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Breed
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Miniature Schnauzer
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The Disease |
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Type B1 Progressive Retinal Atrophy in Miniature Schnauzer is another PRA mutation which causes an early onset form of the disease with symptoms occurring within the first five years of age. This form of PRA is caused by a genetic variant in the HIVEP3 gene.
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Description |
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For some time Optigen, now GeneSeek, has been offering a marker test for Type B PRA in the Miniature Schnauzer. This test examines a genetic variant in the PPT1 gene, which has shown a correlation to symptoms of PRA in a scientific study (Murgiano et al). More recent scientific studies (Kaukonen et al) have now provided further insights:
- This study distinguishes two forms of PRA in miniature schnauzers: according to this study, there is an early form whose symptoms occur in dogs up to the age of 5 years and have a severe course. In addition, there is probably a late form whose symptoms occur in dogs over 7 years and have a mild course. Furthermore, this late form appears to be inherited X-linked.
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- For the early form, a genetic variant in the HIVEP3 gene was found that correlates to 100% in the study cohort and is presumably the causative variant.
The study also tested the PPT1 variant in the cohort. There were differences between the results for PPT1 and HIVEP3. All dogs with signs of the early PRA form showed the PRA/PRA genotype in both tests. However, there were also dogs that had the homozygous affected genotype for PPT1 but not for HIVEP3 and were symptom-free. This confirms that the newly discovered variant in HIVEP3 has a better correlation. Therefore, it is recommended to perform the new test according to Kaukonen et al.
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Trait of Inheritance |
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autosomal recessive
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Inheritance : AUTOSOMAL
RECESSIVE
trait
Sire
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Dam
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Offspring
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clear
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clear
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100% clear
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clear
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carrier
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50% clear + 50%
carriers
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clear
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affected
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100% carriers
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carrier
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clear
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50% clear + 50%
carriers
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carrier
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carrier
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25% clear + 25% affected
+ 50% carriers
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carrier
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affected
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50% carriers + 50%
affected
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affected
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clear
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100% carriers
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affected
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carrier
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50% carriers + 50%
affected
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affected
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affected
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100% affected
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Clear
Genotype: N / N [ Homozygous normal ]
The dog is noncarrier of the mutant gene.
It is very unlikely that the dog will develop Progressive Retinal Atrophy Type B1 PRA (HIVEP3). The dog will never pass the mutation to its offspring, and therefore it can be bred to any other dog.
Carrier
Genotype: N / Type B1 PRA (HIVEP3) [ Heterozygous ]
The dog carries one copy of the mutant gene and one
copy of the normal gene.
It is very unlikely that the dog will develop Progressive Retinal Atrophy Type B1 PRA (HIVEP3) but since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%. Carriers should only be bred to clear dogs. Avoid breeding carrier to carrier because 25% of their offspring is expected to be affected (see table above)
Affected
Genotype: Type B1 PRA (HIVEP3) / Type B1 PRA (HIVEP3) [ Homozygous mutant ]
The dog carries two copies of the mutant gene and
therefore it will pass the mutant gene to its entire offspring.
The dog is likely to develop Progressive Retinal Atrophy Type B1 PRA (HIVEP3) and will pass the mutant gene to its entire offspring
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Price
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£ 48.00 (including VAT)
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