We chose to test to better our understanding of our horses and to make appropriate breeding choices for our horses.
http://www.animalgenetics.us
Polysaccharide Storage Myopathy (PSSM1) In Gypsy Horses
PSSM1 Study funded by the GVHS with the University of Kentucky.
In order to obtain an estimate of the frequency of the PSSM1 mutant allele in horses registered with the Gypsy Vanner Horse Society, 100 hair samples were selected at random from the GVHS database, spanning the years 2003-2015. Samples were tested using the TaqMan assay system for the G>A SNP in exon 6 of the GYS1 gene. Of the 100 samples, 76 had a normal genotype of N/N and 24 tested as heterozygous N/PSSM1. This translates into 176 normal alleles and 24 mutant alleles, giving an allele frequency of 88%
normal and 12% mutant. We did not find any samples that were homozygous for the mutant allele. Using these observed values of allele frequency, our Hardy-Weinberg calculation of the EXPECTED genotype frequencies in the total population are as follows:
Expected genotype frequency for N/N: 77.44%
Expected genotype frequency for N/PSSM1: 21.12%
Expected genotype frequency for PSSM1/PSSM1: 1.44%
Therefore approximately 1 in 5 horses can be expected to be heterozygous for the mutation,
and 1-2 horses per 100 horses can be expected to be homozygous for the mutation.
Kathryn T. Graves, PhD
Director
University of Kentucky Animal Genetic Testing and Research Lab
Upon reviewing the results of this study, the GVHS has contacted the University of Minnesota Equine Center Neuromuscular Diagnostic Laboratory, for their direction on next steps to conduct the scientific research to fully understand what this means for the Gypsy Vanner Breed. More information will be forthcoming once the particulars of this further study have been finalized. GVHS management has finalized an agreement with the University of Kentucky to offer PSSM1 testing to GVHS owners as part of specially priced testing "bundles". Until more study is completed this caution from Dr. Graves still applies: "Please advise your breeders and owners to wait until a scientific estimate of frequency is available and work together to decide how PSSM1 will be dealt with in your breed before valuable breeding stock is lost."
Following is a statement from Animal Genetics lab located in Florida:
We now have several examples of horses that have tested positive genetically with 2 copies of the mutated gene and have had episodes of tying up, muscle stiffness,
sweating, and reluctance or inability to move. Muscle biopsies of these horses were collected during these episodes by veterinarians for further testing. In all cases, muscle
biopsy results of affected horses showed a dramatic accumulation of excess glycogen and abnormal polysaccharides. All symptomatic horses were homozygous for the
genetic variant. In this relatively small study (roughly 50 horses) all horses with 1 copy of the mutated gene did not exhibit any clear symptoms. However, several
horses did show elevated levels of glycogen in muscle tissue samples compared to those horse that tested negative for the genetic mutation. **In each case the symptomatic horse was properly managed through restricted diets and increased regular physical activity. Symptoms related to PSSM1 in all horses decreased or went away completely with in a relatively short period of time. We hope to be able to continue to evaluate all effected horses in the future to help us better understand the condition. Further work and more details will be published in the future but Animal Genetics wanted to get this out to people who have been waiting for information about PSSM1 in Draft breeds like the Gypsy horse as soon as we could. ** It is our opinion that in almost all cases the effects of PSSM1 in Gypsy horses can be managed if the condition is identified properly. Animal Genetics will continue to work with breeders and veterinarians to better understand the condition and identify additional genetic factors that may influence a horse with two copies of the mutated gene.
Foal Immunodeficiency Syndrome (FIS)
Description:Fell Pony syndrome or Foal Immunodeficiency Syndrome (FIS) is a recessive genetic disease that primarily affects two relatively rare native UK pony breeds, the Dales and the Fell pony. FIS is caused by a single mutation in the sodium/myo-inositol cotransporter gene (SLC5A3). This gene plays a vital role in the regulatory response in many tissues including lymphoid tissues. As much as 10% of all Fell ponies born each year suffer from FIS. This has put a strain on the long-term survival of this breed as well as the likely spread of FIS into other breeds. Most recently Animal Genetics has found the mutation that causes FIS in approximately 9% of Gypsy horse breeds in the US and Europe.
Foals must have two copies of the mutated gene in order to be affected with FIS. Therefore, each parent must be a carrier of the mutated gene in order to have an affected foal. Affected foals appear healthy and normal at birth but begin to show signs of weakness, dull coat and anorexia at 2-3 weeks. The first clinical signs of this disease include diarrhoea, nasal discharge, poor growth, pale gums and decreased appetite. Vision may be affected, presumably due to secondary bacterial infections. Mortality rate for foal affected by FIS is 100% despite intensive treatment. All FIS affected foals generally die or are euthanized before they reach the age of 3 months.
