Epistatic interactions of more than two loci are involved in the rat-tail phenotype in cattle

The rat-tail syndrome (RTS) is a bovine congenital, inherited hypotrichosis characterized by various degrees of sparse, curled malformed hair and by missing hair at the animal's tail switch. The defect in hair conformation is restricted to pigmented sections of the pelage and has been observed...

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Bibliographic Details
Published in:Journal of animal science 2016-09, Vol.94, p.156-156
Main Authors: Kühn, C, Weikard, R, Knaust, J, Hadlich, F
Format: Article
Language:English
Subjects:
Animal models
Bovidae
Cattle
Conformation
Dilution
Epistasis
Gene expression
Genetics
Genomes
Genotype & phenotype
Hair
Loci
MC1R gene
Pelage
Phenotypes
Pigmentation
Tails
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Summary:The rat-tail syndrome (RTS) is a bovine congenital, inherited hypotrichosis characterized by various degrees of sparse, curled malformed hair and by missing hair at the animal's tail switch. The defect in hair conformation is restricted to pigmented sections of the pelage and has been observed in crosses between black cattle breeds (e.g., Angus and Holstein) and some European breeds with the specific feature of coat color dilution (e.g., Simmental, Charolais and Hereford). Due to partially controversial results in the literature, the full causal genetic background of RTS is still under debate. Thus, the aim of this study was to monitor the genetic architecture of RTS and to map the locus (or loci) epistatically interacting for RTS. Taking advantage of a resource cross population from German Holstein and Charolais cattle breeds, which was segregating for RTS, we proved that epistatic effects of at least three independent genetic loci are required for the expression of the "rat tail" phenotype. We found that in our population, RTS is exclusively expressed on a eumelanic background with the dominant ED allele at the Extension locus (MC1R gene) located on BTA18. In addition, only individuals heterozygous for the Dilution locus on BTA5 (c.64G > A at the PMEL or SILV gene) were classified as rat-tail phenotype. However, the results of our segregation analysis prove that a two locus model including the Extension and the Dilution locus is obligatory but not sufficient to fully explain the rat-tail phenotype. Our results provide evidence that epistatic interaction with at least a third independent locus is required for its expression. Applying linkage and whole genome association analyses with different models and in different pedigrees, the third locus essential for the expression of the rat-tail phenotype was mapped consistently to the chromosomal region 14-22 Mb on BTA5, obviously affecting hair structure as well as hair pigmentation. We clearly demonstrated that this third locus is distinct from the Dilution locus represented by the PMEL gene. Finally, the results of our study exclude several loci repotted to be associated or underlying hair conformation or pigmentation traits as causal mutation for RTS and also promising functional and positional candidate genes associated with hypotrichosis in humans. RTS with its three locus interaction is a prime example for epistatic interaction of several independent loci required for the expression of a distinct phenotyp
ISSN:0021-8812
1525-3163