News on John's Dwarf Gene?

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Karen S

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HI,

Saw a comment on the other thread (temp to perm) and that someone posted about the good news on John's Dwarf Gene research? Can you enlighten us all on what was said?

Thanks.

Karen
 

horsehug

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Maybe John will come on here and explain in scientific terms if he sees this.

He gave a wonderful presentation about his research over the telephone, at the AMHA convention.

But in laymans' terms he has made great progress in isolating the gene for the main type of dwarfs we normally see, and he said there is a "possibility" a test may be available by this summer of 2009.

Susan O.
 

Jill

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I was just thinking of his project and efforts a couple of days ago. I am very interested to hear news!
 

Leeana

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I was actually just reading over topics last night on the Dwarf forum as i had been thinking about that a few days ago as well, very interested to hear an update too
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JMS Miniatures

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This is HUGE for the breed. Hopefully both registeries will take a serious look at this and help fund it cause it is important. I believe AMHA already does.
 

Arion Mgmt

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Hello all.

Yes there was not a whole lot of "talk" after my report. There was quite an excited response at the meeting, but since I was on the phone, I coundnt tell much. I dont think the vast majority realized what I have finally accomplished. Below is the first abstract of my research to be presented at ESS (Equine Science Society) in May 29-31. This will be refined and expanded with my latest results this week (since the AMHA meeting). I have found the mutation and I am currently designing a test.

Once this work is finished this spring, I will hope to have it accepted to a genetics journal for print.

THere will be other papers along with this one that characterize the phenotypes of dwarfisms in the Miniatures with pathological examinations and characterizations. I hope to work on the other types as well to find those mutations on the side while I work on my PhD thesis, which is not on dwarfism. It is on an inherited reproductive abnormality in all horses.

Investigation of Dwarfism Among Miniature Horses using the Illumina Horse SNP50 Bead Chip.

J. Eberth*, T. Swerczak, E. Bailey; MH Gluck Equine Research Center/ University of Kentucky, Lexington, KY, USA

Introduction

Ponies and Miniature horses differ from full size horse only by their stature. Ponies are often defined as those whose height is not greater than 14.2 hands, however the maximum height for Miniature horses is constitutionally defined as 8.2 hands. This reduced stature is usually the cumulative effect of hundreds of genes, each having a small impact on stature. Unfortunately, there are also dwarfism genes which greatly reduce statute and may negatively impact health and reproduction. This is not considered a desirable genetic trait for Miniature horses. Therefore, the following studies were conducted to discover the genetic basis for dwarfism.

Materials and Methods

Pedigree records suggested that dwarfism occurs as a recessive genetic trait among miniature horses. Pathological examination, involving comparison of skeletal development and other phenotypic traits, suggested that there may be as many as four distinct types of dwarfism segregating among miniature horses. Indeed, among humans there are over 100 genetic mutations found responsible for different forms of dwarfism.

Type I dwarves exhibit cranial abnormalities of a disproportionately large head, large bulging eyes and eye sockets, a forehead with relative frontal domed prominence and a relatively short stubbed muzzle. An underbite of variable severity is commonly seen in this type however some have a normal bite. The midface is often small with a flat nasal bridge and narrow nasal passages and the airway obstruction can be "central" in origin (due to foramen magnum compression) or "obstructive" in origin (due to narrowed nasal passages). Symptoms of airway obstruction include snoring. Other characteristics are shortened limbs, enlarged joints, malformed or bowed legs with limited extension and flexion and overall disproportionate short stature. Progressive hoof deformities resulting from malformed limbs as well as progressive arthritis in the limbs become worse with age. Spinal abnormalities such as roachback may or may not develop later.

To avoid pooling samples from different genetic forms of dwarfism, horses were selected based on a common phenotype and belonging to a common family line. This phenotype was identified as Type I dwarfism of miniature horses. DNA was isolated from blood or tissues of 20 horses exhibiting type I dwarfism and from 20 relatives that did not exhibit the dwarfism traits. The DNA was tested using the Illumina Equine SNP50 bead chip. The results were analyzed using PLINK v 1.04.

Results

A single chromosome region was strongly associated with the trait. EMP2 (empirical P value, corrected for all tests) value of 0.019 was obtained, strongly supporting this candidate region. Within the candidate region a candidate gene was found which causes dwarfism among humans.

