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Understanding and Working with the Vienna Gene

 

The gene responsible for creating the blue eyed white is called the Vienna gene and is expressed in genetic code as vv. This gene is believed to be neither dominant nor recessive, as it lies hidden in certain cases.  When you breed a BEW to a BEW, statistically speaking, you'll get 100% BEW.  However there are exceptions:

(1)  When Himalayan or REW lies hidden, you can get phenotype REW. 

(2)  If shaded, chocolate, or lilac lies behind the BEW you can get BEWs with a ruby cast pupil, and these offspring are not showable. You can, therefore, breed almost any color into your BEWs to improve type, with the exception of your shaded colors, chocolate, and lilac. These colors, and rabbits with these colors in the back ground, should be avoided to prevent the ruby cast pupil.  It has often been a misconception that breeding a REW to a BEW would cause a ruby cast.  This is not the case. A REW will not cause a ruby cast to a BEW’s eye as long as the REW is not hiding shaded, chocolate or lilac. REWs can be an excellent color to use to cross into your BEWs, but you must know what is behind them.

  When you breed any color beside BEW to BEW, you will get what are known as Vienna Marked (VM's) or Vienna Carriers (VC). A VM or VC is expressed in genetic code as Vv.   A Vienna Marked and a Vienna Carrier are genetically the same. They both carry only one Vienna gene. The distinction is that a VM is a rabbit that you can look at and clearly see he carries the gene because he will have white “marks” on him, and/or blue, or partially blue eyes.  On the other hand, a VC will have no outward marks.  There will be a problem if you breed  a VC/VM to a VC/VM cross. This crossing will result in some "normal" offspring, "Normal" refers to a non-Vienna carrying rabbit. There is no way to know which ones could be VC's that didn't get a white marking, and which ones are just plain normal without the Vienna gene. Any offspring from a cross like this should always remain in a BEW program or be sold as pets only.  Breeding one of these animals back into other colors is a big no-no. They will cause major problems for years in the lines with white spots and white nails. BEW is like a one-way street almost anything can come in, but nothing can go out. Should you sell a VC, VM, or possible VC to someone it is important to record on the pedigree that the animal has, or could possibly have the Vienna gene. It is also your responsibility as an ethical breeder to explain what this means to the person buying it.

Below is a chart that shows what you can statistically expect when breeding BEWs.  

                    BEW X BEW = 100% BEW (or REW masking BEW - This is still genetically a BEW)

                    BEW X "Normal" = 100% Vienna carriers, 0% BEW

                    Vienna Carrier X Vienna Carrier = 25% BEW, 50% Vienna carriers, 25% "Normal"

                    Vienna Carrier X BEW = 50% BEW, 50% Vienna carriers

                    Vienna Carriers X "Normal" = 25% Vienna Carriers, 75% "Normal", 0% BEW

 

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Want to go deeper?  Check out the article below:

 

Below is an article that was featured in the 2006 Spring Issue of the Dwarf Digest written by Jennifer Poeschl. It is reprinted here with permission from the Dwarf Digest editor at the time Sandra Wight. It is an excellent scientific explanation of BEWs and the Vienna gene. 

 

"In rabbits, there are two distinct and separate types of albinism. The first is the Ruby-Eyed White gene, found on the c series, which causes complete melanin restriction in fur, eyes, nails, and every other part of the body. This form of albinism can also restrict color to a greater or lesser extent across the body when it is found in a single allele on the c series. Blue-Eyed White is a form of incomplete albinism caused by the restriction of melanin across the majority of the body.

Melanin is formed in the melanosome organelle of the melanocyte. Melanocytes are found in the skin, hair follicles, and pigmented tissues of the eye. The melanin pathway consists of a series of reactions that converts tyrosine into 2 types of melanin, black-brown neumelanin and red-blond pheomelanin. Genetic mutations affecting proteins / enzymes along this pathway inevitably result in reduced melanin production.

The neuroectoderm of the primitive forebrain is the origin of Melanocytes in the retinal pigment epithelium, iris epithelium (anterior and posterior), and ciliary epithelium (outer pigmented and inner nonpigmented). The neural crest is the origin of Melanocytes in the iris stroma, cilliary stroma, and choroid. Melanoblasts from the neural crest migrate to the skin, inner ear, and uveal tract.

