5-350 Lecture Notes - T-Box, Fgf4, Zone Of Polarizing Activity
28 Jan 2013
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Document Summary
Timeline buds appear at 26d somites 8-12 lower buds at 28d somites 24-29 complete at 56d. Embryological origins of limb components: skin = surface ectoderm melanocytes = ncc sensory neurons = ncc motor neurons = neural tube myotome (somites) = muscle somatic lateral plate mesoderm + ectoderm = limb buds (bones, tendons, ligaments, dermis) Aer apical ectodermal ridge divides limb bud into dorsal-ventral transplanted ectoderm can form new aer induced by mesenchyme. **both need to be functioning for proper limb-bud development. Progress zone actively dividing cells adjacent to aer mesenchyme here determines proximal/distal patterning. Rejacketing experiments late mesenchyme + early cap only distal elements form. Fgf-8 induces limb bud formation (which leads to aer formation) Fgf-soaked beads can induce an entire ectopic limb. However, polarity is reversed (mirror-image limb forms) Fgf-10 is initially expressed broadly throughout mesoderm localized fgf expression is necessary for limb bud formation localized fgf levels are also higher concentration.
