Migration Of Primordial Germ Cells Research Articles

The nanos gene of Bombyx mori and its expression patterns in developmental embryos and larvae tissues

The nanos gene encodes a zinc-finger protein which is required for the migration and differentiation of primordial germ cells as well as for their fate maintenance. In this study, a 1913 bp nanos gene was cloned and characterized in silkworm ( Bombyx mori). RT-PCR and Western blot analysis showed that the nanos was expressed in developing embryos and various silkworm larval tissues. The expression patterns of Nanos and Vasa in silkworm larval gonads were analyzed using immunohistochemistry. It was found that, in silkworm larval ovaries, the Nanos and Vasa proteins were expressed in oocytes. While in testes, high expression of Nanos and Vasa was detected in spermatogonia and relatively weaker expression was found in spermatocytes at latter stages.

Lack of c-kit receptor promotes mammary tumors in N-nitrosomethylurea-treated Ws/Ws rats

Backgroundc-kit is expressed in various cell types during development and it has been linked to the promotion of cellular migration, proliferation and/or survival of melanoblasts, hematopoietic progenitors and primordial germ cells. Several reports have proposed a role for the c-kit gene on carcinogenesis. Gain-of-function mutations are associated with diseases such as mastocytosis and gastrointestinal stromal tumors among others. However, very little is known about pathologies associated with loss-of-function mutations. Regarding breast cancer, c-kit protein and mRNA are highly expressed in normal breast but their expression decreases or is absent in the presence of breast cancer. We studied the role of c-kit in mammary carcinogenesis in the Ws/Ws rats carrying spontaneous lack-of-function mutation in the c-kit gene. Fifty day-old virgin female Ws/Ws rats and their wild type counterparts were injected with either 50 mg/kg body weight of the chemical carcinogen N-nitrosomethylurea or with vehicle. The animals were followed-up for 6 months. Fisher 344 rats were used as positive controls for tumor development.ResultsEleven weeks after treatment, palpable tumors were detected in the Ws/Ws rats. The tumor incidence was 80% in Ws/Ws rats, while no tumors were observed in the wild type rats (p = 0.006). Our data show that the lack of c-kit is permissive for the development of mammary tumor in Ws/Ws rats treated with carcinogen.ConclusionWe conclude that the lack of c-kit may contribute to an imbalanced homeostatic state in the mammary gland either by affecting signaling between stroma and epithelium, or through the lack of mast cells.

Effects of 17beta-estradiol on distribution of primordial germ cell migration in male chicks

To assess whether exogenous estradiol has any effect on migration of primordial germ cells (PGCs) in the chick. Fertilized eggs were treated with 17beta-estradiol (E(2)) (80 microg/egg) at stage X (day 0 of incubation), stages 8-10 (incubation 30 h) and 13-15 (incubation 55 h). Controls received vehicle (emulsion) only. Changes in PGC number were measured on different days according to developmental stages. In male right gonads, but not in female left gonads, at stages 28-30 (incubation 132 h) significant decreases in the mean number of PGCs aggregating were observed compared with the controls (P < 0.05) while the total PGC number in the right and left gonads at each stage did not change (P > 0.05). The present study provides evidence that E(2) has significant effects on the localization of PGCs in male right, but not female left, gonads of chicken embryos at stages 28-30, compared with controls.

Testicular Morphogenesis

The organogenesis of a functional testis is the basis for male fertility and perpetuation of each species. In mammals, testicular development is dependent on two crucial events during embryonic and pubertal development. First, primary sex determination is initiated by expression of the Sry gene on the Y chromosome and directs the primordial gonad toward testicular development rather than ovarian differentiation. The male pathway comprises highly regulated cell differentiation of somatic cells within the gonadal primordium, as well as migration of mesonephric cells and primordial germ cells, ultimately leading to the formation of testis cords. These cords present the earliest visible sign of male gonadal differentiation. Second, during puberty immature Sertoli cells cease to proliferate and differentiate into their postmitotic, adult phenotype. The maturation of the Sertoli cells is pivotal for initiation and maintenance of spermatogenesis. The regulation of the two separate functions of Sertoli cells-during testis development and in spermatogenesis-are poorly understood. In this review, different models that have been used to study embryonic gonadal development and testicular maturation are compared. In vivo models, organ, and cell culture systems are discussed as regards their applicability to study testicular organogenesis. Then, a new tissue engineering approach is presented that mimics male embryonic gonadogenesis and that offers novel ways to study early testicular differentiation, as well as Sertoli cell maturation and spermatogonial stem-cell niche formation.

