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Identification of a major locus interacting with MC1R and modifying black coat color in an F₂ Nellore-Angus population.

Hanna LL, Sanders JO, Riley DG, Abbey CA, Gill CA - Genet. Sel. Evol. (2014)

Bottom Line: In most mammals, these alleles are presumed to follow the dominance model of E(D) > E+ > e, although exceptions are found.Fitting SNP haplotypes for a 1 Mb interval that contained all three genes and centered on KIT accounted for the majority of the variation attributed to this major locus, which suggests that one of these genes or associated regulatory elements, is responsible for the majority of variation in degree of reddening.A higher density marker panel and functional analyses will be required to validate the role of PDGFRA or other regulatory variants and their interaction with MC1R for the modification of black coat color in Bos indicus influenced cattle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Animal Science, Texas A& M University, College Station, TX 77843, USA. clare-gill@tamu.edu.

ABSTRACT

Background: In cattle, base color is assumed to depend on the enzymatic activity specified by the MC1R locus, i.e. the extension locus, with alleles coding for black (E(D)), red (e), and wild-type (E+). In most mammals, these alleles are presumed to follow the dominance model of E(D) > E+ > e, although exceptions are found. In Bos indicus x Bos taurus F2 cattle, some E(D)E+ heterozygotes are discordant with the dominance series for MC1R and display various degrees of red pigmentation on an otherwise predicted black background. The objective of this study was to identify loci that modify black coat color in these individuals.

Results: Reddening was classified with a subjective scoring system. Interval analyses identified chromosome-wide suggestive (P < 0.05) and significant (P < 0.01) QTL on bovine chromosomes (BTA) 4 and 5, although these were not confirmed using single-marker association or Bayesian methods. Evidence of a major locus (F = 114.61) that affects reddening was detected between 60 and 73 Mb on BTA 6 (Btau4.0 build), and at 72 Mb by single-marker association and Bayesian methods. The posterior mean of the genetic variance for this region accounted for 43.75% of the genetic variation in reddening. This region coincided with a cluster of tyrosine kinase receptor genes (PDGFRA, KIT and KDR). Fitting SNP haplotypes for a 1 Mb interval that contained all three genes and centered on KIT accounted for the majority of the variation attributed to this major locus, which suggests that one of these genes or associated regulatory elements, is responsible for the majority of variation in degree of reddening.

Conclusions: Recombinants in a 5 Mb region surrounding the cluster of tyrosine kinase receptor genes implicated PDGFRA as the strongest positional candidate gene. A higher density marker panel and functional analyses will be required to validate the role of PDGFRA or other regulatory variants and their interaction with MC1R for the modification of black coat color in Bos indicus influenced cattle.

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Degree of black scoring system. Examples of EDE+ F2 Nellore-Angus cattle that scored a 1 through 9, respectively, starting at the top left and proceeding left to right down the rows.
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Figure 1: Degree of black scoring system. Examples of EDE+ F2 Nellore-Angus cattle that scored a 1 through 9, respectively, starting at the top left and proceeding left to right down the rows.

Mentions: Comparison of resultant genotypes with photographs revealed that EDED homozygotes were black and E+E+ homozygotes ranged in color from yellow to black as expected. However, EDE+ heterozygotes often exhibited various degrees of reddening and were not black as predicted by the dominance series ED > E+ > e. Degree of black was classified from 1 (lightly black; mostly red) to 9 (solid black) from photographs by three evaluators and a consensus score was determined (Figure 1). Photographs taken either in the feedlot or pasture at weaning age or older were available for 213 of the 238 EDE+ ET F2 cattle (four bulls, 115 steers, and 94 females).


Identification of a major locus interacting with MC1R and modifying black coat color in an F₂ Nellore-Angus population.

Hanna LL, Sanders JO, Riley DG, Abbey CA, Gill CA - Genet. Sel. Evol. (2014)

Degree of black scoring system. Examples of EDE+ F2 Nellore-Angus cattle that scored a 1 through 9, respectively, starting at the top left and proceeding left to right down the rows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3924621&req=5

Figure 1: Degree of black scoring system. Examples of EDE+ F2 Nellore-Angus cattle that scored a 1 through 9, respectively, starting at the top left and proceeding left to right down the rows.
Mentions: Comparison of resultant genotypes with photographs revealed that EDED homozygotes were black and E+E+ homozygotes ranged in color from yellow to black as expected. However, EDE+ heterozygotes often exhibited various degrees of reddening and were not black as predicted by the dominance series ED > E+ > e. Degree of black was classified from 1 (lightly black; mostly red) to 9 (solid black) from photographs by three evaluators and a consensus score was determined (Figure 1). Photographs taken either in the feedlot or pasture at weaning age or older were available for 213 of the 238 EDE+ ET F2 cattle (four bulls, 115 steers, and 94 females).

Bottom Line: In most mammals, these alleles are presumed to follow the dominance model of E(D) > E+ > e, although exceptions are found.Fitting SNP haplotypes for a 1 Mb interval that contained all three genes and centered on KIT accounted for the majority of the variation attributed to this major locus, which suggests that one of these genes or associated regulatory elements, is responsible for the majority of variation in degree of reddening.A higher density marker panel and functional analyses will be required to validate the role of PDGFRA or other regulatory variants and their interaction with MC1R for the modification of black coat color in Bos indicus influenced cattle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Animal Science, Texas A& M University, College Station, TX 77843, USA. clare-gill@tamu.edu.

ABSTRACT

Background: In cattle, base color is assumed to depend on the enzymatic activity specified by the MC1R locus, i.e. the extension locus, with alleles coding for black (E(D)), red (e), and wild-type (E+). In most mammals, these alleles are presumed to follow the dominance model of E(D) > E+ > e, although exceptions are found. In Bos indicus x Bos taurus F2 cattle, some E(D)E+ heterozygotes are discordant with the dominance series for MC1R and display various degrees of red pigmentation on an otherwise predicted black background. The objective of this study was to identify loci that modify black coat color in these individuals.

Results: Reddening was classified with a subjective scoring system. Interval analyses identified chromosome-wide suggestive (P < 0.05) and significant (P < 0.01) QTL on bovine chromosomes (BTA) 4 and 5, although these were not confirmed using single-marker association or Bayesian methods. Evidence of a major locus (F = 114.61) that affects reddening was detected between 60 and 73 Mb on BTA 6 (Btau4.0 build), and at 72 Mb by single-marker association and Bayesian methods. The posterior mean of the genetic variance for this region accounted for 43.75% of the genetic variation in reddening. This region coincided with a cluster of tyrosine kinase receptor genes (PDGFRA, KIT and KDR). Fitting SNP haplotypes for a 1 Mb interval that contained all three genes and centered on KIT accounted for the majority of the variation attributed to this major locus, which suggests that one of these genes or associated regulatory elements, is responsible for the majority of variation in degree of reddening.

Conclusions: Recombinants in a 5 Mb region surrounding the cluster of tyrosine kinase receptor genes implicated PDGFRA as the strongest positional candidate gene. A higher density marker panel and functional analyses will be required to validate the role of PDGFRA or other regulatory variants and their interaction with MC1R for the modification of black coat color in Bos indicus influenced cattle.

Show MeSH
Related in: MedlinePlus