scholarly journals PRIMITIVE ERYTHROPOIESIS IN EARLY CHICK EMBRYOGENESIS

1971 ◽  
Vol 50 (3) ◽  
pp. 669-681 ◽  
Author(s):  
G. Le M. Campbell ◽  
H. Weintraub ◽  
B. H. Mayall ◽  
H. Holtzer
Keyword(s):  
Cell Cycle ◽  
Progressive Increase ◽  
Cell Cycles ◽  
Proliferative Phase ◽  
Cell Divisions ◽  
Chick Embryogenesis ◽  
Interphase Cells ◽  
Feulgen Cytophotometry ◽  
Successive Generations ◽  
Primitive Erythropoiesis

Primitive erythroblasts in the circulating blood of the chick embryo continue to divide while synthesizing hemoglobin (Hb). Hb measurements on successive generations of erythroblasts show that there is a progressive increase in the Hb content of both interphase and metaphase cells. Furthermore, for any given embryo the Hb content of metaphase cells is always significantly greater than that of interphase cells. The distribution of Hb values for metaphase cells suggests that there are six Hb classes corresponding to the number of cell cycles in the proliferative phase. The location of erythroblasts in the cell cycle was determined by combining Feulgen cytophotometry with thymidine radioautography on the same cells. Measurements of the Hb content for erythroblasts in different compartments of the cell cycle (G1, S, G2, and M) show a progressive increase through the cycle. Thus, the amount of Hb per cell is a function of the number of cell divisions since the initiation of Hb synthesis and, to a lesser degree, the stage of the cell cycle. Earlier generations of erythroblasts synthesize Hb at a faster rate than the terminal generation. Several models have been proposed to explain these findings.

Expression of the cell cycle control gene, cdc25, is constitutive in the segmental founder cells but is cell-cycle-regulated in the micromeres of leech embryos

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3035-3043 ◽  
Author(s):  
S.T. Bissen
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Control ◽  
Control Gene ◽  
Cdc25 Phosphatase ◽  
Cell Cycles ◽  
Cell Divisions ◽  
Zygotic Transcription ◽  
Founder Cells ◽  
Drosophila Embryos

The identifiable cells of leech embryos exhibit characteristic differences in the timing of cell division. To elucidate the mechanisms underlying these cell-specific differences in cell cycle timing, the leech cdc25 gene was isolated because Cdc25 phosphatase regulates the asynchronous cell divisions of postblastoderm Drosophila embryos. Examination of the distribution of cdc25 RNA and the zygotic expression of cdc25 in identified cells of leech embryos revealed lineage-dependent mechanisms of regulation. The early blastomeres, macromeres and teloblasts have steady levels of maternal cdc25 RNA throughout their cell cycles. The levels of cdc25 RNA remain constant throughout the cell cycles of the segmental founder cells, but the majority of these transcripts are zygotically produced. Cdc25 RNA levels fluctuate during the cell cycles of the micromeres. The levels peak during early G2, due to a burst of zygotic transcription, and then decline as the cell cycles progress. These data suggest that cells of different lineages employ different strategies of cell cycle control.

scholarly journals PRIMITIVE ERYTHROPOIESIS IN EARLY CHICK EMBRYOGENESIS

1971 ◽  
Vol 50 (3) ◽  
pp. 652-668 ◽  
Author(s):  
Harold Weintraub ◽  
Graham Le M. Campbell ◽  
Howard Holtzer
Keyword(s):  
Cell Cycle ◽  
Blood Cells ◽  
Generation Time ◽  
Cell Lineage ◽  
Embryonic Chick ◽  
Average Cell ◽  
Hemoglobin Synthesis ◽  
Chick Embryogenesis ◽  
Primitive Erythropoiesis ◽  
Mitotic Behavior

