Pie bald axolotls

[Azhael]

As far as i know only my cousin and i have it. None of my living relatives do, and i don´t know of any case in my genealogy.
There are some cases of premature "grey" hair, but i don´t think that has anything to do with me.
In most piebaldism cases i´ve seen, both the hair and the skin of the affected area have depigmentation. In my case it´s only the hair, there´s no skin affected anywhere. I´m only saying that in case it makes a difference.

 

[oceanblue]

This is an intriguing thread with so much detail on genetics it's a bit overwhelming. Precious little is off topic.

There is still work to be done understanding the "White"/leucistic mutation. It is far more than a failure of cells to migrate, newly hatched leucistics are beautiful harequins if you look at them with a magnifiying glass. I believe some harlequins and piebalds are environmentally induced variants of leucistic or melanoid leucistic animals.

Pigment cells are derived from the neural crest. Their migration is closely linked with the cells which form the autonomic nervous system and it is not surprising that some pigment abnormalities are associated with autonomic nervous disturbance causing abnormalities such as megacolon.

Jake finds wonderful variants because he breeds large numbers and looks. "Chance favours the prepared mind"-Louis Pasteur. What the genetics are behind "Pirate" and relatives is still a an unsolved problem.

 

[Strogg999]

Azhael,

Have you explored the possibility that it could also be a simple case of mosaicism? It’s quite a common occurrence. This results in the person having two distinct populations of cells. In humans it can be expressed in several ways, for example, different skin textures, etc. Abnormal hair patterns where there are patches different hair colour, or of wooly or coarse hair, or even more porous and susceptible to UV light damage can be common. It maybe a type of hair heterochromia, caused through some somatic mosaicism for the genes affecting your pigmentation. If you are really curious you could visit a dermatologist who could examine it in detail and give you something more conclusive.


Oceanblue,


I’m currently a bit like a kid in a sweet shop researching axolotl genetics, and upto now I’m finding it fascinating, although I am finding some papers quite hard to get hold of. John recently sent me one on albino axolotls (once again, a big thank you!) which helped me out a great deal. The thread on “Pirate” is a great read and actually reminds me of a form of mosaicism found in gerbils. Its quite rare and only occurs alongside the spotting gene (so it’s happening alongside a mutation that causes a delay in pigment cell migration) and its effect is to produce a pseudo-tri-coloured animal. Although it doesn’t observe the normal Mendelian inheritance, once it appears in breeding lines it continues to pop up on a regular basis. In mammals there’s several ways of creating a harlequin phenotype with mutated genes, and all follow the normal Mendelian inheritance patterns, but with pirates I kind of lean to the fact it may be some form of mosaicism.
John mentioned that the particular harlequin strain being discussed earlier breeds true, but has health problems. What exactly are the health issues?
Ed

 

[Darkmaverick]

I would suspect it has something to do with ill thrift or weakened immunity.

 

[Dalabrae]

Firstly this thread is a fantastic read, even for my VB (programming language) addled mind (I just got home from an exam).

Just to add in regard to cats (I noticed we ar flinging about different animals :happy: ), in many Asian countries it is considered lucky for a white cat, blue eyed or otherwise but especially blue eyed, to have a black dot on it's forehead. Invariably these cats are not deaf and often the dot grows out. I've known of three such cats personally and none were deaf.

The first was a long(ish) haired (similar to an angora) that had green eyes, mother was also white and also not deaf, father was unknown.

The second is one of my current cats, Ebony, who has one green eye and one blue. And the last was Ebony's younger sister, from another litter, that had two green eyes. Their mother was a chocolate Burmese, and although with no proof other than looks and proximity, we think Ebony's father was a British Short Hair with the same mixed matched eyes.

After reading this thread I'm inclined to wonder if a similar trait is at work here, that is the black dot is a similar indicator to the coloured ears in the Dalmatians etc.

I am also aware that in cats the colour gene is carried on the X chromosome thus you can get bicoloured females (tortoiseshell) but not males, although this is disregarding somatic mosaicism. Another similarity to note, that tricolour cats (aka calico or tortoiseshell and white) is a form of piebaldism caused by the coloured cells developing from the neural crest and migrating as the skin forms, the white patches being where they fail to get into place before the skin finishes forming.

 

[Strogg999]

Hi dalabrae,

Yes it’s quite true that not all blue-eyed white cats are deaf. What you have to remember with the blue-eyed white cat is that (genetically) there’s several ways to produce them. For example, we know that the Dominant white gene in cats is a masking gene, so it will hide or mask the true pattern of the coat. Both WW and Ww produce a white coat no matter what their underlying genetics are. So you may have a cat that is blue-eyed, but this has been caused by a totally different gene. If your cat is also a colourpoint (say, having the Siamese coat pattern) the blue eyes may come from this source. It’s only problematic when the eyes are blue through the delay of pigment cells migrating from the neural crest, and it is this that causes the iris to lack pigmentation.
It should be noted though that the Dominant White gene in cats is variable in its effect, and as such there’s three possible eye colours. The first is normal orange eyes, odd-eyed, and blue. With odd-eyed, basically you can visually observe that the pigments have reached one eye but not the other. With orange, the pigments have migrated successfully. The third effect, the blue eyes, is often an indicator of problems and a proportion of these cats are deaf. These effects are well documented and are consistently produced, however like I’ve mentioned above there is quite a variable expression of this syndrome, so a white cat may only be mildly affected and have a white coat, orange eyes and normal hearing, where as at the other end of the spectrum the extreme expression of the gene may produce a white coat, blue eyes and deaf in both ears.
You are quite right regarding the “smudge” seen in kittens. This usually disappears as they age, but breeders use this as a guideline, and it seems statistically that these smudges indicate that they have received more functional melanocytes than their siblings, and as such they seem to be less severely affected.


With tortoiseshell you are talking about the O gene in cats. A similar gene in hamsters also exists ( “To” gene) which produces a very similar phenotype. These genes differ from all other colour genes because they are sex linked, so the mode of inheritance is different. Just quickly referring back to the blue-eyed white cat, in some animals the blue-eyed white trait is sex linked. This isn’t the case for cats and the trait occurs equally in both males and females. The gene is carried on an autosome ( a chromosome other than the X or Y sex chromosome)
In tortoiseshell cats, males do exist, but are exceptionally rare, and arise through mishaps in the transmission of the X or Y chromosomes. These males may have Klinefelters syndrome and carry an extra X chromosome, or may even be chimeras, which are the result of the fusion of two differently coloured embryos.
The tri-coloured cat is the result of combining two genes, the tortoisehell and the white spotting gene (S), which shouldn’t be confused with the Dominant white gene. In cats the S gene is very variable in effect. It is an incomplete dominant gene so SS cats will carry more white than Ss. However there is so much variability in its expression that breeders often find it difficult to distinguish between the two genotypes. With extreme expression of this gene in SS individuals, they may appear to have a fully white coat, and may also have blue eyes, but are rarely deaf.
Hope this helps,
Ed