that we define as harlequin.

They are not to be considered double merle (DM), instead the following combinations:

M/Mc

Ma/Ma

Ma/Mc

Mh/Mc

At a phenotypic level, double merle subjects will present themselves with a lot of white on the body and often the spots of the base color (black or red) are not very marked to seem dilutions (but they are not dilutions!), with pink pigment and eyes, if formed, of a color almost always blue tending towards white. Ethically speaking, mating two merle subjects would be absolutely to be avoided, but we must remember that before it was understood that these problems were caused by the merle gene, matings between these colors were normal and at the dawn of the breed they were the vast majority. Simply at the time, those subjects that at birth had too much white were suppressed. I would also add that in the first standards drawn up by ASCA the following was reported: “all white pups should be destroyed at birth, as they will develop blindness or deafness.” Today, mating two merles would be scandalous in Italy and elsewhere (consider that in France the SCC, the equivalent of our ENCI, has actually banned mating between merle-colored dogs for all breeds involved). This is not the case in the United States and other Anglo-Saxon countries and perhaps not only Anglo-Saxon countries, where a mating between merles in our breed, if considered interesting and if it makes sense to do so, is completely accepted. Logically, these are discussions to be reserved only for those breeders who clearly know what they are getting into and who have clear ideas about why to do such a mating. It is obvious that in these cases the Double Merle puppies are then put down at birth. In the United States there is a different concept of the pet, which is much less humanized than in us Europeans. De-clawing a cat, for example, to prevent it from ruining furniture and sofas, is completely normal for Americans, but not for us. Just as it is completely normal to cut tails and ears without anyone crying scandal. They are different ways of living and conceiving animals in general, not only companion animals, but also income-generating animals. Hence these different “morals”. I do not allow myself to express judgments on the matter, especially towards the Americans who created this fantastic breed, but I feel like advising us to leave these “risks” to them and continue to avoid mating Merle x Merle. Let’s see an example of a drawing that could represent a Double Merle:M/M

Some examples from the world of Catahoula

I am now inserting some photos of the Cat’s Cradle Catahoulas breeding http://www.catscradlecatahoulas.com/ that Mary Langevin has allowed me to use and that I thank very much also for the incredible work that she is doing in collaboration with Vemodia, to better understand the Merle gene. Mary has also recently opened this site http://merle-sine-insertion-from-mc-mh.webnode.com/ where she is collecting information on all the breeds affected by the merle gene and is about to complete a book on the subject that should be released in spring, but that you can already order on the same site (I did it). What we will see, therefore, are not photos of Australian, but they help us a lot to understand the different types of merle and therefore to better understand what was explained above. I would also like to point out that these dogs in the photos have been tested by the Vemodia laboratory with which Mary collaborates, so we will see the acronyms used by this laboratory appear. For example, in Ma+/Mc subjects this very dark merle is very evident, probably if they had been Ma/Mc this merle would have been less evident, almost seeming like solids. Another note… it cannot be excluded that in Australians, having these a longer coat and undercoat and subject to variations due to the environment (see sun or diet), these “shades” of merle are even more difficult to see with the naked eye.

Matings between the various types of Merle

Let’s start by understanding how the various types of merles could behave (THE CONDITIONAL IS ALWAYS A MUST!) when they are crossed with each other. Trying to make the article as accessible as possible to everyone, let’s quickly review the Mendelian combinations between the basic colors of the breed, but staying only on the black basic color and the blue merle, since the discussion is identical for dogs with a red basic color, (i.e. solid reds and red merles). Moreover, in the previous examples I also used only dogs with a black basic color, but I think the reason was clear.

Until yesterday, when we talked about the merle gene and explained why you shouldn’t mate two merles, most of the articles reported the following scheme:

Today the discussion is more complex, since as we have seen above, the Merle gene (M) can have different types of alleles. So let’s see what happens in the various matings, specifying that we will not take into consideration examples of mating with subjects having the Mh allele, since this is not very common in Australians and we do not have recent photographic material of dogs used in breeding (if there were ever any), having this particular coloration to deduce the possible phenotypic variants. But it is certain, since I have seen photos of Australians tested by Vemodia that exist and were found to be Mh. So for now we will not deal with this variant precisely so as not to go crazy, but in the future, when we will start testing the merle typology also in our breed, it cannot be excluded that there are several subjects carrying the Mh allele and therefore we will also have more material available to deduce the phenotypic typology given by this allele. I don’t want to sound repetitive, but as written in the introduction, we are really at the dawn, especially here in Italy, in reference to these new concepts on the merle gene, so it will all be a becoming in the next few years of new data and information. We will not even consider mating with Double merle because nobody is interested in them, but I think it is important to point out that Catahoula breeders often use DM subjects in their breeding programs, subjects that like most DMs have vision and hearing problems. Breeders of this breed practically consider them as normal dogs just like the others it seems. A few more clarifications before seeing the various combinations. Pay attention to the drawing of the Mc/Ma dog which may seem like a solid, having had to reduce the size of the drawings, but in reality, if you look carefully by enlarging the image from a smartphone or moving closer to the screen, it clearly shows possible merle spots. Finally, I reiterate for the umpteenth time, these drawings are mere indications of how the dog may appear at a phenotypic level, but only an in-depth genetic test of the merle gene can tell you the genotypic typology of the dog.

Conclusions

As we have seen from the various combinations and their results, there are certainly many topics for discussion. I will not go into more detail, because I think I have already made all the most important concepts clear. The hope is that when we see puppies born with particular colors that can be blacks that tend to gray, reds that tend to yellow, merles with washed-out spots or tending to red or orange, merles with a very light background or vice versa very dark, unexpected litters of all merles or vice versa of all solids, Harlequin or Tweed puppies, merle puppies with very few black spots, let’s not immediately think of diluted dogs, because they almost certainly will not be, but let’s test the breeders for the Merle gene and also the entire litter if we have the possibility. Sharing these results will then be essential, because without it we will have no way of learning, but above all we will have no way of “adjusting the shot” to make selection and therefore understand how to behave. Because here we will open, or rather, we absolutely must open a breeding discussion on how to use any Cryptic or Atypical Merle subjects (or even Mosaic, that is, those with more than two merle alleles), whether to continue using them or whether to exclude them from reproduction to “clean” the blood of the breed. Because it is certain, I assure you, that there are many Cryptic subjects among the Australian Shepherds and it is equally certain that there are several Atypicals, especially in the subjects that we define as normal merles. I will not express myself on the subject for now because I believe a comparison is essential first. A comparison that can take place, however, only after having fully understood these new concepts and after having in hand a certain number of tests that will be fundamental to understand if we are faced with a problem or perhaps with new breeding opportunities.

The World Dog Federation has planned a long genetic selection process so that there are clear concepts for selection for the breeders who are part of it.

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