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Ectodermal Dysplasia X-linked – German Shepherd Type
| Acronym: | ED |
| Gene: | EDA |
| Mutation: | c.910-1G>A |
| Inheritance: | X-linked recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
X-linked Ectodermal Dysplasia (XED) is a genetic disorder characterized by abnormal development of several tissues and organs of ectodermal origin, including teeth, hair, nails, and sweat glands. Few types of ectodermal dysplasias have been discovered to affect humans and animals, including dogs. The type of XED specific to German Shepherd dogs is a consequence of a mutation within the EDA gene coding for ectodysplasin. Ectodysplasin is a transmembrane protein involved in the morphogenesis of hair follicles and tooth buds during fetal development. Defect within that gene results in dysfunctional protein causing marked hypotrichosis and multifocal complete alopecia, almost complete absence of sweat and sebaceous glands, and altered dentition with missing and abnormally shaped teeth in affected dogs.
As the EDA gene lies on the X chromosome, Ectodermal Dysplasia found in German Shepherd dogs shows an X chromosomal recessive mode of inheritance, meaning the specific mutation that causes the disease is located on the sex chromosome. Since male dogs have just one X chromosome, if they carry the mutation, they will develop the disorder. Female dogs have two X chromosomes and hence, dogs with only one copy of the mutated gene will act as carriers, and dogs carrying both mutated genes will show signs of the disease. Early genetic testing can help identify dogs that carry the gene with the specific mutation and prevent their further breeding by the proper selection of mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (female) or hemizygous state (male) (i.e. only healthy allele on X chromosome). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has mutated allele in homozygous state (female) or hemizygous state (male) (i.e. only mutated allele on X chromosome). It is likely the animal will experience a genetic disorder due to this mutation.**It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Penetrance of tested mutation, and potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Casal, M. L., Scheidt, J. L., Rhodes, J. L., Henthorn, P. S., Werner, P. (2005). Mutation identification in a canine model of X-linked ectodermal dysplasia. Mammalian genome : official journal of the International Mammalian Genome Society, 16(7), 524–531. https://doi.org/10.1007/s00335-004-2463-4
Waluk, D. P., Zur, G., Kaufmann, R., Welle, M. M., Jagannathan, V., Drögemüller, C., Müller, E. J., Leeb, T., Galichet, A. (2016). A Splice Defect in the EDA Gene in Dogs with an X-Linked Hypohidrotic Ectodermal Dysplasia (XLHED) Phenotype. G3 (Bethesda, Md.), 6(9), 2949–2954. https://doi.org/10.1534/g3.116.033225
Casal, M. L., Jezyk, P. F., Greek, J. M., Goldschmidt, M. H., Patterson, D. F. (1997). X-linked ectodermal dysplasia in the dog. The Journal of heredity, 88(6), 513–517. https://doi.org/10.1093/oxfordjournals.jhered.a023146