Agouti

[KingstonTodd]

I posted on another forum and had a few emails about dog coat colour, specifically with respect to agouti. I thought I would post it here as well so it can be found if someone searches for it.

Agouti encodes a paracrine signaling molecule which causes hair follicle melanocytes to synthesize reddish yellow pheomelanin instead of black or brown eumelanin, so-called pigment type-switching. The wild type, or normal, or baseline, agouti causes a banding pattern within a hair along its length, like a wolf or GSD.

Now what do Pawsive ID test mean? In a large survey covering thirty seven breeds agouti mutation A82S was present (heterozygous or homozygous (+- or ++) in 41 dogs (22 breeds) with a fawn or sable coat, presumably the fawn is A82S+/+ and sable is A82S+/-.

The other mutation, agouti R96C causes "recessive black" where the genotype at the "E" locus would suggest yellow phoemelanin. For example, we have a brown F1 LD that is bbEe, and R96C+/+. She carries recessive black, meaning that if she was "ee" instead, we would expext her to be yellow from the E/e locus but she would in fact be recessive black. If we mate her to the same colour genotype (bbEeR96C) we will not get any yellow dogs, there will be brown, and all of the "supposed to be yellow" will be recessive black due to agouti R96C+/+.

Back to the basics of E and B genes. The yellow test is for the "E" gene. I think of "E" as an "E"xtension gene, if you have "E" it allows the "B" colour (brown or Black) to be shown and this masks cream-yellow, and if you don't have "E", you are "ee" and it does not allow brown or black and you are cream-yellow by default. So, a Pawsitive ID +/+ for yellow is actually telling you "ee" and the pup should be cream-yellow range, not expressing any "B" gene (brown or black).

The agouti gene is different from parti, it refers to pigment switching within a single hair, dark at one end, and lighter at the other. If you bred A82S+/- to A82S +/-, you would get 25% of the pups with A82S+/+ and there should be some pigment switching in the individual hairs, like a brindle or sable, with lighter roots and darker tips. Agouti has incomplete expression so the banding hair is not present everywhere on the animal and you get patches of brindle and patches of the base colour coat. The other agouti gene R96C is totally different, and makes for recessive black. Any pup that is R96C+/+ and "ee" will be black, when the "ee" tells you it should be cream-yellow.

[MaxandMe]

Todd one moment..........if i read that correctly what you have above
then the

The other agouti gene R96C is totally different, and makes for recessive black. Any pup that is R96C+/+ and "ee" will be black, when the "ee" tells you it should be cream-yellow.

so are you saying the R96C +/+ dominant ? and over the ee which is considered "recessive dominant"if one or both dogs have at least one or two e's
so are you saying the R96C will override all cream yellow and red? cause then that doesn't make sense to me in your previous paragraph
and YOU also have to factor in the K locus which also determines black

ok what is agouti R96c considered in letters? i have the genetic book by Little here and would like to look this up tomorrow

from what i understand in agouti , the Recessive black is a rare or not very common and is in the bottom recessive in the agouti series due to it being recessive to all other A locus genes and denoted by a SMALL "a" meaning recessive

do you mind letting me know what letter the R9C +/+ is,
so i can make sure i am understanding you correctly ....thanks

[lindamarie]

Are you guys speakin' da english??

[MaxandMe]

yeah we beez speakin duh JANETIC INGLISH LINDAH
hhahahahhaaaaaaaaaaaaaaaaaaaaaaa

[KingstonTodd]

The type of pigment synthesized, pheomelanin (yellow-red) or eumelanin (black-brown), depends on the interaction between Agouti protein and the Melanocortin 1 receptor. This receptor (MC1R) is expressed on the surface of melanocytes and is encoded by "E". "E" receptors can make both pigments and "e" can only make pheomelanin. Activation of the MC1R by its ligand, primarily ?-melanocyte stimulating hormone (?-MSH)1, switches biosynthesis from the default pathway for pheomelanin (red-yellow) to production of eumelanin (black-brown). Dogs have a MC1R antagonist, the agouti protein, which competitively binds the MC1R preventing (?-MSH)1-induced eumelanin production (no black-brown). The wild type of agouti, the antagonist gets in the way of (?-MSH)1 binding, and thus inhibits eumelanin (black-brown) and the expression of default pathway for pheomelanin (red-yellow). The inhibition is not complete and continuous, so it results in banding as agouti alternates between bound and unbound states. This is seen classically in the coat of wolves, GSDs.

The A82S mutation causes an agouti that does not bind the MC1R, and therefore there is no intermittent inhibition and coat colour is determined as B's and E's dictate. This allele is found in most breeds.

