Figure 3: Quantitative and dynamic expression of Dlx genes during limb development. (a) Expression of Dlx genes in the hindlimbs (HL) and forelimbs (FL) limbs, at the same embryonic age, by qPCR. In the HL, the expression is always lower, as compared to the FL. This difference, most likely reflecting the developmental lag of the HL compared to the FL, may explain the finding that malformations affecting the HL are more severe. (b) Relative expression of Dlx genes along the length of the AER, from anterior (An) to medial (Me) to posterior (Po) regions (indicated with a color code). The expression of single Dlx genes is not uniform, and considering their partial redundancy the “global” expression is lower in the central wedge. This region of the AER appears to be more “sensitive” to genetic alterations and is specifically affected in SHFM.