Limits...
Melanism in peromyscus is caused by independent mutations in agouti.

Kingsley EP, Manceau M, Wiley CD, Hoekstra HE - PLoS ONE (2009)

Bottom Line: Identifying the molecular basis of phenotypes that have evolved independently can provide insight into the ways genetic and developmental constraints influence the maintenance of phenotypic diversity.While variation in the Mc1r coding region does not correlate with melanism in any population, in a New Hampshire population, we find that a 125-kb deletion, which includes the upstream regulatory region and exons 1 and 2 of Agouti, results in a loss of Agouti expression and is perfectly associated with melanic color.In a second population from Alaska, we find that a premature stop codon in exon 3 of Agouti is associated with a similar melanic phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismic and Evolutionary Biology and the Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, United States of America. ekingsley@oeb.harvard.edu

ABSTRACT
Identifying the molecular basis of phenotypes that have evolved independently can provide insight into the ways genetic and developmental constraints influence the maintenance of phenotypic diversity. Melanic (darkly pigmented) phenotypes in mammals provide a potent system in which to study the genetic basis of naturally occurring mutant phenotypes because melanism occurs in many mammals, and the mammalian pigmentation pathway is well understood. Spontaneous alleles of a few key pigmentation loci are known to cause melanism in domestic or laboratory populations of mammals, but in natural populations, mutations at one gene, the melanocortin-1 receptor (Mc1r), have been implicated in the vast majority of cases, possibly due to its minimal pleiotropic effects. To investigate whether mutations in this or other genes cause melanism in the wild, we investigated the genetic basis of melanism in the rodent genus Peromyscus, in which melanic mice have been reported in several populations. We focused on two genes known to cause melanism in other taxa, Mc1r and its antagonist, the agouti signaling protein (Agouti). While variation in the Mc1r coding region does not correlate with melanism in any population, in a New Hampshire population, we find that a 125-kb deletion, which includes the upstream regulatory region and exons 1 and 2 of Agouti, results in a loss of Agouti expression and is perfectly associated with melanic color. In a second population from Alaska, we find that a premature stop codon in exon 3 of Agouti is associated with a similar melanic phenotype. These results show that melanism has evolved independently in these populations through mutations in the same gene, and suggest that melanism produced by mutations in genes other than Mc1r may be more common than previously thought.

Show MeSH

Related in: MedlinePlus

Melanism evolved multiple times independently in P. maniculatus, twice by mutations in the Agouti gene.(A) Wild type and melanic museum skins from Shrubby Island, AK (C. Conroy, pers. comm.) and Hubbard Brook Experimental Forest, NH [17]. Illustrations of the dorsal hair pattern are shown above each specimen. Black stars represent locales included in this study; white star denotes another location where melanic Peromyscus were reported [18]. (B) Table of polymorphism for Mc1r and Agouti coding sequences. Arrows indicate two sites harboring mutations that are perfectly correlated with melanism.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2713407&req=5

pone-0006435-g004: Melanism evolved multiple times independently in P. maniculatus, twice by mutations in the Agouti gene.(A) Wild type and melanic museum skins from Shrubby Island, AK (C. Conroy, pers. comm.) and Hubbard Brook Experimental Forest, NH [17]. Illustrations of the dorsal hair pattern are shown above each specimen. Black stars represent locales included in this study; white star denotes another location where melanic Peromyscus were reported [18]. (B) Table of polymorphism for Mc1r and Agouti coding sequences. Arrows indicate two sites harboring mutations that are perfectly correlated with melanism.

Mentions: To determine if the same gene and same mutation was responsible for melanism in other populations of P. maniculatus, we sequenced both Mc1r and Agouti in melanic and wild type mice from an additional population. First, we sequenced Mc1r in melanic (N = 2) and non-melanic (N = 4) P. maniculatus from Alaska and found four amino acid polymorphisms segregating in the sample (Figure 4). None of these polymorphisms likely cause the melanic phenotype for several reasons: (1) none of these mutations overlaps with any previously described darkening mutations, (2) all four amino acids appear in other, non-melanic individuals from other populations of P. maniculatus (Figure 4), and (3) none of the polymorphisms correlate with the melanic phenotype in this population.