The primitive line of embryonic chick blood cells develop as a relatively homogeneous cohort of cells. Using an analysis based on the continuous uptake of thymidine-3H, we have established the generation time, G1, S, and G2 for progressively more mature generations of these immature erythroblasts. The data indicate that after the initiation of hemoglobin synthesis, the average cell will yield six generations of hemoglobin producing erythroblasts. The older generations of erythroblasts exhibit a longer generation time, G1, S, and G2 than the earlier generations of erythroblasts. Other methods of analysis corroborated these findings. One of these methods, an estimate of total erythrocyte productivity from the primitive stem cells (hematocytoblasts), led to the conclusion that the erythroblast cell lineage might be initiated as early as the sixth or seventh division following fertilization. In addition, primitive erythroblasts characterized by one set of cell cycle parameters, when grown in serum associated with erythroblasts of different parameters, showed no alteration in mitotic behavior. These results suggest the presence of programmed cell division not immediately cued by extracellular influence.

Timing of the phases of the cell cycle with tritiated thymidine and Feulgen cytophotometry during the period of synchronous division in Lymnaea

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 351-366
Author(s):  
J. A. M. van den Biggelaar
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Tritiated Thymidine ◽  
S Phase ◽  
Energy Requirements ◽  
G1 Phase ◽  
Cell Stage ◽  
Cell Cycles ◽  
Feulgen Cytophotometry

The duration of the phases of the cell cycle during the 1-, the 2- and the 4-cell stage of the Lymnaea egg were determined with [3H]thymidine and with Feulgen cytophotometry. The M, S and G2 phases occupy 48, 27 and 25% of the first three cell cycles. A G1 phase cannot be observed. Only from the 4-cell stage was [3H]thymidine readily incorporated into DNA. The theory that an increase in respiration during the S phase of the 4-cell stage is connected with the energy requirements of DNA synthesis is discussed.

scholarly journals Positive Feedback Between PU.1 and the Cell Cycle Controls Myeloid Differentiation

Science ◽  
2013 ◽  
Vol 341 (6146) ◽  
pp. 670-673 ◽  
Author(s):  
Hao Yuan Kueh ◽  
Ameya Champhekar ◽  
Stephen L. Nutt ◽  
Michael B. Elowitz ◽  
Ellen V. Rothenberg
Keyword(s):  
Cell Cycle ◽  
Cell Fate ◽  
Positive Feedback ◽  
Regulatory Gene ◽  
Control Cell ◽  
Stem Cell Differentiation ◽  
Myeloid Differentiation ◽  
Cycle Duration ◽  
Gene Circuits ◽  
Cell Cycles

Regulatory gene circuits with positive-feedback loops control stem cell differentiation, but several mechanisms can contribute to positive feedback. Here, we dissect feedback mechanisms through which the transcription factor PU.1 controls lymphoid and myeloid differentiation. Quantitative live-cell imaging revealed that developing B cells decrease PU.1 levels by reducing PU.1 transcription, whereas developing macrophages increase PU.1 levels by lengthening their cell cycles, which causes stable PU.1 accumulation. Exogenous PU.1 expression in progenitors increases endogenous PU.1 levels by inducing cell cycle lengthening, implying positive feedback between a regulatory factor and the cell cycle. Mathematical modeling showed that this cell cycle–coupled feedback architecture effectively stabilizes a slow-dividing differentiated state. These results show that cell cycle duration functions as an integral part of a positive autoregulatory circuit to control cell fate.

scholarly journals A Genetic Screen for Suppressors and Enhancers of the Drosophila Cdk1-Cyclin B Identifies Maternal Factors That Regulate Microtubule and Microfilament Stability

Genetics ◽  
2002 ◽  
Vol 162 (3) ◽  
pp. 1179-1195 ◽  
Author(s):  
Jun-Yuan Ji ◽  
Marjan Haghnia ◽  
Cory Trusty ◽  
Lawrence S B Goldstein ◽  
Gerold Schubiger
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Genetic Screen ◽  
Cyclin B ◽  
Gene Products ◽  
Nuclear Movement ◽  
Cell Cycles ◽  
Major Mechanism ◽  
Cytoskeletal Dynamics ◽  
Chromosome Bridges

