Signaling pathways controlling primordial germ cell migration in zebrafish

CXCR4 and CXCR7 cooperate during tangential migration of facial motoneurons

Migration of facial motoneurons in the zebrafish hindbrain depends on SDF1/CXCL12 signaling. Recent studies demonstrated that SDF1 can bind two chemokine receptors, CXCR4 and CXCR7. Here we explore the expression and function of the cxcr7b gene in zebrafish hindbrain development. By the time cxcr4b-expressing motoneurons migrate from rhombomere (r) r4 to r6, expression of cxcr7b is rapidly restricted to the ventral part of r5. Inactivation of either cxcr7b or cxcr4b impairs motoneuron migration, with however different phenotypes. Facial motoneurons preferentially accumulate in r5 in cxcr7b morphant embryos, while they are distributed between r4, r5 and r6 in cxcr4b morphants. Simultaneous inactivation of both receptors leads to yet a third phenotype, with motoneurons mostly distributed between r4 and r5. The latter phenotype resembles that of sdf1a morphant embryos. Double inactivation of sdf1a and cxcr7b indeed did not lead to a complete arrest of migration but rather to a partial rescue of r5 arrest of motoneuron migration. This result is in accordance with the functional hypothesis that SDF1 might interact with CXCR7 and that they have an antagonistic effect within r5. The ectopic expression of a truncated CXCR7 receptor leads to a motoneuron migration defect. Altogether, we show that CXCR7 is required, for proper tangential migration of facial motoneurons, by determining a permissive migration pathway through r5.

Germ cell migration in zebrafish is cyclopamine-sensitive but Smoothened-independent

Primordial germ cells (PGCs) are the progenitors of reproductive cells in metazoans and are an important model for the study of cell migration in vivo. Previous reports have suggested that Hedgehog (Hh) protein acts as a chemoattractant for PGC migration in the Drosophila embryo and that downstream signaling proteins such as Patched (Ptc) and Smoothened (Smo) are required for PGC localization to somatic gonadal precursors. Here we interrogate whether Hh signaling is required for PGC migration in vertebrates, using the zebrafish as a model system. We find that cyclopamine, an inhibitor of Hh signaling, causes strong defects in the migration of PGCs in the zebrafish embryo. However, these defects are not due to inhibition of Smoothened (Smo) by cyclopamine; rather, we find that neither maternal nor zygotic Smo is required for PGC migration in the zebrafish embryo. Cyclopamine instead acts independently of Smo to decrease the motility of zebrafish PGCs, in part by dysregulating cell adhesion and uncoupling cell polarization and translocation. These results demonstrate that Hh signaling is not required for zebrafish PGC migration, and underscore the importance of regulated cell-cell adhesion for cell migration in vivo.

Chemokines in neuroectodermal development and their potential implication in cancer stem cell-driven metastasis

Chemokines regulate proliferation and migration of various types of normal stem and progenitor cells, including precursor cells of neuroectodermal origin. Based on this it is conceivable that the established role of chemokines in cancer cell proliferation and organ-specific metastasis might also be associated with stem cell-like cells present in the tumor. Such cancer stem cells (CSCs) represent a small subpopulation of tumor cells that are thought to initiate and sustain tumor formation. More recently, characteristics of stem cells have also been observed in metastatic cancer cells, and it has been suggested that CSCs might play a crucial role in the metastatic process as such. Intriguingly, first evidence has been provided that the metastatic spread of specific CSCs is driven by chemokine signaling. Thus it is possible that chemokine-mediated CSC regulation might be a general feature of metastasis formation.