The epithelium does have Melanocytes present. The origin of these Melanocytes is different from the origin of the Melanocytes of the stroma in the case of the BEW, the blue pigment is derived from the melanin formed by the Melanocytes in the epithelium. The REW eye contains no pigment at all, which is the cause of the ruby eye.

The blue of the BEWs eyes is caused by the pigment being restricted in the stoma, with only the pigment in the epithelium remaining. In the case of the Vienna marked rabbits (those carrying only one v gene), the pigment across the entire body is not restricted, but only in certain portions. It's likely the melanin in the eyes is less likely to be restricted in the partial marked rabbits, so you typically only get the marbling or blue eyes when sufficient restriction across the rest of the rabbit occurs. Deafness is a common side affect in blue-eyed albinos across all mammalian species. The genes that restrict the melanin production seem to be closely linked to the genes that affect hearing.

The Vienna gene, when single, restricts a certain amount of melanin production in the rabbit's body and (in some cases) the eyes. It does not restrict all melanin production, and the melanin factors. Doubled, the Vienna gene restricts all melanin production from Melanocytes that originate in the neural crest. Melanin production from Melanocytes, that originate in places other than in the neural crest, are not restricted, which allows the blue eyes.

 

The REW gene, when doubled, restricts melanin production when coupled with most of the genes on the C series. Unlike the Vienna gene, it does not restrict melanin production totally in certain areas of the body, but acts as a sort of blanket that leaches a certain amount of the melanin across the entire body in general. This is how we get correctly colored Siamese Sables, for instance, and why Himalayans and chinchilla rabbits that carry REW tend to be washed out.

There is a misconception that BEW rabbits are "whiter" than REW rabbits. This is a false myth. The melanin restriction is more complete in the REW rabbit, as every source of melanin is restricted. The REW rabbit, however, is also not "whiter" than the BEW rabbit as the only source of melanin production in the BEW rabbit is in the neuroectoderm of the primitive forebrain, which affects ONLY the epithelium layer of the eye. Proof of this can be found in a REW rabbit which carries one Vienna gene. This rabbit does not present a "marbled" affect of white on white, despite the fact that the Vienna gene would create white patches on the rabbit if it had been colored.

Melanin restriction occurs with conception. At no time does an albino rabbit carry any form of color, and therefore it cannot be said that a REW which carries BEW is a "BEW" rabbit, any more than it can be said a REW rabbit that carries AA-BB-cc-DD-VV is a "chestnut" rabbit. As with all of our varieties, the rabbit is classified by its phenotype, (what you see) rather than by genotype, so a REW is a REW, despite what other genes it might carry. Record-keeping is, however, important, as it can be detrimental to many programs to insert REWs carrying the Vienna gene (single or double)."

2006 Spring issue of the Dwarf Digest written by Jennifer Poeschl.    

 

 

  Epilepsy / Seizures in BEWs

 

There are breeders who want to claim that epilepsy/seizures no longer exists in BEWs, that it has been bred out. That's just not true. In every single bloodline I acquired when starting with BEW Netherland Dwarfs I found epilepsy/seizures. It has been my experience breeders

don't like to talk about it. Lets face it no one wants to be the breeder to have others say "Oh their rabbits have seizures/epilepsy" but, the fact is it

happens. I have seen it in BEWs, VMs, and VC and no some of these animals were not inbreed at all. Some came from totally different lines. I have seen it happen more often in BEWs than VMs (this could also be because we produce more BEWs than VMs) and I have seen it in does more than bucks. I also believe that seizures are not limited to BEW NDs, as I have had people tell me that it has happened with their NDs and where there was no BEW in them.

 

My experience and thoughts on epilepsy/seizures in BEWs doesn't indicate line breeding is a contributing factor. The majority of the lines I purchased when I started were unrelated lines going back 3-4 generations. One line was line bred, but I didn't experience an increase in epilepsy/seizures in this line over the others. In developing my own herd of BEWs I have line bred and haven't noticed an increase in the occurrence of epilepsy. I have found line breeding important in developing a strong line of BEW Dwarfs.

