ZOO 3050 Lecture Notes - Lecture 19: Apical Ectodermal Ridge, Lateral Plate Mesoderm, Limb Bud
13 Apr 2018
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Document Summary
Limb formation is not essential for embryonic life: syndactyly, 2 or more digits are fused together, polydactyly, extra digit, triphalangal thumb, 3 phalanges instead of 2. If all adjacent cells are removed limb still develops: limb field, limb development-mesenchyme cells proliferate from limb field, lateral plate mesoderm-limb skeletal precursor, somites-limb muscle precursors. Infestation of larval abdomen by parasitic trematodes: eggs split tadpole limb bud in several places. Models of limb development: two-signal model for limb proximodistal patterning, one-signal model for limb proximodistal patterning. Early signal inductions in fore- and hindlimb development. Type of limb formed depends on tbx protein expressed at fgf source: fgf placed close to hindlimb area. Induced limb bud exposed to high tbx4 levels hindlimb: fgf placed close to forelimb area. Induced limb bud exposed to high tbx5 levels forelimb: bud induced in centre express tbx5 in anterior of extra limb and tbx4 in posterior portion, limb develops as mixed structure.
