Morphogenesis of the Drosophila fusome and its implications for oocyte specification

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2781-2789 ◽  
Author(s):  
M. de Cuevas ◽  
A.C. Spradling
Keyword(s):  
Stem Cells ◽  
Daughter Cell ◽  
Cyst Formation ◽  
The Other ◽  
Cytoplasmic Organelle ◽  
Ring Canal ◽  
Cell Cycles ◽  
Ring Canals ◽  
Asymmetrically Distributed ◽  
Cyst Growth

The Drosophila oocyte develops within a cyst of 16 germline cells interconnected by ring canals. Polarized, microtubule-based transport of unknown determinants is required for oocyte formation, but whether polarity is established during or after cyst formation is not clear. We have analyzed how polarity develops in stem cells and dividing cysts by following the growth of the fusome, a vesiculated cytoplasmic organelle. Our studies show that the fusome grows by a regular, polarized process throughout the stem cell and cyst cell cycles. Each polarization cycle begins in mitosis, when the fusome segregates to a single daughter cell of each pair. Following mitosis, a ‘plug’ of fusomal material forms in each nascent ring canal and gradually fuses with the pre-existing fusome. In stem cells, the ring canal is transient and closes down after the fusome is partitioned through it. In dividing cysts, as the fusome plugs move toward the pre-existing fusome, their associated ring canals also move, changing the geometry of the cyst. At the end of each cycle of cyst growth, the fusome remains asymmetrically distributed within the cyst; one of the two cells with four ring canals retains a bigger piece of fusome than any other cell, including the other cell with four ring canals. Based on these observations, we argue that the oocyte is specified at the first cyst division.

scholarly journals Zebrafish dazl regulates cystogenesis and germline stem cell specification during the primordial germ cell to germline stem cell transition

Development ◽  
2021 ◽  
Vol 148 (7) ◽  
Author(s):  
Sylvain Bertho ◽  
Mara Clapp ◽  
Torsten U. Banisch ◽  
Jan Bandemer ◽  
Erez Raz ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Rna Binding ◽  
Process Analysis ◽  
Primordial Germ Cell ◽  
Cyst Formation ◽  
Rapid Expansion ◽  
Germline Stem Cell ◽  
Cell Specification ◽  
Ring Canals

ABSTRACT Fertility and gamete reserves are maintained by asymmetric divisions of the germline stem cells to produce new stem cells or daughters that differentiate as gametes. Before entering meiosis, differentiating germ cells (GCs) of sexual animals typically undergo cystogenesis. This evolutionarily conserved process involves synchronous and incomplete mitotic divisions of a GC daughter (cystoblast) to generate sister cells connected by intercellular bridges that facilitate the exchange of materials to support rapid expansion of the gamete progenitor population. Here, we investigated cystogenesis in zebrafish and found that early GCs are connected by ring canals, and show that Deleted in azoospermia-like (Dazl), a conserved vertebrate RNA-binding protein (Rbp), is a regulator of this process. Analysis of dazl mutants revealed the essential role of Dazl in regulating incomplete cytokinesis, germline cyst formation and germline stem cell specification before the meiotic transition. Accordingly, dazl mutant GCs form defective ring canals, and ultimately remain as individual cells that fail to differentiate as meiocytes. In addition to promoting cystoblast divisions and meiotic entry, dazl is required for germline stem cell establishment and fertility.

scholarly journals Drosophila neural stem cells are polarized by their daughter cells

2017 ◽  
Author(s):  
Nicolas Loyer ◽  
Jens Januschke
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Cell Fate ◽  
Live Cell Imaging ◽  
Daughter Cell ◽  
Positional Information ◽  
Larval Brain ◽  
Cell Cycles ◽  
Intrinsic Cues ◽  
Daughter Cells

AbstractControlling the orientation of cell division is important in the context of cell fate choices and tissue morphogenesis. However, the mechanisms providing the required positional information remain incompletely understood. Here we use stem cells of the Drosophila larval brain that stably maintain their axis of polarity and division between cell cycles to identify cues that orient cell division. Using live cell imaging of cultured brains, laser ablation and genetics we reveal that these cells use the position of their last-born daughter cell as a polarizing cue. Remarkably, this daughter cell derived signal received at one pole of the stem cell has an effect on the opposite pole influencing where apical will be in the next mitosis, thereby directing the orientation of division. Therefore, in addition to known intrinsic cues, stem cells in the developing fly brain are polarized by an extrinsic signal that acts upstream of apico-basal polarity establishment.

