Breeds Affected: Samoyed, Siberian Husky
Samples Accepted: Blood, Buccal Swabs
Disease Information: XLPRA is adult-onset, usually diagnosed between 3 – 5 years of age. Starting off as difficulty seeing in low light, the disease progresses to complete blindness.
Inheritance Information: XLPRA is X-linked recessive, because the RPGR gene is located on the X-chromosome. Male animals with the mutation (which have only one X chromosome) are affected. Females may have one normal and one mutated version and be asymptomatic carriers.
The possible genotypes are:
XX This dog is a normal female.
XXPRA This dog is a carrier female. She is clinically normal, but will pass the mutation (XPRA) to 50% of her offspring. When bred to a normal male, she can have pups of all four genotypes: normal female (XX), carrier female (XXPRA), normal male (XY), and affected male (XPRAY).
XY This dog is a normal male.
XPRAY This dog is an affected male. If he lives long enough to reproduce, when bred to a normal female, all daughters will be carriers (XXPRA), but all sons will be normal (XY).
– Female offspring of a carrier female should be genetically tested to determine if they are normal or carriers (XX or XXPRA).
– Carrier females (XXPRA) should not be bred, because affected males can be produced.
– Affected males (XPRAY) should only be bred to normal females, and all female offspring should be tested to determine if they are normal or carriers (XX or XXPRA).
Test Information: This mutation test identifies a deletion mutation in the RPGR gene.
Zhang, Q., Acland, GM., Wu, WX., Johnson, JL., Pearce-Kelling, S., Tulloch, B., Vervoort, R., Wright, AF., Aguirre, GD.: Different RPGR exon ORF15 mutations in Canids provide insights into photoreceptor cell degeneration. Hum Mol Genet 11:993-1003, 2002. Pubmed reference: 11978759.
Further information is available at the Online Mendelian Inheritance in Animals website.