hh expression and function in embryonic leg development. (A)
hh mRNA is expressed in early embryos in a segmental pattern along the anterior posterior axis. (B) The segmental expression persists and hh mRNA expands to the developing limb buds. (C) As the legs extend, hh mRNA becomes prominent in a posterior stripe in all the legs with additional lateral stripes (arrowheads). (D) Mild hh RNAi phenotype shows little segmentation defects such that the boundary between T2 and T3 segments appears to be fused (arrowhead). Mildly affected embryos show truncation of distal leg segments (arrow). (E) Moderate hh RNAi embryos showing patterning defects. (F) Segmentation defects aggravate in severe hh RNAi where only the head and the first thoracic segment could be distinguished, and all the legs are distally truncated. (G) Measurement of mild hh RNAi legs showing increased length of the femur in all three legs. Note that the tarsi and tibias in these embryos were partially or entirely missing. Leg measurements for T1 legs, T2 legs, and T3 legs are represented in the different bars; the three measured leg segments - the femur, the tibia, and the tarsus - are represented in the segments of each bar. N = 10; error bars represent ±1 standard error. ANOVA test performed using leg length divided by individual embryo length was used to correct for individual size variations. An asterisk indicates that the test was significant at (P ≤ 0.01). hh: hedgehog; RNAi: gene knockdown using ribonucleic acid interference; T1, 2, 3: thoracic segments 1, 2, 3; WT: wild type.