Role of Retinoic acid in Limb Regeneration

两栖动物肢体再生胚被广泛用于再生能力和模式形成的分析。由于无尾两栖动物在变态过程中再生能力逐渐下降，因此被认为是一种有趣的分析材料。维甲酸可以调节尾纲两栖动物的肢体形态。断肢后在含维甲酸的水中饲养，由于位置值从远端到近端、从前方到后方、从背部到腹部的变化，诱导了近端到远端的重复肢体、前半囊胚完全成肢和后半囊胚完全成肢。本项目旨在与stocum教授合作，探讨维甲酸对无尾两栖动物再生肢胚的影响。stocum教授发现尾尾肢胚位置值的变化。所得结果如下：1。作为位置值后发化的分子标记，我们检测了音hedgehog基因在非洲爪猴中的表达。2. SHH在肢芽后缘和胚芽中表达，首次证实了SHH在胚芽中表达。维甲酸抑制肢体发育和再生。位置值是否发生变化仍不确定。通过嫁接由游离肢芽间充质组成的重组肢芽，形成了30-50趾足，这可能是由于胚基中不同位置值的间充质被分选，调节效力丧失所致。维甲酸对这种多指形成的影响的研究目前正在进行中

Regeneration blastema of amphibian limbs has been widely used for the analysis of regeneration potency and pattern formation. Anuran amphibians were regarded as an interesting material for such analysis since the regeneration potency gradually decreased during the course of metamorphosis.Retinoic acid is known to modulate limb pattern in urodela amphibians. By rearing the animal in retinoic acid-contaning water after limb amputation, the proximo-distal duplication of limbs, complete limb formation from anterior half blastema and complete limb formationfrom dorsal half blastema have been induced which were caused by the changes in positional values from distal to proximal, from anterior to posterior and from dorsal to ventral.The aim of this project is to examine the effects of retinoic acid administration on the rehenerating limb blastema of anuran amphibians by collaborting with Prof.Stocum who found the changes in positional values in urodela limb blastema.The results obtained were as fllows :1.As a molecular marker for the posteriorization of positional value, sonic hedgehog expression (shh) was examined in Xenopus.shh was expressed in the posterior margin of limb bud and blastema, which was the first evidence on shh expression in the blastema.2.Retinoic acid inhibited the limb development and regeneration.It remains uncertain whether the chages in positional value occur or not.3.By grafting recombinant limb bud composed of dissociated limb bud mesenchyme, feet with 30-50 digits were formed, which may be induced by the sorting out of the mesenchyme with different positional values and loss of regulation potency in the blastema.The study on the effects of retinoic acid on this multiple digit formation is now in progress