Point mutations in the melanocortin-4 receptor cause variable obesity in mice

Thomas P. Meehan, Koichi Tabeta, Xin Du, Lanette S. Woodward, Karen Firozi, Bruce Beutler, Monica J. Justice

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Mutations in the melanocortin-4 receptor (MC4R) are associated with early-onset obesity in humans. Furthermore, a null Mc4r allele in mice leads to severe obesity due to hyperphagia and decreased energy expenditure. As part of independent N-ethyl- N-nitrosourea (ENU) mutagenesis screens, two obesity mutants, Fatboy and Southbeach, were isolated. Mapping revealed linkage to the melanocortin-4 receptor (Mc4r) and sequencing found single amino acid changes in Mc4r for each line. Expression of the mutant receptors in HEK 293 cells revealed defects in receptor signaling. The mutated Fatboy receptor (I194T) shows an increase in the effective concentration necessary for 50% of maximal signaling (EC50) when stimulated with α-MSH. Based on competitive binding, I194T is expressed on the cell surface at lower levels than the nonmutated receptor. In contrast, Southbeach (L300P) displays minimal receptor signaling when stimulated with the natural ligand α-MSH or the synthetic agonist NDP-α-MSH. Cell surface binding is absent, which usually indicates a lack of cell surface expression. However, antibody binding to Flag-tagged receptors by flow cytometry analysis and immunofluorescence demonstrates that L300P is translocated to the plasma membrane at a level comparable to the wild-type receptor. These results indicate a correlation with remaining receptor activity and the severity of the obesity in the mice homozygous for the mutations. Southbeach has less receptor activity and becomes more obese. These mutants will serve as good models for the variability in phenotype in humans carrying mutations in the MC4R gene.

Original languageEnglish (US)
Pages (from-to)1162-1171
Number of pages10
JournalMammalian Genome
Volume17
Issue number12
DOIs
StatePublished - Dec 2006

Fingerprint

Receptor, Melanocortin, Type 4
Point Mutation
Obesity
Melanocyte-Stimulating Hormones
Mutation
Ethylnitrosourea
Hyperphagia
Competitive Binding
Morbid Obesity
HEK293 Cells
Chromosome Mapping
Mutagenesis
Energy Metabolism
Fluorescent Antibody Technique
Flow Cytometry
Alleles
Cell Membrane
Ligands
Phenotype
Amino Acids

ASJC Scopus subject areas

  • Genetics

Cite this

Meehan, T. P., Tabeta, K., Du, X., Woodward, L. S., Firozi, K., Beutler, B., & Justice, M. J. (2006). Point mutations in the melanocortin-4 receptor cause variable obesity in mice. Mammalian Genome, 17(12), 1162-1171. https://doi.org/10.1007/s00335-006-0073-z

Point mutations in the melanocortin-4 receptor cause variable obesity in mice. / Meehan, Thomas P.; Tabeta, Koichi; Du, Xin; Woodward, Lanette S.; Firozi, Karen; Beutler, Bruce; Justice, Monica J.

In: Mammalian Genome, Vol. 17, No. 12, 12.2006, p. 1162-1171.

Research output: Contribution to journalArticle

Meehan, TP, Tabeta, K, Du, X, Woodward, LS, Firozi, K, Beutler, B & Justice, MJ 2006, 'Point mutations in the melanocortin-4 receptor cause variable obesity in mice', Mammalian Genome, vol. 17, no. 12, pp. 1162-1171. https://doi.org/10.1007/s00335-006-0073-z
Meehan, Thomas P. ; Tabeta, Koichi ; Du, Xin ; Woodward, Lanette S. ; Firozi, Karen ; Beutler, Bruce ; Justice, Monica J. / Point mutations in the melanocortin-4 receptor cause variable obesity in mice. In: Mammalian Genome. 2006 ; Vol. 17, No. 12. pp. 1162-1171.
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