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Mesenchyme Cells (mesenchyme + cell)
Selected AbstractsPrimary mesenchyme cell-ring pattern formation in 2D-embryos of the sea urchinDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2000Hideki Katow Primary mesenchyme cell (PMC) migration during PMC-ring pattern formation was analyzed using computer-assisted time-lapse video microscopy in spread embryos (2D-embryo) of the sea urchin, Mespilia globulus, and a computer simulation. The PMC formed a near normal ring pattern in the 2D-embryos, which were shown to be an excellent model for the examination of cell behavior in vivo by time-lapse computer analysis. The average migration distance of the ventro-lateral PMC aggregate-forming cells (AFC) and that of the dorso-ventral PMC cable-forming cells (CFC) showed no significant difference. All PMC took a rather straightforward migration path to their destinations with little lag time after ingression. This in vivo cell behavior fitted well to a computer simulation with a non-diffusable chemotaxis factor in the cyber-cell migration field. This simulation suggests that PMC recognize their destination from a very early moment of cell migration from the vegetal plate, and implicates that a chemoattractive region is necessary for making the PMC migration pattern. The left- and right-lateral AFC and dorso and ventral CFC were each derived from an unequally divided one-quarter segment of the vegetal plate. This suggests that AFC and CFC have a distinctive ancestor in the vegetal plate, and the PMC are a heterogeneous population at least in terms of their destination in the PMC-ring pattern. [source] Commitment and response to inductive signals of primary mesenchyme cells of the sea urchin embryoDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2004Masato Kiyomoto In the sea urchin embryo, primary mesenchyme cells (PMC) are committed to produce the larval skeleton, although their behavior and skeleton production are influenced by signals from the embryonic environment. Results from our recent studies showed that perturbation of skeleton development, by interfering with ectoderm,extracellular matrix (ECM) interactions, is linked to a reduction in the gene expression of a transforming growth factor (TGF)-beta growth factor, Pl-univin, suggesting a reduction in the blastocoelic amounts of the protein and its putative involvement in signaling events. In the present study, we examined PMC competence to respond to environmental signals in a validated skeleton perturbation model in Paracentrotus lividus. We found that injection of blastocoelic fluid (BcF), obtained from normal embryos, into the blastocoelic cavity of skeleton-defective embryos rescues skeleton development. In addition, PMC from skeleton-defective embryos transplanted into normal or PMC-less blastula embryos are able to position in correct regions of the blastocoel and to engage spicule elongation and patterning. Taken together, these results demonstrate that PMC commitment to direct skeletogenesis is maintained in skeleton perturbed embryos and confirm the role played by inductive signals in regulating skeleton growth and shape. [source] Differential distribution of spicule matrix proteins in the sea urchin embryo skeletonDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2000Takashi Kitajima Spicule matrix proteins are the products of primary mesenchyme cells, and are present in calcite spicules of the sea urchin embryo. To study their possible roles in skeletal morphogenesis, monoclonal antibodies against SM50, SM30 and another spicule matrix protein (29 kDa) were obtained. The distribution of these proteins in the embryo skeleton was observed by immunofluorescent staining. In addition, their distribution inside the spicules was examined by a ,spicule blot' procedure, direct immunoblotting of proteins embedded in crystallized spicules. Our observations showed that SM50 and 29 kDa proteins were enriched both outside and inside the triradiate spicules of the gastrulae, and also existed in the corresponding portions of growing spicules in later embryos and micromere cultures. The straight extensions of the triradiate spicules and thickened portions of body rods in pluteus spicules were also rich in these proteins. The SM30 protein was only faintly detected along the surface of spicules. By examination using the spicule blot procedure, however, SM30 was clearly detectable inside the body rods and postoral rods. These results indicate that SM50 and 29 kDa proteins are concentrated in radially growing portions of the spicules (normal to the c-axis of calcite), while SM30 protein is in the longitudinally growing portions (parallel to the c-axis). Such differential distribution suggests the involvement of these proteins in calcite growth during the formation of three-dimensionally branched spicules. [source] Cell dissociation experiments reveal that positional information operates in the chicken frontonasal massGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 3 2006Masayoshi Kawakami Abstract In this study we examined the role of cell,cell affinity in patterning the avian frontonasal mass,the facial prominence that forms the prenasal cartilage and premaxillary bone. Reconstituted cell pellets derived from undifferentiated, frontonasal mass mesenchyme were recombined with facial epithelium and grafted to host embryos to continue development. We determined that the cells reestablished a recognizable frontonasal mass pattern and were able to induce egg teeth in overlying ectoderm. Further analysis revealed there were region-specific differences in the cartilage patterns such that central recombinations were more likely to form a straight cartilage rod, whereas lateral mesenchyme pellets were more likely to form complex, branched cartilage patterns. The basis for the pattern differences was that central mesenchyme cells showed preferential clustering in the cartilage condensations in the center of the graft, whereas lateral cells were spread throughout as determined by dye labeling and quail chicken chimeras. The disruption of cell contacts temporarily delayed onset of gene expression but by 48 h both Msx2 and Dlx5 were expressed. Msx2, in particular, had very clear edges to the expression domains and often the pattern of expression correlated with type of cartilage morphology. Together, these data suggest that an important patterning mechanism in the face is the ability of mesenchymal cells to sort out according to position and that Msx2 may help repress chondrogenic potential in the lateral frontonasal mass. genesis 44:105,114, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||