Germ Cell Migration Research Articles

Thoraco-abdominal mature teratoma in a left diaphragmatic hernia

This case describes a contiguous mediastinal and retroperitoneal mature teratoma in a congenital diaphragmatic defect, a combination that is hitherto unreported in literature. It substantiates embryological chronology of events during the cephalad migration of the primordial germ cells through the developing diaphragm, prior to its closure.

Perturbation of Notch/Suppressor of Hairless pathway disturbs migration of primordial germ cells in Xenopus embryo

Primordial germ cells (PGCs) in Xenopus embryo are specified in the endodermal cell mass and migrate dorsally toward the future gonads. The role of the signal mediated by Notch and Suppressor of Hairless [Su(H)] was analyzed on the migrating PGCs at the tailbud stage. X-Notch-1 and X-Delta-1 are expressed in the migrating PGCs and surrounding endodermal cells, whereas X-Delta-2 and X-Serrate-1 are expressed preferentially in the PGCs. Suppression and constitutive activation of the Notch/Su(H) signaling in the whole endoderm region or selectively in the PGCs resulted in an increase in ectopic PGCs located in lateral or ventral regions. Knocking down of the Notch ligands by morpholino oligonucleotides revealed that X-Delta-2 was indispensable for the correct PGC migration. The ectopic PGCs seemed to have lost their motility in the Notch/Su(H) signal-manipulated embryos. Our results suggest that a cell-to-cell interaction via the Notch/Su(H) pathway has a significant role in the PGC migration by regulating cell motility.

Inter-species transplantation and migration of primordial germ cells in cyprinid fish

Primordial germ cells (PGCs) are the only cells in developing embryos that can transmit genetic information to the next generation. PGCs therefore have considerable potential value for gene banking and cryopreservation, particularly via production of donor gametes using germ-line chimeras. In some animal species, including teleost fish, the feasibility of using PGC transplantation to obtain donor-derived offspring, within and between species, has been demonstrated. Successful use of PGC transplantation to produce germ-line chimeras is absolutely dependent on the migration of the transplanted cells from the site of transplantation to the host gonadal region. Here, we induced germ-line chimeras between teleost species using two different protocols: blastomere transplantation and single PGC transplantation. We evaluated the methods using the rate of successful migration of transplanted PGCs to the gonadal region of the host embryo. First, we transplanted blastomeres from zebrafish, pearl danio, goldfish, or loach into blastula-stage zebrafish embryos. Some somatic cells, derived from donor blastomeres, were co-transplanted with the PGCs and formed aggregates in the host embryos; a low efficiency of PGC transfer was achieved. Second, a single PGC from the donor species was transplanted into a zebrafish embryo. In all inter-species combinations, the donor PGC migrated toward the gonadal region of the host embryo at a comparatively high rate, regardless of the phylogenetic relationship of the donor and host species. These transplantation experiments showed that the mechanism of PGC migration is highly conserved beyond the family barrier in fish and that transplantation of a single PGC is an efficient method for producing inter-species germ-line chimeras.

Migration and Accumulation of Primordial Germ Cells of Early Embryo in Quail

In this research, we have identified primordial germ cells (PGCs) in quail embryo using Quail Hemangioblastic Lineage (QH1) monoclonal antibody analysis. Quail PGCs originated from the opaca of unincubated blastodisc, and then transferred to the pellucida and the germinal crescent. At 27 hours post-incubation, a few PGCs first appeared in blood vessels of the pellucida, where many PGCs accumulated at 36 hours post-incubation. The PGCs scattered or clustered from head to omphalo mesenteric and mainly settled down in the mesenchymal blood vessels of head at 45 hours post-incubation. The size of PGCs population increased significantly (P<0.05) from stage XII (12.8±4.82 µm) to primitive streak stage (106.7±8.74 µm) and from Head process stage (95.8±19.74 µm) to tenth somite stage (199.4±19.97 µm). It is concluded that the PGCs scattered in the head area before migration to the germinal crescent and distributed randomly in both gland. The number of PGCs varied at different stages with two peaks, primitive streak stage (18 hours post-incubation) and tenth somite (36 hours post-incubation).