Migration and Proliferation of Primordial Germ Cells in the Early Chicken Embryo

In avian species, primordial germ cells (PGC) use the vascular system as a vehicle to transport them to the future gonadal region. The aim of this study was to elucidate the details of migration system and size of the PGC population in the early chicken embryo. We analyzed whole chicken embryos during stages X and 2 to 17 by immunohistochemical staining using specific antibody raised against chicken vasa homolog. At stage X, PGC were dense in the central zone of the area pellucida. Following the formation of the primitive streak, PGC moved anteriorly to the edge of the extraembryonic region. The size of the PGC population increased gradually during stages X (130.4 ± 31.9) to 10 (439.3 ± 93.6). At stage 10, PGC began to accumulate in the region anterior to the head, and then we could observe that PGC invaded into the vascular system in this region. At stage 11, the number of PGC decreased in the region anterior to the head (129.8 ± 42.5 to 46.7 ± 4.2) and increased in the blood vessels (194.0 ± 41.6 to 285.0 ± 7.5). No PGC could be recognized in the intermediate mesoderm, the future gonadal region, until stage 14, but they first appeared there at stage 15. The number of PGC recognized in the intermediate mesoderm increased from stage 15 to 17. Interestingly, the number of PGC between the left and right sides of this region was consistently and significantly different (P < 0.05) in females and males. The present study mainly clarified that chicken PGC continue to proliferate throughout early development, many PGC invaded into the vascular system from the region anterior to the head in stage 11, and PGC actively left the blood vessels and migrated to the intermediate mesoderm from stage 15.

Interactions between migratory primordial germ cells and cellular substrates in the mouse.

In previous in vitro studies we found that contact between mouse primordial germ cells and other cell types (neighbouring somatic cells or established TM4 or STO cell lines) is crucial for supporting primordial germ cell survival and proliferation and for activating their motility. We have studied primordial germ cell adhesion to different cell monolayers (STO, TM4, COS and F9 cells) as an in vitro model for interactions between primordial germ cells and cellular substrates. The results suggest that these cell interactions are mediated by multiple mechanisms involving Steel factor and its receptor encoded by c-kit, carbohydrates and possibly other unknown factors. We find that Steel factor and leukaemia inhibitory factor are survival rather than proliferation factors for primordial germ cells. Both molecules prevent primordial germ cell death in culture by suppressing apoptosis. Morphological and molecular features of primordial germ cell apoptosis in vitro are reported. Activation of protein kinase C does not promote primordial germ cell proliferation, but compounds known to enhance intracellular levels of cAMP (i.e. dibutyryl cAMP and forskolin) markedly stimulate primordial germ cells to proliferate in culture. We have preliminary results indicating that neuropeptides PACAP-27 and PACAP-28 are possible physiological activators of adenylate cyclase in primordial germ cells.

Primordial germ cell migration.

Primordial germ cells are migratory cells. They arise very early in embryogenesis and have a similar pattern of migration in Drosophila, Xenopus, chick and mouse. In each case the primordial germ cells associate with the developing gut from which they migrate to the gonads during organogenesis. Germ cells proliferate mitotically from the time they begin to migrate to the time they colonize the genital ridges. From the study of mouse primordial germ cells, we now know of a number of agents which affect primordial germ cell proliferation, migration and adhesion in vitro. More recently, we have studied the interactions between primordial germ cells and the cells and extracellular matrix molecules on their migratory route. By labelling germ cells in whole-mount preparations with an antibody to the germ cell marker SSEA-1, we have studied the spatial distribution of germ cells in situ using confocal microscopy. This study has revealed that germ cells link up with each other forming extensive networks during migration.

