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Genetic effects on coat colour in cattle: dilution of eumelanin and phaeomelanin pigments in an F2-Backcross Charolais x Holstein population.

GutiƩrrez-Gil B, Wiener P, Williams JL - BMC Genet. (2007)

Bottom Line: Highly significant genome-wide associations were detected on chromosome 5 for the three traits analysed in the marker interval [ETH10-DIK5248].A region on chromosome 28 influences the intensity of pigment within coat colour categories, and therefore may include a modifier of the Dc locus.A candidate gene for this effect, LYST, was identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Roslin Institute (Edinburgh), Roslin, Midlothian, Scotland. beatriz.gutierrez@unileon.es

ABSTRACT

Background: In cattle, the gene coding for the melanocortin receptor 1 (MC1R) is known to be the main regulator of the switch between the two coat colour pigments: eumelanin (black pigment) and phaeomelanin (red pigment). Some breeds, such as Charolais and Simmental, exhibit a lightening of the original pigment over the whole body. The dilution mutation in Charolais (Dc) is responsible for the white coat colour of this breed. Using an F2-Backcross Charolais x Holstein population which includes animals with both pigment backgrounds, we present a linkage mapping study of the Charolais dilution locus.

Results: A Charolais x Holstein crossbred population was investigated for genetic effects on coat colour dilution. Three different traits representing the dilution of the phaeomelanin, eumelanin, and non-pigment-specific dilution were defined. Highly significant genome-wide associations were detected on chromosome 5 for the three traits analysed in the marker interval [ETH10-DIK5248]. The SILV gene was examined as the strongest positional and functional candidate gene. A previously reported non-synonymous mutation in exon 1 of this gene, SILV c.64A>G, was associated with the coat colour dilution phenotype in this resource population. Although some discrepancies were identified between this mutation and the dilution phenotype, no convincing recombination events were found between the SILV c.64A>G mutation and the Dc locus. Further analysis identified a region on chromosome 28 influencing the variation in pigment intensity for a given coat colour category.

Conclusion: The present study has identified a region on bovine chromosome 5 that harbours the major locus responsible for the dilution of the eumelanin and phaeomelanin seen in Charolais crossbred cattle. In this study, no convincing evidence was found to exclude SILV c.64A>G as the causative mutation for the Charolais dilution phenotype, although other genetic effects may influence the coat colour variation in the population studied. A region on chromosome 28 influences the intensity of pigment within coat colour categories, and therefore may include a modifier of the Dc locus. A candidate gene for this effect, LYST, was identified.

Show MeSH
Coat colour categories used for visual scoring of the second-generation individuals of the F2-Backcross population studied. The primary analysis was based on the five category colour scoring (White, Grey, Light-Red, Dark-Red and Black). The initial visual scoring had considered seven subcategories (White, Off-White, Light-Grey, Dark-Grey, Light-Red, Dark-Red and Black).
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Figure 1: Coat colour categories used for visual scoring of the second-generation individuals of the F2-Backcross population studied. The primary analysis was based on the five category colour scoring (White, Grey, Light-Red, Dark-Red and Black). The initial visual scoring had considered seven subcategories (White, Off-White, Light-Grey, Dark-Grey, Light-Red, Dark-Red and Black).

Mentions: The number of individuals scored in each of five colour categories (White, Grey, Light-Red, Dark-Red and Black; See Figure 1) is detailed in Table 1A. The phenotypic proportions observed for the CB1, HB1 and F2 were consistent with the assumption of fixation of alternative alleles at the Dilution locus in the Charolais and Holstein founders. A total of 141 individuals were included in the analysis of the Grey-Intensity trait, with 91 individuals scored as Light-Grey and 50 as Dark-Grey. The number of animals included in these two sub-categories for each genetic background group is detailed in Table 1B.


Genetic effects on coat colour in cattle: dilution of eumelanin and phaeomelanin pigments in an F2-Backcross Charolais x Holstein population.

GutiƩrrez-Gil B, Wiener P, Williams JL - BMC Genet. (2007)

Coat colour categories used for visual scoring of the second-generation individuals of the F2-Backcross population studied. The primary analysis was based on the five category colour scoring (White, Grey, Light-Red, Dark-Red and Black). The initial visual scoring had considered seven subcategories (White, Off-White, Light-Grey, Dark-Grey, Light-Red, Dark-Red and Black).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1994163&req=5

Figure 1: Coat colour categories used for visual scoring of the second-generation individuals of the F2-Backcross population studied. The primary analysis was based on the five category colour scoring (White, Grey, Light-Red, Dark-Red and Black). The initial visual scoring had considered seven subcategories (White, Off-White, Light-Grey, Dark-Grey, Light-Red, Dark-Red and Black).
Mentions: The number of individuals scored in each of five colour categories (White, Grey, Light-Red, Dark-Red and Black; See Figure 1) is detailed in Table 1A. The phenotypic proportions observed for the CB1, HB1 and F2 were consistent with the assumption of fixation of alternative alleles at the Dilution locus in the Charolais and Holstein founders. A total of 141 individuals were included in the analysis of the Grey-Intensity trait, with 91 individuals scored as Light-Grey and 50 as Dark-Grey. The number of animals included in these two sub-categories for each genetic background group is detailed in Table 1B.

Bottom Line: Highly significant genome-wide associations were detected on chromosome 5 for the three traits analysed in the marker interval [ETH10-DIK5248].A region on chromosome 28 influences the intensity of pigment within coat colour categories, and therefore may include a modifier of the Dc locus.A candidate gene for this effect, LYST, was identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Roslin Institute (Edinburgh), Roslin, Midlothian, Scotland. beatriz.gutierrez@unileon.es

ABSTRACT

Background: In cattle, the gene coding for the melanocortin receptor 1 (MC1R) is known to be the main regulator of the switch between the two coat colour pigments: eumelanin (black pigment) and phaeomelanin (red pigment). Some breeds, such as Charolais and Simmental, exhibit a lightening of the original pigment over the whole body. The dilution mutation in Charolais (Dc) is responsible for the white coat colour of this breed. Using an F2-Backcross Charolais x Holstein population which includes animals with both pigment backgrounds, we present a linkage mapping study of the Charolais dilution locus.

Results: A Charolais x Holstein crossbred population was investigated for genetic effects on coat colour dilution. Three different traits representing the dilution of the phaeomelanin, eumelanin, and non-pigment-specific dilution were defined. Highly significant genome-wide associations were detected on chromosome 5 for the three traits analysed in the marker interval [ETH10-DIK5248]. The SILV gene was examined as the strongest positional and functional candidate gene. A previously reported non-synonymous mutation in exon 1 of this gene, SILV c.64A>G, was associated with the coat colour dilution phenotype in this resource population. Although some discrepancies were identified between this mutation and the dilution phenotype, no convincing recombination events were found between the SILV c.64A>G mutation and the Dc locus. Further analysis identified a region on chromosome 28 influencing the variation in pigment intensity for a given coat colour category.

Conclusion: The present study has identified a region on bovine chromosome 5 that harbours the major locus responsible for the dilution of the eumelanin and phaeomelanin seen in Charolais crossbred cattle. In this study, no convincing evidence was found to exclude SILV c.64A>G as the causative mutation for the Charolais dilution phenotype, although other genetic effects may influence the coat colour variation in the population studied. A region on chromosome 28 influences the intensity of pigment within coat colour categories, and therefore may include a modifier of the Dc locus. A candidate gene for this effect, LYST, was identified.

Show MeSH