Sdf1/Cxcr4 signaling controls the dorsal migration of endodermal cells during zebrafish gastrulation

During vertebrate gastrulation, both mesodermal and endodermal cells internalize through the blastopore beneath the ectoderm. In zebrafish, the internalized mesodermal cells move towards the dorsal side of the gastrula and, at the same time, they extend anteriorly by convergence and extension (C&E) movements. Endodermal cells showing characteristic filopodia then migrate into the inner layer within the hypoblast next to the yolk syncytial layer (YSL). However, little is known about how the movement of endodermal cells is regulated during gastrulation. Here we show that sdf1a- and sdf1b-expressing mesodermal cells control the movements of the cxcr4a-expressing endodermal cells. The directional migration of endodermal cells during gastrulation is inhibited by knockdown of either cxcr4a or sdf1a/sdf1b (sdf1). We also show that misexpressed Sdf1 acts as a chemoattractant for cxcr4a-expressing endodermal cells. We further found, using the endoderm-specific transgenic line Tg(sox17:EGFP), that Sdf1/Cxcr4 signaling regulates both the formation and orientation of filopodial processes in endodermal cells. Moreover, the accumulation of phosphoinositide 3,4,5-trisphosphate (PIP(3)), which is known to occur at the leading edge of migrating cells, is not observed at the filopodia of endodermal cells. Based on our results, we propose that sdf1-expressing mesodermal cells, which overlie the endodermal layer, guide the cxcr4a-expressing endodermal cells to the dorsal side of the embryo during gastrulation, possibly through a PIP(3)-independent pathway.

Zebrafish primordial germ cell cultures derived from vasa::RFP transgenic embryos

Although embryonic germ (EG) cell-mediated gene transfer has been successful in the mouse for more than a decade, this approach is limited in other species due to the difficulty of isolating the small numbers of progenitors of germ cell lineage (PGCs) from early-stage embryos and the lack of information on the in vitro culture requirements of the cells. In this study, methods were established for the culture of PGCs obtained from zebrafish embryos. Transgenic embryos that express the red fluorescent protein (RFP) under the control of the PGC-specific vasa promoter were used, making it possible to isolate pure populations of PGCs by fluorescence-activated cell sorting (FACS) and to optimize the culture conditions by counting the number of fluorescent PGC colonies produced in different media. Cultures initiated from 26-somite-stage embryos contained the highest percentage of PGCs that proliferated in vitro to generate colonies. The effect of growth factors, including Kit ligand a and b (Kitlga and Kitlgb) and stromal cell-derived factor 1a and 1b (Sdf-1a and Sdf-1b), on PGC proliferation was studied. Optimal in vitro growth and survival of the zebrafish PGCs was achieved when recombinant Kitlga and Sdf-1b were added to the culture medium through transfected feeder cells, resulting in a doubling of the number of PGC colonies. Results from RT-PCR and in situ hybridization analysis demonstrated that PGCs maintained in culture expressed the kita receptor, even though receptor expression was not detected in PGCs isolated by FACS directly from dissociated embryos. In optimal growth conditions, the PGCs continued to proliferate for at least 4 months in culture. The capacity to establish long-term PGC cultures from zebrafish will make it possible to conduct in vitro studies of germ cell differentiation and EG cell pluripotency in this model species and may be valuable for the development of a cell-mediated gene transfer approach.

CXCR4 signaling in the regulation of stem cell migration and development

The regulated migration of stem cells is a feature of the development of all tissues and also of a number of pathologies. In the former situation the migration of stem cells over large distances is required for the correct formation of the embryo. In addition, stem cells are deposited in niche like regions in adult tissues where they can be called upon for tissue regeneration and repair. The migration of cancer stem cells is a feature of the metastatic nature of this disease. In this article we discuss observations that have demonstrated the important role of chemokine signaling in the regulation of stem cell migration in both normal and pathological situations. It has been demonstrated that the chemokine receptor CXCR4 is expressed in numerous types of embryonic and adult stem cells and the chemokine SDF-1/CXCL12 has chemoattractant effects on these cells. Animals in which SDF-1/CXCR4 signaling has been interrupted exhibit numerous phenotypes that can be explained as resulting from inhibition of SDF-1 mediated chemoattraction of stem cells. Hence, CXCR4 signaling is a key element in understanding the functions of stem cells in normal development and in diverse pathological situations.