C‐KIT is frequently mutated in bilateral germ cell tumours and down‐regulated during progression from intratubular germ cell neoplasia to seminoma

Testicular germ cell tumours (TGCTs) are the most frequent cancer type in young men; 5% of these patients develop a second TGCT in the contralateral testis. The pathogenesis of TGCT is closely linked to primordial germ cells (PGCs) or gonocytes. The receptor tyrosine kinase (c-KIT) is necessary for migration and survival of PGCs and is expressed in intratubular neoplastic germ cells (IGCNUs) and seminomas. We studied the frequency of c-KIT exon 11 and 17 mutations in 155 unilateral (108 seminomas and 47 non-seminomas) and 22 bilateral (18 seminomas, two embryonal carcinomas, two IGCNU) cases. While no mutations were detected in exon 11, the mutation frequency in exon 17 was significantly higher in bilateral (14/22, 63.6%) compared to unilateral TGCT (10/155, 6.4%) (p < 0.001). Different activating mutations (Y823D, D816V, D816H and N822K) were detected in bilateral TGCT. Y823D mutation was identical in both testes in three cases and quantitative pyrosequencing showed that up to 76% of the cells analysed in tumour samples carried this mutation. One bilateral synchronous seminoma revealed a S821F mutation in one testis and a Y823D mutation contralaterally. To study the role of c-KIT in TGCT progression, we compared its expression in 41 seminomas and adjacent IGCNUs. Immunohistochemical analysis revealed that c-KIT expression was significantly reduced in seminomas compared to IGCNUs (p < 0.006) and that there were no significant changes in c-KIT mRNA copy numbers in progressed compared to low-stage seminomas. In summary, our study shows that patients with c-KIT mutations are more prone to develop a bilateral TGCT and suggests that in a portion of bilateral TGCTs, c-KIT mutations occur early during embryonal development, prior to the arrival of PGCs at the genital ridge. Furthermore, our findings show that c-KIT down-regulation occurs during the progression of IGCNU to seminoma.

GERMLINE DEVELOPMENT AND GERM CELL TUMORS IN THE ZEBRAFISH SYSTEM

The development of the germline requires precise control of the specification and migration of primordial germ cells, and of gonadal stem cell self-renewal and differentiation. Defects in these processes are linked to infertility and to germ cell cancers. Despite intensive investigation, the genes controlling normal and abnormal germline development are incompletely understood. To address these problems, we are using zebrafish as a genetically tractable, relevant vertebrate model of germline development. Zebrafish germ cells are well characterized, and the key pathways governing the development of primordial germ cells are highly conserved from fish to human. To discover the genes underlying the development of germ cell tumors, we introduced random mutations into the zebrafish genome and recovered a line of fish that reproducibly develops testicular germ cell tumors at high penetrance. The tumors resemble human seminomas and recapitulate many features of human TGCTs, including post-pubertal onset, and an apparent progression from carcinoma in situ to invasive disease. The mutation is dominantly inherited, and homozygotes are affected more severely than heterozygotes. We have localized the mutation to a chromosome via interval haplotype mapping, and we are attempting to clone the mutant gene through analysis of linked markers in affected kindreds. In parallel work, we are investigating the role of specific molecular pathways in normal and abnormal germ cell development. We are also using in vitro culture of zebrafish germ cells as a tool to understand the regulation of gametogenesis, and as a platform for facile manipulation of the zebrafish genome.

The protein encoded by the germ plasm RNA Germes associates with dynein light chains and functions in Xenopus germline development

Germ plasm plays a prominent role in germline formation in a large number of animal taxons. We previously identified a novel maternal RNA named Germes associated with Xenopus germ plasm. In the present work, we addressed possible involvement of Germes protein in germ plasm function. Expression in oocytes followed by confocal microscopy revealed that the EGFP fused to Germes, in contrast to the free EGFP, co-localized with the germ plasm. Overexpression of intact Germes and Germes lacking both leucine zipper motifs (GermesΔLZs) resulted in a statistically significant reduction of the number of primordial germ cells (PGCs). Furthermore, the GermesΔLZs mutant inhibited PGC migration and produced abnormalities in germ plasm intra-cellular distribution at tailbud stages. To begin unraveling biochemical interactions of Germes during embryogenesis, we searched for Germes partners using yeast two-hybrid (YTH) system. Two closely related sequences were identified, encoding Xenopus dynein light chains dlc8a and dlc8b. Tagged versions of Germes and dlc8s co-localize in VERO cells upon transient expression and can be co-immunoprecipitated after injection of the corresponding RNAs in Xenopus embryos, indicating that their interactions occur in vivo. We conclude that Germes is involved in organization and functioning of germ plasm in Xenopus, probably through interaction with motor complexes.

