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. Author manuscript; available in PMC: 2012 Oct 5.
Published in final edited form as: Dev Dyn. 2011 May;240(5):1212–1222. doi: 10.1002/dvdy.22634

Figure 4. Identification of a unique single base pair change in the ZRS of the Silkie and Polydactyly chicken PPD mutants.

Figure 4

(A) Day E10 cartilage stained Silkie foot with preaxial extra digit 1 (arrow-top). (B) St. 26 Silkie Breed limb demonstrating ectopic anterior Shh mRNA expression (arrow-top), in addition to broadened posterior Shh expression in the ZPA (bottom). (C) The normal conserved ZRS sequence in the nonpolydactylous chicken strains: White Leghorn (WL), Brown Leghorn (BL), strain 003 and Hyline (HL). An identical base pair change C to A within the ZRS region (red) denoted by an asterisk, was found in the PPD Silkie and Polydactyly (Po) chicken strains. The PPD Dorking strain was found to have a normal sequence throughout the ZRS. (D) Posterior Shh expression was expanded distally and anteriorly in Silkie limb buds at all stages analyzed (shown here, St. 23–24). (E-G)β-galactosidase staining in wild type limbs electroporated with a reporter construct containing the ZRS sequence from Silkie chickens [Si-ZRS-cShh-lacZ (Si lacZ)]. (E, F) St 23–24 showed no detectable anterior staining, but posterior β-gal activity was expanded similar to the expansion of Shh expression in the Silkie limb at St 23–24. (G) St. 25+ limb showed both ectopic anterior and expanded posterior β-gal activity.