 

I have done research on the subject and found several sites which mention seizures/epilepsy in rabbits. The first site I think is important because it states idiopathic epilepsy has been observed in white furred, blue-eyed rabbits. Idiopathic epilepsy is a specific term referring to a seizure disorder that has no identifiable cause. It is also referred to as genetic or congenital epilepsy. The terms epilepsy, seizure, fit or convulsion

all mean the same thing, the physical manifestation of a sudden, excessive electrical discharge of neurons in the brain that results in a series of involuntary contractions of the voluntary muscles, abnormal sensations, abnormal behaviors, or some combination of these events.

 

Idiopathic epilepsy is found in most species including humans. A close friend suffered from a rare epilepsy/seizures as a young child. Her Dr. thought she would grow out of it, which she did in her early teenage years. I've noticed most of my rabbits which exhibit epilepsy/seizures are young juniors in growth stages and rarely do they seizure as an adult unless under stress. One of my does will have an epilepsy seizure when she is three weeks pregnant. This is a time when her body is under increased stress from the growing kits. I give her added B vitamin, house her in a cage where she can see the door so she isn't startled by me entering the rabbitry and keep a radio on. It seems to help her not become startled and most of the time I avoid her having an episode.

 

Here is some of the research I have done on the subject.

 

www.medirabbit.com/EN/Neurology/seizure.htm

 

forums.petlovers.com/vb/archive/index.php/t-16043.html

 

This article below comes from the Merck vet manual and is most interesting. It's about gerbils, but I've found in my herd the more the kits are handled from birth the less likely mine are to show signs of seizure. 

 

"Epilepsy (Seizures): Gerbils may develop spontaneous epileptiform seizures. Precipitating factors include sudden stress, improper handling, or introduction to a novel environment. The incidence is reported to be 20%. This condition appears to be inherited and related to deficiency of cerebralglutamine synthetase . Clinical onset begins in 2- to 3-mo-old gerbils, with seizure incidence and severity increasing up to 6 mo of age, after which occurrences decrease with age. Seizures last several minutes and range from mild hypnotic episodes with twitching ears and whiskers to severe myoclonic convulsions with extensor rigidity. Mortality is rare and there is no permanent damage. A refractory period of ≤5 days can follow more severe seizures. Seizures can be suppressed in genetically predisposed gerbils" if they are frequently stimulated by handling during the first 3 wk of life.Anticonvulsant therapy is unnecessary. " - Merck Vet Manual

 

We do believe in using colored dwarfs of quality to produce VMs & VCs. This is important to improve type and create new bloodlines, but personally I do not believe this helps with seizures/epilepsy issues. This is just my opinion in what I have experienced over the years. I believe that the Vienna gen and the dwarf gen combined plays a large roll in seizures/epilepsy issues. Again just my opinion and I do not have scientific data to back it up.

 

I do want to point out that I many people make this in to a huge issue. I do not feel this way. I see this as a rarity,that happens. One animal may have one as a baby (going through a growth state) and then never have one again as an adult. I view it much like Maxfactors, and peanuts. We are breeding a DWARF which in it's self has all kinds of abnormalities.

 

I have never seen a rabbit die from having a seizures or epilepsy episode. The seizures or epilepsy episode are normally very short 10 to 60 seconds. I have seen them range from a grand mal seizure being very violent, to a petit mal seizures where it was just a small facial twitch and hardly noticeable. In both cases the rabbit is totally back to normal in a matter of minutes. Seizures seem to be "triggered" when the rabbit becomes startled, by a noise or action during times of high stress, or growth.  I have never seen it be quite in the barn and a rabbit just go into a seizures/epilepsy episode.

 

For me the occurrence of epilepsy/seizures isn't great. In my opinion and experience it's a reality of BEW Netherland Dwarfs, but nothing in my opinion to be alarmed about. I do believe that it is something to be aware of and it's time it was talked about in the open. This subject has been very taboo for a long time. I know I have felt that way about it, but I don't think it betters our breed or variety to try and pretend it has all been bred out and no longer happens. I encourage you to visit the links I have provided and do some of your own research on the subject. The more we learn the better we can make our breed.