Levy-Strumpf Naomi, Krizus Meghan, Zheng Hong, Brown Louise, Culotti Joseph G
Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital, Toronto, Ontario, Canada.
Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
PLoS Genet. 2015 Aug 20;11(8):e1005446. doi: 10.1371/journal.pgen.1005446. eCollection 2015 Aug.
Wnt and Netrin signaling regulate diverse essential functions. Using a genetic approach combined with temporal gene expression analysis, we found a regulatory link between the Wnt receptor MOM-5/Frizzled and the UNC-6/Netrin receptor UNC-5. These two receptors play key roles in guiding cell and axon migrations, including the migration of the C. elegans Distal Tip Cells (DTCs). DTCs migrate post-embryonically in three sequential phases: in the first phase along the Antero-Posterior (A/P) axis, in the second, along the Dorso-Ventral (D/V) axis, and in the third, along the A/P axis. Loss of MOM-5/Frizzled function causes third phase A/P polarity reversals of the migrating DTCs. We show that an over-expression of UNC-5 causes similar DTC A/P polarity reversals and that unc-5 deficits markedly suppress the A/P polarity reversals caused by mutations in mom-5/frizzled. This implicates MOM-5/Frizzled as a negative regulator of unc-5. We provide further evidence that small GTPases mediate MOM-5's regulation of unc-5 such that one outcome of impaired function of small GTPases like CED-10/Rac and MIG-2/RhoG is an increase in unc-5 function. The work presented here demonstrates the existence of cross talk between components of the Netrin and Wnt signaling pathways and provides further insights into the way guidance signaling mechanisms are integrated to orchestrate directed cell migration.
Wnt和Netrin信号传导调节多种重要功能。通过结合时间基因表达分析的遗传方法,我们发现了Wnt受体MOM-5/卷曲蛋白与UNC-6/Netrin受体UNC-5之间的调控联系。这两种受体在引导细胞和轴突迁移中起关键作用,包括秀丽隐杆线虫远端末梢细胞(DTC)的迁移。DTC在胚胎后迁移经历三个连续阶段:第一阶段沿前后(A/P)轴迁移,第二阶段沿背腹(D/V)轴迁移,第三阶段沿A/P轴迁移。MOM-5/卷曲蛋白功能丧失会导致迁移的DTC在第三阶段出现A/P极性反转。我们发现UNC-5的过表达会导致类似的DTC A/P极性反转,并且unc-5缺陷明显抑制了由mom-5/卷曲蛋白突变引起的A/P极性反转。这表明MOM-5/卷曲蛋白是unc-5的负调节因子。我们进一步提供证据表明,小GTP酶介导MOM-5对unc-5的调节,使得像CED-10/Rac和MIG-2/RhoG这样的小GTP酶功能受损的一个结果是unc-5功能增加。本文介绍的工作证明了Netrin和Wnt信号通路成分之间存在相互作用,并为指导信号机制如何整合以协调定向细胞迁移提供了进一步的见解。