Tetraploid complementation assay


The tetraploid complementation assay is a technique in biology in which cells of two mammalian embryos are combined to form a new embryo. It is used to construct genetically modified organisms, to study the consequences of certain mutations on embryonal development, and in the study of pluripotent stem cells.

Procedure

Normal mammalian somatic cells are diploid: each chromosome is present in duplicate. The assay starts with producing a tetraploid cell in which every chromosome exists fourfold. This is done by taking an embryo at the two-cell stage and fusing the two cells by applying an electrical current. The resulting tetraploid cell will continue to divide, and all daughter cells will also be tetraploid.
Such a tetraploid embryo can develop normally to the blastocyst stage and will implant in the wall of the uterus. The tetraploid cells can form the extra-embryonic tissue ; however, a proper fetus will rarely develop.
In the tetraploid complementation assay, one now combines such a tetraploid embryo with normal diploid embryonic stem cells from a different organism. The embryo will then develop normally; the fetus is exclusively derived from the ES cell, while the extra-embryonic tissues are exclusively derived from the tetraploid cells.

Applications