Multiple roles of chemokine CXCL12 in the central nervous system: a migration from immunology to neurobiology

Chemotactic cytokines (chemokines) have been traditionally defined as small (10-14kDa) secreted leukocyte chemoattractants. However, chemokines and their cognate receptors are constitutively expressed in the central nervous system (CNS) where immune activities are under stringent control. Why and how the CNS uses the chemokine system to carry out its complex physiological functions has intrigued neurobiologists. Here, we focus on chemokine CXCL12 and its receptor CXCR4 that have been widely characterized in peripheral tissues and delineate their main functions in the CNS. Extensive evidence supports CXCL12 as a key regulator for early development of the CNS. CXCR4 signaling is required for the migration of neuronal precursors, axon guidance/pathfinding and maintenance of neural progenitor cells (NPCs). In the mature CNS, CXCL12 modulates neurotransmission, neurotoxicity and neuroglial interactions. Thus, chemokines represent an inherent system that helps establish and maintain CNS homeostasis. In addition, growing evidence implicates altered expression of CXCL12 and CXCR4 in the pathogenesis of CNS disorders such as HIV-associated encephalopathy, brain tumor, stroke and multiple sclerosis (MS), making them the plausible targets for future pharmacological intervention.

PDK1 regulates cancer cell motility by antagonising inhibition of ROCK1 by RhoE

In three-dimensional matrices cancer cells move with a rounded, amoeboid morphology that is controlled by ROCK-dependent contraction of acto-myosin. In this study, we show that PDK1 is required for phosphorylation of myosin light chain and cell motility, both on deformable gels and in vivo. Depletion of PDK1 alters the localization of ROCK1 and reduces its ability to drive cortical acto-myosin contraction. This form of ROCK1 regulation does not require PDK1 kinase activity, but instead involves direct binding of PDK1 to ROCK1 at the plasma membrane; PDK1 competes directly with RhoE for binding to ROCK1. In the absence of PDK1, negative regulation by RhoE predominates, causing reduced acto-myosin contractility and motility. This work uncovers a novel non-catalytic role for PDK1 in regulating cortical acto-myosin and cell motility.

Angiogenesis and vasculogenesis: inducing the growth of new blood vessels and wound healing by stimulation of bone marrow-derived progenitor cell mobilization and homing

During embryonic development, the vasculature is among the first organs to form and is in charge of maintaining metabolic homeostasis by supplying oxygen and nutrients and removing waste products. As one would expect, blood vessels are critical not only for organ growth in the embryo but also for repair of wounded tissue in the adult. An imbalance in angiogenesis (a time-honored term that globally refers to the growth of new blood vessels) contributes to the pathogenesis of numerous malignant, inflammatory, ischemic, infectious, immune, and wound-healing disorders. This review focuses on the central role of the growth of new blood vessels in ischemic and diabetic wound healing and defines the most current nomenclature that describes the neovascularization process in wounds. There are now two well-defined, distinct, yet interrelated processes for the formation of postnatal new blood vessels, angiogenesis, and vasculogenesis. Reviewed are recent new data on vasculogenesis that promise to advance the field of wound healing.

