Graphic: corner
spacer
Graphic: corner
spacer spacer
nav left edge
nav right edge
spacer

Rod Cone Dysplasia Type 4      rcd4-PRA Test      Code 314

Test Pricing

For breeds: Australian Cattle Dog, English (& Llewellyn) Setter, Gordon Setter, Irish Setter, Irish Red & White Setter, Japanese Spitz, Miniature Poodle, Polish Lowland Sheepdog, Tibetan Terrier, Small Munsterlander and Standard Poodle

The research team at the Animal Health Trust (AHT) in the UK recently has identified a PRA-causing mutation in the C2orf71 gene in Gordon and Irish Setters from the UK and USA (1). Subsequently, this mutation has also been observed in additional PRA-affected breeds. OptiGen is pleased to provide the rcd4-PRA mutation test for all the breeds listed - and others upon special request where rcd4 may be suspected.

rcd4-PRA is a Late Onset PRA
The disease caused by the
C2orf71 mutation does not typically result in vision loss until dogs are in their senior years--beyond 7 years of age. The initial data cited in the AHT publication indicate that the average age of onset of PRA symptoms in dogs that inherit two copies of the C2orf71 mutation is 10 years of age however variation in age of onset is common in many forms of PRA and some dogs may not show symptoms of rcd4-PRA until they are 12 or older.

Prevalence of the C2orf71 mutation and how to best manage breeding strategies
The frequency of the rcd4-PRA mutation may be quite high in some breeds. Downs et al. estimated that 37% of Gordon Setters from the UK carry the rcd4 mutation. Gordon Setters from the USA were roughly half as likely to carry the mutation; 18% were reported as rcd4 Carriers. A research cohort of 136 Irish Setters from 8 countries showed 29% of Irish Setters carry the rcd4 mutation. No Irish Red and White Setters were observed carrying the rcd4 mutation however the test is made available to this breed given their close ancestry with Irish Setters. The high prevalence of the rcd4 mutation within some breeds, along with the typical late age of disease onset, calls for careful consideration as one weighs the importance of rcd4 in a breeding program.

Multiple forms of PRA exist in many breeds
As our understanding of the causes of PRA grows and new mutations are identified, it has become clear that many breeds are likely to harbor more than one form of inherited PRA. This is clearly the case with the Irish Setter where a very early onset of retinal degeneration is caused by another mutation, rcd1. Dogs that are homozygous (i.e. have 2 copies of) the rcd1 mutation typically become completely blind by the time they are ~1-2 years of age. In addition to the early rcd1-PRA and the late rcd4-PRA there are also uncharacterized cases of PRA in many breeds, including the Irish Setter. OptiGen welcomes the submission of blood samples form PRA-diagnosed pedigreed dogs and tests them at no charge as a part of our ongoing PRA research program. If you have a pedigreed dog that has been diagnosed with PRA, please contact genetest@optigen.com to inquire about OptiGen's Free DNA testing and PRA research. A recent chapter, "Genetic and phenotypic variations of inherited retinal disease in dogs: The power of within-and across-breed studies" by Miyadera, Acland & Aguirre provides a useful review of this topic (2).

Expected results for breeding strategies using the
 
rcd4-PRA test

Parent 1

Status

Parent 2 Status

Normal/Clear

Carrier

Affected

Normal/Clear

All = Normal/Clear

1/2 = Normal/Clear

1/2 = Carrier

All = Carrier

Carrier

1/2 = Normal/Clear

1/2 = Carrier

1/4 = Normal/Clear

1/2 = Carrier

1/4 = Affected

1/2 = Carrier

1/2 = Affected

Affected

All = Carrier

1/2 = Carrier

1/2 = Affected

All = Affected

Note that dogs with a Normal/Clear or Carrier genotype do not show symptoms of rcd4. Matings should aim to produce litters with the gray highlighted outcome, i.e. no rcd4-Affected genotypes. 

 References:

1.  Downs et al., Animal Genet. 2013 Apr:44(2): 169-77.

2. Miyadera et al., Mamm Genome. 2012 Feb,23(1-2):40-61.


spacer
Graphic: footer bar left
OptiGen®, LLC · Cornell Business & Technology Park · 767 Warren Road, Suite 300 · Ithaca, New York 14850
Tel: 607 257 0301 · Fax: 607 257 0353 · email: genetest@optigen.com or optigen@clarityconnect.com
Graphic: footer bar right
spacer spacer
spacer
spacer
spacer