VI 胚层发育与器官系统发生(II).ppt
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1、Developmental Biology,Chapter 6: Organogenesis development of the vertebrate limb,The embryonic chick wing,The vertebrate limb development is a particularly good system in which to study pattern formation during organogenesis (I),The vertebrate limb is a complex organ with three developmental axes:
2、the proximo-distal axis running from the base of the limb to the tip, the antero-posterior axis running parallel with the body AP axis, and the dorso-ventral axis running from the back of the hand to the palm. Thus, the limb development is a particularly good system in which to study pattern formati
3、on Since the limbs, unlike heart or brain, are not essential for embryonic life, one can experimentally remove or transplant parts of the developing limb, or create limb-specific mutants without interfering with the vital processes of the organism. This is good advantage of studying pattern formatio
4、n in organogenesis,The vertebrate limb development is a particularly good system in which to study pattern formation during organogenesis (II),The limb is a good model for studying cellular interactions within a structure containing a large number of cells, and for elucidating the role of intercellu
5、lar signaling in development. Recently, particular signal proteins have been identified to function in patterning along each of three limb axes: FGF family in Pr-D axial patterning Sonic hedgehog (Shh) protein in A-P axial patterning Wnt7a in D-V axial patterning,The vertebrate limb develops from a
6、limb bud,3 The limb development 3.1 Specification and formation of the limb bud 3.2 The limb outgrowth and generation of the proximal-distal axis 3.3 The anterior-posterior axial patterning 3.4 Patterning the dorsal-ventral axis 3.5 Coordinating the three axes 3.6 Development of the digits,Developme
7、nt of the vertebrate limb,3 The limb development 3.1 Specification and formation of the limb bud 3.2 The limb outgrowth and generation of the proximal-distal axis 3.3 The anterior-posterior axial patterning 3.4 Patterning the dorsal-ventral axis 3.5 Coordinating the three axes 3.6 Development of the
8、 digits,Development of the vertebrate limb,The vertebrate limb develops from a limb bud,Proliferation of mesodermal cells from the lateral plate mesoderm causes the limb bud to bulge outward,While the lateral plate mesodermal cells generate the skeletal elements of the limb, cells from the somites p
9、rovide the limbs musculature,FGF10 secreted from the lateral plate mesoderm cells is the signal for limb bud induction,A: FGF10 becomes expressed in the lateral plate mesoderm of the limb bud-forming region B: Ectopic expression of FGF10 beneath the flank ectoderm induces extra limb,FGF10,Ectopic li
10、mb,FGF10 initiates the limb bud-forming interactions between the ectoderm and the mesoderm via dual signaling induction,A: FGF10 is originally expressed throughout the lateral plate mesoderm B: FGF10 becomes restricted to the limb bud-forming regions, controlled by Wnt 2b and Wnt 8c respectively C:
11、Dual induction between FGF10 in the mesoderm and FGF8 in the apical ectoderm ridge (AER),Molecular model for the initiation of the limb bud in the chick between 48 and 54 hours of gestation,3 The limb development 3.1 Specification and formation of the limb bud 3.2 The limb outgrowth and generation o
12、f the proximal-distal axis 3.3 The anterior-posterior axial patterning 3.4 Patterning the dorsal-ventral axis 3.5 Coordinating the three axes 3.6 Development of the digits,Development of the vertebrate limb,Apical ectodermal ridge (AER) Progress zone (PZ),The AER is required for both the outgrowth o
13、f limb and the correct proximo-distal patterning,FGF8 is expressed in the apical ectodermal ridge (AER),FGF8 can functionally substitute for the AER,The similar results can be obtained with FGF4, indicating that FGF8/FGF4 are key signals for the AER,The mesenchyme cells: induce and sustain the AER,
14、and determine the type of limb to be formed. The AER: a major signaling center for the developing limb, and maintains the mesenchyme in a proliferating phase that enables the Pr-D growth of the limb,The proximal-distal growth of the limb bud involves interactions between the AER and the underlying m
15、esenchyme,Role of the AER or the PZ (progress zone) in specifying the proximal-distal axis? The mechamisms underlying the PD axis specification and patterning?,How is development of the proximal-distal axis accomplished during the limb outgrowth ?,Specification of proximal-distal axis is controlled
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