by Margret Casal, med. vet, PhD Section of Medical Genetics Veterinary Hospital of the University of Pennsylvania  What happens to the blood samples that you have been collecting and sending to the
Section of Medical Genetics at the Veterinary Hospital of the University of Pennsylvania? The
goal of this project is to find the cause of the seizures in the Irish Wolfhound. Since we are
dealing with a genetic disease, the answer lies in the DNA. More specifically, there is a
mutation (alteration) in one or several genes that is responsible for this type of epilepsy.There are about 80,000 genes that make up every individual's DNA and each gene
codes for a specific protein. Proteins are not only the building blocks of almost everything in the
body but they are also responsible for regulating biochemical processes. Therefore, it is
possible that a defective gene may lead to a malformed or absent protein resulting in disease.
For example, a single gene is defective in SCID (severe combined immunodeficiency; the
disease that the boy in the bubble had) and although as a result just one single protein is
missing, the disease is very severe as the affected children and dogs have no immune system.Unfortunately, we don't know which genes cause seizures. Therefore, we have to scan
the whole genome (all of the DNA) to find the defect. When we receive blood samples (see
picture), the blood is centrifuged to separate the white blood cells from the serum and the red
blood cells. The white blood cells contain nuclei, which in turn contain DNA. Thus, the walls of
the white blood cells and the nuclei must be broken down (lysed) to release the DNA. Then the
DNA sample is washed and processed to eliminate cell walls and other proteins. Finally, the
sample is treated with chemicals to precipitate (concentrate) the DNA so that it can be used for
analysis. Although this process may sound simple, it is a sophisticated method that took years
to develop. The sample must be handled very carefully and many different chemicals are used
at exactly defined concentrations in order not to damage the DNA. Today, we are fortunate to
have some of the chemicals available prepared and premixed, but it still takes one-and-a-half to
two days to extract high quality DNA necessary for genetic analysis.But this was the easy part. Part 2 and Part 3 will describe the tests and experiments
needed to find the defective gene(s) responsible for the Irish Wolfhound type seizures. In the
meantime, keep sending those blood samples from normal and affected dogs; the more we
obtain, the quicker we will able to find the cause of the seizures.
For inquiries regarding submission of blood samples, contact: Anne Janis PO Box 928, Fayetteville, GA 30214  |