Abstract Coordination between cell-cycle progression and cytoskeletal dynamics is important for faithful transmission of genetic information. In early Drosophila embryos, increasing maternal cyclin B leads to higher Cdk1-CycB activity, shorter microtubules, and slower nuclear movement during cycles 5-7 and delays in nuclear migration to the cortex at cycle 10. Later during cycle 14 interphase of six cycB embryos, we observed patches of mitotic nuclei, chromosome bridges, abnormal nuclear distribution, and small and large nuclei. These phenotypes indicate disrupted coordination between the cell-cycle machinery and cytoskeletal function. Using these sensitized phenotypes, we performed a dosage-sensitive genetic screen to identify maternal proteins involved in this process. We identified 10 suppressors classified into three groups: (1) gene products regulating Cdk1 activities, cdk1 and cyclin A; (2) gene products interacting with both microtubules and microfilaments, Actin-related protein 87C; and (3) gene products interacting with microfilaments, chickadee, diaphanous, Cdc42, quail, spaghetti-squash, zipper, and scrambled. Interestingly, most of the suppressors that rescue the astral microtubule phenotype also reduce Cdk1-CycB activities and are microfilament-related genes. This suggests that the major mechanism of suppression relies on the interactions among Cdk1-CycB, microtubule, and microfilament networks. Our results indicate that the balance among these different components is vital for normal early cell cycles and for embryonic development. Our observations also indicate that microtubules and cortical microfilaments antagonize each other during the preblastoderm stage.

The murine Ki-67 cell proliferation antigen accumulates in the nucleolar and heterochromatic regions of interphase cells and at the periphery of the mitotic chromosomes in a process essential for cell cycle progression

1996 ◽  
Vol 109 (1) ◽  
pp. 143-153 ◽  
Author(s):  
M. Starborg ◽  
K. Gell ◽  
E. Brundell ◽  
C. Hoog
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Tandem Repeats ◽  
Sequence Motifs ◽  
Mitotic Chromosomes ◽  
Proliferating Cells ◽  
Ki 67 ◽  
Cycle Progression ◽  
Conserved Sequence ◽  
Interphase Cells

We have isolated the murine homologue of the human Ki-67 antigen. The Ki-67 antigen is used as a marker to assess the proliferative capacity of tumour cells; however, its cellular function is not known. The murine Ki-67 cDNA sequence (TSG126) was found to contain 13 tandem repeats, making up more than half of the total protein size. A comparison of this repetitive sequence block to its human counterpart, which contains 16 consecutive repeat units, revealed several conserved sequence motifs, including one motif frequently observed in proteins interacting with DNA. An antiserum developed against the product of the TSG126 cDNA clone identified a protein with an apparent molecular mass of 360 kDa, mainly expressed in proliferating cells. The TSG126 protein begins to accumulate during the late G1 stage of the cell cycle and is first seen as numerous small granules evenly distributed throughout the nucleus. During the S and the G2 phases, larger foci that overlap with the nucleoli and the heterochromatic regions are formed. At the onset of mitosis the TSG126 protein undergoes a dramatic redistribution process and becomes associated with the surface of the condensed chromosomes. The relative absence of the TSG126 protein from G1 interphase cells strongly argues against a model where the association of the TSG126 protein with mitotic chromosomes merely reflects a mechanism for the symmetrical distribution of nucleolar proteins between daughter cells. Instead, the intracellular distribution of the TSG126 protein during the cell cycle suggests that it could have a chromatin-associated function in both interphase and mitotic cells. Microinjection of anti-TSG126 antibodies into proliferating Swiss-3T3 fibroblasts was found to delay cell cycle progression, indicating that the TSG126 protein has an essential nuclear function.

