Nodal信号靶基因dusp4抑制斑马鱼中内胚层形成

The Nodal regulated dusp4 inhibits mesendoderm formation during zebrafish gastrulation

丝裂原活化蛋白激酶磷酸酶-2(MKP-2/DUSP4)具有酪氨酸磷酸酶和丝氨酸/苏氨酸磷酸酶活性,可以作用于MAPKs(Mitogen-activated protein kinases)底物,使其去磷酸化。但dusp4在脊椎动物胚胎发育中的功能还所知甚少。为深入了解dusp4在发育中的作用,文章首先检测了其在斑马鱼胚胎的表达。通过整胚原位杂交实验,发现dusp4是斑马鱼母源表达的基因,并且随着发育的进行,在原肠早期特异表达在中内胚层区域。进一步的实验表明,Nodal信号对dusp4的表达至关重要。过表达Nodal信号的配体sqt、dusp4的表达水平明显升高,而在缺失Nodal信号的突变体MZoep中,几乎检测不到dusp4的表达。此外,文章利用反义核苷酸Morpholino(MO)敲降dusp4的表达,中内胚层标识基因gsc、sox17和sox32的表达水平显著升高,而过表达dusp4对中内胚层的形成没有明显的影响,表明dusp4对中内胚层形成的抑制作用是必需的,但不是充分的,可能还有其他未被鉴定的协同作用因子。以上研究结果表明,dusp4基因的表达受到Nodal信号调控,在原肠期具有抑制中内胚层形成的作用。

MAP kinase phosphatase-2 （MKP-2/DUSP4）, a dual specificity protein phosphatase with tyrosine/serine/ threonine phosphatase activity, is associated with cellular proliferation and differentiation, but its functions during embryo development are unclear. To study the developmental function of dusp4, we first examined the spatiotemporal expression pattern of this gene during zebrafish embryonic development by whole mount in situ hybridization. We found that dusp4 was maternally expressed since its transcripts were present from the one-cell to the 256-cell stages. At early gastrulation stages, dusp4 transcripts specifically distributed at margin region, where the mesendodermal cells were located. Furthermore, Nodal signal was crucial for dusp4 expression. The expression of dusp4 was obviously increased in Nodal ligand overexpressed embryos, while its expression was almost lost in the Nodal signal-deficient MZoep mutants. In addition, dusp4 MO was also designed to knock down its expression in embryos. The mesendoderm formation was significantly increased in dusp4 morphants, but not obviously changed in dusp4 overexpressed embryos, suggesting that dusp4 is necessary, but not sufficient for the inhibitory of mesendoderm induction. Thus, our results indicate that Nodal regulated dusp4 plays a repressive role in mesendoderm induction.