定向细胞运动和分裂解释早期肢芽形态发生学
The vertebrate limb bud arises from lateral plate mesoderm and its overlying ectoderm. Despite progress regarding the geneticrequirements for limb development, morphogenetic mechanisms that generate early outgrowth remain relatively undefined. Weshow by live imaging and lineage tracing in different vertebrate models that the lateral plate contributes mesoderm to the earlylimb bud through directional cell movement. The direction of cell motion, longitudinal cell axes and bias in cell division planes lielargely parallel to one another along the rostrocaudal (head-tail) axis in lateral plate mesoderm. Transition of these parametersfrom a rostrocaudal to a mediolateral (outward from the body wall) orientation accompanies early limb bud outgrowth.Furthermore, we provide evidence that Wnt5a acts as a chemoattractant in the emerging limb bud where it contributes to theestablishment of cell polarity that is likely to underlie the oriented cell behaviours.