The fusome organizes the microtubule network during oocyte differentiation in Drosophila

Development ◽  
2000 ◽  
Vol 127 (19) ◽  
pp. 4253-4264 ◽  
Author(s):  
N.C. Grieder ◽  
M. de Cuevas ◽  
A.C. Spradling
Keyword(s):  
Germ Cell ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Crucial Role ◽  
Skeletal Structure ◽  
Network Organization ◽  
Microtubule Network ◽  
Complex Process ◽  
Gamma Tubulin ◽  
Oocyte Differentiation

Differentiation of the Drosophila oocyte takes place in a cyst of 16 interconnected germ cells and is dependent on a network of microtubules that becomes polarized as differentiation progresses (polarization). We have investigated how the microtubule network polarizes using a GFP-tubulin construct that allows germ-cell microtubules to be visualized with greater sensitivity than in previous studies. Unexpectedly, microtubules are seen to associate with the fusome, an asymmetric germline-specific organelle, which elaborates as cysts form and undergoes complex changes during cyst polarization. This fusome-microtubule association occurs periodically during late interphases of cyst divisions and then continuously in 16-cell cysts that have entered meiotic prophase. As meiotic cysts move through the germarium, microtubule minus ends progressively focus towards the center of the fusome, as visualized using a NOD-lacZ marker. During this same period, discrete foci rich in gamma tubulin that very probably correspond to migrating cystocyte centrosomes also associate with the fusome, first on the fusome arms and then in its center, subsequently moving into the differentiating oocyte. The fusome is required for this complex process, because microtubule network organization and polarization are disrupted in hts(1) mutant cysts, which lack fusomes. Our results suggest that the fusome, a specialized membrane-skeletal structure, which arises in early germ cells, plays a crucial role in polarizing 16-cell cysts, at least in part by interacting with microtubules and centrosomes.

scholarly journals Somatic regulation of female germ cell regeneration and development in planarians

2021 ◽  
Author(s):  
Umair W. Khan ◽  
Phillip A Newmark
Keyword(s):  
Germ Cell ◽  
Germ Cells ◽  
Pluripotent Stem Cells ◽  
Cell Development ◽  
Molecular Signatures ◽  
Germ Cell Development ◽  
Ovarian Cells ◽  
Planarian Regeneration ◽  
Female Germ Cell ◽  
Oocyte Differentiation

Female germ cells develop into oocytes, with the capacity for totipotency. In most animals, these remarkable cells are specified during development and cannot be regenerated. By contrast, planarians, known for their regenerative prowess, can regenerate germ cells. To uncover mechanisms required for female germ cell development and regeneration, we generated gonad-specific transcriptomes and identified genes whose expression defines progressive stages of female germ cell development. Strikingly, early female germ cells share molecular signatures with the pluripotent stem cells driving planarian regeneration. We uncovered spatial heterogeneity within somatic ovarian cells and found that a regionally enriched FoxL homolog is required for oocyte differentiation, but not specification, suggestive of functionally distinct somatic compartments. Unexpectedly, a neurotransmitter-biosynthetic enzyme, AADC, is also expressed in somatic gonadal cells, and plays opposing roles in female and male germ cell development. Thus, somatic gonadal cells deploy conserved factors to regulate germ cell development and regeneration in planarians.

The Drosophila stonewall gene encodes a putative transcription factor essential for germ cell development

Development ◽  
1996 ◽  
Vol 122 (3) ◽  
pp. 937-950 ◽  
Author(s):  
K.A. Clark ◽  
D.M. McKearin
Keyword(s):  
Germ Cell ◽  
Germ Cells ◽  
Nuclear Protein ◽  
Cell Development ◽  
Nurse Cells ◽  
Cell Specification ◽  
Germ Cell Development ◽  
Specialized Nurse ◽  
Putative Transcription Factor ◽  
Oocyte Differentiation

The differentiation of Drosophila germ cells is a useful model for studying mechanisms of cell specification. We report the identification of a gene, stonewall, that is required for germ cell development. Mutations in stonewall block proper oocyte differentiation and frequently cause the presumptive oocyte to develop as a nurse cell. Eventually, germ cells degenerate apoptotically. Stonewall is a germ cell nuclear protein; Stonewall has a DNA binding domain that shows similarities to the Myb and Adf-1 transcription factors and has other features that suggest that it is a transcription activating factor. We suggest that Stonewall transcriptional regulation is essential in cystocytes for maturation into specialized nurse cells and oocyte.

scholarly journals Absence of mDazl produces a final block on germ cell development at meiosis

