Golgi orientation and cell behaviour in the developing pattern of chondrogenic condensations in chick limb-bud mesenchyme

Abstract

Using a silver-impregnation method, the occurrence and significance of Golgi apparatus orientation has been studied in cells contributing to the cartilage condensations in the developing skeleton of the chick limb bud, both in normal embryos and in the talpid mutant, in which the pattern of condensation in situ, and cell behaviour in vitro, is abnormal. Analysis of photographed sections made up as photomontages with a final magnification of X 1000, indicates a sequence of changing Golgi orientation in the course of establishing cartilage condensations in the mesenchyme in normal limb buds, including at an early stage an orientation of one population of cells towards the condensation centre and of another population in the contrary direction, and a modification of the sequence in the mutant. The changing patterns of cell orientation has been further analysed in scanning electron microscope studies on the formation of cartilage condensations in vitro.

The Role of Spatially Controlled Cell Proliferation in Limb Bud Morphogenesis

“…Golgi orientation in the developing limb bud mesenchyme has previously been explored with respect to the ectoderm [45] and the developing mesenchymal condensations [46],[47]. Interestingly, whereas a slight bias towards the ectoderm was previously reported at later stages of limb development (>E12.5 in the mouse or HH24 in chick), we already see a clear bias at HH21 (Figure 8A,B).…”

Budding behaviors: Growth of the limb as a model of morphogenesis

“…Golgi position relative to the nucleus, a measure of cell polarity, was biased toward the nearest ectoderm as assessed by immunostaining. Earlier studies identified a comparable, though modest, bias during the later stages of mesenchymal outgrowth and condensation Trelstad, 1977, 1980;Ede and Wilby, 1981). Previous investigations also revealed the presence of numerous mesenchymal filopodia from freezefracture and scanning electron microscopy analysis (Ede et al, 1974;Kelley and Fallon, 1983).…”

Morphological foundations of precartilage development in mesenchyme

“…At both the light and ultrastructural level, the observed increase in cell density and apparent increase in cell contact in the core areas of the limb suggests cell movement into the area. Mesenchymal cell motility has been argued as a property of limb mesenchyme and as a basis for condensation formation (Bell and Ede, 1978;Ede and Agerbak, 1968;Ede and Wilby, 1981;Gould et al, 1972;Searls, 1967;Thorogood and Hinchliffe, 1975). The failure of cells to move away from a region during growth likewise may contribute as a mechanism to aggregation phenomena (Gould et al, 1972(Gould et al, , 1974.…”

“…Changing Golgi orientation in the peripheral nonchondrogenic mesenchymal cells (Holmes and Trelstad, 1977) and in the condensing mesenchymal cells (Ede and Wilby, 1981) accompanies the spatial reorganization of the mesenchyme. A concentric arrangement of cells is centered upon the core cells of the condensing field, these core cells being the first to produce a cartilaginous matrix.…”

“…The occurrence of small movements undetectable by microscopic techniques cannot be excluded and may support the spatial organization of different tissues of the limb (Ede and Agerbak, 1968;Mauger and Kieny, 1980). Analysis of Golgi orientation suggests that an orderly change in cell polarity (i.e., Golgi placement) accompanies the initial stages of condensation formation and matrix synthesis in the mouse and chick limb bud (Ede and Wilby, 1981;Holmes and Trelstad, 1981). The relocation of the Golgi to a position behind the nucleus relative to the direction of cell movement indicates cell motility as the mesenchyme begins the process of condensation formation (Ede and Wilby, 1981).…”