What is FN (Familial Nephropathy)?

FN disease is a juvenile-onset fatal kidney (renal) disease recognized in cocker spaniels worldwide. It has been associated with the breed for more than 50 years. 'FN' invariably is progressive & ultimately fatal; however, the rate of disease progression observed in affected dogs is more rapid in some individuals than in others.

Cocker Spaniels with 'FN' typically develop chronic renal failure between 6 months & 2 years of age, with eventual and sometimes rapid destruction of both kidneys.

Familial Nephropathy (FN) has been referred to in several ways: kidney failure, fatal renal disease, juvenile nephropathy, renal cortical hypoplasia, hereditary nephritis (HN) & Autosomal Hereditary Recessive Nephropathy (AHRN) in canines. The disease is also found in humans and is referred to as Alport Syndrome.

Symptoms

The early clinical signs (symptoms) are the same as those associated with chronic renal failure due to any other cause. These include excessive water consumption, excessive urine volume, pale urine, reduced growth rate or weight loss, poor quality hair coat, reduced appetite & unexplained vomiting.

Early in the disease course, a diagnosis can be difficult to determine as many renal diseases show identical symptoms. Definitive clinical diagnosis requires specialist examination of kidney tissue after the death of the dog. With the advent of a DNA test, dogs with renal symptoms can also be DNA tested to determine whether they are affected by Familial Nephropathy.

How FN is inherited

FN is inherited in an Autosomal recessive pattern in the cocker spaniel. This means the gene mutation responsible for FN is located on an Autosome (that is a chromosome that is not a sex chromosome) and FN disease results when the gene mutation is passed to the offspring by both the mother & the father.

As FN is inherited as a recessive trait, this means a mutant gene must be inherited from each parent in order to cause disease in an offspring. A 'carrier' has one disease gene and one normal gene, and is termed “heterozygous” for the disease. A 'normal' dog has no copies of the mutant gene and is termed “homozygous normal” – both copies of the gene are the same. Moreover, a dog with two disease genes is termed “homozygous affected” – both copies of the gene are abnormal.

DNA Testing For FN

Late in 2006, a new DNA test for FN (Familial Nephropathy) was developed by Dr. Lee's and his team at the A & M University in America. 

Two companies are licensed to perform DNA FN testing for Cocker Spaniels, OptiGen in the US and Antagene in France (for European resident dogs).

The OptiGen/Antagene FN test is a DNA-based test that accurately diagnoses a fatal kidney disease that occurs in Cocker Spaniels. The test also detects CARRIERS of this disease and clears dogs that are genetically NORMAL. Carriers have the potential to pass the disease onto their offspring & should therefore only be mated to CLEAR dogs to avoid the risk of producing affected puppies.

Antagene FN DNA Test Report & OptiGen FN DNA Test Report

The FN DNA Test

The FN DNA test is performed on a small sample of blood from the dog. Blood can be drawn from dogs of any age, cocker puppies need to be approx. 4 weeks old (in order they are ‘big’ enough to micro-chip & so that the blood draw is easier).

The DNA is extracted from the sample & is analysed for the gene mutation. The result of the test is a genotype - a fingerprint - that allows separation of dogs into three groups for Cocker Spaniels: Clear, Carrier and Affected.

The FN test can also be performed on a DNA sample collected via a cheek swab (Buccal Cheek Swab), however OptiGen do not recommend this method due to the risk of cross contamination. If using the cheek cells method, it is advisable that puppies are fully weaned and independent from their mother before sampling (in order that their mouths are not harbouring traces of their mothers DNA).

Our personal feelings are that FN is too devastating a disease to risk getting a false "Clear" due to contaminated DNA & we continue to opt for testing via blood samples. The risk of cross contamination is too common with DNA samples derived from cheek cells and we personally prefer to continue with testing via blood samples. The risk of cross contamination (from other dogs in our household) is totally removed and we can be sure that the results for our dogs are from their DNA and not their household companions!

Arranging The Test

Visit the Antagene website, open up the 'order' tab, check the price list & then download the 'Sampling Certificate' and 'Order Form'. Complete these, take the 'sampling certificate' to the vets for them to draw the blood or collect the cheek samples & for the vet to certify the sample and the dogs micro-chip number.  Once this is done, post the blood and the documentation to Antagene in France.  If you require cheek swabs, send an email to Antagene requesting them before you visit your vet for sample collection.

Cost Of Testing

The current cost to DNA test a dog for FN is (approximately £10 for the vet to collect the blood sample) and approximately £64 per dog to Antagene for the DNA test. Current test prices are listed on the Antagene website.

Results

Notes:

Although 'carrier' dogs are not at risk of developing FN themselves, if mated to another 'carrier' they WILL produce 'affected' offspring. Unless a 'carrier' dog is of particular merit or valuable to the gene pool, it is a recommendation that 'carrier' dogs do not form part of a breeding programme. The risk of any puppies sold going on to be bred (indiscriminately) by their new owners in the future is too much of a risk.

FN is inherited as a recessive trait. This means a disease gene must be inherited from each parent in order to cause disease in an offspring. A 'carrier' has one disease gene and one 'normal' gene, and is termed “heterozygous” for the disease. A 'normal' dog has no disease gene and is termed “homozygous normal” – both copies of the gene are the same, a dog with two disease genes is termed “homozygous affected” – both copies of the gene are abnormal. Although FN is inherited, it can be avoided in future generations by testing dogs before breeding.

For an explanation of Autosomal inheritance visit this page.

With Mendelian inheritance, there is the "Law of Independent Assortment.” In independent assortment, the chromosomes that end up in a newly-formed gamete (new puppy) are randomly sorted from all possible combinations of maternal & paternal chromosomes.

Because of the “Law of Independent Assortment” and because ratios are calculated in percentages, unless the same two parents produce 100 offspring together (probably impossible!!) the difference between expected outcomes and actual results can vary hugely due to the small sample size i.e. a litter containing 6 pups as opposed to 100 puppies!

If you mate, a "clear" to a "carrier" the expected ratio of "clear" to "carrier" offspring is 50/50, however it is possible that the entire litter could be "carriers"! Mate the same parents again & the next litter could be 25% "clear" and 75% "carriers,” mate the parents again and the entire litter could be "clear"! The inheritance of genes is a random process and in a small litter, all could be "carriers" or all could be "clear" (when mating "clear" to "carrier"). Therefore, do not rely on predicted outcomes when planning breeding's, always DNA test any offspring used for breeding unless both parents are 'Clear'.

To see Powerscourt FN test results please visit our health testing page.

Please visit our Cocker Spaniel Health Tests page for a list of testing schemes available for cocker spaniels.