Pair-Wise Regulation of Convergence and Extension Cell Movements by Four Phosphatases via RhoA

Abstract

Various signaling pathways regulate shaping of the main body axis during early vertebrate development. Here, we focused on the role of protein-tyrosine phosphatase signaling in convergence and extension cell movements. We identified Ptpn20 as a structural paralogue of PTP-BL and both phosphatases were required for normal gastrulation cell movements. Interestingly, knockdowns of PTP-BL and Ptpn20 evoked similar developmental defects as knockdown of RPTPα and PTPε. Co-knockdown of RPTPα and PTP-BL, but not Ptpn20, had synergistic effects and conversely, PTPε and Ptpn20, but not PTP-BL, cooperated, demonstrating the specificity of our approach. RPTPα and PTPε knockdowns were rescued by constitutively active RhoA, whereas PTP-BL and Ptpn20 knockdowns were rescued by dominant negative RhoA. Consistently, RPTPα and PTP-BL had opposite effects on RhoA activation, both in a PTP-dependent manner. Downstream of the PTPs, we identified NGEF and Arhgap29, regulating RhoA activation and inactivation, respectively, in convergence and extension cell movements. We propose a model in which two phosphatases activate RhoA and two phosphatases inhibit RhoA, resulting in proper cell polarization and normal convergence and extension cell movements.

Protein tyrosine phosphatases in health and disease

“…Interestingly, comparison of PTP sequences in five distinct fish genomes led to the surprising discovery that Ptpn20 encodes a large PTP with multiple functional domains, closely resembling PTP‐BAS like (PTP‐BL), rather than a small protein encoding little more than a PTP domain. In fact, the human PTPN20 gene has a similar structure to that of zebrafish ptpn20 , which was confirmed by reverse transcription PCR . All but three mammalian PTP genes are represented in the zebrafish genome.…”

“…Interestingly, these knockdowns were rescued by dominant negative RhoA, while RPTPα and PTPε knockdowns were rescued by constitutively active RhoA. A model is emerging in which PTP‐mediated modulation of RhoA activity results in proper cell polarization, which is at the basis of normal convergence and extension cell movements during gastrulation .…”

Evolutionarily conserved gene expression patterns for affective disorders revealed using cross-species brain transcriptomic analyses in humans, rats and zebrafish

“…The NGEF (Neuronal Guanine Nucleotide Exchange Factor) gene 120 is expressed in the caudate nucleus and is involved in the activation of RhoA, Rac1, and Cdc42 (the Ras superfamily-associated proteins), hence modulating mitogen-activated protein kinase (MAPK) signaling and cell junction 121 . NGEF is also a downstream signaling component of the ephrin-A (EphA4) tyrosine kinase receptor, responsible for the formation of neural networks, nerve growth, and changes in cell morphology involved in cell motility 122 – 126 . Some genetic studies also implicate NGEF in schizophrenia 127 , 128 .…”

Protein Phosphatase 1 β Paralogs Encode the Zebrafish Myosin Phosphatase Catalytic Subunit

“…The Wnt-PCP pathway requires finely balanced regulation to elicit polarize cell movement as either gain or loss-of-function of Wnt-PCP components results in severe gastrulation defects [68–75]. RhoA is controlled by several additional regulators during zebrafish gastrulation including the non-receptor tyrosine kinases Fyn and Yes [76,77], which signal along with tyrosine phosphatases Shp2 [78], RPTPα and PTPε [79,80] In addition pathways dependent on Gα12 and Gα13 [81], AKAP12 (Gravin) [29,82] Adhesion-associated GAPs [83] and several Rho-GEFs [84–87] control RhoA signaling and disruption of any of these regulators causes severe gastrulation and body axis elongation defects. Critical targets of RhoA during gastrulation include formins [88], which control actin polymerization, and the Rho-dependent kinase Rock [30,89] and myosin phosphatase [9], which control actomyosin contractility [20].…”