Ectopic germline cells in embryos of Xenopus laevis

Whether all descendants of germline founder cells inheriting the germ plasm can migrate correctly to the genital ridges and differentiate into primordial germ cells (PGCs) at tadpole stage has not been elucidated in Xenopus. We investigated precisely the location of descendant cells, presumptive primordial germ cells (pPGCs) and PGCs, in embryos at stages 23-48 by whole-mount in situ hybridization with the antisense probe for Xpat RNA specific to pPGCs and whole-mount immunostaining with the 2L-13 antibody specific to Xenopus Vasa protein in PGCs. Small numbers of pPGCs and PGCs, which were positively stained with the probe and the antibody, respectively, were observed in ectopic locations in a significant number of embryos at those stages. A few of the ectopic PGCs in tadpoles at stages 44-47 were positive in TdT-mediated dUTP digoxigenin nick end labeling (TUNEL) staining. By contrast, pPGCs in the embryos until stage 40, irrespective of their location and PGCs in the genital ridges of the tadpoles at stages 43-48 were negative in TUNEL staining. Therefore, it is evident that a portion of the descendants of germline founder cells cannot migrate correctly to the genital ridges, and that a few ectopic PGCs are eliminated by apoptosis or necrosis at tadpole stages.

PLA2 and PI3K/PTEN pathways act in parallel to mediate chemotaxis

Directed cell migration involves signaling events that lead to local accumulation of PI(3,4,5)P(3), but additional pathways act in parallel. A genetic screen in Dictyostelium discoideum to identify redundant pathways revealed a gene with homology to patatin-like phospholipase A(2). Loss of this gene did not alter PI(3,4,5)P(3) regulation, but chemotaxis became sensitive to reductions in PI3K activity. Likewise, cells deficient in PI3K activity were more sensitive to inhibition of PLA(2) activity. Deletion of the PLA(2) homolog and two PI3Ks caused a strong defect in chemotaxis and a reduction in receptor-mediated actin polymerization. In wild-type cells, chemoattractants stimulated a rapid burst in an arachidonic acid derivative. This response was absent in cells lacking the PLA(2) homolog, and exogenous arachidonic acid reduced their dependence on PI3K signaling. We propose that PLA(2) and PI3K signaling act in concert to mediate chemotaxis, and metabolites of PLA(2) may be important mediators of the response.

Differential expression of anti-Müllerian hormone (amh) and anti-Müllerian hormone receptor type II (amhrII) in the teleost medaka

In mammals, the anti-Müllerian hormone (Amh) is responsible for the regression of the Müllerian ducts; therefore, Amh is an important factor of male sex differentiation. The amh gene has been cloned in various vertebrates, as well as in several teleost species. To date, all described species show a sexually dimorphic expression of amh during sex differentiation or at least in differentiated juvenile gonads. We have identified the medaka amh ortholog and examined its expression pattern. Medaka amh shows no sexually dimorphic expression pattern. It is expressed in both developing XY male and XX female gonads. In adult testes, amh is expressed in the Sertoli cells and in adult ovaries in granulosa cells surrounding the oocytes, like in mammals. To better understand the function of amh, we cloned the anti-Müllerian hormone receptor type II (amhrII) ortholog and compared its expression pattern with amh, aromatase (cyp19a1), and scp3. During gonad development, amhrII is coexpressed with medaka amh in somatic cells of the gonads and shows no sexually dimorphic expression. Only the expression level of the Amh type II receptor gene was decreased noticeably in adult female gonads. These results suggest that medaka Amh and AmhrII are involved in gonad formation and maintenance in both sexes.

Insulin-like growth factor receptor 1b is required for zebrafish primordial germ cell migration and survival

Insulin-like growth factor (IGF) signaling is a critical regulator of somatic growth during fetal and adult development, primarily through its stimulatory effects on cell proliferation and survival. IGF signaling is also required for development of the reproductive system, although its precise role in this regard remains unclear. We have hypothesized that IGF signaling is required for embryonic germline development, which requires the specification and proliferation of primordial germ cells (PGCs) in an extragonadal location, followed by directed migration to the genital ridges. We tested this hypothesis using loss-of-function studies in the zebrafish embryo, which possesses two functional copies of the Type-1 IGF receptor gene (igf1ra, igf1rb). Knockdown of IGF1Rb by morpholino oligonucleotides (MO) results in mismigration and elimination of primordial germ cells (PGCs), resulting in fewer PGCs colonizing the genital ridges. In contrast, knockdown of IGF1Ra has no effect on PGC migration or number despite inducing widespread somatic cell apoptosis. Ablation of both receptors, using combined MO injections or overexpression of a dominant-negative IGF1R, yields embryos with a PGC-deficient phenotype similar to IGF1Rb knockdown. TUNEL analyses revealed that mismigrated PGCs in IGF1Rb-deficient embryos are eliminated by apoptosis; overexpression of an antiapoptotic gene (Bcl2l) rescues ectopic PGCs from apoptosis but fails to rescue migration defects. Lastly, we show that suppression of IGF signaling leads to quantitative changes in the expression of genes encoding CXCL-family chemokine ligands and receptors involved in PGC migration. Collectively, these data suggest a novel role for IGF signaling in early germline development, potentially via cross-talk with chemokine signaling pathways.

