Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2013-07-01

Characterization of Ca2 + signaling in the external yolk syncytial layer during the late blastula and early gastrula periods of zebrafish development

Michael Y.F. Yuen, Sarah E. Webb, Ching Man Chan, Bernard Thisse, Christine Thisse, Andrew L. Miller

Index: Biochim. Biophys. Acta 1833(7) , 1641-56, (2013)

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Abstract

Preferential loading of the complementary bioluminescent (f-aequorin) and fluorescent (Calcium Green-1 dextran) Ca2+ reporters into the yolk syncytial layer (YSL) of zebrafish embryos, revealed the generation of stochastic patterns of fast, short-range, and slow, long-range Ca2+ waves that propagate exclusively through the external YSL (E-YSL). Starting abruptly just after doming (~4.5h post-fertilization: hpf), and ending at the shield stage (~6.0hpf) these distinct classes of waves propagated at mean velocities of ~50 and ~4μm/s, respectively. Although the number and pattern of these waves varied between embryos, their initiation site and arcs of propagation displayed a distinct dorsal bias, suggesting an association with the formation and maintenance of the nascent dorsal-ventral axis. Wave initiation coincided with a characteristic clustering of YSL nuclei (YSN), and their associated perinuclear ER, in the E-YSL. Furthermore, the inter-YSN distance (IND) appeared to be critical such that Ca2+ wave propagation occurred only when this was <~8μm; an IND >~8μm was coincidental with wave termination at shield stage. Treatment with the IP3R antagonist, 2-APB, the Ca2+ buffer, 5,5′-dibromo BAPTA, and the SERCA-pump inhibitor, thapsigargin, resulted in a significant disruption of the E-YSL Ca2+ waves, whereas exposure to the RyR antagonists, ryanodine and dantrolene, had no significant effect. These findings led us to propose that the E-YSL Ca2+ waves are generated mainly via Ca2+ release from IP3Rs located in the perinuclear ER, and that the clustering of the YSN is an essential step in providing a CICR pathway required for wave propagation. This article is part of a Special Issue entitled: 12th European Symposium on Calcium.