Polymorphism in the MSHR gene of different cattle breeds

The melanocyte stimulating hormone receptor (MSHR) is involved in coat colo ur determination in mammals by controlling the relative amounts of eumelani n (black/brown) and phaeomelanin (red/yellow). MSHR is activated by alpha m elanocyte stimulating hormone (a-MSH). However, alleles of the MSHR gene ha ve been described, which encode for a constitutively active receptor result ing in the production of eumelanin and a non-functional receptor resulting in the production of phaeomelanin. In this study the complete coding sequen ces of the MSHR gene from Holstein, Red Holstein, Simmental and Brown Swiss cattle were amplified, cloned into a plasmid vector and sequenced. Four di fferent 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 po sition 667 and a duplication of 12 nucleotides at position 650. Combination s of the polymorphic sites result in 5 different alleles with the deduced a mino acid sequences. The allele containing a deletion and therefore a frame shift of the open reading frame was found in red animals. The allele contai ning a Proline at position 99, an Arginine at position 223 and missing a du plication was found in black animals. Three different alleles were found in Brown Swiss. All of them contained a Leucine at position 99 and no deletio n, the other two sites were polymorphic. The obtained results support our h ypothesis, that the allele with a Proline at position 99 encodes a constitu tively active receptor, while the allele with a frameshift encodes an inact ive receptor and the alleles found in Brown Swiss produce the receptors con trolled 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.