Mechanisms guiding primordial germ cell migration: strategies from different organisms.

The regulated migration of cells is essential for development and tissue homeostasis, and aberrant cell migration can lead to an impaired immune response and the progression of cancer. Primordial germ cells (PGCs), precursors to sperm and eggs, have to migrate across the embryo to reach somatic gonadal precursors, where they carry out their function. Studies of model organisms have revealed that, despite important differences, several features of PGC migration are conserved. PGCs require an intrinsic motility programme and external guidance cues to survive and successfully migrate. Proper guidance involves both attractive and repulsive cues and is mediated by protein and lipid signalling.

In vitro germ cell differentiation during sex differentiation in a teleost fish

To clarify the sexually dimorphic mechanisms of gonadal sex differentiation, we established an in vitro culture system for gonadal sex differentiation using the teleost fish Oreochromis niloticus. In vivo, the entry of germ cells into meiosis occurs around 35 days after hatching (dah) in XX gonads, whereas in XY gonads, meiotic cells became differentiated around 85 dah. In our in vitro culture system using gonads from young fry at 23 dah, the meiotic cells in the XX gonads appeared after 21 days of culture. In contrast, in the XY gonads, no meiotic cells were detected after 21 days. These results indicate that germ cell differentiation in this culture system progresses in a manner similar to that in vivo. To identify the gene products that are involved in the entry of germ cells into meiosis or in the arrest of germ cells at the gonial stage of gonadal sex differentiation, we performed subtractive hybridization screening with this in vitro culture system. From the screening process, we identified the female-related gene, FR-3, which is a homolog of zebrafish nanos-related gene (nos). The nos gene was expressed after gonadal formation around 35 dah in XX gonads, but not in XY gonads. In situ hybridization indicated that nos is expressed in oogenic meiotic cells, but not in spermatogenic meiotic cells. Further examination revealed that nos was expressed in oogenic meiotic cells after gonadal formation, specifically in teleost fish. Together, nos may be also involved in oogenic meiosis, with the exception of primordial germ cell migration.

Isolation of teleost primordial germ cells using flow cytometry

Primordial germ cells (PGCs) generate gametes, the only cells that can transmit genetic information to the next generation. A previous report demonstrated that a fusion construct of green fluorescent protein (gfp) and zebrafish nos 1 3UTR mRNA could be used to label PGCs in a number of fish species. Here, we sought to exploit this labeling strategy to isolate teleost PGCs by flow cytometry (FCM), and to use these isolated PGCs to examine germ cell migration to the gonadal region. In zebrafish, medaka and goldfish, the PGCs were labeled by injecting the gfp-nos1 3UTR mRNA into 1- 4 cell embryos. When the embryos had developed to the somitogenesis or later stages, they were enzymatically disaggregated and GFP positive cells isolated using FCM. PGCs in the different species clustered in the same segments of the FCM scatter diagrams for total embryonic cells produced by plotting the forward scatter intensity against GFP intensity. In situ hybridization showed that the sorted zebrafish cells expressed vasa RNA in their cytoplasm, suggesting that they were PGCs. When the migration ability of the sorted cells from zebrafish was examined in an in vivo transplantation experiment, approximately 30% moved to the gonadal region of host embryos. These observations demonstrate that PGCs can be isolated without use of transgenic fishes and that the isolated PGCs retain the ability to migrate. Our data indicate that this technique will be of value for isolating PGCs from a range of fish species.

Gonad morphogenesis in vertebrates: divergent means to a convergent end.

A critical element of successful sexual reproduction is the generation of sexually dimorphic adult reproductive organs, the testis and ovary, which produce functional gametes. Examination of different vertebrate species shows that the adult gonad is remarkably similar in its morphology across different phylogenetic classes. Surprisingly, however, the cellular and molecular programs employed to create similar organs are not evolutionarily conserved. We highlight the mechanisms used by different vertebrate model systems to generate the somatic architecture necessary to support gametogenesis. In addition, we examine the different vertebrate patterns of germ cell migration from their site of origin to colonize the gonad and highlight their roles in sex-specific morphogenesis. We also discuss the plasticity of the adult gonad and consider how different genetic and environmental conditions can induce transitions between testis and ovary morphology.