Discussion

The candidate gene is currently being sequenced for horses with the hope of discovering a mutation responsible for the trait. Additional work will entail identifying a haplotype signature for Type I dwarfism that could be used to estimate its frequency in the population and determine the phenotypic heterogeneity associated with this haplotype.

ACKNOWLEDGEMENTS

Morris Animal Foundation and the American Miniature Horse Association provided funds for this research.
 

Mona

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Thank you so much John for all your hard work to get this done for the Miniature Horse community! I for one will be sooooo VERY happy to finally have a test available to us breeders. I hope you will post back here with updates when you can. Thanks again!
 

rabbitsfizz

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John this is truly wonderful news and I look forward to the day when I can test every animal I own!!
 

kaykay

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This is awesome news!

I have always wondered though once there is a test what will breeders do with ones that test as a carrier?? What if the number of carriers is huge??

If you test your horse and it is a carrier is it going to be taken out of the breeding pool?? It could be a huge number.

I also wonder what the registries stand point will be. Will it be noted on the horses papers or ??

Please dont take me wrong I am thrilled that it is finally being done, but I do wonder what the repercussions will be.
 
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JMS Miniatures

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This is awesome news!
I have always wondered though once there is a test what will breeders do with ones that test as a carrier?? What if the number of carriers is huge??

If you test your horse and it is a carrier is it going to be taken out of the breeding pool?? It could be a huge number.

I also wonder what the registries stand point will be. Will it be noted on the horses papers or ??

Please dont take me wrong I am thrilled that it is finally being done, but I do wonder what the repercussions will be.
I wonder about that too. It will for sure be interesting thats for sure. I would hope there could be a place on the horse's papers. This is a serious topic and I feel like this test could make it better for the breed or make it worse, depending on the results of the tests. But we all want to make it better we need to get our animals tested.
 

Candice

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This is awesome news!
I have always wondered though once there is a test what will breeders do with ones that test as a carrier?? What if the number of carriers is huge??

If you test your horse and it is a carrier is it going to be taken out of the breeding pool?? It could be a huge number.

I also wonder what the registries stand point will be. Will it be noted on the horses papers or ??

Please dont take me wrong I am thrilled that it is finally being done, but I do wonder what the repercussions will be.

For so long everyone has wanted this testing available, it would be a shame and a tragedy for people to continue to breed horses known to be carriers. I think it is just awesome that John has made this level of progress.

Thankyou John,
 

targetsmom

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Thank you John for all your work on this and congratulations for getting your paper accepted. This is a phenomenal accomplishment!!!

I have a feeling that what will happen is that responsible breeders will test their animals and will heavily promote stallions that tested negative for the dwarf gene. I wonder if the dwarf and DNA tests should be done at the same time to show that it is the same horse? Anyway, I think when people start advertising their negative test results, silence will speak volumes.
 

Reble

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Well, as we know, the ones that test positive should not be bred with positive.

Other wise we know they do not become dwarfs?

Is this not correct, so this will just be like LWO positive.
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Now of course the ones that look dwarfs should never be bred as we all know.
 
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targetsmom

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Yes, I think it would be like LWO, as long as it is correct that it takes 2 dwarf genes - one from each parent - to produce a dwarf. So if you test your stallion and he is negative, you could breed any of your mares to him without worrying about a Type 1 dwarf. BUT you would need to test the foals, so it would probably be better in the long run to test your mares too.
 

Knighthawke

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I was wondering about that to. Will they put it on the papers like the AQHA does with HYPP.

If they do I assume the results will tell if it says they are +/- like some quarter horses are with HYPP then most people dont breed them but they still keep there papers because carriers look normal and could be shown but with breeding would be questionable.

But then if they limited breeding the carriers you never know how may off are previous national champions might carry it.

I think it would be great to know because they you could at least not breed positive to positive.

Which the arabian breed has a problem with I think it is called SID or CID and you dont want to breed to positive but they still breed positive but to a neg horse.

Time will tell?

Barb
 

sedeh

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I suspect if we tested all of our horses we would be surprised to see how prevalent this gene is. I don't think you'll be able to remove from the breeding stock all of the horses with the recessive gene. I do think that if we use this like the LWO test and not breed carriers to carriers the gene will become less prevalent over time.
 
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