Department of Molecular Neurobiology, Graduate School of Comprehensive Human Sciences, Institute of Basic Medical Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
Biochem Biophys Res Commun. 2010 Sep 10;400(1):66-71. doi: 10.1016/j.bbrc.2010.08.008. Epub 2010 Aug 6.
Autotaxin, encoded by the Enpp2 gene, generates lysophosphatidic acid (LPA) extracellularly, eliciting various cellular responses through specific LPA receptors. Previous studies have revealed that Enpp2(-/-) mice die at E9.5 owing to angiogenic defects in the yolk sac. Moreover, Enpp2(-/-) embryos show growth retardation, allantois malformation, no axial turning, and head cavity formation. We have also demonstrated that lysosome biogenesis is impaired in yolk sac visceral endoderm cells of Enpp2(-/-) embryos as a result of the downregulation of the Rho-ROCK (Rho-associated coiled-coil containing protein kinase)-LIM kinase pathway. In this study, we examine what signaling defect(s) is responsible for head cavity formation and yolk sac angiogenic defects. By using a whole embryo culture system, we show that 10 μM Ki16425, an antagonist for the LPA receptors, induces head cavity formation and yolk sac angiogenic defects in wild-type embryos. Moreover, 1 μM Ki16425 induces both phenotypes in Enpp2 heterozygous embryos at significantly higher incidence than in wild-type embryos, suggesting an interaction between autotaxin and LPA receptor signaling. Furthermore, we show that inhibition of the Rho-ROCK pathway induces head cavity formation, whereas multiple pathways are involved in yolk sac angiogenic defects. These results reveal the signal transduction defects that underlie the abnormalities in Enpp2(-/-) embryos.
自分泌酶（Autotaxin）由 Enpp2 基因编码，可在细胞外生成溶血磷脂酸（LPA），通过特定的 LPA 受体引发各种细胞反应。先前的研究表明，Enpp2(-/-) 小鼠在 E9.5 时因卵黄囊中的血管生成缺陷而死亡。此外，Enpp2(-/-) 胚胎表现出生长迟缓、尿囊畸形、无轴向转动和头部腔形成。我们还证明，由于 Rho-ROCK（Rho 相关卷曲螺旋蛋白激酶）-LIM 激酶途径下调，Enpp2(-/-) 胚胎的卵黄囊内脏内胚层细胞中的溶酶体生物发生受损。在这项研究中，我们研究了导致头部腔形成和卵黄囊血管生成缺陷的信号缺陷。通过使用整个胚胎培养系统，我们表明 10μM Ki16425（LPA 受体的拮抗剂）可诱导野生型胚胎形成头部腔和卵黄囊血管生成缺陷。此外，1μM Ki16425 在 Enpp2 杂合子胚胎中诱导这两种表型的发生率明显高于野生型胚胎，表明自分泌酶和 LPA 受体信号之间存在相互作用。此外，我们表明 Rho-ROCK 途径的抑制可诱导头部腔形成，而多个途径参与卵黄囊血管生成缺陷。这些结果揭示了 Enpp2(-/-) 胚胎异常的信号转导缺陷。
