Intracellular calcium release channel expression during embryogenesis

The release of intracellular calcium (Ca2+) via either inositol 1,4,5-trisp hosphate receptors (IP3R) or ryanodine receptors (RyR) activates a wide var iety of signaling pathways in virtually every type of cell. In the present study we demonstrate that at early stages of development IP3R mRNA and func tional IP3 gated Ca2+ release channels are widely expressed in virtually al l tissues in murine embryos. As organogenesis proceeds, more specialized Ry R channels are expressed in many cell types and the triggering mechanisms f or intracellular Ca2+ release become more diverse to include IP3-dependent and voltage-dependent and Ca2+-induced Ca2+ release. As development proceed s virtually all cell types continue to express IP3R channels but in excitab le cells including skeletal and cardiac muscles the major Ca2+ release chan nels are RyRs. This developmental switch from predominantly IP3-mediated to both IP3-mediated and IP3-independent pathways for intracellular Ca2+ rele ase is consistent with data showing that IP3R plays an important regulatory role in cellular proliferation and apoptosis, whereas RyR is required for other cellular functions including muscle contraction. (C) 1999 Academic Pr ess.