scholarly journals Biological and microbiological interactions of Ti-35Nb-7Zr alloy and its basic elements on bone marrow stromal cells: good prospects for bone tissue engineering

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Daphne de Camargo Reis Mello ◽  
Lais Morandini Rodrigues ◽  
Fabia Zampieri D’Antola Mello ◽  
Thais Fernanda Gonçalves ◽  
Bento Ferreira ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Differentiation ◽  
Stromal Cells ◽  
Biofilm Formation ◽  
Bone Marrow Stromal Cells ◽  
Pure Titanium ◽  
Marrow Stromal Cells ◽  
The Other ◽  
Cell Based Therapy

Abstract Background An effective biomaterial for bone replacement should have properties to avoid bacterial contamination and promote bone formation while inducing rapid cell differentiation simultaneously. Bone marrow stem cells are currently being investigated because of their known potential for differentiation in osteoblast lineage. This makes these cells a good option for stem cell-based therapy. We have aimed to analyze, in vitro, the potential of pure titanium (Ti), Ti-35Nb-7Zr alloy (A), niobium (Nb), and zirconia (Zr) to avoid the microorganisms S. aureus (S.a) and P. aeruginosa (P.a). Furthermore, our objective was to evaluate if the basic elements of Ti-35Nb-7Zr alloy have any influence on bone marrow stromal cells, the source of stem cells, and observe if these metals have properties to induce cell differentiation into osteoblasts. Methods Bone marrow stromal cells (BMSC) were obtained from mice femurs and cultured in osteogenic media without dexamethasone as an external source of cell differentiation. The samples were divided into Ti-35Nb-7Zr alloy (A), pure titanium (Ti), Nb (niobium), and Zr (zirconia) and were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). After predetermined periods, cell interaction, cytotoxicity, proliferation, and cell differentiation tests were performed. For monotypic biofilm formation, standardized suspensions (106 cells/ml) with the microorganisms S. aureus (S.a) and P. aeruginosa (P.a) were cultured for 24 h on the samples and submitted to an MTT test. Results All samples presented cell proliferation, growth, and spreading. All groups presented cell viability above 70%, but the alloy (A) showed better results, with statistical differences from Nb and Zr samples. Zr expressed higher ALP activity and was statistically different from the other groups (p < 0.05). In contrast, no statistical difference was observed between the samples as regards mineralization nodules. Lower biofilm formation of S.a and P.a. was observed on the Nb samples, with statistical differences from the other samples. Conclusion Our results suggest that the basic elements present in the alloy have osteoinductive characteristics, and Zr has a good influence on bone marrow stromal cell differentiation. We also believe that Nb has the best potential for reducing the formation of microbial biofilms.

Antagonism of endogenous putative P2Y receptors reduces the growth of MDCK-derived cysts cultured in vitro

2007 ◽  
Vol 292 (1) ◽  
pp. F15-F25 ◽  
Author(s):  
Clare M. Turner ◽  
Brian F. King ◽  
Kaila S. Srai ◽  
Robert J. Unwin
Keyword(s):  
Therapeutic Potential ◽  
Cyst Formation ◽  
P2y Receptors ◽  
P2x Receptor ◽  
P2y Receptor ◽  
Cyst Size ◽  
Reactive Blue 2 ◽  
Cyst Growth