Asymmetry of the spindle pole bodies and spg1p GAP segregation during mitosis in fission yeast

1999 ◽  
Vol 112 (14) ◽  
pp. 2313-2321 ◽  
Author(s):  
L. Cerutti ◽  
V. Simanis
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Spindle Pole Body ◽  
Mitotic Cell ◽  
Spindle Pole ◽  
The Other ◽  
Septum Formation ◽  
Spindle Pole Bodies ◽  
Interphase Cells ◽  
Early Mitosis

In the fission yeast Schizosaccharomyces pombe, the onset of septum formation is induced by a signal transduction network involving several protein kinases and a GTPase switch. One of the roles of the spg1p GTPase is to localise the cdc7p protein kinase to the poles of the mitotic spindle, from where the onset of septation is thought to be signalled at the end of mitosis. Immunofluorescence studies have shown that cdc7p is located on both spindle pole bodies early in mitosis, but only on one during the later stages of anaphase. This is mediated by inactivation of spg1p on one pole before the other. The GAP for spg1p is a complex of two proteins, cdc16p and byr4p. Localisation of cdc16p and byr4p by indirect immunofluorescence during the mitotic cell cycle showed that both proteins are present on the spindle pole body in interphase cells. During mitosis, byr4p is seen first on both poles of the spindle, then on only one. This occurs prior to cdc7p becoming asymmetric. In contrast, the signal due to cdc16p decreases to a low level during early mitosis, before being seen strongly on the same pole as byr4p. Double staining indicates that this is the opposite pole to that which retains cdc7p in late anaphase. Examination of the effect of inactivating cdc16p at various stages of the cell cycle suggests that cdc16p, together with cdc2p plays a role in restraining septum formation during interphase. The asymmetric inactivation of spg1p is mediated by recruitment of the cdc16p-byr4p GAP to one of the poles of the spindle before the other, and the asymmetry of the spindle pole bodies may be established early during mitosis. Moreover, the spindle pole bodies appear to be non-equivalent even after division has been completed.

scholarly journals Genome-Wide Identification and Analysis of Cell Cycle Genes in Birch

Forests ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 120
Author(s):  
Yijie Li ◽  
Song Chen ◽  
Yuhang Liu ◽  
Haijiao Huang
Keyword(s):  
Cell Cycle ◽  
Growth And Development ◽  
Betula Pendula ◽  
Cell Cycle Gene ◽  
Expression Data ◽  
Rna Seq ◽  
Specific Expression ◽  
Cell Cycles ◽  
Cell Cycle Genes ◽  
Genome Wide

Research Highlights: This study identified the cell cycle genes in birch that likely play important roles during the plant’s growth and development. This analysis provides a basis for understanding the regulatory mechanism of various cell cycles in Betula pendula Roth. Background and Objectives: The cell cycle factors not only influence cell cycles progression together, but also regulate accretion, division, and differentiation of cells, and then regulate growth and development of the plant. In this study, we identified the putative cell cycle genes in the B. pendula genome, based on the annotated cell cycle genes in Arabidopsis thaliana (L.) Heynh. It can be used as a basis for further functional research. Materials and Methods: RNA-seq technology was used to determine the transcription abundance of all cell cycle genes in xylem, roots, leaves, and floral tissues. Results: We identified 59 cell cycle gene models in the genome of B. pendula, with 17 highly expression genes among them. These genes were BpCDKA.1, BpCDKB1.1, BpCDKB2.1, BpCKS1.2, BpCYCB1.1, BpCYCB1.2, BpCYCB2.1, BpCYCD3.1, BpCYCD3.5, BpDEL1, BpDpa2, BpE2Fa, BpE2Fb, BpKRP1, BpKRP2, BpRb1, and BpWEE1. Conclusions: By combining phylogenetic analysis and tissue-specific expression data, we identified 17 core cell cycle genes in the Betulapendula genome.

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