The role of bioelectrics during early embryonic development in Danio rerio

Different non-excitable cells have been found to have different resting membrane potentials. Changes in voltage membrane potentials, such as depolarizing or hyperpolarizing a cell, leads to activation of intracellular cascades that then enter the nucleus altering gene regulation (Tseng et changes in membrane potentials bioelectric signals can lead to important cellular responses even the regulation of cell type identity. This process is referred to as bioelectrics. Use of fluorescent voltage reporters and genetically encoded voltage indicators have recorded differential patterns in voltage membrane potentials across whole tissues and organisms. Through pharmacological and/or genetic approaches to manipulate voltage potentials the role of bioelectrics has been demonstrated to be required for many late and post-embryonic processes such as fin growth, craniofacial formation, and regeneration. No studies have investigated whether bioelectrics plays essential roles during early embryonic development. We use Danio rerio to study whether different voltage potentials may regulate axis determination during early embryonic development. Through the use of fluorescent voltage reporters, Dibac and RhodamineG6, we record potential bioelectric patterns for both depolarized and hyperpolarized state cells during the gastrulation stage of embryonic development. Through the use of genetically encoded voltage indicators (GEVI), the depolarized cell state pattern was supported by showing ArcLight Q239, which detects changes in voltage membrane potential, presented a similar pattern of concentrated region of depolarized state cells in the dorsal shield of the embryo. Manipulation of bioelectric functions through pharmacological drugs blocking or activating potassium (K+) channels led to a more depolarized or hyperpolarized state, respectively. When the depolarizer and potassium channel blocker, 4-aminopyridine, was introduced to gastrula staged embryos it caused modest reductions to the ventral tissues of the embryo’s tail. It is well known that during morphogens like FGFs, Chordin and Noggins are secreted in a concentration gradient across the dorsal to ventral axis of the gastrula, and function to antagonize BMP signaling for proper axis determination. . Through inhibition of Fgf signaling we recorded tail defects such as tail ventralization and shortened elongation. Intriguingly so, combination of depolarizer, 4 aminopyridine, and Fgf inhibitor a full rescue of the tail defects was observed, suggesting bioelectric patterns in the embryo are interacting with morphogens with a proposed model where depolarized state cells in the gastrula activate intracellular mechanisms leading to regulate normal dorsal to ventral axis formation