LIMB-PATTERNING ACTIVITY AND RESTRICTED POSTERIOR LOCALIZATION OF THE AMINO-TERMINAL PRODUCT OF SONIC HEDGEHOG CLEAVAGE
LIMB-PATTERNING ACTIVITY AND RESTRICTED POSTERIOR LOCALIZATION OF THE AMINO-TERMINAL PRODUCT OF SONIC HEDGEHOG CLEAVAGE
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DOI：
10.1016/s0960-9822(95)00156-4
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发表时间：
1995-07-01
期刊：
影响因子：
9.2
通讯作者：
FALLON, JF
中科院分区：
文献类型：
--
作者：
LOPEZMARTINEZ, A;CHANG, DT;FALLON, JF
背景：音速刺猬（Shh）是果蝇节段极性基因刺猬（hh）的脊椎动物同源物，与发育中的雏鸡肢体的模式有关。这种作用是通过Shh沿着后肢芽边缘的限制性表达以及通过观察表达Shh的异源细胞具有类似于来自后肢芽边缘极化区域的细胞的肢体极化活性来暗示的。然而，尚未证明仅声波刺猬蛋白 (SHH) 就足以形成肢体模式。 SHH 已被证明可在体内进行自蛋白水解切割，产生两种较小的产物。因此，确定 SHH 的加工是否发生在发育中的肢体中以及这种加工如何影响 SHH 的功能是有意义的。结果：我们证明 SHH 在发育中的雏鸡肢体中进行蛋白水解加工。表达与各个裂解产物相对应的 SHH 蛋白变体的细胞移植物表明，诱导模式化基因表达和将形态模式强加于肢芽的能力仅限于 SHH 蛋白水解裂解的氨基末端产物 (SHH-N)。我们还证明，从植入的珠子中释放的细菌合成和纯化的 SHH-N 足以进行肢体图案化活动。最后，我们表明内源性氨基末端裂解产物紧密定位于肢芽的后缘。结论：我们的数据表明，在 SHH 自蛋白水解产生的两种裂解产物中，在移植异源细胞中表达或以纯化形式提供的 SHH-N 足以将模式强加于发育中的肢体。此外，内源性氨基末端SHH裂解产物仅限于鸡肢芽的后缘，这使得其图案化活性不太可能是由于其在前后轴上以宽梯度分布而产生的。与观察到的定位更一致的是一个模型，其中氨基末端 SHH 裂解产物通过极化区域内或附近的局部诱导发挥其模式效应，启动基因表达级联，最终延伸到发育中的肢体。
Background: Sonic hedgehog (Shh), a vertebrate homolog of the Drosophila segment polarity gene hedgehog (hh), has been implicated in patterning of the developing chick limb. Such a role is suggested by the restricted expression of Shh along the posterior limb bud margin, and by the observation that heterologous cells expressing Shh have limb-polarizing activity resembling that of cells from the polarizing region of the posterior limb bud margin. It has not been demonstrated, however, that the Sonic hedgehog protein (SHH) alone is sufficient for limb patterning. SHH has been shown to undergo autoproteolytic cleavage in vitvo, yielding two smaller products. It is of interest, therefore, to determine whether processing of SHH occurs in the developing limb and how such processing influences the function of SHH.Results: We demonstrate that SHH is proteolytically processed in developing chick limbs. Grafts of cells expressing SHH protein variants that correspond to individual cleavage products demonstrate that the ability to induce patterned gene expression and to impose morphological pattern upon the limb bud is limited to the amino-terminal product (SHH-N) of SHH proteolytic cleavage. We also demonstrate that bacterially synthesized and purified SHH-N, released from implanted beads, is sufficient for limb-patterning activity. Finally, we show that the endogenous amino-terminal cleavage product is tightly localized to the posterior margin of the limb bud.Conclusions: Our data show that, of the two cleavage products resulting from SHH autoproteolysis, SHH-N expressed in grafted heterologous cells or supplied in purified form is sufficient to impose pattern upon the developing limb. Moreover, the restricted localization of the endogenous amino-terminal SHH cleavage product to the posterior border of the chick limb bud makes it unlikely that its patterning activity results from it being distributed in a broad gradient across the antero-posterior axis. More consistent with the observed localization is a model in which the amino-terminal SHH cleavage product exerts its patterning effects by local induction in or near the polarizing region, initiating a cascade of gene expression that ultimately extends across the developing limb.