BAX regulates follicular endowment in mice

It is believed that the endowment of primordial follicles in mammalian ovaries is finite. Once follicles are depleted, infertility ensues. Thus, the size of the initial endowment has consequences for fertility and reproductive longevity. Follicular endowment is comprised of various processes that culminate with the incorporation of meiosis-arrested oocytes into primordial follicles. Apoptosis is prominent during follicular endowment, and apoptosis regulatory genes are involved in its regulation. Conflicting data exist with regard to the role of the proapoptotic Bcl-2 associated X protein (BAX) in follicular endowment. Therefore, we investigated the role of BAX during follicular endowment in embryonic and neonatal ovaries. We found that BAX is involved in regulating follicular endowment in mice. Deletion of Bax yields increased oocyte numbers in embryonic ovaries and increased follicle numbers in neonatal ovaries when compared with wild-type ovaries. Increased follicular endowment in Bax -/- ovaries is not due to enhanced germ cell viability. Further, it is not due to an increased primordial germ cell (PGC) allotment, a delay in the onset of meiosis, or altered proliferative activity of oogonia. Instead, our data suggest that the regulatory activity of BAX in follicular endowment likely occurs during PGC migration, prior to PGC colonization of the gonad.

Crystal structure of recombinant human stromal cell‐derived factor‐1α

Crystal structure of recombinant human stromal cell‐derived factor‐1α

Effects of larval exposure to estradiol on spermatogenesis and in vitro gonadal steroid secretion in African clawed frogs, Xenopus laevis

Estrogen or eco-estrogenic chemicals can disrupt normal gonadal sex differentiation, causing intersex formation and feminization in amphibians. The cellular basis for estrogen-induced sex reversal is not well understood. In the present study, we investigated the concentration- and stage-dependent effects of estradiol (E 2) exposure during the larval period on histological characteristics of gonadal sex differentiation and gonadal sex steroid secretion in vitro in the African clawed frog, Xenopus laevis. Embryos were exposed to E 2 (1, 10, or 100 μg/L) or vehicle control through metamorphosis and then allowed to develop in untreated medium for 2-mo post-metamorphosis. To investigate gonadal sex differentiation and development during and after exposure, gonadal samples were collected at different developmental stages. Gonadal sex differentiation did not occur before NF stage 52 in any group. At NF stage 54–55 primordial germ cells (PGCs) were observed in both cortical and medullary regions of developing tadpoles gonads in the control, 1 and 10 μg/L E 2 treatments, but were observed only in the cortical region of tadpoles exposed to 100 μg/L E 2. E 2 increased the percent of spermatocytes, spermatids, and spermatozoa compared to controls. Larval E 2 exposure did not alter hCG-induced gonadal testosterone secretion in vitro but significantly increased E 2 secretion from ovaries of juvenile frogs. Our results indicate that E 2 exposure during larval development appears to prevent PGC migration to the medulla of developing gonads in a concentration-dependent manner. The degree of PGC migration to the medulla may be related to the degree of E 2-induced intersex formation and feminization in X. laevis. E 2 exposure during the larval period accelerates spermatogenesis and can increase ovarian E 2 secretion in juvenile frogs.