Sonographic and Magnetic Resonance Imaging of a Massive Epidermoid Cyst of the Pelvis and Buttock

Germ cell tumors are most commonly located within the gonads. 1 Rare extragonadal locations of these tumors include the retroperitoneum, mediastinum, sacrococcygeum, and central nervous system and are considered to result from aberrant migration of germ cells from the yolk sac during fetal development. 1―4 We present transvaginal sonographic and magnetic resonance imaging (MRI) findings of a massive epidermoid cyst extending from the pelvis to the buttock.

Analysis of SDF-1/CXCR4 signaling in primordial germ cell migration and survival or differentiation in Xenopus laevis

Directional migration of primordial germ cells (PGCs) toward future gonads is a common feature in many animals. In zebrafish, mouse and chicken, SDF-1/CXCR4 chemokine signaling has been shown to have an important role in PGC migration. In Xenopus, SDF-1 is expressed in several regions in embryos including dorsal mesoderm, the target region that PGCs migrate to. CXCR4 is known to be expressed in PGCs. This relationship is consistent with that of more well-known animals. Here, we present experiments that examine whether chemokine signaling is involved in PGC migration of Xenopus. We investigate: (1) Whether injection of antisense morpholino oligos (MOs) for CXCR4 mRNA into vegetal blastomere containing the germ plasm or the precursor of PGCs disturbs the migration of PGCs? (2) Whether injection of exogenous CXCR4 mRNA together with MOs can restore the knockdown phenotype? (3) Whether the migratory behavior of PGCs is disturbed by the specific expression of mutant CXCR4 mRNA or SDF-1 mRNA in PGCs? We find that the knockdown of CXCR4 or the expression of mutant CXCR4 in PGCs leads to a decrease in the PGC number of the genital ridges, and that the ectopic expression of SDF-1 in PGCs leads to a decrease in the PGC number of the genital ridges and an increase in the ectopic PGC number. These results suggest that SDF-1/CXCR4 chemokine signaling is involved in the migration and survival or in the differentiation of PGCs in Xenopus.

20-P022 A role for XtSulf1 in germ cell migration

20-P022 A role for XtSulf1 in germ cell migration

S20-01 Germ cell migration in zebrafish

S20-01 Germ cell migration in zebrafish

Migration and differentiation of primordial germ cells in Sturnira lilium and Artibeus jamaicensis

Migration and differentiation of primordial germ cells in Sturnira lilium and Artibeus jamaicensis

Highlights From The Literature

Highlights From The Literature

Dimerization of Kit‐ligand and efficient cell‐surface presentation requires a conserved Ser‐Gly‐Gly‐Tyr motif in its transmembrane domain

Kit-ligand (Kitl), also known as stem cell factor, is a membrane-anchored, noncovalently bound dimer signaling via the c-kit receptor tyrosine kinase, required for migration, survival, and proliferation of hematopoietic stem and germ cells, melanocytes, and mastocytes. Despite its fundamental role in morphogenesis and stem cell biology, the mechanisms that regulate Kitl dimerization are not well understood. By employing cell-permeable cross-linker and quantitative bimolecular fluorescence complementation of wild-type and truncated forms of Kitl, we determined that Kitl dimerization is initiated in the endoplasmic reticulum and mediated to similar levels by the transmembrane and the extracellular growth factor domain. Further biochemical and mutational analysis revealed a conserved Ser-Gly-Gly-Tyr-containing motif that is required for transmembrane domain dimerization and efficient cell-surface expression of Kitl. A novel intracellular capture assay with the Kitl transmembrane domain as bait revealed specific interactions with Kitl, but not with unrelated transmembrane proteins. During evolution, the transmembrane dimerization motif appeared in Kitl at the transition from teleosts to tetrapods, which correlates with the emergence of Kitl as a supporter of stem cell populations. Thus, transmembrane-mediated association of membrane-anchored growth factors consists of a novel mechanism to improve paracrine signaling and morphogenesis.

