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Signaling factor interaction affecting Shh, Wnt, and BMP expression during pattern formation in the developimg limb

信号因子相互作用影响发育肢体模式形成过程中的 Shh、Wnt 和 BMP 表达

基本信息

批准号：
13680813
负责人：
NOHNO Tsutomu
金额：
$ 2.3万
依托单位：
KAWASAKI MEDICAL SCHOOL
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Expression of Shh and FGF4 is maintained in the limb bud through positive feedback induction, as indicated by ectodermal FGF4 expression by Shh protein applied to the anterior limb bud. We have shown here that FGF4 protein can also induce Shh and Hoxd13 expression in the hindlimb bud, but not in the forelimb bud, leading to respecification of the positional value.Overexpression of Wnt10a normally expressed in the apical ectodermal ridge(AER) resulted in ectodermal expansion of FGF8 expression outside of the AER, through beta-catenin accumulation in the cellular fraction, as demonstrated by Western blotting.Inhibition of cell sorting with PI-PLC and anti-EphA4 antibody suggests involvement of ephrin-A and EphA interaction during position dependent cartilage formation in the limb bud. Overexpression of ephrin-A2 that intensely expressed in the proximal limb bud can induce syndactyly and bifurcation of the phalangeal bones distally, where EphA4 is intensely expressed.Overexpression of Wnt-inhibiting Sfrp3(Frzb1) or dominant-negative form of LEF1 maintains undifferentiated limb chondrocytes, whereas misexpression of Wnt8 or constitutive-active form of LEF1 promotes chondrocyte maturation and hypertrophy, leading to calcification of cartilage. Wnt5a, Wnt11,Wnt7a, and Wnt3a show region specific expression in the developing limb bud. Overexpression of these Wnts with RCAS affects myoblast proliferation and differentiation in the limb bud. Wnt5a promotes slow muscle fiber differentiation and inhibits fast muscle fiber differentiation. Dominant-negative form of Wnt11 has similar effect on muscle fibretype differentiation, which is reversed by wild-type Wnt11. Wnt-binding protein Sfrp2 is expressed in the myoblast progenitor cells and has inhibitory effect on muscle differentiaion upon misexpression.

Shh和FGF 4的表达通过正反馈诱导维持在肢芽中，如通过施用于前肢芽的Shh蛋白的外胚层FGF 4表达所指示的。我们在这里已经表明，FGF 4蛋白也可以诱导Shh和Hoxd 13在后肢芽中表达，但在前肢芽中不诱导，导致位置值的重新指定。Wnt 10a的过表达通常在顶端外胚层嵴（AER）中表达，通过β-连环蛋白在细胞组分中的积累，用PI-PLC和抗EphA 4抗体抑制细胞分选表明在肢芽中位置依赖性软骨形成期间肝配蛋白-A和EphA相互作用的参与。在近端肢芽中强烈表达的ephrin-A2的过表达可以诱导并指畸形和远端指骨分叉，其中EphA 4强烈表达。Wnt抑制性Sfrp 3（Frzb 1）或显性阴性形式的LEF 1的过表达维持未分化的肢体软骨细胞，而Wnt 8或组成型活性形式的LEF 1的错误表达促进软骨细胞成熟和肥大，导致软骨钙化。Wnt 5a、Wnt 11、Wnt 7a和Wnt 3a在发育中的肢芽中显示区域特异性表达。这些Wnt与RCAS的过表达影响肢芽中成肌细胞的增殖和分化。Wnt 5a促进慢肌纤维分化，抑制快肌纤维分化。Wnt 11的显性负性形式对肌纤维型分化具有类似的作用，这被野生型Wnt 11逆转。Wnt结合蛋白Sfrp 2在成肌祖细胞中表达，错误表达时对肌肉分化具有抑制作用。