The other mutation R96C has been identified in black dogs (eg GSD) but there is no clear explanation of how it leads to dark pigment production. Its deemed recessive because you have to have two mutated alleles to have it expressed as a phenotpye, but since is leads to a black dog over yellow, I guess it is dominant over "ee" since the "e" type MC1R does not lead to the production of eumalanin but the mutatued agouti here somehow leads to this signalling, I presume by bypassing the need for receptor activation by (?-MSH)1. Since it is not acting in the pathway that agouti normally does it is sometimes called non-agouti.

Its late, I'l proofread this in the am to make sure I make at least a little sense.

[lindamarie]

Todd and annmarie,
I just wanted you guys to know that I use to teach this kind of stuff. It's so funny how now, it makes me think too hard!
I didn't mean to interrupt your thread....
I'm in a silly mood..............from a bad mood to silly.

[MaxandMe]

Todd i have to go back but off the cuff from what i remember to have an all black dog with recessive genes and no other colors
like yellow or red
or simply a recessive nonblack dog to be solid black you need
kk, ee and aa

what happens is that even though we have genotype (genetic makeup)and phenotype (what you see)
recessive genes override dominanct genes in breeding when at least one parent has the 2 recessive genes and one parent has at least one recessive gene
what is the roll of the dice is where it lies on the gene in the differing locus: a, k, d, e, b etc
dilution, agouti, black, and now we also have rufus gene which is red like in the toller dogs, irish setters etc

so

genetics no matter how much we map it out is a predicability with no 100% guarantee.

i have to go to work but i do have something that tries to explain all solid black dog and also an all solid black dog that shows brown as it ages
is called bronzing due to sunlight and USUALLY shows up on muzzle and back or part of the legs.

[KingstonTodd]

Originally Posted by MaxandMe

a recessive nonblack dog to be solid black you need kk, ee and aa

I think we are speaking the same language now, if aa (recessive black agouti) resulting in black in the presence of "ee" is the R96C allele. This is what i mean by "ee" tells you the dog should be yellow, but is black because of R96C+/+. This is seen, rarely, when two yellow labs, both "ee", have a black puppy. It happens and it is because the puppy is "ee" and is supposed to be yellow as well, but the parents each had one R96C, or "a" and passed them on the the puppy to make "aa" or R96C+/+. I really wish they used the same terminology everywhere!!!

The wild type normal agouti resulting in banding within a hair, is a(w).

The defective agouti A82S results in fawn if you are -/- and clear sable if you are +/- is a(y)

I dont know what the mutation code for black and tan, a(t) is yet.

[Jac]

Well, okay, NOW it makes a little more sense to me...I, too, wish they would be consistent in naming this...it is hard enough to wrap my brain around one concept but when they start calling it different things, I am lost!
This is very interesting! And, weird...because you say that the Agouti R96C is rare...but I just checked my dogs' PID records and I have three dogs with this! (No wonder I always get black!!)
Sooo, if a puppy from this type of litter is born black...will it CARRY the yellow?
Chase, my brown Poodle stud, carries:

Yellow +/-
Melanistic Mask +/-
Agouti R96C +/-
Brown G +/-
Brown H +/-

So, my question about Chase is 1) about the brown...since he has the two different types, what does that mean? 2) does his two browns make the R96C stronger than if he had two of the same brown or does that matter?

Rosie, my UNRELATED golendoodle is:

Yellow +/+
Agouti R96C +/-

She and Chase produced a litter of 12 puppies...2 cream, 2 black and the rest apricot. I thought that the black came from Rosie, but could it have come from the Agouti instead? Does Rosie's black AND agouti make her more likely to have black pups?

My other Agouti dog is Gerry (Chase's daughter), she carries:

Yellow +/+
Brown +/+
Agouti R96C +/-

So, is it possible that she could have all black pups??? (OMG please say it ain't so!!!)

I have a headache.

[MaxandMe]

hi.at work right now so i don't have my word docs i've created on this particular subject

why not give me the color genetics of the breeding pairs Jac and Todd and let's take it from there
when i get home i'll be able to concentrate on this and chart it out

[KingstonTodd]

Originally Posted by Jac

Well, okay, NOW it makes a little more sense to me...I, too, wish they would be consistent in naming this...it is hard enough to wrap my brain around one concept but when they start calling it different things, I am lost!
This is very interesting! And, weird...because you say that the Agouti R96C is rare...but I just checked my dogs' PID records and I have three dogs with this! (No wonder I always get black!!)
Sooo, if a puppy from this type of litter is born black...will it CARRY the yellow?
Chase, my brown Poodle stud, carries:

Yellow +/-
Melanistic Mask +/-
Agouti R96C +/-
Brown G +/-
Brown H +/-

So, my question about Chase is 1) about the brown...since he has the two different types, what does that mean? 2) does his two browns make the R96C stronger than if he had two of the same brown or does that matter?