Evidence for crucial role of hindgut expansion in directing proper migration of primordial germ cells in mouse early embryogenesis

During mouse gastrulation, primordial germ cells (PGCs) become clustered at the base of the allantois and move caudally into the hindgut endoderm before entering the genital ridges. The precise roles of endoderm tissues in PGC migration, however, remain unclear. By using Sox17 mutants with a specific endoderm deficiency, we provide direct evidence for the crucial role of hindgut expansion in directing proper PGC migration. In Sox17-null embryos, PGCs normally colonize in the allantois and then a small front-row population of PGCs moves properly into the most posterior gut endoderm. Defective hindgut expansion, however, causes the failure of further lateral PGC movement, resulting in the immobilization of PGCs in the hindgut entrance at the later stages. In contrast, the majority of the remaining PGCs moves into the visceral endoderm layer, but relocate outside of the embryonic gut domain. This leads to a scattering of PGCs in the extraembryonic yolk sac endoderm. This aberrant migration of Sox17-null PGCs can be rescued by the supply of wildtype hindgut cells in chimeric embryos. Therefore, these data indicate that hindgut morphogenic movement is crucial for directing PGC movement toward the embryonic gut side, but not for their relocation from the mesoderm into the endoderm.

Molecular mechanisms by which hormones and cytokines regulate cell junction dynamics in the testis

Hormones and cytokines are known to regulate cellular functions in all tissues including testis. These two groups of biomolecules exert a broad spectrum of effects on various aspects of spermatogenesis. Among them, one of the regulatory effects on spermatogenesis is to modulate cell junction restructuring between Sertoli cells and between Sertoli and germ cells in the seminiferous epithelium. The restructuring of cell junctions is crucial to enable the migration of germ cells along the seminiferous epithelium from the basement membrane towards the tubular lumen, and at the same time for their attachment to Sertoli cells for support. This review will summarize the recent findings that focus on the role of hormones (FSH and testosterone) and cytokines (transforming growth factor-betas and tumor necrosis factor-alpha) on cell junction restructuring in the testis and the molecular mechanisms.

Medaka vasa is required for migration but not survival of primordial germ cells

vasa is essential for germline development. However, the precise processes in which vasa involves vary considerably in diverse animal phyla. Here we show that vasa is required for primordial germ cell (PGC) migration in the medakafish. vasa knockdown by two morpholinos led to the PGC migration defect that was rescued by coinjection of vasa RNA. Interestingly, vasa knockdown did not alter the PGC number, identity, proliferation and motility even at ectopic locations. We established a cell culture system for tracing PGCs at the single cell level in vitro. In this culture system, control and morpholino-injected gastrulae produced the same PGC number and the same time course of PGC survival. Importantly, vasa-depleted PGCs in culture had similar motility and locomotion to normal PGCs. Expression patterns of wt1a, sdf1b and cxcr4b in migratory tissues remained unchanged by vasa knockdown. By chimera formation we show that PGCs from vasa-depleted blastulae failed to migrate properly in the normal environment, whereas control PGCs migrated normally in vasa-disrupted embryos. Furthermore, ectopic PGCs in vasa-depleted embryos also retained all the PGC properties examined. Taken together, medaka vasa is cell-autonomously required for PGC migration, but dispensable to PGC proliferation, motility, identity and survival.

The Lure of Lipids

Germ cell migration in the fruit fly relies on a lipid-modified attractant secreted by a system analogous to that of yeast mating pheromone.

Hedgehog does not guide migrating Drosophila germ cells

In many species, the germ cells, precursors of sperm and egg, migrate during embryogenesis. The signals that regulate this migration are thus essential for fertility. In flies, lipid signals have been shown to affect germ cell guidance. In particular, the synthesis of geranylgeranyl pyrophosphate through the 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (Hmgcr) pathway is critical for attracting germ cells to their target tissue. In a genetic analysis of signaling pathways known to affect cell migration of other migratory cells, we failed to find a role for the Hedgehog (Hh) pathway in germ cell migration. However, previous reports had implicated Hh as a germ cell attractant in flies and suggested that Hh signaling is enhanced through the action of the Hmgcr pathway. We therefore repeated several critical experiments and carried out further experiments to test specifically whether Hh is a germ cell attractant in flies. In contrast to previously reported findings and consistent with findings in zebrafish our data do not support the notion that Hh has a direct role in the guidance of migrating germ cells in flies.