Sdf1a patterns zebrafish melanophores and links the somite and melanophore pattern defects in choker mutants

Pigment pattern formation in zebrafish presents a tractable model system for studying the morphogenesis of neural crest derivatives. Embryos mutant for choker manifest a unique pigment pattern phenotype that combines a loss of lateral stripe melanophores with an ectopic melanophore ;collar' at the head-trunk border. We find that defects in neural crest migration are largely restricted to the lateral migration pathway, affecting both xanthophores (lost) and melanophores (gained) in choker mutants. Double mutant and timelapse analyses demonstrate that these defects are likely to be driven independently, the collar being formed by invasion of melanophores from the dorsal and ventral stripes. Using tissue transplantation, we show that melanophore patterning depends upon the underlying somitic cells, the myotomal derivatives of which--both slow--and fast-twitch muscle fibres--are themselves significantly disorganised in the region of the ectopic collar. In addition, we uncover an aberrant pattern of expression of the gene encoding the chemokine Sdf1a in choker mutant homozygotes that correlates with each aspect of the melanophore pattern defect. Using morpholino knock-down and ectopic expression experiments, we provide evidence to suggest that Sdf1a drives melanophore invasion in the choker mutant collar and normally plays an essential role in patterning the lateral stripe. We thus identify Sdf1 as a key molecule in pigment pattern formation, adding to the growing inventory of its roles in embryonic development.

In vivo migration: a germ cell perspective

The basic concepts of the molecular machinery that mediates cell migration have been gleaned from cell culture systems. However, the three-dimensional environment within an organism presents migrating cells with a much greater challenge. They must move between and among other cells while interpreting multiple attractive and repulsive cues to choose their proper path. They must coordinate their cell adhesion with their surroundings and know when to start and stop moving. New insights into the control of these remaining mysteries have emerged from genetic dissection and live imaging of germ cell migration in Drosophila, zebrafish, and mouse embryos. In this review, we first describe germ cell migration in cellular and mechanistic detail in these different model systems. We then compare these systems to highlight the emerging principles. Finally, we contrast the migration of germ cells with that of immune and cancer cells to outline the conserved and different mechanisms.

Migration of Zebrafish Primordial Germ Cells: A Role for Myosin Contraction and Cytoplasmic Flow

The molecular and cellular mechanisms governing cell motility and directed migration in response to the chemokine SDF-1 are largely unknown. Here, we demonstrate that zebrafish primordial germ cells whose migration is guided by SDF-1 generate bleb-like protrusions that are powered by cytoplasmic flow. Protrusions are formed at sites of higher levels of free calcium where activation of myosin contraction occurs. Separation of the acto-myosin cortex from the plasma membrane at these sites is followed by a flow of cytoplasm into the forming bleb. We propose that polarized activation of the receptor CXCR4 leads to a rise in free calcium that in turn activates myosin contraction in the part of the cell responding to higher levels of the ligand SDF-1. The biased formation of new protrusions in a particular region of the cell in response to SDF-1 defines the leading edge and the direction of cell migration.