The Transitioning Germ Line

![Figure][1] CREDIT: GETTY IMAGES/VISUALS UNLIMITED Germline constancy is a must for species continuity, but the life of the germ cell itself is full of change. The trek to and from the germ line includes numerous transitions and decisions deftly choreographed for the gametes' unique ability in nature to develop into a complex animal and pass on genetic information. This special section highlights the transitioning germ line and otherwise expands on intriguing aspects of these cells of heredity. In the early embryo, cells decide between becoming soma or germ line. Mechanisms protect germ cells from a somatic fate, just as somatic cells require insulation from the germline differentiation pathway. Strome and Lehmann (p. [392][2]) outline activities in the fly and worm, such as transcriptional quiescence and inheritance of germ cell determinants, and Hayashi et al. (p. [394][3]) tell of the murine system, invoking an inductive signal. Although model systems use different strategies, common themes exist. A new class of molecules reportedly participates in germ cell development. Lin (p. [397][4]) describes the generation and role of germline-specific small RNAs termed piRNAs. Functions as diverse as posttranscriptional regulation and epigenetic programming are suggested. Another epigenetic event—de novo DNA methylation—silences imprinted genes and repeat elements during vertebrate gametogenesis. Schaefer et al. (p. [398][5]) detail this heritable silencing mechanism and its sexual dimorphism. As the germ cell transitions to the mature form, more decisions are made: to enter mitosis or meiosis and to differentiate as sperm or egg, with possible linkage of these decisions as proposed by Kimble and Page (p. 400). Stem cell self-renewal versus differentiation in the Drosophila male and female germ lines is discussed by Fuller and Spradling (p. [402][6]). Switching to vertebrate germline stem cells, Brinster (p. [404][7]) reports methods for the recovery, culture, and transplantation of spermatogonial stem cells; and Daley (p. 409) summarizes advances in embryonic stem cell (ESC) differentiation to a germline fate: procedures with research and clinical applications but not without limitations. In an Editorial, McLaren (p. [339][8]) takes the discussion further, highlighting ethical and social issues surrounding ESC-derived germ cells. Changes continue as the oocyte transitions to the fertilized egg. Stitzel and Seydoux (p. 407) detail the oocyte-to-zygote transition, with associated alterations in protein synthesis, protein and RNA degradation, and organelle remodeling; and Schier (p. 406) discusses zygotic genome silencing and maternal messenger RNA degradation around the maternal-zygotic transition. In News, Travis (p. 390) discusses “urbisexuality” with a biologist pondering the evolution of germ cell specification, and Leslie (p. 388) details how oocyte freezing has become more effective and acceptable despite questions about the long-term health of offspring. Finally, in [ Science 's STKE][9], McClure discusses how poppies reject self-pollen, and Boldajipour and Raz highlight similarities in Drosophila and mouse mechanisms involved in the migration of primordial germ cells and elimination of ectopic cells. The articles here give but a sampling of exciting ongoing research on the seeds of life—themselves products of change. Advances bear fruit in understanding development and its underlying genetics, as well as infertility. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1140846 [3]: /lookup/doi/10.1126/science.1137545 [4]: /lookup/doi/10.1126/science.1137543 [5]: /lookup/doi/10.1126/science.1137544 [6]: /lookup/doi/10.1126/science.1140861 [7]: /lookup/doi/10.1126/science.1137741 [8]: /lookup/doi/10.1126/science.1142267 [9]: http://www.sciencemag.org/sciext/germcells/#section_in-stke

IGF signaling cell-autonomously promotes primordial germ cell migration in zebrafish

IGF signaling cell-autonomously promotes primordial germ cell migration in zebrafish

Effect of soft X-ray irradiation on the migratory ability of primordial germ cells in chickens

1. The present study was conducted to elucidate the effect of soft X-ray irradiation on the migratory ability of primordial germ cells (PGCs) to the germinal ridges of chicken embryos. 2. PGCs (Barred Plymouth Rock, BPR) were isolated from embryonic blood and irradiated with soft X-rays for 1–10 min. Then, the PGCs were transfected in vitro with GFP gene by lipofection. The manipulated PGCs were transferred to recipient embryos (White Leghorn, WL) and migration to the germinal ridges was analysed by examining GFP gene expression in the gonads of recipient embryos under UV light at ×40 magnifications. The expression of GFP gene was detected in all the gonads of recipient embryos examined up to 10·5 d of culture. 3. Migration of PGCs irradiated with soft X-rays to the germinal ridges was also confirmed by detecting a single nucleotide polymorphism in the D-loop region of the mitochondrial DNA of BPR and WL chickens. Freshly collected PGCs (BPR) were transferred to the bloodstream of recipient embryos (WL). The fate of the transferred donor PGCs was traced by detecting the single nucleotide polymorphism in the D-loop region of the mitochondrial DNA in BPR and WL used in this study. Transferred donor PGC-derived cells were detected in all the gonads of 17-d cultured embryos by PCR. 4. The results suggest that PGCs irradiated with soft X-rays still retain the ability to migrate to the germinal ridges of recipient embryos.

