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Unformatted text preview: ears brown from a distance, is produced by the
combined actions of Agouti and -MSH and consists of individual hairs that
are banded black-yellow-black. The yellow band in the middle of a black hair Surprisingly, a pathway homologous to the agouti signaling pathway
in the skin functions in the hypothalamus to regulate body weight.
Recently, sequence similarityawas used to identify an agouti-related
gene among hundreds of thousands of anonymous cDNA clones,
so-called expressed sequence tags (ESTs)23,24. This gene, Agrp,
encodes a melanocortin receptor antagonist, as does agouti.
Biochemical experiments with recombinant protein demonstrated
that Agrp is a selective antagonist of Mc3r and Mc4r (Table 1)23.
Thus, the spectrum of Agrp- and agouti-responsive receptors overlap
predominantly at Mc4r. Whereas agouti comes in contact with Mc4r
only in the context of rare mutations, Agrp is expressed in the hypothalamus of normal mice and humans23,24 and is likely to be a natural
antagonist of Mc4r and possibly also of Mc3r.
Mouse studies have provided further evidence...
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This document was uploaded on 04/02/2014.
- Fall '14