P2Y receptors couple to G proteins and either mobilize intracellular Ca2+ or alter cAMP levels to modulate the activity of Ca2+- and cAMP-sensitive ion channels. We hypothesize that increased ion transport into the lumen of MDCK cysts can osmotically drive fluid movement and increase cyst size. Furthermore, activation of the adenylate cyclase/cAMP pathway may trigger cell proliferation via an extracellular signal-related kinase cascade. To test this hypothesis, several P2Y receptor inhibitors were used on the MDCK in vitro model of renal cyst formation. The nonspecific P2 receptor inhibitors reactive blue 2 and suramin reduced cyst growth significantly, as did PPADS and, to a lesser extent, the P2Y1-specific antagonist MRS2179. Cyst growth was reduced by ∼50% when ATP was removed from the culture medium with apyrase, although stable analogs of ATP failed to increase cyst size. The nonselective P2X receptor inhibitor Coomassie brilliant blue G was ineffective at reducing cyst growth, suggesting no involvement of P2X receptors. Finally, the presence of selective inhibitors of ERK activation (either PD98059 or U0126) greatly reduced cyst growth, whereas in untreated cysts ERK activity was observed to increase with time. We conclude that stimulation of endogenous P2Y receptors by extracellular ATP increases growth of MDCK cysts via cAMP-dependent activation of the ERK pathway. P2Y receptor antagonists may have therapeutic potential in reducing cyst size and slowing disease progression; although further studies in vitro and in vivo are needed to investigate the specificity and role of these P2Y receptors in renal cystic diseases.

scholarly journals Phase Separation and Mechanical Forces in Regulating Asymmetric Cell Division of Neural Stem Cells

2021 ◽  
Vol 22 (19) ◽  
pp. 10267
Author(s):  
Yiqing Zhang ◽  
Heyang Wei ◽  
Wenyu Wen
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Phase Separation ◽  
Cell Division ◽  
Neural Stem Cells ◽  
Asymmetric Cell Division ◽  
Stem Cell Population ◽  
Mechanical Forces ◽  
Major Mechanism ◽  
Asymmetrically Distributed

Asymmetric cell division (ACD) of neural stem cells and progenitors not only renews the stem cell population but also ensures the normal development of the nervous system, producing various types of neurons with different shapes and functions in the brain. One major mechanism to achieve ACD is the asymmetric localization and uneven segregation of intracellular proteins and organelles into sibling cells. Recent studies have demonstrated that liquid-liquid phase separation (LLPS) provides a potential mechanism for the formation of membrane-less biomolecular condensates that are asymmetrically distributed on limited membrane regions. Moreover, mechanical forces have emerged as pivotal regulators of asymmetric neural stem cell division by generating sibling cell size asymmetry. In this review, we will summarize recent discoveries of ACD mechanisms driven by LLPS and mechanical forces.

scholarly journals Effect of lentivirus-mediated growth and differentiation factor-5 transfection on differentiation of rabbit nucleus pulposus mesenchymal stem cells

2022 ◽  
Vol 27 (1) ◽  
Author(s):  
Kun Zhu ◽  
Rui Zhao ◽  
Yuchen Ye ◽  
Gang Xu ◽  
Changchun Zhang
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Nucleus Pulposus ◽  
Lentiviral Vector ◽  
The Other ◽  
Cell Phenotype ◽  
Mrna Levels ◽  
Qrt Pcr ◽  
Differentiation Factor ◽  
Gdf5 Gene

Abstract Background Intervertebral disc degeneration (IDD) is a natural progression of age-related processes. Associated with IDD, degenerative disc disease (DDD) is a pathologic condition implicated as a major cause of chronic lower back pain, which can have a severe impact on the quality of life of patients. As degeneration progression is associated with elevated levels of inflammatory cytokines, enhanced aggrecan and collagen degradation, and changes in the disc cell phenotype. The purpose of this study was to investigate the biological and cytological characteristics of rabbit nucleus pulposus mesenchymal stem cells (NPMSCs)—a key factor in IDD—and to determine the effect of the growth and differentiation factor-5 (GDF5) on the differentiation of rabbit NPMSCs transduced with a lentivirus vector. Methods An in vitro culture model of rabbit NPMSCs was established and NPMSCs were identified by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Subsequently, NPMSCs were randomly divided into three groups: a transfection group (the lentiviral vector carrying GDF5 gene used to transfect NPMSCs); a control virus group (the NPMSCs transfected with an ordinary lentiviral vector); and a normal group (the NPMSCs alone). FCM, qRT-PCR, and western blot (WB) were used to detect the changes in NPMSCs. Results The GDF5-transfected NPMSCs displayed an elongated shape, with decreased cell density, and significantly increased GDF5 positivity rate in the transfected group compared to the other two groups (P < 0.01). The mRNA levels of Krt8, Krt18, and Krt19 in the transfected group were significantly higher in comparison with the other two groups (P < 0.01), and the WB results were consistent with that of qRT-PCR. Conclusions GDF5 could induce the differentiation of NPMSCs. The lentiviral vector carrying the GDF5 gene could be integrated into the chromosome genome of NPMSCs and promoted differentiation of NPMSCs into nucleus pulposus cells. Our findings advance the development of feasible and effective therapies for IDD.