Chemoattractant action and molecular signaling pathways of Kit ligand on mouse primordial germ cells

Using a Transwell chamber as migration assay for mouse primordial germ cells (PGCs), we show here that these cells posses directional migration in the absence of somatic cell and defined matrix support and in response to a Kit ligand (KL) gradient or medium conditioned by Aorta/Gonad/Mesonephros and gonadal ridges. Other putative PGC chemoattractants such as SDF1 and TGFβ did not exert any attractive action on PGCs. The chemoattractant activity of KL and conditioned medium was also evidenced by their ability to stimulate actin reorganization in PGCs. In the aim to identify downstream signaling pathways governing KL chemoattraction on PGCs, we demonstrated that in such cells KL rapidly (5 min) increased autophosphorylation of its receptor c-Kit and caused phosphorylation of the serine–threonine kinase AKT through the action of PI3K. 740Y-P peptide, a direct activator of PI3 kinase, stimulated PGC migration at levels similar to those elicited by KL. LY294002 (a specific inhibitor of PI3K) abolished KL-dependent PGC migration or the chemoattractant activity of the conditioned medium and inhibited AKT phosphorylation; Src kinase inhibitors PP2 and SU6656, caused significant reduction of the KL-dependent PGC migration and AKT phosphorylation, while U0126, a selective inhibitor of the MEK/ERK protein kinase cascade, reduced PGC migration and AKT phosphorylation at lesser extent. SU6656 completely abolished the chemoattractant activity of the conditioned medium. Finally, SB202190 (a p38 inhibitor) and rapamycin (mTOR inhibitor) did not affect PGC migration. In addition, to demonstrate that somatic cells are not essential for PGC motility and directional migration, we evidenced a novel role for KL as PGC chemoattractant and for PI3K/AKT and Src kinase, as players involved in the activation of the PGC migratory machinery and likely important for their directional movement towards the gonadal ridges.

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.

Interaction and signal transduction between oocyte and samatic cells in the ovary

Follicular development and differentiation are sequential events which are tightly regulated by endocrine hormones, intraovarian regulators and cell-cell interactions. Balanced cell proliferation and apoptosis play an important role in the selection of dominant follicle. The formation of primordial follicle is initiated after a migratory primordial germ cell establishes a transitory close contact with the somatic cells in the genital ridge. Primordial germ cell migration and homing within the gonadal ridge requires integrated signals involving contact of primordial germ cells with extra-cellular matrix proteins and cellular substrates and attraction by the developing gonads. The oocyte-secreted polypeptide growth factors, such as the growth and differentiation factor 9, bone morphogenetic proteins and the gap junction participate in cell-cell communication direct growth and differentiation of granulosa cells and cross-talk between oocyte and somatic cell in the ovary. Maturation of cumulus-oocyte complexes which is controlled by lutenizing hormone requires activation of mitogen-activated protein kinase in granulosa cells. In this review the insights gained on cell-cell interaction and signal transduction during follicular development and differentiation is summarized, mainly focusing on signaling factors produced by oocyte and somatic cells which regulate primordial follicular growth initiation and development.

Carbohydrate characterization of quail primordial germ cells during migration and gonadal differentiation

A selection of lectins were used to study changes in the distribution of sugar residues in primordial germ cells (PGCs) during gonadal colonization and differentiation. Although the cytochemical characteristics of PGCs have been described in the chick, little is known about such characteristics in other avian species of interest to experimental biology. Therefore, we studied embryos of Japanese quail (Coturnix coturnix japonica) by light and laser confocal scanning microscopy, using the QH1 antibody as a tool to identify PGCs in both sexes and at all stages. LEA, WGA and RCA-I bound to PGCs in a similar way to QH1. LEA was the best marker for all stages. The presence of acid phosphatase and the intense reaction of LEA, WGA, RCA-I and WFA at the cell surface were shown to be a useful tool in the study of the migratory PGCs of the quail. Quails were sexed histologically in younger embryos than in chick; results were confirmed by PCR. The lectin-binding pattern changed drastically in differentiated gonads. Cell surface reactivity was almost entirely lost. Quail differentiating oogonia showed a characteristic binding pattern to QH1 and to the lectins WGA, RCA-I and WFA. Binding was observed in intense spots in the Golgi complex, and there was a specific PNA reaction. These results suggest that some selective sugar binding sites on the PGCs play a significant role in their migration, colonization and maturation.