Calcium dependence of rhythmic contractions of the Oryzias latipes blastoderm

Calcium signaling in extraembryonic domains during early teleost development

It is becoming recognized that the extraembryonic domains of developing vertebrates, that is, those that make no cellular contribution to the embryo proper, act as important signaling centers that induce and pattern the germ layers and help establish the key embryonic axes. In the embryos of teleost fish, in particular, significant progress has been made in understanding how signaling activity in extraembryonic domains, such as the enveloping layer, the yolk syncytial layer, and the yolk cell, might help regulate development via a combination of inductive interactions, cellular dynamics, and localized gene expression. Ca(2+) signaling in a variety of forms that include propagating waves and standing gradients is a feature found in all three teleostean extraembryonic domains. This leads us to propose that in addition to their other well-characterized signaling activities, extraembryonic domains are well suited (due to their relative stability and continuity) to act as Ca(2+) signaling centers and conduits.

Calcium signaling in developing embryos: focus on the regulation of cell shape changes and collective movements

During morphogenesis tissues significantly remodel by coordinated cell migrations and cell rearrangements. Central to this problem are cell shape changes that are driven by distinct cytoskeletal reorganization responsible for force generation. Calcium is a versatile and universal messenger that is implicated in the regulation of embryonic development. Although calcium transients accrue clearly and more intensely in tissues undergoing rearrangement/migration, it is far from clear what the role of these calcium signals is. Here we summarize the evidence implicating calcium participation in tissue movements, cell shape changes and the reorganization of contractile cytoskeletal elements in developing embryos. We also discuss a novel hypothesis that short-lived calcium spikes are required in cells and tissues undergoing migration and rearrangements as a fine tuning response mechanism to prevent local, abnormally high fluctuations in cytoskeletal activities.

In vivo time-lapse imaging in medaka – n-heptanol blocks contractile rhythmical movements

Medaka is an ideal model system for developmental studies as it combines the advantages of powerful genetics and classical embryology. Due to the accessibility, transparency and fast development, embryogenesis and morphogenesis can be followed in vivo. Microscopic time-lapse imaging, however, requires the immobilization of the object to be observed. In medaka rhythmical contractile movements of the blastoderm during early development hampered time-lapse studies, as they cause the embryo to rotate vividly. Here we show that the contractile movements can be reduced by continuous treatment with the gap-junction uncoupling agent n-heptanol up to the 12-somite stage (stage 23) without interfering with development. This allows for the first time to perform high-resolution time-lapse studies in medaka.

Calcium signalling during embryonic development

Consider a hypothetical design specification for an integrated communication-control system within an embryo. It would require short-range (subcellular) and long-range (pan-embryonic) abilities, it would have to be flexible and, at the same time, robust enough to operate in a dynamically changing environment without information being lost or misinterpreted. Although many signalling elements appear, disappear and sometimes reappear during development, it is becoming clear that embryos also depend on a ubiquitous, persistent and highly versatile signalling system that is based around a single messenger, Ca2+.