Nuclear microinjection to assess how heterologously expressed proteins impact Ca²⁺ signals in Xenopus oocytes

The Xenopus oocyte is frequently used for heterologous expression and for studying the spatiotemporal patterning of Ca²⁺ signals. Here, we outline a protocol for nuclear microinjection of the Xenopus oocyte for the purpose of studying how subsequently expressed proteins impact intracellular Ca²⁺ signals evoked by inositol trisphosphate (InsP₃). Injected oocytes can easily be identified by reporter technologies and the impact of heterologously expressed proteins on the generation and properties of InsP₃-evoked Ca²⁺ signals can be resolved using caged InsP₃ and fluorescent Ca²⁺ indicators.