scholarly journals In Vivo Analysis of Cell Division, Cell Growth, and Differentiation at the Shoot Apical Meristem in Arabidopsis

2003 ◽  
Vol 16 (1) ◽  
pp. 74-87 ◽  
Author(s):  
Olivier Grandjean ◽  
Teva Vernoux ◽  
Patrick Laufs ◽  
Katia Belcram ◽  
Yuki Mizukami ◽  
...  
2011 ◽  
Vol 67 (6) ◽  
pp. 1116-1123 ◽  
Author(s):  
Pascale Milani ◽  
Maryam Gholamirad ◽  
Jan Traas ◽  
Alain Arnéodo ◽  
Arezki Boudaoud ◽  
...  

BioMetals ◽  
2014 ◽  
Vol 27 (5) ◽  
pp. 857-874 ◽  
Author(s):  
Anne Blais ◽  
Cuibai Fan ◽  
Thierry Voisin ◽  
Najat Aattouri ◽  
Michel Dubarry ◽  
...  

Development ◽  
1972 ◽  
Vol 27 (1) ◽  
pp. 245-260
Author(s):  
D. A. Ede ◽  
O. P. Flint

Aggregates were prepared from dissociated mesenchyme cells obtained from normal and talpid mutant chick limb buds at stage 26 and were maintained for 4 days in culture. They were shown by autoradiographic techniques to consist initially of populations of unifoimly dedifferentiated cells within which chondrogenesis was initiated between 1 and 2 days, leading to the formation of areas of precartilage in the interior of the aggregates. Measurements of cell population density, cell death and cell division were made in precartilage and non-cartilage regions on sections prepared from normal and mutant aggregates fixed at 1-day intervals and were related to the pattern of chondrogenesis. Non-cartilage areas consisted of cells surrounding the precartilage areas and extended to the surface of the aggregate; these cells showed no special pattern or histochemical reaction. Precartilage areas consisted of one or more “;condensations”, comprising cells arranged in concentric rings around a central cell or group of cells, characterized by uptake of [35S]sulphate and taking up alcian blue stain in the intercellular matrix. Chondrogenesis was initiated al the condensation foci and spread centrifugally. Condensations were arranged in a simple pattern, roughly equidistantly from each other and never at the surface of the aggregate. The shape and arrangement of the cells comprising them suggested that they were formed by a process of aggregation towards the condensation foci. The relation of these observations to events in the intact limb bud developing in vivo is discussed.


Development ◽  
2002 ◽  
Vol 129 (13) ◽  
pp. 3207-3217 ◽  
Author(s):  
Jean-Luc Gallois ◽  
Claire Woodward ◽  
G. Venugopala Reddy ◽  
Robert Sablowski

Almost all aerial parts of plants are continuously generated at the shoot apical meristem (SAM). To maintain a steady pool of undifferentiated cells in the SAM while continuously generating new organs, it is necessary to balance the rate of cell division with the rate of entrance into differentiation pathways. In the Arabidopsis meristem, SHOOT MERISTEMLESS (STM) and WUSCHEL (WUS) are necessary to keep cells undifferentiated and dividing. Here, we tested whether ectopic STM and WUS functions are sufficient to revert differentiation and activate cell division in differentiating tissues. Ectopic STM and WUS functions interacted non-additively and activated a subset of meristem functions, including cell division, CLAVATA1 expression and organogenesis, but not correct phyllotaxy or meristem self-maintenance. Our results suggest that WUS produces a non-cell autonomous signal that activates cell division in combination with STM and that combined WUS/STM functions can initiate the progression from stem cells to organ initiation.


2003 ◽  
Vol 23 (17) ◽  
pp. 6327-6337 ◽  
Author(s):  
Aparna Sreenivasan ◽  
Anthony C. Bishop ◽  
Kevan M. Shokat ◽  
Douglas R. Kellogg

