Message Number: YG3069 | New FHL Archives Search
From: Brett Middleton
Date: 2001-04-30 13:31:00 UTC
Subject: Re: Bob C: Albinism, Depigmentation, and Domestication

IANBC (I Am Not Bob C), but this is too much fun for me to resist.
Bob's answer will be even longer than mine, since I only have a single
weak copy of the lecture gene, but it's still probably as long as you
can stand. B-)

Regina J. Hart" <ferret@u...> wrote:
> In light of your discussion regarding depigmentation, is it possible
> for a ferret to express a depigmented pattern (e.g. blaze, mitt,
> panda, bib, etc.) without the presence of the Star Gene and/or
> Waardenburg's Syndrome?

Sure. But that doesn't mean that the resulting depigmentation isn't
associated with problems. There are lots of genes involved in the
development, structure and functioning of pigment cells, and any one of
them could have one or more alleles that result in some degree of
depigmentation. Since many (maybe even most) genes affect more than
one trait, an allele that causes depigmentation is likely to have other

White patterns associated with deafness are NOT always caused by the
genes associated with Waardenburg's Syndrome (WS). There are five
genes that are implicated in the different types of WS. These genes
are called PAX3, MITF, EDNRB, EDN3 and SOX10. However, most white
markings in domestic animals appear to be related to the KIT gene,
which is often referred to as the "S" ("spotting") locus in discussions
of coat-color genetics. White markings caused by alleles of this gene
are also associated with deafness, and can range from forehead markings
to extreme piebald patterns. For example, this is the gene that is
responsible for the coat pattern of Dalmatian dogs, as well as the high
incidence of deafness in that breed. (Question: has anyone actually
SHOWN that deaf ferrets with white markings are usually suffering from
WS, or have we just been going along with an assumption somebody once
made? My guess is that we've been using the term far too casually, and
that the KIT gene is largely responsible for blazes, pandas, etc.)

More about problems related to white markings below. But, first it's
interesting to ask if there exist any genetic mechanisms that can cause
depigmentation with NO associated problems. My guess on this would be
yes. There are a number of species that appear to exhibit some type of
depigmentation, but certainly aren't domesticated (no Star gene):
skunks have stripes, badgers have blazes, zebras are striped, and panda
bears are ... well ... panda. It seems unlikely that these patterns
would persist in the wild if they were associated with some detrimental
condition such as deafness, which means that the underlying genetic
causes are probably different than the common causes of depigmentation
in domestic animals. (OTOH, it is possible that these species derive
so much survival benefit from their coloration that it more than makes
up for a certain percentage of defective offspring. Somehow I find
this hard to believe, though.)

So, why aren't these "safe" depigmentation genes working in our
domestic animals? Darned if I know. They aren't all that common in
the wild, so maybe we just need to wait a couple million years for the
right mutation to show up. Or, maybe they *are* here, but we just
can't tell. For example, if I have two panda ferrets that aren't deaf,
how would I know if one was a mild case of WS while the other has some
"safe" genotype? Someday maybe there will be a Ferret Genome Project
and we will then have genetic tests that can tell the difference.

(I should also note that there is a difference between "depigmented"
and "white". If the hair is white but the skin can produce pigment,
then the animal is not depigmented. For example, Samoyed dogs are
depigmented, but polar bears are not, having black skin.)

> In addition to auditory and visual problems, what -if any- other
> problems are documented in Star Gene and/or Waardenburg's Syndrome
> individuals?

There are a zillion problems (scientifically speaking B-) associated
with various types of depigmentation. Failure of the neural tube to
close, cleft palate, enlarged colon, anemia, infertility, behavioral
disorders, reduced intelligence, limb malformations, problems with
balance, etc. It all depends on which gene or genes are causing the

There are some interesting aspects to hearing problems associated with
white markings, especially where the KIT gene is involved. For
example, I mentioned that this gene is involved with both spotting and
deafness in Dalmatians. However, the incidence of hearing loss in
Dalmatians with black patches on the ears is much lower. The KIT gene
is also responsible for the white head, belly, feet and tail switch of
Hereford cattle, yet I've never heard that deafness is a particular
problem for this breed. Note that Herefords have pigmented ears.
While I don't know what genes are responsible for the markings of panda
bears, I do note that they, also, have pigmented ears. This seems to
indicate that genotypes exist that allow pigment cells to migrate to
the ear during embryonic development -- resulting in normal hearing --
while restricting migration to the skin and coat sufficiently to
produce the white markings that many find desirable. Unfortunately, we
don't yet know how this works, though it probably involves some
modifier gene(s) that interact with the KIT gene. We also don't know
if ferrets are one of the species in which this could be accomplished.
(We also don't know how far we could go in eliminating deafness in
Dalmatians. Patches are considered a disqualification in the Dalmatian
breed standard! Talk about shooting yourself in the foot ...)

Behavioral problems associated with depigmentation are another
interesting phenomenon, and are related to all types of depigmentation
(such as albinism), not just those types caused by a lack of pigment
cells. For example, albino mice are known to be much more "emotional"
or "reactive" than pigmented mice. Viennese white rabbits are subject
to seizures. Pointer dogs suffering from the "nervous behavior" defect
tend to be highly depigmented. Holstein cows with large amounts of
white are more nervous and less productive. White pigs are more likely
to suffer from Porcine Stress Syndrome, which kills them when they are
subjected to stress or exertion. (It would be interesting to know just
how many of these phenomena are directly related to reduced auditory
and/or visual acuity. For example, I don't think anyone ever bothered
to check those nervous white Holstein cows to see if they were hard of
hearing or had bad eyesight. We certainly know that deaf ferrets
require special handling to avoid provoking fear and aggression.)

> OK, make that three - What is your personal opinion with regard to
> the breeding of these individuals?

I, myself, would not. As I see it, there are only two other choices:
breed them without regard for health (not very ethical), or embark on a
full-scale program to develop healthy strains of marked ferrets (which
would involve large amounts of inbreeding and ruthless culling, with
all the attendant heartbreak). All for the sake of a characteristic
that is of no particular benefit to the animals or the species. Look
at all the horrible things that have been done to so many breeds of
dog, cat and livestock -- all resulting from breeding programs that
treat animals as some kind of artwork to be molded according to some
abstract esthetic standard divorced from any concept of biological

The responsibility of breeders to consider the well-being of the animal
in their selection programs is an aspect of animal welfare that is too
often neglected. Too many people who would never consider beating or
starving their animals suddenly seem to lose all sense of ethical
limits when it comes to breeding them. Temple Grandin at Colorado
State University has written quite a bit on this subject, and her
articles are well worth the time to read. I recommend the following
two for starters:

> While I'm directing these questions specifically at Bob, I'd be
> really interested in hearing from anyone who can provide insight!

I'd like to hear what Bob thinks of the idea that H. Sapiens actually
qualifies as a domestic animal! We may very well have domesticated
ourselves before we started on the others. B-)

Brett Middleton brettm@a... (706) 542-0986
Asst Rsch Scientist Animal & Dairy Science University of Georgia

*SLMW 1.0* Animal Breeders do it with Frequency and Variation.