From:
Sukie Crandall
Date: 2005-08-27 22:38:59 UTC
Subject: neural crest variant related medical disorders
To: ferrethealth@smartgroups.com
Message-id: <106C8B62-7A2A-49D4-943F-43C8ECDA9DD2@mac.com>
I was just out harvesting purslane seeds and talking with a neighbor
who is a human medical genetics counselor, and we got onto the topic
of the genetic variants to neural crest cells seen widely in
mammals. She said that among humans it is now considered very
established that the rate of cardiomyopathy (esp. hypertrophic) cases
is increased by such variants (and certainly that is documented in
other non-primate species).
Also -- and I did not know this -- in humans researchers have
recently found a connection of neural crest variations to some brain
development variations which can have medical consequences. (I'll
have to find out more on that some time.)
She said that the connection of neural crest variants to increased
rates of syndactyly and polydactyly is considered to be due to
improper neural development which alters fetal development.
The neural crest is a very early fetal cell set which later migrates
to multiple regions. (It is derived from the cardiac neural crest
which later becomes the neural crest and the cardiac crest that forms
the heart and major vessels, so you can see how very early these
changes happen and why how they express themselves varies greatly
among individuals.) The neural crest forms a great many nerves in
the body, as well as some ear structures, some mandibular structure,
some pigmentation cells, etc.
Some variations, such as the KIT oncogene, are thought to be involved
in a risk of increased malignancy rates.
Although we in the ferret community are used to thinking -- from
HABIT -- of Waardensburg syndrome for these ferrets, classical
geneticist, Dr. Brett Middleton has pointed out that for many the KIT
Oncogene is a better fit.
The cardiomyopathy increase may be due to differences in the cardiac
neural crest, but a new hypothesis is that the parasympathetic nerves
servicing the heart have been altered.
Ferrets who have neural crest variants can be spotted many times from
things seen throughout life (not added later) like jaws that will not
open fully, or possible poor innervation of the intestines, or eyes
set noticeably wider than normal on the skull, or white heads, or
head blazes, or extraneous white spotting anywhere on the body, etc.
(This is one reason that it would make sense to not consider any
ferret with white feet to be a "mitt". There is what appears to be a
totally different and safe pigment only marking type where the
ferrets have full mitts and bibs which are bilateral and cleanly
margined, and complete. The individuals may have one symptom or
many, and how badly the variation expresses itself over generations
is not consistent, so that a hearing blaze certainly can have kits
who will have a host of health problems.
I think I need to read at least one of the current embryology texts
(if I can afford to...) because it sounds like those would be most
useful for learning more.
Anyway, just a reminder that there is steadily increasing evidence in
a range of mammals that indicate that for health reasons a person
really does not want to breed panda headed or blaze ferrets.
Also, when you have such individuals (and at least 2 of ours clearly
have such markings -- interestingly our two who get cystine stones so
I should have asked if there is anything in human genetics med
counseling lit which would connect the two) it pays to have medical
exams and tests more often and start older age testing earlier, also
to look for hypertrophic cardiomyopathy (the harder type to find)
somewhat harder for these ferrets.
Sukie (not a vet)
Ferret Health List co-moderator
http://www.smartgroups.com/groups/ferrethealth
FHL Archives fan and regular user
http://fhl.sonic-weasel.org
International Ferret Congress advisor
http://www.ferretcongress.org