Developmental Biology 肢芽在躯干上的形成部位可能 受视黄酸和hox基因的控制 如多种动物的前肢芽都 出现于Hoxc-6表达谱的 最前部边界,即第一胸 椎所处位置。 Figure 18.4 Legs regenerating from the tail blastema of a marbled balloon frog tadpole. The tail blastema had bcen treated with retinoic acid after amputation. (From Mohanty-Heimadi et al., 1992, courtesy of P. Mohanty-Heimadi
Developmental Biology 肢芽在躯干上的形成部位可能 受视黄酸和hox基因的控制 如多种动物的前肢芽都 出现于Hoxc-6表达谱的 最前部边界，即第一胸 椎所处位置
胶体细胞的来源 肌肉细胞前体:来源于体节的轴下生肌区; 骨细胞前体:侧板中胚层的体细胞区间质细胞。 肢芽的形成受来自于中间中胚层 (intermediate mesoderm)如肾前体的信 号诱导,移去中肾或在中肾与肢芽细胞间插入不透膜可使肢芽停止增大。 Figure 16.3 .imb bud formation.(AI Proliferation of mesodermal cells from of myotome cells( purple)into the limb bud. This computer recon the somatic region ot the later al plate mesoderm causes the limb struction was m. de trom scctions from an in situ hybridization to bud in the amphibi an embryo to bulge outward. These cells gener. the myf mRNA tound in developing muscle cells. If you can cross ate the skeletal elements of the limb. Contributions of cells from the your eyes. the three dimensionality of the stereogram will become myotome prowide the source of the limbs musculature. (B) Entry apparent. (B courtesy of 1. Streicher and G. Muller. A Epaxial Central mvotome bud dermatome Myotome Hypaxial Sckerolotne myotome bud I imb musle precu Iimh bud Notochord Pronephros L imb skeletal Endoderm precusors teraI pL. mesoderm
Developmental Biology 肢体细胞的来源 肌肉细胞前体：来源于体节的轴下生肌区； 骨细胞前体：侧板中胚层的体细胞区间质细胞。 肢芽的形成受来自于中间中胚层(intermediate mesoderm)如肾前体的信 号诱导，移去中肾或在中肾与肢芽细胞间插入不透膜可使肢芽停止增大
Developmental Biology 新的研究表明,侧板中胚层中将要产生肢体间质 细胞的细胞分泌的FGF10诱导了肢芽的形成。 (AI Fiqure 16.4 FGFIO expression and action in the form. ( B) When cells geneticall developing chick limb. (A)FGFlo constructed to secrete FGFIO are becomes expressed in the lateral placed into the flanks of chick en olate mesoderm in precisely those bryos, the FGF10 can cause the for- positions where limbs normally mation of an ectopic limb(arrow)
Developmental Biology 新的研究表明，侧板中胚层中将要产生肢体间质 细胞的细胞分泌的FGF10诱导了肢芽的形成
Developmental Biology 顶端外胚层嵴( apical ectodermal ridge.,AER)的形成 AER:中胚层间质细胞诱导 其外侧的外胚层细胞形成突起结 构,位于肢芽的远端边缘背腹交 界处,是肢体生长的主要信号中 AER的作用: 1.维持其内侧的间质细胞的增生 能力,使肢体沿 Proximal- Distal轴线生长。 2.维持A一P轴线控制因子的表 达 3.与控制A一P和DV轴线的因 子互作,以指导细胞的分化。 Apical ectodermal ridge Fiqure 18.8 Scanning electron micrograph of an early chick forelimb bud, with its apical ectodermal ridge in the foreground
Developmental Biology 顶端外胚层嵴(apical ectodermal ridge, AER)的形成 AER：中胚层间质细胞诱导 其外侧的外胚层细胞形成突起结 构，位于肢芽的远端边缘背腹交 界处，是肢体生长的主要信号中 心。 AER的作用： 1. 维持其内侧的间质细胞的增生 能力，使肢体沿Proximal－ Distal轴线生长。 2. 维持A－P轴线控制因子的表 达。 3. 与控制A－P和D－V轴线的因 子互作，以指导细胞的分化
AER的形成依赖于背部外胚层和腹部外胚层的互作 证据:①将一个肢芽的腹部外胚层细胞移植到另一肢芽的背部外胚层 中,将产生一个额外的AER;②在肢芽外胚层背部化的突变体上,因缺 少腹部外胚层而不能生成AER,造成无肢体 Figure 18.9 stage.(B)After 2b hours incubation, an Formation of an ectopic AER when ven ectopic AER has formed(the original tral tissue is transplanted into dorsal AER is denoted by an arrow, the ectopi limb bud tissue. (A)Operation whereby AER by an arrowhead). (C)As the AER ventral ecoderm from a chick hindlimb forms, radical fringe expression(arrow bud is transplanted into the dorsal sur- head) in the limb bud becomes confined face of a host hindlimb bud at the same to the dorsal cells at the D/V junction which will form the Aer 18/19 host Stage 18/19 donor leg bud ectodermal jacket y Ectoderm graft AER mites
Developmental Biology AER的形成依赖于背部外胚层和腹部外胚层的互作 证据：①将一个肢芽的腹部外胚层细胞移植到另一肢芽的背部外胚层 中，将产生一个额外的AER；②在肢芽外胚层背部化的突变体上，因缺 少腹部外胚层而不能生成AER，造成无肢体