Machine learning-assisted imaging analysis of a human epiblast model

2021 ◽  
Author(s):  
Agnes M Resto Irizarry ◽  
Sajedeh Nasr Esfahani ◽  
Yi Zheng ◽  
Robin Zhexuan Yan ◽  
Patrick Kinnunen ◽  
...  
Keyword(s):  
Machine Learning ◽  
Stem Cells ◽  
Cell Tracking ◽  
Complex Structure ◽  
Cyst Formation ◽  
System Level ◽  
Imaging Data ◽  
Cell Level ◽  
Human Blastocyst ◽  
Cell Cell

Abstract The human embryo is a complex structure that emerges and develops as a result of cell-level decisions guided by both intrinsic genetic programs and cell–cell interactions. Given limited accessibility and associated ethical constraints of human embryonic tissue samples, researchers have turned to the use of human stem cells to generate embryo models to study specific embryogenic developmental steps. However, to study complex self-organizing developmental events using embryo models, there is a need for computational and imaging tools for detailed characterization of cell-level dynamics at the single cell level. In this work, we obtained live cell imaging data from a human pluripotent stem cell (hPSC)-based epiblast model that can recapitulate the lumenal epiblast cyst formation soon after implantation of the human blastocyst. By processing imaging data with a Python pipeline that incorporates both cell tracking and event recognition with the use of a CNN-LSTM machine learning model, we obtained detailed temporal information of changes in cell state and neighborhood during the dynamic growth and morphogenesis of lumenal hPSC cysts. The use of this tool combined with reporter lines for cell types of interest will drive future mechanistic studies of hPSC fate specification in embryo models and will advance our understanding of how cell-level decisions lead to global organization and emergent phenomena. Insight, innovation, integration: Human pluripotent stem cells (hPSCs) have been successfully used to model and understand cellular events that take place during human embryogenesis. Understanding how cell–cell and cell–environment interactions guide cell actions within a hPSC-based embryo model is a key step in elucidating the mechanisms driving system-level embryonic patterning and growth. In this work, we present a robust video analysis pipeline that incorporates the use of machine learning methods to fully characterize the process of hPSC self-organization into lumenal cysts to mimic the lumenal epiblast cyst formation soon after implantation of the human blastocyst. This pipeline will be a useful tool for understanding cellular mechanisms underlying key embryogenic events in embryo models.

The Drosophila fusome, a germline-specific organelle, contains membrane skeletal proteins and functions in cyst formation

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 947-956 ◽  
Author(s):  
H. Lin ◽  
L. Yue ◽  
A.C. Spradling
Keyword(s):  
Cyst Formation ◽  
Nurse Cells ◽  
Germline Stem Cells ◽  
Cytoplasmic Structure ◽  
Ring Canals ◽  
Alpha Spectrin ◽  
Polarized Transport ◽  
Form Ring ◽  
Molecular Components ◽  
Number Of Cells

Oogenesis in Drosophila takes place within germline cysts that support polarized transport through ring canals interconnecting their 15 nurse cells and single oocyte. Developing cystocytes are spanned by a large cytoplasmic structure known as the fusome that has been postulated to help form ring canals and determine the pattern of nurse cell-oocyte interconnections. We identified the adducin-like hts product and alpha-spectrin as molecular components of fusomes, discovered a related structure in germline stem cells and documented regular associations between fusomes and cystocyte centrosomes. hts mutations completely eliminated fusomes, causing abnormal cysts containing a reduced number of cells to form. Our results imply that Drosophila fusomes are required for ovarian cyst formation and suggest that membrane skeletal proteins regulate cystocyte divisions.

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