ABSTRACT In budding yeast, the Elm1 kinase is required for coordination of cell growth and cell division at G2/M. Elm1 is also required for efficient cytokinesis and for regulation of Swe1, the budding yeast homolog of the Wee1 kinase. To further characterize Elm1 function, we engineered an ELM1 allele that can be rapidly and selectively inhibited in vivo. We found that inhibition of Elm1 kinase activity during G2 results in a phenotype similar to the phenotype caused by deletion of the ELM1 gene, as expected. However, inhibition of Elm1 kinase activity earlier in the cell cycle results in a prolonged G1 delay. The G1 requirement for Elm1 kinase activity occurs before bud emergence, polarization of the septins, and synthesis of G1 cyclins. Inhibition of Elm1 kinase activity during early G1 also causes defects in the organization of septins, and inhibition of Elm1 kinase activity in a strain lacking the redundant G1 cyclins CLN1 and CLN2 is lethal. These results demonstrate that the Elm1 kinase plays an important role in G1 events required for bud emergence and septin organization.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 26-26
Author(s):  
Davide Bagnara ◽  
Matthew Kaufman ◽  
Xiao J. Yan ◽  
Kanti Rai ◽  
Nicholas Chiorazzi

Abstract B-cell type chronic lymphocytic leukemia (B-CLL), an incurable disease of unknown etiology, results from the clonal expansion of a CD5+CD19+ B lymphocyte. Progress into defining the cell of origin of the disease and identifying a stem cell reservoir has been impeded because of the lack of reproducible models for growing B-CLL cells in vitro and in vivo. To date, attempts to adoptively transfer B-CLL cells into immune deficient mice and achieve engraftment and growth are sub-optimal. At least one possible cause for this is the murine microenvironment’s inability to support B-CLL survival and proliferation. We have attempted to overcome this barrier by creating a human hematopoietic microenvironment by reconstituting the tibiae of NOD/SCID/γcnull mice by intrabone (ib) injection of 1–3 × 105 CD34+ cord blood cells along with ~106 bone marrow-derived human mesenchymal stem cells (hMSCs). When human engraftment of 1–10% CD45+ cells was documented in the blood by immunofluorescence using flow cytometry, a total of 108 PBMCs from individual B-CLL patients were injected into the same bones. Before injection, B-CLL PBMCs were labeled with CFSE to permit distinction of leukemic B cells from normal B cells that might arise from the injected CD34+ cells. CFSE labeling also permitted tracking initial rounds of cell division in vivo. Every two weeks after B-CLL injection, peripheral blood from the mice was examined for the presence of cells bearing human CD45, CFSE, and various human lineage markers by flow cytometry. In the presence of a human hematopoietic microenvironment, CD5+CD19+ leukemic cells underwent at least 6 cell doublings, after which CFSE fluorescence was no longer detectable. Timing of B-CLL cell division varied among patients, occurring between 2 to 6 weeks after the injection of PBMC. In contrast, leukemic cells injected into mice that were not reconstituted by ib injection with hCD34+ cells and hMSCs or were reconstituted with only hMSCs failed to proliferate. Moreover the number of CFSE+CD5+CD19+ cells detected in the blood of mice with a human hematopoietic microenvironment far exceeded that in mice receiving only hMSC. Robust T-cell expansion occurred in several mice receiving CD34+ cells; in some instances T-cell growth was also found without hCD34+ cell injection, although in these cases it was usually less extensive. Based on genome-wide SNP analyses, the T cells were of B-CLL patient origin and not from hCD34+ cells. Furthermore, most of the mice with significant T-cell overexpansion died within 6 weeks of B-CLL cell injection from apparent graft vs. host disease. Therefore in subsequent experiments, we eliminated T cells by injecting an anti-CD3 antibody (OKT3); this treatment led to an inhibition of B-CLL cell proliferation. Moreover the percentage of CD38+ cells in the CFSE+CD5+CD19+ cell fraction was similar to that in the donor patient inoculum only in the mice in which T-cell-mediated B-CLL cell proliferation occurred. The percentage and intensity of CD38− expressing B-CLL cells was higher in the spleen and bone marrow (BM) of mice not treated with OKT3 antibody. Finally, the percentage of CFSE+CD5+CD19+ cells in the spleen far exceeded that in the blood, BM, liver and peritoneum, even when leukemic cells were no longer present in the blood and other organs; these findings suggest that the spleen is better at supporting B-CLL cell viability and proliferation than the other anatomic sites. These studies demonstrate conditions making adoptive xenogeneic transfer and clonal expansion of B-CLL cells into a mouse model possible. Factors conferring an advantage in this model include both a human hematopoietic environment and autologous T cell growth. Increased numbers of CD38+ B-CLL cells, similar to those in the patient, were only found when leukemic B cell division occurred. The optimal site for B-CLL cell growth was murine spleen. Since non-genetic factors promoting B-CLL expansion are not completely known, this model will be useful in discovering these as well as for studying the basic biology of this disease, such as if leukemic stem cells exist and also to conduct preclinical tests on possible therapeutics.


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