Dissection of amoeboid movement into two mechanically distinct modes

The current dominant model of cell locomotion proposes that actin polymerization pushes against the membrane at the leading edge producing filopodia and lamellipodia that move the cell forward. Despite its success, this model does not fully explain the complex process of amoeboid motility, such as that occurring during embryogenesis and metastasis. Here, we show that Dictyostelium cells moving in a physiological milieu continuously produce `blebs' at their leading edges, and demonstrate that focal blebbing contributes greatly to their locomotion. Blebs are well-characterized spherical hyaline protrusions that occur when a patch of cell membrane detaches from its supporting cortex. Their formation requires the activity of myosin II, and their physiological contribution to cell motility has not been fully appreciated. We find that pseudopodia extension, cell body retraction and overall cell displacement are reduced under conditions that prevent blebbing, including high osmolarity and blebbistatin, and in myosin-II-null cells. We conclude that amoeboid motility comprises two mechanically different processes characterized by the production of two distinct cell-surface protrusions, blebs and filopodia-lamellipodia.

Attraction rules: germ cell migration in zebrafish

The migration of zebrafish primordial germ cell towards the region where the gonad develops is guided by the chemokine SDF-1a. Recent studies show that soon after their specification, the cells undergo a series of morphological alterations before they become motile and are able to respond to attractive cues. As migratory cells, primordial germ cells move towards their target while correcting their path upon exiting a cyclic phase in which morphological cell polarity is lost. In the following stages, the cells gather at specific locations and move as cell clusters towards their final target. In all of these stages, zebrafish germ cells respond as individual cells to alterations in the shape of the sdf-1a expression domain, by directed migration towards their target - the position where the gonad develops.

Cyclooxygenase-1-derived PGE2 promotes cell motility via the G-protein-coupled EP4 receptor during vertebrate gastrulation

Gastrulation is a fundamental process during embryogenesis that shapes proper body architecture and establishes three germ layers through coordinated cellular actions of proliferation, fate specification, and movement. Although many molecular pathways involved in the specification of cell fate and polarity during vertebrate gastrulation have been identified, little is known of the signaling that imparts cell motility. Here we show that prostaglandin E(2) (PGE(2)) production by microsomal PGE(2) synthase (Ptges) is essential for gastrulation movements in zebrafish. Furthermore, PGE(2) signaling regulates morphogenetic movements of convergence and extension as well as epiboly through the G-protein-coupled PGE(2) receptor (EP4) via phosphatidylinositol 3-kinase (PI3K)/Akt. EP4 signaling is not required for proper cell shape or persistence of migration, but rather it promotes optimal cell migration speed during gastrulation. This work demonstrates a critical requirement of PGE(2) signaling in promoting cell motility through the COX-1-Ptges-EP4 pathway, a previously unrecognized role for this biologically active lipid in early animal development.

G Protein-Coupled Receptor Roles in Cell Migration and Cell Death Decisions

Recognition of external conditions and the elicitation of appropriate responses are critical to a cell's ability to adjust to various developmental and environmental cues. G protein-coupled receptors (GPCRs) are a large class of receptors that act to relay external information into the cell by initiating signaling pathways that allow the cell to adapt to its present conditions. There are numerous ligands that activate GPCRs to initiate a multitude of intracellular signaling cascades involved in critical decisions including cell growth, differentiation, proliferation, migration, survival, and death. This article focuses on the signaling pathways involved in cell migration, survival, and death decisions with an emphasis on germ cells from various organisms.

