Ca²⁺ SIGNALLING AND EARLY EMBRYONIC PATTERNING DURING ZEBRAFISH DEVELOPMENT

Abstract

1. It has been proposed that Ca2+ signalling, in the form of pulses, waves and steady gradients, may play a crucial role in key pattern-forming events during early vertebrate development. 2. With reference to the embryo of the zebrafish (Danio rerio), herein we review the Ca2+ transients reported from the cleavage to segmentation periods. This time-window includes most of the major pattern-forming events of early development, which transform a single-cell zygote into a complex multicellular embryo with established primary germ layers and body axes. 3. Data are presented to support our proposal that intracellular Ca2+ waves are an essential feature of embryonic cytokinesis and that propagating intercellular Ca2+ waves (both long and short range) may play a crucial role in: (i) the establishment of the embryonic periderm and the coordination of cell movements during epiboly, convergence and extension; (ii) the establishment of the basic embryonic axes and germ layers; and (iii) definition of the morphological boundaries of specific tissue domains and embryonic structures, including future organ anlagen. 4. The potential downstream targets of these Ca2+ transients are also discussed, as well as how they may integrate with other pattern-forming signalling pathways known to modulate early developmental events.

Bcl-wav and the mitochondrial calcium uniporter drive gastrula morphogenesis in zebrafish

“…Interestingly, components of the Wnt/PCP pathway can also modulate Ca 2 þ signalling 37,38 . These data are consistent with observations in zebrafish, showing that throughout gastrulation Ca 2 þ waves occur in the vicinity of the dorsal axis of the embryo, where C&E movements take place 39 . During these Ca 2 þ waves, cells are exposed to high Ca 2 þ concentrations, which may be detrimental; thus, mitochondrial Ca 2 þ uptake is presumably critical for maintaining Ca 2 þ homoeostasis in migrating blastomeres.…”

CaMK-II is a PKD2 target that promotes pronephric kidney development and stabilizes cilia

“…These sites of CaMK-II activation are consistent with known locations of prolonged Ca 2+ elevation in embryos of zebrafish and other species (Webb and Miller, 2003;Webb and Miller, 2007). These locations are also consistent with tissues that exhibit morphogenic defects after CaMK-II suppression (Francescatto et al, 2010;Rothschild et al, 2009).…”

“…For example, cellular behaviors during gastrulation, somitogenesis and trunk, eye, brain and organ formation have been associated with Ca 2+ flux through specific channels (Porter et al, 2003;Webb and Miller, 2003;Webb and Miller, 2007;Whitaker, 2006), but have not been attributed to specific Ca 2+ -dependent effectors. CaMK-II, the Ca 2+ /calmodulin-dependent protein kinase type II, is best known as an enzyme enriched in the central nervous system and important for long-term potentiation (Hudmon and Schulman, 2002).…”

Ca2+ coding and decoding strategies for the specification of neural and renal precursor cells during development

“…In intact zebrafish (Danio rerio) embryos, for example, localized and transient elevations of intracellular Ca 2+ are generated in the ventral side of the blastoderm margin during early gastrulation. As gastrulation proceeds, additional localized Ca 2+ transients are generated around the blastoderm margin, and these signals are the sources for long-range propagating Ca 2+ waves that either circumnavigate the blastoderm margin or propagate along the forming embryonic This is the Pre-Published Version axis [32]. By the end of gastrulation, the periodic Ca 2+ waves originate exclusively from the embryonic shield (or organizer) in the dorsal region of the embryo [32].…”

“…As gastrulation proceeds, additional localized Ca 2+ transients are generated around the blastoderm margin, and these signals are the sources for long-range propagating Ca 2+ waves that either circumnavigate the blastoderm margin or propagate along the forming embryonic This is the Pre-Published Version axis [32]. By the end of gastrulation, the periodic Ca 2+ waves originate exclusively from the embryonic shield (or organizer) in the dorsal region of the embryo [32]. These distinct Ca 2+ signalling patterns correlate both temporally and spatially with neural induction.…”