Torok M A, Gardiner D M, Izpisúa-Belmonte J C, Bryant S V
Developmental Biology Center, University of California, Irvine 92697, USA.
J Exp Zool. 1999 Jul 1;284(2):197-206.
Sonic hedgehog (shh) expression is detectable in the posterior mesenchyme of many developing vertebrate limbs. We have isolated an RT-PCR fragment from the axolotl, Ambystoma mexicanum, that has high identity to other vertebrate shh genes. We describe the localization of this transcript during development and regeneration and in response to tissue grafts and retinoic acid (RA) exposure in the axolotl. Even though axolotl digits show a reversed polarity of differentiation (anterior [A] to posterior [P]) when compared to other tetrapods (P to A), shh is nevertheless expressed on the posterior margin of developing and regenerating limb buds. When A cells are grafted adjacent to P cells, an ectopic domain of shh is induced. Exposure to retinoic acid (RA), a molecule known to alter pattern in all three limb axes in urodeles, results in ectopic expression of shh in anterior cells of the regeneration blastema. Prior to this induced expression in response to RA, there is an earlier response by the endogenous domain of shh, which is downregulated within the first few hours of exposure.
音猬因子（shh）的表达在许多发育中的脊椎动物肢体的后间充质中可被检测到。我们从墨西哥钝口螈（Ambystoma mexicanum）中分离出一个逆转录聚合酶链式反应（RT-PCR）片段，它与其他脊椎动物的shh基因具有高度同源性。我们描述了该转录本在墨西哥钝口螈发育、再生过程中的定位，以及对组织移植和视黄酸（RA）暴露的反应。尽管与其他四足动物相比，墨西哥钝口螈的指显示出相反的分化极性（从前[前]到后[后]），但shh仍在发育中和再生的肢芽的后缘表达。当A细胞移植到P细胞附近时，会诱导出一个shh的异位区域。视黄酸（RA）是一种已知会改变有尾目动物所有三个肢体轴模式的分子，它会导致再生芽基的前体细胞中shh的异位表达。在这种由RA诱导的表达之前，shh的内源性区域会有更早的反应，该区域在暴露的最初几个小时内会被下调。
