An analysis of salivary gland morphogenesis: role of cytoplasmic microfilaments and microtubules.

The roles of microfilaments and microtubules as causative organelles in the cell shape changes required for in vitro morphogenesis of embryonic mouse salivary epithelium have been explored by use of the drugs cytochalasin B and colchicine. Cytochalasin inhibits morphogenesis, causes flattening of the epithelium and loss of the clefts that were present at the time of drug application. These effects correlate with a specific disruption of cytoplasmic microfilaments when viewed with the electron microscope. Removal of cytochalasin results in reappearance of ordered microfilaments and resumption of morphogenesis. Colchicine disrupts microtubules and halts morphogenesis, but does not cause flattening of the epithelium or loss of clefts. Treatment with cytochalasin followed by recovery in the presence of colchicine demonstrates that recovery clefts can form in the absence of microtubules. It is proposed that normal salivary gland morphogenesis includes microfilament participation via contractile activity, in addition to mitosis and to extracellular stabilization processes.