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Presenting Author(s) Trent Stephens
Abstract Title What factors determine limb location in vertebrate embryos?
Full author List Trent Stephens
Text of abstract What factors are involved in determining where a limb bud will form on a vertebrate embryo? What factors determine where in an embryo an ensemble of genes will turn on, or not turn off, to impart limbness to a specific region of that embryo? Those questions encompass a large portion of the issue of limb initiation. In attempting to answer those questions, a much more basic question may be posed: is limb position a dependent or an independent phenomenon? That is, is the position of the limb unrelated to that of other structures in the embryo or does it correlate with the positions of any other structures? Research in my laboratory has previously demonstrated that there is a correlation between limb position and the position of other structures in the embryo, such as the ends of the yolk sac. We have demonstrated the existence of a limb forming zone (LFZ) extending nearly the entire length of vertebrate embryos. We have also demonstrated, in salamander embryos, that experimentally shortening the caudal end of the yolk sac causes the hind limbs to shift cranially as much as five segments within the LFZ. Our current research focuses on the experimental manipulation of forelimb location in chick embryos. If Hensen's node is blocked or removed during a very narrow temporal window (stages 9 and 10), the wing buds will form up to six somites cranial to their normal location. Hypotheses that may explain this positional shift will be discussed. Hypothesis 1: cells accumulate in front of the implanted barrier or functional end of the embryo providing a site of enhanced cell proliferation within the LFZ. Hypothesis 2: the barrier or abrupt end of the embryo causes some axial- or paraxial-derived signal to accumulate and stimulate limb development at that location.
Which session is your work most relevant to: Limb initiation