FIS is an autosomal recessive trait, meaning a foal can only be affected if the foal inherits the disease from both parents. Parents that are carriers do not have any symptoms associated with FIS. However, they will pass on a copy of the defective gene to their offspring 50% of the time.
Animal Genetics offers DNA testing for both the FIS mutation found in Dale and Fell Pony as well as any horses with Dale and Fell Pony blood lines.
Breeds Affected:Dale Pony, Fell Pony and Gypsy horse breeds well as any horses having Dale and or Fell Pony blood lines.
Test Results:Animal Genetics offers DNA testing for Foal Immunodeficiency Syndrome (FIS). The genetic test verifies the presence of the mutated SLC5A3 Gene and presents results as one of the following:
Color Testing
Base Color Every horse has a base color, which can be black, bay, or red. This is controlled by the Extension (Red/Black Factor) and Agouti genes. The Extension gene controls the production of black or red pigment throughout the coat. The allele for black color (E) is dominant over the red allele (e), so a horse only needs one copy of the black allele to appear black-based.
The Agouti gene can then modify black pigment by pushing it the the points of the horse, creating a bay. The Agouti gene is dominant, so a black pigmented horse only needs one copy of the Agouti gene (A) to appear bay. Agouti does not have any effect on red pigment.
There may be some variation in the intensity of the base colors, for example, dark bays compared to light bays or liver chestnuts to sorrels. This could be caused by a variation in the expression of the genes or interaction of other genetic factors.
Dilutions The rest of the color genes act as modifiers on the base coat of the horse. There are several genes that dilute the color of the horse, including Cream, Pearl, Champagne, Silver, and Dun. While these genes all function to dilute pigment, they are not all expressed in the same manner. The Dun and Champagne genes are dominant, as is Silver, although Silver does not affected red pigment. The Cream gene is incompletely dominant, meaning you will see different effects with the number of Cream genes present, and the Pearl Gene is recessive. The Cream and Pearl genes do have additive effects, so color testing can be an important tool to determine the correct color of a horse and what it may be able to pass on. The Grey gene causes a horse to 'grey out' over time, and is dominant, although homozygous horses tend to grey out faster. It is thought that there are other color modifiers, such as Flaxen or Sooty, but the genetic basis to these colors have not yet been determined.
Patterns and depigmentation. The pattern genes also modify the color of the horse by deleting color. These genes include Frame Overo, Splashed White Overo, Sabino1, Tobiano, Dominant White, and Leopard Print or Appaloosa.
http://www.animalgenetics.us
Polysaccharide Storage Myopathy (PSSM1) In Gypsy Horses
PSSM1 Study funded by the GVHS with the University of Kentucky.
In order to obtain an estimate of the frequency of the PSSM1 mutant allele in horses registered with the Gypsy Vanner Horse Society, 100 hair samples were selected at random from the GVHS database, spanning the years 2003-2015. Samples were tested using the TaqMan assay system for the G>A SNP in exon 6 of the GYS1 gene. Of the 100 samples, 76 had a normal genotype of N/N and 24 tested as heterozygous N/PSSM1. This translates into 176 normal alleles and 24 mutant alleles, giving an allele frequency of 88%
normal and 12% mutant. We did not find any samples that were homozygous for the mutant allele. Using these observed values of allele frequency, our Hardy-Weinberg calculation of the EXPECTED genotype frequencies in the total population are as follows:
Expected genotype frequency for N/N: 77.44%
Expected genotype frequency for N/PSSM1: 21.12%
Expected genotype frequency for PSSM1/PSSM1: 1.44%
Therefore approximately 1 in 5 horses can be expected to be heterozygous for the mutation,
and 1-2 horses per 100 horses can be expected to be homozygous for the mutation.
Kathryn T. Graves, PhD
Director
University of Kentucky Animal Genetic Testing and Research Lab
Upon reviewing the results of this study, the GVHS has contacted the University of Minnesota Equine Center Neuromuscular Diagnostic Laboratory, for their direction on next steps to conduct the scientific research to fully understand what this means for the Gypsy Vanner Breed. More information will be forthcoming once the particulars of this further study have been finalized. GVHS management has finalized an agreement with the University of Kentucky to offer PSSM1 testing to GVHS owners as part of specially priced testing "bundles". Until more study is completed this caution from Dr. Graves still applies: "Please advise your breeders and owners to wait until a scientific estimate of frequency is available and work together to decide how PSSM1 will be dealt with in your breed before valuable breeding stock is lost."