Reproduction ◽  
2003 ◽  
pp. 589-597 ◽  
Author(s):  
PT Saunders ◽  
JM Turner ◽  
M Ruggiu ◽  
M Taggart ◽  
PS Burgoyne ◽  
...  
Keyword(s):  
Germ Cell ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Rna Binding ◽  
Developmental Stages ◽  
Cell Loss ◽  
Functional Differentiation ◽  
Autosomal Gene ◽  
Fetal Life ◽  
Male And Female

The autosomal gene DAZL is a member of a family of genes (DAZL, DAZ, BOULE), all of which contain a consensus RNA binding domain and are expressed in germ cells. Adult male and female mice null for Dazl lack gametes. In order to define more precisely the developmental stages in germ cells that require Dazl expression, the patterns of germ cell loss in immature male and female wild-type (+/+, WT) and Dazl -/- (DazlKO) mice were analysed. In females, loss of germ cells occurred during fetal life and was coincident with progression of cells through meiotic prophase. In males, testes were recovered from WT and DazlKO males obtained before and during the first wave of spermatogenesis (days 2-19). Mitotically active germ cells were present up to and including day 19. Functional differentiation of spermatogonia associated with detection of c-kit positive cells did not depend upon expression of Dazl. RBMY-positive cells (A, intermediate, B spermatogonia, zygotene and preleptotene spermatocytes) were reduced in DazlKO compared with WT testes. Staining of cell squashes from day 19 testes with anti-gamma-H2AX and anti-SCP3 antibodies showed that germ cells from DazlKO males were unable to progress beyond the leptotene stage of meiotic prophase I. It was concluded that in the absence of Dazl, germ cells can complete mitosis, and embark on functional differentiation but that, in both sexes, progression through meiotic prophase requires this RNA binding protein.

scholarly journals OBSERVATIONS ON EARLY GERM CELL DEVELOPMENT AND PREMEIOTIC RIBOSOMAL DNA AMPLIFICATION IN XENOPUS LAEVIS

1974 ◽  
Vol 62 (2) ◽  
pp. 460-472 ◽  
Author(s):  
Marvin R. Kalt ◽  
Joseph G. Gall
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Ribosomal Dna ◽  
Germ Cells ◽  
Dna Hybridization ◽  
Meiotic Prophase ◽  
Germ Line ◽  
Tritiated Thymidine ◽  
Gradient Centrifugation ◽  
Dna Amplification

The origin of premeiotic ribosomal DNA (rDNA) amplification in germ-line cells of Xenopus laevis has been examined using in situ RNA-DNA hybridization on cytological preparations, tritiated thymidine autoradiography, and isopycnic density gradient centrifugation. Primordial germ cells (PGC), from the time they first become localized in the genital ridge at day no. 4 of development, until approximately day no. 22, remain in an extended interphase condition. During this time PGC do not incorporate tritiated thymidine, have near diploid levels of rDNA as demonstrated by cytological RNA-DNA hybridization, and possess only one or two nucleoli. Starting on day no. 22–24, mitosis, sexual differentiation, and rDNA gene amplification all begin in the germ cells. Multiple nucleoli also make their appearance at this stage. Ribosomal DNA amplification continues in gonial cells as long as they remain mitotically active. Amplified copies of rDNA are lost from germ cells at the onset of meiotic prophase. This loss is probably permanent in the male germ line, but variable and temporary in the female germ line. Early gonial cells in the ovary have been deduced to have an average cycle time for each mitotic division of between 3.8 and 4.3 days at a temperature of 21°C. Some oogonia appear to divide only four times before entering meiotic prophase, while the average during the initial wave of germ cell division is nine. Finally, a satellite DNA has been isolated from adult testes which has a density in neutral cesium chloride corresponding to the density of amplified oocyte rDNA. This satellite is not present in DNA isolated from somatic tissues of Xenopus.

scholarly journals Cap-Independent mRNA Translation in Germ Cells

2019 ◽  
Vol 20 (1) ◽  
pp. 173 ◽  
Author(s):  
Brett D. Keiper
Keyword(s):  
Germ Cell ◽  
Germ Cells ◽  
Translation Initiation ◽  
Translational Control ◽  
Structural Damage ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Cellular Mrnas ◽  
A Minor ◽  
Oocyte Differentiation