Transition from non-motile behaviour to directed migration during early PGC development in zebrafish

The migration of zebrafish primordial germ cells (PGCs) is directed by SDF-1a and serves as a model for long-range chemokine-guided cell migration. Whereas the development and migration of zebrafish PGCs have been studied in great detail starting at mid-gastrulation stages when the cells exhibit guided active migration [7-8 hours post fertilization (hpf)], earlier stages have not yet been examined. Here we show that the PGCs acquire competence to respond to the chemokine following discrete maturation steps. Using the promoter of the novel gene askopos and RNA elements of nanos1 to drive GFP expression in PGCs, we found that immediately after their specification (about 3 hpf) PGCs exhibit simple cell shape. This stage is followed by a phase at which the cells assume complex morphology yet they neither change their position nor do they respond to SDF-1a. During the third phase, a transition into a ;migratory stage' occurs as PGCs become responsive to directional cues provided by somatic cells secreting the chemokine SDF-1a. This transition depends on zygotic transcription and on the function of the RNA-binding protein Dead end and is correlated with down regulation of the cell adhesion molecule E-cadherin. These distinctive morphological and molecular alterations could represent a general occurrence in similar processes critical for development and disease.

Human embryonic germ cells for future neuronal replacement therapy

Stem cell therapy offers exciting potential for ambitious cellular replacement to treat human (h) disease, such as Parkinson's disease, Alzheimer's disease or even replacement of the cell death that follows thromboembolic stroke. The realisation of these treatments requires cellular resources possessing three essential characteristics: (i) self-renewal, (ii) the ability to differentiate to physiologically normal cell types and (iii) lack of tumourigenicity. Here, we describe work on human embryonic germ cells (hEGCs), a population of cells alongside human embryonic stem cells (hESCs) with the potential to address these issues.

Evaluating human embryonic germ cells: concord and conflict as pluripotent stem cells

The realization of cell replacement therapy derived from human pluripotent stem cells requires full knowledge of the starting cell types as well as their differentiated progeny. Alongside embryonic stem cells, embryonic germ cells (EGCs) are an alternative source of pluripotent stem cell. Since 1998, four groups have described the derivation of human EGCs. This review analyzes the progress on derivation, culture, and differentiation, drawing comparison with other pluripotent stem cell populations.

Signaling to cytoskeletal dynamics during chemotaxis

We review insights in signaling pathways controlling cell polarization and cytoskeletal organization during chemotactic movement in Dictyostelium amoebae and neutrophils. We compare and contrast these insights with our current understanding of pathways controlling chemotactic movements in more-complex multicellular developmental contexts.

The Chemokine Receptor CCR7 Activates in Dendritic Cells Two Signaling Modules That Independently Regulate Chemotaxis and Migratory Speed

CCR7 is necessary to direct dendritic cells (DCs) to secondary lymphoid nodes and to elicit an adaptative immune response. Despite its importance, little is known about the molecular mechanisms used by CCR7 to direct DCs to lymph nodes. In addition to chemotaxis, CCR7 regulates the migratory speed of DCs. We investigated the intracellular pathways that regulate CCR7-dependent chemotaxis and migratory speed. We found that CCR7 induced a G(i)-dependent activation of MAPK members ERK1/2, JNK, and p38, with ERK1/2 and p38 controlling JNK. MAPK members regulated chemotaxis, but not the migratory speed, of DCs. CCR7 induced activation of PI3K/Akt; however, these enzymes did not regulate either chemotaxis or the speed of DCs. CCR7 also induced activation of the GTPase Rho, the tyrosine kinase Pyk2, and inactivation of cofilin. Pyk2 activation was independent of G(i) and Src and was dependent on Rho. Interference with Rho or Pyk2 inhibited cofilin inactivation and the migratory speed of DCs, but did not affect chemotaxis. Interference with Rho/Pyk2/cofilin inhibited DC migratory speed even in the absence of chemokines, suggesting that this module controls the speed of DCs and that CCR7, by activating its components, induces an increase in migratory speed. Therefore, CCR7 activates two independent signaling modules, one involving G(i) and a hierarchy of MAPK family members and another involving Rho/Pyk2/cofilin, which control, respectively, chemotaxis and the migratory speed of DCs. The use of independent signaling modules to control chemotaxis and speed can contribute to regulate the chemotactic effects of CCR7.