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A missense mutation in PMEL17 is associated with the Silver coat color in the horse
Emma Brunberg1, Leif Andersson, Gus Cothran
1Dept of Medical Biochemistry and Microbiology, Uppsala University, SE-751 24 Uppsala, Sweden. a1emmbru@stud.slu.se
Background:
The Silver coat color, also called Silver dapple, in the horse is characterized by dilution of the black pigment in the hair. This phenotype shows an autosomal dominant inheritance. The effect of the mutation is most visible in the long hairs of the mane and tail, which are diluted to a mixture of white and gray hairs. Herein we describe the identification of the responsible gene and a missense mutation associated with the Silver phenotype.
Results:
Segregation data on the Silver locus (Z) were obtained within one half-sib family that consisted of a heterozygous Silver colored stallion with 34 offspring and their 29 non-Silver dams. We typed 41 genetic markers well spread over the horse genome, including one single microsatellite marker (TKY284) close to the candidate gene PMEL17 on horse chromosome 6 (ECA6q23). Significant linkage was found between the Silver phenotype and TKY284 (theta = 0, z = 9.0). DNA sequencing of PMEL17 in Silver and non-Silver horses revealed a missense mutation in exon 11 changing the second amino acid in the cytoplasmic region from arginine to cysteine (Arg618Cys). This mutation showed complete association with the Silver phenotype across multiple horse breeds, and was not found among non-Silver horses with one clear exception; a chestnut colored individual that had several Silver offspring when mated to different non-Silver stallions also carried the exon 11 mutation. In total, 64 Silver horses from six breeds and 85 non-Silver horses from 14 breeds were tested for the exon 11 mutation. One additional mutation located in intron 9, only 759 bases from the missense mutation, also showed complete association with the Silver phenotype. However, as one could expect to find several non-causative mutations completely associated with the Silver mutation, we argue that the missense mutation is more likely to be causative.
Conclusion:
The present study shows that PMEL17 causes the Silver coat color in the horse and enable genetic testing for this trait.
Insights
Researchers identified the PMEL17 gene mutation responsible for the Silver coat color in horses. This discovery allows for genetic testing of this dominant equine trait.
Area of Science:
- Equine genetics
- Animal coat color genetics
Background:
- The Silver coat color in horses, also known as Silver dapple, is a dominant trait diluting black pigment.
- This dilution is most apparent in the mane and tail, appearing as a mix of white and gray hairs.
Purpose of the Study:
- To identify the specific gene and mutation responsible for the Silver coat color phenotype in horses.
- To establish a genetic basis for the Silver trait for diagnostic purposes.
Main Methods:
- Segregation analysis was performed on a half-sib family to map the Silver locus (Z).
- Genetic markers, including microsatellite TKY284 near PMEL17, were used to identify linkage.
- DNA sequencing of the PMEL17 gene was conducted in Silver and non-Silver horses to detect mutations.
Main Results:
- Significant linkage was found between the Silver phenotype and the PMEL17 gene on horse chromosome 6.
- A missense mutation (Arg618Cys) in exon 11 of PMEL17 was identified and strongly associated with the Silver phenotype across multiple breeds.
- An intronic mutation in PMEL17 also showed association, but the missense mutation is considered more likely causative.
Conclusions:
- The PMEL17 gene is confirmed as the cause of the Silver coat color in horses.
- The identified PMEL17 mutation enables reliable genetic testing for the Silver trait in horses.
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