Cellular mRNAs in plants and animals have a 5′-cap structure that is accepted as the recognition point to initiate translation by ribosomes. Consequently, it was long assumed that the translation initiation apparatus was built solely for a cap-dependent (CD) mechanism. Exceptions that emerged invoke structural damage (proteolytic cleavage) to eukaryotic initiation factor 4 (eIF4) factors that disable cap recognition. The residual eIF4 complex is thought to be crippled, but capable of cap-independent (CI) translation to recruit viral or death-associated mRNAs begrudgingly when cells are in great distress. However, situations where CI translation coexists with CD translation are now known. In such cases, CI translation is still a minor mechanism in the major background of CD synthesis. In this review, I propose that germ cells do not fit this mold. Using observations from various animal models of oogenesis and spermatogenesis, I suggest that CI translation is a robust partner to CD translation to carry out the translational control that is so prevalent in germ cell development. Evidence suggests that CI translation provides surveillance of germ cell homeostasis, while CD translation governs the regulated protein synthesis that ushers these meiotic cells through the remarkable steps in sperm/oocyte differentiation.

scholarly journals Spermatogenesis in testes of Dazl null mice after transplantation of wild-type germ cells

Reproduction ◽  
2003 ◽  
pp. 599-604 ◽  
Author(s):  
R R ◽  
R Speed ◽  
M Taggart ◽  
HJ Cooke
Keyword(s):  
Stem Cells ◽  
Germ Cell ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Spermatogonial Stem Cells ◽  
Cell Suspensions ◽  
Male Mice ◽  
Wild Type

Dazl knockout male mice are infertile because their germ cells are unable to complete the first meiotic prophase in the first wave of spermatogenesis and thereafter decrease in number due to a block at the A-aligned to A1 transition. The ability of the surviving somatic components of the testes to retain their function in the absence of mature germ cells was tested by injecting marked wild-type germ cell suspensions containing spermatogonial stem cells. Comparison of the frequency and extent of colonization of Dazl knockout testes with that of testes chemically depleted of germ cells showed little if any difference. It was concluded that Dazlko testes seem unimpaired in their ability to support spermatogenesis. Therefore, Dazlko testes provide a useful and reliable recipient in which to evaluate spermatogonial stem cells. The results furthermore demonstrate that the somatic compartment of the testis of these animals retains functionality.

Germ cell expression of the transcriptional co-repressor TIF1β is required for the maintenance of spermatogenesis in the mouse

Development ◽  
2002 ◽  
Vol 129 (10) ◽  
pp. 2329-2337 ◽  
Author(s):  
Philipp Weber ◽  
Florence Cammas ◽  
Christelle Gerard ◽  
Daniel Metzger ◽  
Pierre Chambon ◽  
...  
Keyword(s):  
Germ Cell ◽  
Chromatin Remodeling ◽  
Germ Cells ◽  
Sertoli Cells ◽  
Crucial Role ◽  
Cell Lineage ◽  
Meiotic Chromosomes ◽  
Cell Subpopulations ◽  
Cell Expression ◽  
Testicular Degeneration

The gene for transcriptional intermediary factor 1β (TIF1β) encodes a transcriptional co-repressor known to play essential roles in chromatin remodeling as well as in early embryonic development. During spermatogenesis, TIF1β is preferentially associated with heterochromatin structures of Sertoli cells and round spermatids, as well as with meiotic chromosomes. Its expression is tightly regulated within spermatocyte and spermatid populations, and it is undetectable in spermatogonia. Spatiotemporally controlled ablation of TIF1β by using a germ cell lineage-specific CreERT/loxP system leads to testicular degeneration. This degeneration is not due to impairment of chromatin remodeling processes during meiosis and spermiogenesis, as TIF1β-deficient spermatocytes are able to complete their differentiation into spermatozoa. It rather occurs as a consequence of shedding of immature germ cells (spermatocytes and spermatids), and disappearance of stem spermatogonia. These results indicate that TIF1β has important functions in the homeostasis of the seminiferous epithelium, and probably plays a crucial role in the network of paracrine interactions between germ cell subpopulations and/or Sertoli cells.

scholarly journals Analysis of the multiple roles of gld-1 in germline development: interactions with the sex determination cascade and the glp-1 signaling pathway.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 607-630 ◽  
Author(s):  
R Francis ◽  
E Maine ◽  
T Schedl
Keyword(s):  
Sex Determination ◽  
Germ Cell ◽  
Signaling Pathway ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Tumor Formation ◽  
Germline Development ◽  
Epistasis Analysis ◽  
Cell Ablation ◽  
Genetic Epistasis

