Calcium, microfilaments and morphogenesis.

Morphogenesis, the generation of tissue form, is important not only in the embryogenesis of a new individual, but also because a change in morphogenesis may be involved in the establishment of differences between individuals during evolution. Morphogenetic movements are effected in part by coordinated changes in the shapes of individual cells and over the past decade the cellular organelles responsible for cell shape have been identified as microfilaments and microtubules. In non-embryonic systems the contraction of microfilaments is controlled by the level of intracellular free calcium, and so calcium is implicated as an intermediate control mechanism in morphogenisis. Through techniques which perturb the calcium balance of cells, or which measure calcium ion concentration directly, evidence is accumulating that calcium is involved in morphogenetic movements such as gastrulation and neurulation, and related phenomena such as wound healing. Thus fundamental questions about the control of morphogenesis in embryogenesis and evolution may now be couched in more precise terms of the control of intracellular calcium ion balance.