# Lethal white syndrome



## daisymay (Jan 7, 2013)

I have been assigned lethal white syndrome as a genetic research project for my Equine science class. Having been involved with horses for many years I was surprised that I have never heard of this before. I have started researching the topic and am absolutely shocked with the results. I can not believe I have never heard of this genetic disorder before! I have a few unanswered questions that I was hoping to get help with.
1. What is the genetic makeup of the foal with lethal white?
2. What is being affected genetically and physically?
3. Does it work under codominance or complete?
4. Is it plieotrophic?
Any information over lethal white syndrome will be greatly appreciated!


----------



## Dreamcatcher Arabians (Nov 14, 2010)

daisymay said:


> I have been assigned lethal white syndrome as a genetic research project for my Equine science class. Having been involved with horses for many years I was surprised that I have never heard of this before. I have started researching the topic and am absolutely shocked with the results. I can not believe I have never heard of this genetic disorder before! I have a few unanswered questions that I was hoping to get help with.
> 1. What is the genetic makeup of the foal with lethal white?
> 2. What is being affected genetically and physically?
> 3. Does it work under codominance or complete?
> ...


1. The foal will be homozygous for the frame overo allele (OO), they will not be affected if only heterozygous (nO) but will then be a carrier. 

2. This allele causes improper intestinal development, aganglionosis of the bowel. Thus the foal will die within 72 hrs, if not euthanized prior. It also causes the lack of pigment in the coat. 

3. See answer 1, it is recessive and requires 2 copies

4. Yes, the frame overo allele affects both coat color and the lack of intestinal development

From a paper on OLWS at K State:

What is OLWS?

This is a condition where a foal has inherited a recessive gene from both parents that encodes for a mutated protein located on some cells. The protein directly influences cells developing into color (pigment) and nerve cells. What this means is that OLWS foals are white (non-pigmented) and do not have normal nerve cells signaling to the intestines, because of the altered protein receptor. Ultimately, the result is a foal with little to no coat coloration (mostly or completely white) and cannot process milk, resulting in colic. 

Here's a link to the entire paper, it should answer your questions pretty thoroughly. 

College of Veterinary Medicine Veterinary Health Center


----------



## Chiilaa (Aug 12, 2010)

I just wanted to throw a spanner in the works here, if I may. LWO is a "fun" gene in that the "lethal" part is recessive, but the colour part is dominant. So for a lethal white foal to occur you need two copies, but the colour will display with just one.


----------



## Dreamcatcher Arabians (Nov 14, 2010)

Chiilaa said:


> I just wanted to throw a spanner in the works here, if I may. LWO is a "fun" gene in that the "lethal" part is recessive, but the colour part is dominant. So for a lethal white foal to occur you need two copies, but the colour will display with just one.


You're right, I zeroed in on the Lethal portion and forgot to metion the color portion.


----------



## daisymay (Jan 7, 2013)

Thank you!! You helped me greatly!


----------

