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Polymorphism in the MSHR gene of different cattle breeds

GRAPHODATSKAYA D, JOERG H, STRANZINGER G
Veterinarni Medicina 45, 2000, 290-295

The melanocyte stimulating hormone receptor (MSHR) is involved in coat colour determination in mammals by controlling the relative amounts of eumelanin (black/brown) and phaeomelanin (red/yellow). MSHR is activated by alpha melanocyte stimulating hormone (a-MSH). However, alleles of the MSHR gene have been described, which encode for a constitutively active receptor resulting in the production of eumelanin and a non-functional receptor resulting in the production of phaeomelanin. In this study the complete coding sequences of the MSHR gene from Holstein, Red Holstein, Simmental and Brown Swiss cattle were amplified, cloned into a plasmid vector and sequenced. Four different variants are characterised: a deletion of one G at position 310 or 311, a T/C base substitution at position 296, a T/C base substitution at position 667 and a duplication of 12 nucleotides at position 650. Combinations of the polymorphic sites result in 5 different alleles with the deduced amino acid sequences. The allele containing a deletion and therefore a frameshift of the open reading frame was found in red animals. The allele containing a Proline at position 99, an Arginine at position 223 and missing a duplication was found in black animals. Three different alleles were found in Brown Swiss. All of them contained a Leucine at position 99 and no deletion, the other two sites were polymorphic. The obtained results support our hypothesis, that the allele with a Proline at position 99 encodes a constitutively active receptor, while the allele with a frameshift encodes an inactive receptor and the alleles found in Brown Swiss produce the receptors controlled by alpha -MSH stimulation. The stimulation of the cells expressing the different MSHR alleles with alpha -MSH will be done in view of finding functional differences between the alleles


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