Testing hypotheses of growth in the developing chicken limb bud

Abstract

Morphogenesis is not only a story of genes and phenotypes, but also one of growth and movement. To explain the large‐scale changes in shape and size that the developing vertebrate limb undergoes, a more complete understanding of mechanisms acting between gene expression and the developed phenotype is needed. Recent evidence has indicated that there is an anterior to posterior direction in the relative movement of cells compared to the contour of the chick wing bud at an early stage, HH16 (Hamburger and Hamilton, 1951, Wyngaarden et al., 2010; doi: 10.1242/dev.046987). Although older evidence has indicated that at later stages (HH20–27) there is an opposite posterior to anterior movement of cells relative to the margin of the limb bud (Vargesson et al., 1997; Development 124). Dii injections into the developing chicken wing at various stages were performed to establish the timing and directionality of movements of cells relative to the margin of the developing limb. We found these anterior to posterior movements of cells relative to the movement of the wing margin occur only at a restricted early phase of limb development and posterior to anterior movements are present generally throughout the remainder of limb bud outgrowth.Grant Funding Source: by NSERC, McGill University, and a Canada Research Chair to HCEL