Biology Department, University of York, York YO10 5YW, United Kingdom.
Biology Department, University of York, York YO10 5YW, United Kingdom.
Dev Biol. 2014 Jul 15;391(2):207-18. doi: 10.1016/j.ydbio.2014.04.010. Epub 2014 Apr 24.
Genetic studies have established that heparan sulphate proteoglycans (HSPGs) are required for signalling by key developmental regulators, including Hedgehog, Wnt/Wg, FGF, and BMP/Dpp. Post-synthetic remodelling of heparan sulphate (HS) by Sulf1 has been shown to modulate these same signalling pathways. Sulf1 codes for an N-acetylglucosamine 6-O-endosulfatase, an enzyme that specifically removes the 6-O sulphate group from glucosamine in highly sulfated regions of HS chains. One striking aspect of Sulf1 expression in all vertebrates is its co-localisation with that of Sonic hedgehog in the floor plate of the neural tube. We show here that Sulf1 is required for normal specification of neural progenitors in the ventral neural tube, a process known to require a gradient of Shh activity. We use single-cell injection of mRNA coding for GFP-tagged Shh in early Xenopus embryos and find that Sulf1 restricts ligand diffusion. Moreover, we find that the endogenous distribution of Shh protein in Sulf1 knockdown embryos is altered, where a less steep ventral to dorsal gradient forms in the absence of Sulf1, resulting in more a diffuse distribution of Shh. These data point to an important role for Sulf1 in the ventral neural tube, and suggests a mechanism whereby Sulf1 activity shapes the Shh morphogen gradient by promoting ventral accumulation of high levels of Shh protein.
遗传研究已经证实，硫酸乙酰肝素蛋白聚糖（HSPGs）对于包括 Hedgehog、Wnt/Wg、FGF 和 BMP/Dpp 在内的关键发育调节剂的信号转导是必需的。硫酸乙酰肝素（HS）的 Sulf1 后合成修饰已被证明可以调节这些相同的信号通路。Sulf1 编码一种 N-乙酰葡萄糖胺 6-O-内切硫酸酯酶，该酶特异性地从 HS 链的高度硫酸化区域中的葡萄糖胺中去除 6-O 硫酸基。Sulf1 在所有脊椎动物中的表达的一个显著方面是其与 Sonic hedgehog 在神经管的基板中的共定位。我们在这里表明，Sulf1 是正常规范腹侧神经管中的神经祖细胞所必需的，已知该过程需要 Shh 活性的梯度。我们使用编码 GFP 标记的 Shh 的 mRNA 在早期 Xenopus 胚胎中进行单细胞注射，并发现 Sulf1 限制配体扩散。此外，我们发现 Sulf1 敲低胚胎中 Shh 蛋白的内部分布发生改变，在没有 Sulf1 的情况下，形成了一个不太陡峭的从腹侧向背侧的梯度，导致 Shh 蛋白的分布更加弥散。这些数据表明 Sulf1 在腹侧神经管中具有重要作用，并表明 Sulf1 活性通过促进高水平 Shh 蛋白的腹侧积累来塑造 Shh 形态发生梯度的机制。
