White Cat/Blue Eyes

[a_loveless_gem]

Well I have heard about not getting a white cat with blue eyes due to them being prone to deafness. I have also read documentation about it but none answering my questions in full.

I'd like to know why they are prone to deafness. Is it just the white fur-blue eye combination that is prone to deafness or are there others? What are the proportion of the population of white cats with blue eyes that are not deaf? How does this compare with the cat population as a whole?

Thanking you in advance.

 

[kiwideus]

I am interested in the answer to this because I have a white cat with blue eyes who is deaf also.

Thanks!

 

[elizabeth a.]

Genes work through body chemistry (I'm not a biochemistry enthusiast, but I have to admit it's important!!). And nature is efficient, so genes often influence more than one aspect of body chemistry, we just don't always see these multiple effects.
It turns out that there is actually a layer of pigment cells in the ear, playing an integral role in hearing. So that dominant white gene, which tells all the pigment-producing cells in the body to stop doing their thing is also giving the same instructions to that cell layer in the ear. So...deaf white cat!
Now, cats can be white because of other genes, e.g., so much white spotting that we don't see any patches of color. Gnes like that are giving different instructions, so those cats are probably not going to be deaf.
I haven't seen statistics for populations, but I believe that most cats that have that dominant white gene are deaf.

 

[kiwideus]

Thank you! I love my white, blue eyed deaf cat - his name is Kahu and has the sweetest personality!

 

[a_loveless_gem]

Thank you! I study chemistry and delved a little into biochemistry but I'm no fan of it either.

 

[caterpillar]

Can white cats with green eyes be deaf? The only white cats that I've noticed have green eyes.

 

[elizabeth a.]

Yes they can!

 

[elizabeth a.]

I'm going to add something to what I said already about this white/deaf association.
There's the dominant white gene I've already described, and that can be associated with a lot of different eye colors.
But there's also the "blue-eyed white" gene that is in the same family as siamese and burmese, but recessive to both. This also causes deafness, I believe by changing something in brainstem development in the embryo.
So two different routes of action by two different genes, one recessive and one dominant, but resulting in the same phenotype for us: deaf white cats!

 

[Anne]

Just to add - not sure if this is true or not.

I read somewhere that the dominant white gene that makes white cats deaf by affecting the ear has a special way of displaying itself. As I understand, it's the same gene that creates the piebald pattern. I read that the effect of the while begins in the lower body parts and then moves upwards. So we are more likely to see cats with a white tummy and some color on their back, tail and top of the head. The reverse is usually not seen (a cat with a colored tummy and white back). If the gene displays itself all over the cats's body, including the very top of the head and tip of the tail, then it may or may not move on to affect the eyes. If it does, then we get a white blue-eyed cat. If it doesn't, then we may have a white cat with greeen or yellow eyes. Only then does it move on to effect the ears. If it hits the ears, then the cat is also deaf (as Liz explained, it effects a pigmented part of the hearing mechanism in the ear). So, you could have a blue eyed white that isn't deaf, but if the gene has gone as far as the eyes, you also have a chance of its having affected the ears.

Sometimes you get odd-eyes cats, where one eye is blue and the other is yellow. This means the gene had affected the side of the head with the blue eye, and possibly the ear on the same side as well. However, as it didn't effect the side with the yellow eye, the ear on that side should be ok as well.

This is what I've read a long time ago - not 100% sure it's true - but it did make sense at the time

They also said there are 3 types of genes that can create a totally white cat - so when you see a white cat you can't be sure it's one of the genes that may also cause deafness.

 

[elizabeth a.]

I'll see your 3 ways and raise you one!! You're totally right that there are many ways to get a white cat!
1. dominant white gene
2. blue-eyed white gene
3. true albino
4. really extensive white spotting
That last one is what you're talking about, and it's a totally different gene to the dominant white gene.
Spotting can cover so much of the body that you don't notice any colored hairs, so say the cat is white. The genes that it passes on for whiteness are spotting genes however, so it will produce very different litters to those produced by a dominant white.
Where spotting shows up is as you describe. It's all related to where pigment cells originate in an embryo (spinal area) and how they migrate as the skin is formed in the embryo. That spotting gene affects rate of migration somehow, so the most distant parts (tummy, etc.) don't get the pigment-forming cells. Remember, white isn't a color genetically, it's "no color"!