Limits...
A recurrent regulatory change underlying altered expression and Wnt response of the stickleback armor plates gene EDA.

O'Brown NM, Summers BR, Jones FC, Brady SD, Kingsley DM - Elife (2015)

Bottom Line: An identical T → G base pair change is found in EDA enhancers of divergent low-plated fish.Recreation of the T → G change in a marine enhancer strongly reduces expression in posterior armor plates.Thus parallel evolution of low-plated sticklebacks has occurred through a shared DNA regulatory change, which reduces the sensitivity of an EDA enhancer to Wnt signaling, and alters expression in developing armor plates while preserving expression in other tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology, Stanford University School of Medicine, Stanford, United States.

ABSTRACT
Armor plate changes in sticklebacks are a classic example of repeated adaptive evolution. Previous studies identified ectodysplasin (EDA) gene as the major locus controlling recurrent plate loss in freshwater fish, though the causative DNA alterations were not known. Here we show that freshwater EDA alleles have cis-acting regulatory changes that reduce expression in developing plates and spines. An identical T → G base pair change is found in EDA enhancers of divergent low-plated fish. Recreation of the T → G change in a marine enhancer strongly reduces expression in posterior armor plates. Bead implantation and cell culture experiments show that Wnt signaling strongly activates the marine EDA enhancer, and the freshwater T → G change reduces Wnt responsiveness. Thus parallel evolution of low-plated sticklebacks has occurred through a shared DNA regulatory change, which reduces the sensitivity of an EDA enhancer to Wnt signaling, and alters expression in developing armor plates while preserving expression in other tissues.

Show MeSH
Wnt signaling regulates armor plate development.Live Calcein staining of 6-month-old fish marks newly ossified bones ingreen. (A) Armor plates in an untreated high-plated adultmarine fish. The normal morphologies of two individual plates are outlinedwith dashed lines. (B) Control beads soaked in PBS wereimplanted between the two outlined plates at two months of age. After beadimplantation, fish continued to develop a full set of armor plates, withminimal changes in plate morphology (n = 8). (C)Implantation of Wnt-3a beads results in hypermorphic growth and armor platefusion in the regions surrounding the exogenous Wnt-3a signal (n =11). (D) Conversely, beads soaked in the Wnt inhibitor Dkk-1inhibit plate formation surrounding the site of bead implantation (n= 10). Scale bar in D is 2 mm long.DOI:http://dx.doi.org/10.7554/eLife.05290.008
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4384742&req=5

fig5: Wnt signaling regulates armor plate development.Live Calcein staining of 6-month-old fish marks newly ossified bones ingreen. (A) Armor plates in an untreated high-plated adultmarine fish. The normal morphologies of two individual plates are outlinedwith dashed lines. (B) Control beads soaked in PBS wereimplanted between the two outlined plates at two months of age. After beadimplantation, fish continued to develop a full set of armor plates, withminimal changes in plate morphology (n = 8). (C)Implantation of Wnt-3a beads results in hypermorphic growth and armor platefusion in the regions surrounding the exogenous Wnt-3a signal (n =11). (D) Conversely, beads soaked in the Wnt inhibitor Dkk-1inhibit plate formation surrounding the site of bead implantation (n= 10). Scale bar in D is 2 mm long.DOI:http://dx.doi.org/10.7554/eLife.05290.008

Mentions: Previous studies have shown that Wnt signaling acts upstream of EDAin the early proliferation and specification of tissues in many vertebrates (Laurikkala et al., 2002; Cui and Schlessinger, 2006; Häärä et al., 2011; Arte et al., 2013). To test whether Wnt also acts upstream of platedevelopment in sticklebacks, we tested whether implants of either Wnt-3a or Dkk-1 (aninhibitor of Wnt signaling, Glinka et al.,1998) altered normal patterns of armor plate formation. Beads soaked inPBS, Wnt-3a, or Dkk-1 proteins were surgically implanted into the mid-flank of2-month-old marine fish, and fish were then aged to 6 months to test for effects onplate size and number. Control bead implantation had no significant effect on overallplate morphology (Figure 5A,B). In contrast,exposure to ectopic Wnt signaling at the juvenile stage induced hypermorphic platedevelopment, characterized by adult fish with larger plates and plate fusionssurrounding the sites of Wnt-3a bead implantation (Figure 5C). Conversely, the addition of the Wnt inhibitor Dkk-1 resultedin a hypomorphic phenotype marked by the absence of plates surrounding the beadimplantation site (Figure 5D), suggesting thatWnt signaling plays an important role in normal plate development.10.7554/eLife.05290.008Figure 5.Wnt signaling regulates armor plate development.