Following is a statement from Animal Genetics lab located in Florida:
We now have several examples of horses that have tested positive genetically with 2 copies of the mutated gene and have had episodes of tying up, muscle stiffness,
sweating, and reluctance or inability to move. Muscle biopsies of these horses were collected during these episodes by veterinarians for further testing. In all cases, muscle
biopsy results of affected horses showed a dramatic accumulation of excess glycogen and abnormal polysaccharides. All symptomatic horses were homozygous for the
genetic variant. In this relatively small study (roughly 50 horses) all horses with 1 copy of the mutated gene did not exhibit any clear symptoms. However, several
horses did show elevated levels of glycogen in muscle tissue samples compared to those horse that tested negative for the genetic mutation. **In each case the symptomatic horse was properly managed through restricted diets and increased regular physical activity. Symptoms related to PSSM1 in all horses decreased or went away completely with in a relatively short period of time. We hope to be able to continue to evaluate all effected horses in the future to help us better understand the condition. Further work and more details will be published in the future but Animal Genetics wanted to get this out to people who have been waiting for information about PSSM1 in Draft breeds like the Gypsy horse as soon as we could. ** It is our opinion that in almost all cases the effects of PSSM1 in Gypsy horses can be managed if the condition is identified properly. Animal Genetics will continue to work with breeders and veterinarians to better understand the condition and identify additional genetic factors that may influence a horse with two copies of the mutated gene.
Foal Immunodeficiency Syndrome (FIS)
Description:Fell Pony syndrome or Foal Immunodeficiency Syndrome (FIS) is a recessive genetic disease that primarily affects two relatively rare native UK pony breeds, the Dales and the Fell pony. FIS is caused by a single mutation in the sodium/myo-inositol cotransporter gene (SLC5A3). This gene plays a vital role in the regulatory response in many tissues including lymphoid tissues. As much as 10% of all Fell ponies born each year suffer from FIS. This has put a strain on the long-term survival of this breed as well as the likely spread of FIS into other breeds. Most recently Animal Genetics has found the mutation that causes FIS in approximately 9% of Gypsy horse breeds in the US and Europe.
Foals must have two copies of the mutated gene in order to be affected with FIS. Therefore, each parent must be a carrier of the mutated gene in order to have an affected foal. Affected foals appear healthy and normal at birth but begin to show signs of weakness, dull coat and anorexia at 2-3 weeks. The first clinical signs of this disease include diarrhoea, nasal discharge, poor growth, pale gums and decreased appetite. Vision may be affected, presumably due to secondary bacterial infections. Mortality rate for foal affected by FIS is 100% despite intensive treatment. All FIS affected foals generally die or are euthanized before they reach the age of 3 months.
FIS is an autosomal recessive trait, meaning a foal can only be affected if the foal inherits the disease from both parents. Parents that are carriers do not have any symptoms associated with FIS. However, they will pass on a copy of the defective gene to their offspring 50% of the time.
Animal Genetics offers DNA testing for both the FIS mutation found in Dale and Fell Pony as well as any horses with Dale and Fell Pony blood lines.
Breeds Affected:Dale Pony, Fell Pony and Gypsy horse breeds well as any horses having Dale and or Fell Pony blood lines.
Test Results:Animal Genetics offers DNA testing for Foal Immunodeficiency Syndrome (FIS). The genetic test verifies the presence of the mutated SLC5A3 Gene and presents results as one of the following:
Color Testing
Base Color Every horse has a base color, which can be black, bay, or red. This is controlled by the Extension (Red/Black Factor) and Agouti genes. The Extension gene controls the production of black or red pigment throughout the coat. The allele for black color (E) is dominant over the red allele (e), so a horse only needs one copy of the black allele to appear black-based.
The Agouti gene can then modify black pigment by pushing it the the points of the horse, creating a bay. The Agouti gene is dominant, so a black pigmented horse only needs one copy of the Agouti gene (A) to appear bay. Agouti does not have any effect on red pigment.
There may be some variation in the intensity of the base colors, for example, dark bays compared to light bays or liver chestnuts to sorrels. This could be caused by a variation in the expression of the genes or interaction of other genetic factors.
Dilutions The rest of the color genes act as modifiers on the base coat of the horse. There are several genes that dilute the color of the horse, including Cream, Pearl, Champagne, Silver, and Dun. While these genes all function to dilute pigment, they are not all expressed in the same manner. The Dun and Champagne genes are dominant, as is Silver, although Silver does not affected red pigment. The Cream gene is incompletely dominant, meaning you will see different effects with the number of Cream genes present, and the Pearl Gene is recessive. The Cream and Pearl genes do have additive effects, so color testing can be an important tool to determine the correct color of a horse and what it may be able to pass on. The Grey gene causes a horse to 'grey out' over time, and is dominant, although homozygous horses tend to grey out faster. It is thought that there are other color modifiers, such as Flaxen or Sooty, but the genetic basis to these colors have not yet been determined.
Patterns and depigmentation. The pattern genes also modify the color of the horse by deleting color. These genes include Frame Overo, Splashed White Overo, Sabino1, Tobiano, Dominant White, and Leopard Print or Appaloosa.