Maand: juli 2017

DNA NADDNA NAD

Neuroaxonal Dystrophy Papillon Type (NAD)

Neuroaxonal dystrophy Papillon type (NAD) is an inherited neurodegenerative disorder affecting the Papillon dog breed. It is a type of lipid storage disorder that primarily affects the nervous system.  NAD has been diagnosed in various mammalian species, including humans, dogs, sheep, cattle, horses, cats, rabbits, rats and mice. Different NAD affected species share same pathological feature, which includes ”spheroids” in the central nervous system, but affected animals differ in time of symptoms’ onset and genetic mutation. In dogs, NAD has been recognized in several breeds, such as Rottweilers, Collie sheepdogs, Papillons, Jack Russell terriers, Spanish Water dogs etc. Among these breeds, NAD causative mutation has been so far identified only in Spanish Water dogs. Recent research has identified the NAD causative mutation also in Papillons, enabling performance of DNA test in order to recognize carrier and affected dogs.

Characteristics and Symptoms

Affected Papillons show symptoms of NAD from an early age, starting as early as 4 months of age. Symptoms include loss of coordination, such as wobbling gait and inability to stand upright (astasia). At 6 months of age neurological symptoms develope, which include blindness, loss of menace response, tremor and development of crossed eyes (strabismus). MRI examination shows cerebellar atrophy, with intact other regions of nervous system. With further disorder’s progression, dog shows difficulty while eating. Due to the low quality of life, affected dogs are usually euthanized at owner’s request.

Histopathological examination revealed a number of axonal spheroids throughout the central nervous system (CNS), including the thalamus, hippocampus, mesencephalon, cerebellar cortex, cerebellar nuclei, medulla oblongata, and dorsal horn of the spinal cord. The number of Purkinje cells in the cerebellum was moderately decreased. A few spheroids may be as well present in the optic nerve.

Genetics

Neuroaxonal dystrophy Papillon type (NAD) is caused by a mutation in the PLA2G6 gene. NAD in Papillons is inherited in an autosomal recessive pattern. Healthy parents of affected puppy are obligate heterozygotes, and therefore carry one mutant allele. Heterozygotes have no symptoms. Dogs homozygous for the mutation will display the symptoms of the Neuroaxonal Dystrophy PapillonType (NAD). At conception, when mating two carrier dogs, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.

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PRA 1PRA 1

Common Symptoms

Progressive retinal Atrophy, PRA1 (papillon type) is an adult-onset, inherited eye disease affecting papillons. Progressive retinal atrophy, PRA1 (papillon type) occurs as a result of degeneration of the Rod type Photoreceptor Cells of the Retina, which are important for vision in low light. Affected dogs typically present between 4 to 6 years of age with poor vision in dim light. On a veterinary eye exam affected dogs have changes in reflectivity and appearance of a structure behind the retina called the Tapetum as well as thinning of the retinal blood vessels, signifying decreased blood flow to the retina. Progressive retinal atrophy, PRA1 (papillon type) is slowly progressive and some affected dogs maintain vision in daylight for many years, sometimes for the remainder of their life.


Breed-Specific Information for the Papillon

The Mutation of the CNGB1 gene associated with progressive retinal Atrophy, PRA1 (papillon type) has been identified in the papillon. Though the exact frequency in the overall papillon population is unknown, 17.2% out of 145 papillons and the closely related breed phalenes from a randomly selected population from Finland had one copy of the mutation and were therefore carriers of the mutation.


Testing Tips

Genetic testing of the CNGB1 gene in papillons will reliably determine whether a dog is a genetic Carrier of progressive retinal Atrophy, PRA1 (papillon type). Progressive retinal atrophy, PRA1 (papillon type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the CNGB1 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Papillons that are not found to have this specific mutation have no increased risk of having affected pups. However, because there are multiple types of progressive retinal atrophy caused by mutations in other genes, a normal result in CNGB1 does not exclude progressive retinal atrophy in a pedigree.

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Angel, Bella, Leandra, Andy en Kay vrij getest van NADAngel, Bella, Leandra, Andy en Kay vrij getest van NAD

Helemaal blij, Angel, Bella, Leandra, Andy en Kay zijn middels DNA vrij getest van NAD. NAD staat voor NEUROAXONAL DYSTROPHY. Neuroaxonale Dystrofie is een erfelijke, neurodegeneratieve ziekte. De ziekte heeft invloed op de zenuw axonen in de hersenen en andere delen van het lichaam. NAD is blijkbaar geassocieerd met een abnormale opbouw van stoffen door het zenuwstelsel, waardoor ze voorkomen dat ze werken zoals ze zouden moeten. Door middel van DNA is uit te sluiten of Papillons Leider, drager of vrij zijn en gelukkig zijn onze Papillons door middel van de DNA test uitgevoerd door Laboklin allemaal vrij.

Voor wie zich afvraagt wat NAD is, hieronder een beschrijving (helaas in het engels)

http://www.pcagenetics.com/ARTICLES/074-NAD-Neuroaxonal-Dystrophy.pdf

Een filmpje van NAD bij een Papillon

https://www.youtube.com/watch?v=ECMCk1Ysu9M

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