Microinjection into Xenopus Oocytes


Microinjection of genetic information in the form of complimentary ribonucleic acid (cRNA) into the Xenopus oocyte leads to the functional expression of the encoded proteins. In this novel environment, exogenous proteins may be functionally characterised under well‐defined conditions. Complimentary deoxyribonucleic acid (cDNA) coding for the protein may be mutated, the altered cDNA transcribed and polyadenylated in vitro to the corresponding cRNA and the function of the resulting altered protein is compared with that of the wild‐type protein. The oocyte is a major expression system used in membrane protein structure–function studies. It is especially popular for expression of membrane transport proteins such as carriers and ion channels. In another approach, total messenger RNA (mRNA) may be prepared from a tissue of choice, microinjected into oocytes, the encoded functions characterised and the encoding genetic information isolated.

Key Concepts:

  • Proteins can be ‘transplanted’ into the Xenopus oocyte.

  • The Xenopus oocyte may be used as a test tube for newly introduced protein functions.

  • Genetic information in the form of cRNA may be prepared in vitro from the coding cDNA.

  • The Xenopus oocyte translates foreign microinjected cRNA.

  • The Xenopus oocyte is favourite expression system for structure–function studies.

  • Expression cloning can identify genes purely based on protein function.

Keywords: Xenopus laevis oocyte; protein expression; mRNA; cDNA; expression cloning; microinjection

Figure 1.

Schematic representation of the use of the Xenopus oocyte for the expression of functional proteins after microinjection of the oocyte with genetic information in the form of RNA or DNA. cDNA, complementary DNA and mRNA, .

Figure 2.

Photograph of a portion of a cut open ovary lobe showing oocytes at different stages of maturity. Immature oocytes are small and whitish, whereas mature oocytes are 1–1.2 mm in diameter with a darkly pigmented animal hemisphere and a yellowish‐vegetal hemisphere. Photograph (© Sigel, ) of a portion of a cut open ovary lobe showing oocytes at different stages of maturity.

Figure 3.

Photograph of the microinjection procedure. The follicles containing the oocytes are submersed in medium and lined up on a nylon mesh. A glass capillary with a tip diameter of approximately 15 μm is inserted into the oocyte cytoplasm and the RNA solution is microinjected. Photograph (© Sigel, ) of the microinjection procedure.



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Sigel, E(Sep 2010) Microinjection into Xenopus Oocytes. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0002658.pub2]