Mammalian Genome

, Volume 10, Issue 1, pp 39–43

Molecular and pharmacological characterization of dominant black coat color in sheep

Authors

  • Dag Inge  Våge
    • Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 Ås, Norway
  • Helge  Klungland
    • Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 Ås, Norway
  • Dongsi  Lu
    • The Vollum Institute, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97201, USA
  • Roger D.  Cone
    • The Vollum Institute, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97201, USA

DOI: 10.1007/s003359900939

Cite this article as:
Våge, D., Klungland, H., Lu, D. et al. (1999) 10: 39. doi:10.1007/s003359900939

Abstract.

Dominant black coat color in sheep is predicted to be caused by an allele ED at the extension locus. Recent studies have shown that this gene encodes the melanocyte stimulating hormone receptor (MC1-R). In mouse and fox, naturally occurring mutations in the coding region of MC1-R produce a constitutively activated receptor that switches the synthesis from phaeomelanin to eumelanin within the melanocyte, explaining the black coat color observed phenotypically. In the sheep, we have identified a Met→Lys mutation in position 73 (M73K) together with a Asp → Asn change at position 121 (D121N) showing complete cosegregation with dominant black coat color in a family lineage. Only the M73K mutation showed constitutive activation when introduced into the corresponding mouse receptor (mMC1-R) for pharmacological analysis; however, the position corresponding to D121 in the mouse receptor is required for high affinity ligand binding. The pharmacological profile of the M73K change is unique compared to the constitutively active E92K mutation in the sombre mouse and C123R mutation in the Alaska silver fox, indicating that the M73K change activates the receptor via a mechanism distinct from these previously characterized mutations.

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© Springer-Verlag New York Inc. 1999