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Notes from web browsing instead of finishing my talk for the ECNR
Ear shape: The dumbo mutation produces a wide variety of ear shapes and sizes. Most desirable among pet rat breeders are large, round, low-set ears. But the dumbo mutation may also produce creased, bent, folded, wrinkled, curled, misshapen, narrow, pointed, oblong and tubular ears. Ears may be positioned higher or lower on the skull. Ears may also be asymmetrical.
Skull shape: The top of the skull may be flat and broad. Some dumbo skulls may be concave. Skull may have a prominent occiput (back of skull), which may give the rat a hunchback appearance.
Jaw shape: Some dumbos may have have a small lower jaw.
Eye shape: Some dumbos may show differences in eye shape and position (pers. comm. Dann 2005).
Body shape: Body may be stocky.
Ear movement: some owners report that their female dumbo rats do not vibrate their ears when they are in heat (pers. comm. Dann 2005).
Temperament: Dumbos are reputed to have a docile, calm temperament.
This really makes me think of cleidocranial dysplasia combined with Goldenhar syndrome (fused cervical vertebrae and small, low-set ears).
This is what I wrote to the webpage owner:
I stumbled quite by accident, when preparing a course on facial development, on your page devoted to the dumbo rat (http://www.ratbehavior.org/DumboRatMutation.htm).
First, my sincere congratulations on your resume of pharyngeal arch diseases and your setting forth your hypothesis online.
Have other developmental biologists contacted you about this mutation?
The phenotype bears a great deal of similarity to cleidocranial dysplasia, which is caused by mutations in the Runx2 gene. All except the ears, and the teeth problems found in people that I think could cause some problems for the rat, except that rodent dentition is fairly different and less crowded. There are some related syndromes that are covered here and which may be relevant, although looking closer at the Crane-Heise syndrome, most of these lead to very severe phenotypes that also affect the body skeleton.
One possibility is that there is a deletion or insertion in the rat chromosome 9q region that affects Runx2 activation specifically in the head. Vegfa is right nearby, and is involved in vascular development. Some features of your rats resemble the Goldenhar syndrome, as you pointed out already, which might be a vascular development problem of one of the anterior pharyngeal arteries.
Well, it's fun to speculate.