How is PKD Inherited?
In humans, there are two modes of inheritance: autosomal dominant and autosomal recessive (with at least two, and possibly three different autosomal dominant forms of PKD caused by different genes at different loci). To date, only the autosomal dominant form has been identified in cats. To quote Dr. DiBartola, Professor of Veterinary Clinical Sciences at The Ohio State University College of Veterinary Medicine, and Co-Editor of the Journal of Veterinary Internal Medicine (one of the Dr. Biller’s co-investigators and a co-author of many of the published PKD research results): “While it is true that we do not know yet the actual gene for PKD in the Persian, there are some things to keep in mind: (1) in our experience, all affected cats have had at least one affected parent (this supports dominant inheritance) (2) two affected cats CAN produce an unaffected cat (this RULES OUT recessive inheritance) (3) the disease in humans (caused by either PKD1 or PKD2 gene defects) is known to be a do
PKD comes in two forms: autosomal dominant (ADPKD); and autosomal recessive (ARPKD). ADPKD is the more common form of the disease, and is the most common of all life threatening genetically inherited diseases. In ADPKD, an affected parent has a 50% chance of passing the disease off to each child. The gene is considered dominant because it has to come from only one parent to cause the disease. The disease does not skip generations, so if a grandparent has the disease but their child does not, then their grandchildren are not at risk of developing ADPKD. However, within a family, although the gene that causes ADPKD is the same, the disease will often follow a different pattern of progression in each person. Thus, it is difficult to predict what one family member will face based on what happened in older generations. Additionally, there is a 10% rate of spontaneous mutation for ADPKD. This means that 10% of the people with the disease did not acquire it from a parent, but had a gene mutat
PKD is the result of a single, autosomal, dominant gene abnormality. This means that:- – Every cat with the abnormal gene will have PKD; there are no unaffected carriers of the gene. – Every cat with PKD will have the abnormal gene, even if that cat only has a few small cysts in its kidneys. – A cat only needs one of its parents to be affected with PKD in order to inherit the abnormal gene. – Every breeding cat with PKD will pass the disease on to a proportion of its kittens, even if it is mated with an unaffected cat. – It appears that inheriting two copies of the abnormal gene, ie, one from each parent, causes such severe disease that the affected kitten dies before birth. All affected cats are therefore considered to be heterozygous (ie they carry one PKD gene and one normal gene). Why has PKD become so common? PKD doesn’t usually cause kidney failure until quite late in life, so an affected cat may have been used to produce a large number of litters of kittens before it becomes ill
AD-PKD is the result of a single, autosomal, dominant gene abnormality. This means that:- Every cat with the abnormal gene will have AD-PKD; there are no unaffected carriers of the gene. Every cat with AD-PKD will have the abnormal gene, even if that cat only has a few small cysts in its kidneys. A cat only needs one of its parents to be affected with AD-PKD in order to inherit the abnormal gene. Every breeding cat with AD-PKD will pass the disease on to a proportion of its kittens, even if it is mated with an unaffected cat. Inheriting two copies of the abnormal gene (one from each parent, ie, being homozygous) causes such severe disease that the affected kitten dies before birth. All affected cats therefore carry one AD-PKD gene and one normal gene (ie, they are heterozygous). How can I find out if my cat is affected? Testing for AD-PKD can be done in two ways. A gene test is available which accurately identifies all cats with the abnormal gene. This test can be run on a blood sample
Genetic studies in cats have shown that PKD in cats is autosomal (non sex linked gene) dominant. This means only one parent needs the gene to pass it onto the offspring. There is a 50% chance of a cat inheriting PKD if a parent has it. If a cat is genetically free of PKD it is not possible to pass it onto offspring.
