Increase of intracellular Ca2+ and relocation of E-cadherin during experimental decompaction of mouse embryos.

To determine the role of intracellular Ca2+ in compaction, the first morphogenetic event in embryogenesis, we analyzed preimplantation mouse embryos under several decompacting conditions, including depletion of extracellular Ca2+, blocking of Ca2+ channels, and inhibition of microfilaments, calmodulin, and intracellular Ca2+ release. Those treatments induced decompaction of mouse morulae and simultaneously induced changes in cytosolic free Ca2+ concentration and deregionalization of E-cadherin and fodrin. When morulae were allowed to recompact, the location of both proteins recovered. In contrast, actin did not change its cortical location with compaction nor with decompaction-recompaction. Calmodulin localized in areas opposite to cell-cell contacts in eight-cell stage embryos before and after compaction. Inhibition of calmodulin with trifluoperazine induced its delocalization while morulae decompacted. A nonspecific rise of intracellular free Ca2+ provoked by ionomycin did not affect the compacted shape. Moreover, the same decompacting treatments when applied to uncompacted embryos did not produce any change in intracellular Ca2+. Our results demonstrate that in preimplantation mouse embryos experimentally induced stage-specific changes of cell shape are accompanied by changes of intracellular free Ca2+ and redistribution of the cytoskeleton-related proteins E-cadherin, fodrin, and calmodulin. We conclude that intracellular Ca2+ specifically is involved in compaction and probably regulates the function and localization of cytoskeleton elements.

In vitro formation of cysts derived from a rat model of autosomal dominant polycystic kidney disease.

In this study, we report a model of spontaneous cyst formation in vitro and a procedure to obtain large quantities of cysts from polycystic rat kidney cells. Furthermore, we assess the effects of epidermal growth factor, a modulator of morphogenesis, and of taxol, a stabilizer of microtubules, which has recently been proposed as a useful treatment of human polycystic kidney disease (PKD). It is anticipated that data generated from in vitro studies using cysts from PKD-affected rat kidneys may yield further insights to the pathophysiological and cellular basis of fatal renal cyst formation processes, and may lead to specific therapeutic strategies directed at controlling the growth of cysts, thereby reducing the number of animal tests.