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Incontinentia Pigmenti (IP)
| Acronym: | IP |
| Gene: | IKBKG |
| Mutation: | c.202C>T |
| Inheritance: | X-Linked dominant |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Incontinentia Pigmenti (IP) is an inherited dermal disease observed in several animals, including horses. Horses with IP have characteristic skin lesions which evolve over time, as well as dental, nail, and ocular abnormalities. The distinguished skin signs occur in four cutaneous stages: inflammatory vesicles, verrucous patches, a pattern of hyperpigmentation, and dermal scarring. IP is caused by a genetic mutation in the IKBKG gene, which provides instructions for producing the IKK protein complex. IKK complex regulates the activity of nuclear factor kappa-B that binds to DNA and controls the activity of other genes. The nonsense mutation in the IKBKG gene causes inhibition of nuclear factor kappa-B resulting in cell death, leading to embryonic death in males and inactivation of one X chromosome in females.
IP is inherited as an X-linked dominant disease and is usually lethal prenatally in males. Therefore, the typical IP phenotype can only be seen in hemizygous females. IP is observed in several horse breeds, but it is most prevalent in the Quarter Horse breed. The disease is incurable, but early detection by genetic testing can help identify affected females and prevent further breeding with careful 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. |
AFFECTED HETEROZYGOTE |
Tested mutation was detected in animal with „affected heterozygote“ result. Animal tested as affected heterozygote has one wild-type and one mutation allele, it is in heterozygous state. It is likely to 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:
Smahi, A., Courtois, G., Vabres, P., Yamaoka, S., Heuertz, S., Munnich, A., … Nelson, D.L. (2000). Genomic rearrangement in NEMO impairs NF-κB activation and is a cause of incontinentia pigmenti. Nature, 405(6785), 466–472. doi:10.1038/35013114
Towers, R. E., Murgiano, L., Millar, D. S., Glen, E., Topf, A., Jagannathan, V., … Leeb, T. (2013). A Nonsense Mutation in the IKBKG Gene in Mares with Incontinentia Pigmenti. PLoS ONE, 8(12), e81625. doi:10.1371/journal.pone.0081625