A recurrent regulatory change underlying altered expression and Wnt response of the stickleback armor plates gene EDA.

O'Brown NM, Summers BR, Jones FC, Brady SD, Kingsley DM - Elife (2015)

Wnt signaling regulates armor plate development.Live Calcein staining of 6-month-old fish marks newly ossified bones ingreen. (A) Armor plates in an untreated high-plated adultmarine fish. The normal morphologies of two individual plates are outlinedwith dashed lines. (B) Control beads soaked in PBS wereimplanted between the two outlined plates at two months of age. After beadimplantation, fish continued to develop a full set of armor plates, withminimal changes in plate morphology (n = 8). (C)Implantation of Wnt-3a beads results in hypermorphic growth and armor platefusion in the regions surrounding the exogenous Wnt-3a signal (n =11). (D) Conversely, beads soaked in the Wnt inhibitor Dkk-1inhibit plate formation surrounding the site of bead implantation (n= 10). Scale bar in D is 2 mm long.DOI:http://dx.doi.org/10.7554/eLife.05290.008
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384742&req=5

fig5: Wnt signaling regulates armor plate development.Live Calcein staining of 6-month-old fish marks newly ossified bones ingreen. (A) Armor plates in an untreated high-plated adultmarine fish. The normal morphologies of two individual plates are outlinedwith dashed lines. (B) Control beads soaked in PBS wereimplanted between the two outlined plates at two months of age. After beadimplantation, fish continued to develop a full set of armor plates, withminimal changes in plate morphology (n = 8). (C)Implantation of Wnt-3a beads results in hypermorphic growth and armor platefusion in the regions surrounding the exogenous Wnt-3a signal (n =11). (D) Conversely, beads soaked in the Wnt inhibitor Dkk-1inhibit plate formation surrounding the site of bead implantation (n= 10). Scale bar in D is 2 mm long.DOI:http://dx.doi.org/10.7554/eLife.05290.008
Mentions: Previous studies have shown that Wnt signaling acts upstream of EDAin the early proliferation and specification of tissues in many vertebrates (Laurikkala et al., 2002; Cui and Schlessinger, 2006; Häärä et al., 2011; Arte et al., 2013). To test whether Wnt also acts upstream of platedevelopment in sticklebacks, we tested whether implants of either Wnt-3a or Dkk-1 (aninhibitor of Wnt signaling, Glinka et al.,1998) altered normal patterns of armor plate formation. Beads soaked inPBS, Wnt-3a, or Dkk-1 proteins were surgically implanted into the mid-flank of2-month-old marine fish, and fish were then aged to 6 months to test for effects onplate size and number. Control bead implantation had no significant effect on overallplate morphology (Figure 5A,B). In contrast,exposure to ectopic Wnt signaling at the juvenile stage induced hypermorphic platedevelopment, characterized by adult fish with larger plates and plate fusionssurrounding the sites of Wnt-3a bead implantation (Figure 5C). Conversely, the addition of the Wnt inhibitor Dkk-1 resultedin a hypomorphic phenotype marked by the absence of plates surrounding the beadimplantation site (Figure 5D), suggesting thatWnt signaling plays an important role in normal plate development.10.7554/eLife.05290.008Figure 5.Wnt signaling regulates armor plate development.

Bottom Line: An identical T → G base pair change is found in EDA enhancers of divergent low-plated fish.Recreation of the T → G change in a marine enhancer strongly reduces expression in posterior armor plates.Thus parallel evolution of low-plated sticklebacks has occurred through a shared DNA regulatory change, which reduces the sensitivity of an EDA enhancer to Wnt signaling, and alters expression in developing armor plates while preserving expression in other tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology, Stanford University School of Medicine, Stanford, United States.

ABSTRACT
Armor plate changes in sticklebacks are a classic example of repeated adaptive evolution. Previous studies identified ectodysplasin (EDA) gene as the major locus controlling recurrent plate loss in freshwater fish, though the causative DNA alterations were not known. Here we show that freshwater EDA alleles have cis-acting regulatory changes that reduce expression in developing plates and spines. An identical T → G base pair change is found in EDA enhancers of divergent low-plated fish. Recreation of the T → G change in a marine enhancer strongly reduces expression in posterior armor plates. Bead implantation and cell culture experiments show that Wnt signaling strongly activates the marine EDA enhancer, and the freshwater T → G change reduces Wnt responsiveness. Thus parallel evolution of low-plated sticklebacks has occurred through a shared DNA regulatory change, which reduces the sensitivity of an EDA enhancer to Wnt signaling, and alters expression in developing armor plates while preserving expression in other tissues.

Show MeSH