Abstract The Caenorhabditis elegans gene gld-1 is essential for oocyte development; in gld-1 (null) hermaphrodites, a tumor forms where oogenesis would normally occur. We use genetic epistasis analysis to demonstrate that tumor formation is dependent on the sexual fate of the germline. When the germline sex determination pathway is set in the female mode (terminal fem/fog genes inactive), gld-1 (null) germ cells exit meiotic prophase and proliferate to form a tumor, but when the pathway is set in the male mode, they develop into sperm. We conclude that the gld-1 (null) phenotype is cell-type specific and that gld-1(+) acts at the end of the cascade to direct oogenesis. We also use cell ablation and epistasis analysis to examine the dependence of tumor formation on the glp-1 signaling pathway. Although glp-1 activity promotes tumor growth, it is not essential for tumor formation by gld-1 (null) germ cells. These data also reveal that gld-1(+) plays a nonessential (and sex nonspecific) role in regulating germ cell proliferation before their entry into meiosis. Thus gld-1(+) may negatively regulate proliferation at two distinct points in germ cell development: before entry into meiotic prophase in both sexes (nonessential premeiotic gld-1 function) and during meiotic prophase when the sex determination pathway is set in the female mode (essential meiotic gld-1 function).

Electron microscope study of the effects of radiation on insect fertility

1990 ◽  
Vol 48 (3) ◽  
pp. 72-73
Author(s):  
Judy Ju-Hu Chiang ◽  
Robert Kuo-Cheng Chen
Keyword(s):  
Electron Microscopy ◽  
Germ Cell ◽  
Germ Cells ◽  
Electron Microscope Study ◽  
Radiation Treatment ◽  
Light And Electron Microscopy ◽  
Stem Borer ◽  
Metabolic Energy ◽  
Rice Stem Borer ◽  
Effects Of Radiation

Germ cells from the rice stem borer Chilo suppresalis, were examined by light and electron microscopy. Damages to organelles within the germ cells were observed. The mitochondria, which provide the cell with metabolic energy, were seen to disintegrate within the germ cell. Lysosomes within the germ cell were also seen to disintegrate. The subsequent release of hydrolytic enzymesmay be responsible for the destruction of organelles within the germ cell. Insect spermatozoa were seen to lose the ability to move because of radiation treatment. Damage to the centrioles, one of which is in contact with the tail, may be involved in causing sperm immobility.

Examination of the dynamics of global DNA methylation pattern establishment during spermatogenesiss

2007 ◽  
Vol 30 (4) ◽  
pp. 90
Author(s):  
Kirsten Niles ◽  
Sophie La Salle ◽  
Christopher Oakes ◽  
Jacquetta Trasler
Keyword(s):  
Dna Methylation ◽  
Germ Cell ◽  
Germ Cells ◽  
Epigenetic Modification ◽  
Methylation Pattern ◽  
Chromosome 9 ◽  
Specific Gene ◽  
Global Methylation ◽  
Dna Methylation Pattern ◽  
Methylation Patterns

Background: DNA methylation is an epigenetic modification involved in gene expression, genome stability, and genomic imprinting. In the male, methylation patterns are initially erased in primordial germ cells (PGCs) as they enter the gonadal ridge; methylation patterns are then acquired on CpG dinucleotides during gametogenesis. Correct pattern establishment is essential for normal spermatogenesis. To date, the characterization and timing of methylation pattern acquisition in PGCs has been described using a limited number of specific gene loci. This study aimed to describe DNA methylation pattern establishment dynamics during male gametogenesis through global methylation profiling techniques in a mouse model. Methods: Using a chromosome based approach, primers were designed for 24 regions spanning chromosome 9; intergenic, non-repeat, non-CpG island sequences were chosen for study based on previous evidence that these types of sequences are targets for testis-specific methylation events. The percent methylation was determined in each region by quantitative analysis of DNA methylation using real-time PCR (qAMP). The germ cell-specific pattern was determined by comparing methylation between spermatozoa and liver. To examine methylation in developing germ cells, spermatogonia from 2 day- and 6 day-old Oct4-GFP (green fluorescent protein) mice were isolated using fluorescence activated cell sorting. Results: As compared to liver, four loci were hypomethylated and five loci were hypermethylated in spermatozoa, supporting previous results indicating a unique methylation pattern in male germ cells. Only one region was hypomethylated and no regions were hypermethylated in day 6 spermatogonia as compared to mature spermatozoa, signifying that the bulk of DNA methylation is established prior to type A spermatogonia. The methylation in day 2 spermatogonia, germ cells that are just commencing mitosis, revealed differences of 15-20% compared to day 6 spermatogonia at five regions indicating that the most crucial phase of DNA methylation acquisition occurs prenatally. Conclusion: Together, these studies provide further evidence that germ cell methylation patterns differ from those in somatic tissues and suggest that much of methylation at intergenic sites is acquired during prenatal germ cell development. (Supported by CIHR)

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