We say "aa" or R96C+/+ is rare because it is rare to have one and even more rare to have two, but also you have to have 2 to have it do anything, because it is recessive, and therefore it appears in the phenotype of the dog less often, carriers are not affected. About Chase, he only has one R96C, (+/-), or one "a" so he isnt passing recessive black to his puppies unless mated to R96C+/+, "aa", and even then he only passes his recessive balck agouti to 50% of his puppies, and unless the other dog has it as well, then its mostly not an issue, but you could check it out. Yes he carries yellow. Yellow is the default colour and all dogs have it, just some have it masked becasue they have "E". The presence of one E makes dark pigment and covers up yellow. Chase is Ee from his yellow test so 1/2 of his puppies get E from him, being dark pigment (brown), and the other 1/2 get "e" from his and could be yellow if the other dogs also gives "e". Any dark pigment from him is brown, but if the mama dog has black, all his brown is covered up and the puppies he passed "E" to are now black from mom.

We are in a similar situation with Hershey so we have had to select men carefully to get all chocolate She is Ee like Chase, but we mated her to EE so all the puppies had at least one E, 1/2 were Ee and half were EE and thus were all dark (chocolate in our case, since the stud was brown, not having any black to pass on). To get lighter pigmented puppies from Chase (or Hershey) you have to mate to a ee dog, that is not R96+/+. As for the brown gene, there is only one gene, but they have three test for it. By having +/- for two test I think it means he has two "b"'s which makes sense because he is brown. Now, he is bbEeaa(w), and Hershey is bbEeaa, so if they mated we would get bbEE 25% (brown), bbEe 50%, (brown), and bbee 25% (most yellow but possibly 25% of 25% "aa" or R96C +/+ recessive black). Cool. We should shedule a visit before they retire!

Originally Posted by Jac

Rosie, my UNRELATED golendoodle is:

Yellow +/+
Agouti R96C +/-

She and Chase produced a litter of 12 puppies...2 cream, 2 black and the rest apricot. I thought that the black came from Rosie, but could it have come from the Agouti instead? Does Rosie's black AND agouti make her more likely to have black pups?

YES, you almost have it, from her and Chase you would have 25% aa, or R96C+/+ recessive black.These puppies would be recessive balck if any puppies that are "ee". But none are "ee" since she gives at least one "E" to each puppy so no recessive black expression. But does she have any brown? I suspect not, and if not then because all the puppies are at least one E, the black/brown colour is from the B/b gene, and most goldens are B (black), so that is where the black is coming from. Her B is covering up Chase's b (brown) in most of the puppies, although they all carry brown.

Originally Posted by Jac

My other Agouti dog is Gerry (Chase's daughter), she carries:

Yellow +/+
Brown +/+
Agouti R96C +/-

So, is it possible that she could have all black pups??? (OMG please say it ain't so!!!)

I have a headache.

If you mate Gerry to a black dog, or a yellow with a black nose, you will get black puppies. if the yellow dog is BB, 100% black, if Bb (carry chocolate) 50/50 black and brown. MAte to brown, 100% brown. Again, because EE, all puppies have at least one E, therefore agouti recessive black is not an issue.

Did I help?

[Jac]

Thanks Todd...and this is a very interesting topic...hard for me, but interesting.
The only thing that I don't understand is when you said:

"Chase, he only has one R96C, (+/-), or one "a" so he isnt passing recessive black to his puppies unless mated to R96C+/+, "aa", "

Because Gerry is Chase's daughter and (I don't believe) that her mother carries the agouti...so didn't she HAVE to get that from Chase?

I am here to tell you that Chase is one fantastic dog! His pups are great!

[KingstonTodd]

Originally Posted by Jac

Thanks Todd...and this is a very interesting topic...hard for me, but interesting.
The only thing that I don't understand is when you said:

"Chase, he only has one R96C, (+/-), or one "a" so he isnt passing recessive black to his puppies unless mated to R96C+/+, "aa", "

Because Gerry is Chase's daughter and (I don't believe) that her mother carries the agouti...so didn't she HAVE to get that from Chase?

I am here to tell you that Chase is one fantastic dog! His pups are great!

Yup. Chase is a carrier, and is 50/50 if he passes it or not, and if the other parent is not a carrier/doesnt have it, then Gerry must have got it from Chase and Gerry is a carier too, like Chase.

[Jac]

hahahahaha...we just can't escape black!
But, you know, they are soooo beautiful...and now that I was thinking I didn't have many more black pups lined up, everyone is looking for black! ha! (I am amazed at the breeders announcing their new studs or new breeding stock and they are black!)

[CharlieBear's Mom]

I was browsing this and you guys might as well have been talking in greek -- sounds complicated