Melanism in peromyscus is caused by independent mutations in agouti.

Kingsley EP, Manceau M, Wiley CD, Hoekstra HE - PLoS ONE (2009)

Melanism evolved multiple times independently in P. maniculatus, twice by mutations in the Agouti gene.(A) Wild type and melanic museum skins from Shrubby Island, AK (C. Conroy, pers. comm.) and Hubbard Brook Experimental Forest, NH [17]. Illustrations of the dorsal hair pattern are shown above each specimen. Black stars represent locales included in this study; white star denotes another location where melanic Peromyscus were reported [18]. (B) Table of polymorphism for Mc1r and Agouti coding sequences. Arrows indicate two sites harboring mutations that are perfectly correlated with melanism.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713407&req=5

pone-0006435-g004: Melanism evolved multiple times independently in P. maniculatus, twice by mutations in the Agouti gene.(A) Wild type and melanic museum skins from Shrubby Island, AK (C. Conroy, pers. comm.) and Hubbard Brook Experimental Forest, NH [17]. Illustrations of the dorsal hair pattern are shown above each specimen. Black stars represent locales included in this study; white star denotes another location where melanic Peromyscus were reported [18]. (B) Table of polymorphism for Mc1r and Agouti coding sequences. Arrows indicate two sites harboring mutations that are perfectly correlated with melanism.
Mentions: To determine if the same gene and same mutation was responsible for melanism in other populations of P. maniculatus, we sequenced both Mc1r and Agouti in melanic and wild type mice from an additional population. First, we sequenced Mc1r in melanic (N = 2) and non-melanic (N = 4) P. maniculatus from Alaska and found four amino acid polymorphisms segregating in the sample (Figure 4). None of these polymorphisms likely cause the melanic phenotype for several reasons: (1) none of these mutations overlaps with any previously described darkening mutations, (2) all four amino acids appear in other, non-melanic individuals from other populations of P. maniculatus (Figure 4), and (3) none of the polymorphisms correlate with the melanic phenotype in this population.

Bottom Line: Identifying the molecular basis of phenotypes that have evolved independently can provide insight into the ways genetic and developmental constraints influence the maintenance of phenotypic diversity.While variation in the Mc1r coding region does not correlate with melanism in any population, in a New Hampshire population, we find that a 125-kb deletion, which includes the upstream regulatory region and exons 1 and 2 of Agouti, results in a loss of Agouti expression and is perfectly associated with melanic color.In a second population from Alaska, we find that a premature stop codon in exon 3 of Agouti is associated with a similar melanic phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismic and Evolutionary Biology and the Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, United States of America. ekingsley@oeb.harvard.edu

ABSTRACT
Identifying the molecular basis of phenotypes that have evolved independently can provide insight into the ways genetic and developmental constraints influence the maintenance of phenotypic diversity. Melanic (darkly pigmented) phenotypes in mammals provide a potent system in which to study the genetic basis of naturally occurring mutant phenotypes because melanism occurs in many mammals, and the mammalian pigmentation pathway is well understood. Spontaneous alleles of a few key pigmentation loci are known to cause melanism in domestic or laboratory populations of mammals, but in natural populations, mutations at one gene, the melanocortin-1 receptor (Mc1r), have been implicated in the vast majority of cases, possibly due to its minimal pleiotropic effects. To investigate whether mutations in this or other genes cause melanism in the wild, we investigated the genetic basis of melanism in the rodent genus Peromyscus, in which melanic mice have been reported in several populations. We focused on two genes known to cause melanism in other taxa, Mc1r and its antagonist, the agouti signaling protein (Agouti). While variation in the Mc1r coding region does not correlate with melanism in any population, in a New Hampshire population, we find that a 125-kb deletion, which includes the upstream regulatory region and exons 1 and 2 of Agouti, results in a loss of Agouti expression and is perfectly associated with melanic color. In a second population from Alaska, we find that a premature stop codon in exon 3 of Agouti is associated with a similar melanic phenotype. These results show that melanism has evolved independently in these populations through mutations in the same gene, and suggest that melanism produced by mutations in genes other than Mc1r may be more common than previously thought.

Show MeSH
Related in: MedlinePlus