Extended Data Figure 7. The conditional gain of Hoxa11 using the Hoxa13Cre allele results in the formation of supernumerary digits.

a, b, Autopod of Rosa^Hoxa11/+ (a) and Rosa^Hoxa11 Hoxa13Cre (b) at E15.5. Anterior is up. The Rosa26 locus and Hoxa13Cre allele being on the same chromosome (Chr6), the gain-of-function phenotype was assessed with only one copy of the Rosa^Hoxa11 allele. c–e, Autopod skeletons of Prx1Cre; Rosa^{Hoxa11/Hoxa11} mice at P0 from four distinct mutants (anterior is up). The number of digits varies from 6 to 7, with often a small post-axial extra-digit (posterior). The extra-digit phenotype is fully penetrant upon Cre-activation of two copies of the Rosa^Hoxa11 allele (n = 10). Original magnification, × 20. d, Quantification of Hoxa11 expression level by quantitative reverse transcriptase PCR (RT-qPCR) on RNA extracted from E11.5 forelimb, relative to both Gapdh and Tbp mRNA of Prx1Cre; Rosa^{Hoxa11/Hoxa11} embryos. Two-tailed t-test was performed. Error bars indicate s.d (n = 4).