With the exception of sperm and eggs, mammalian cells all contain a diploid genome with two copies of each gene, one copy inherited from each parent. Now, an international team of collaborators from New York and Israel report the production of human embryonic stem cells (hESCs) from an unfertilized egg. The new report from the labs of Drs. Dieter Egli at Columbia University and the New York Stem Cell Foundation, and Nissim Benvenisty at the Hebrew University in Jerusalem, was published in Nature. In normal mammalian development, an egg will not divide until fertilized by a sperm. The scientists used a laboratory trick to cause an unfertilized egg to start dividing, and then derived ESCs from it without any contribution of DNA from sperm. Close examination of the haploid ESCs revealed some differences compared with standard diploid hESCs, but the new cells proved surprisingly capable of normal differentiation into different tissue types. Although similar work was previously shown with mouse and other mammalian ESCs, it was still generally thought that proper development requires tight regulation of gene expression enabled by having two copies of the genome. These new cells and their developmental potential have both basic and therapeutic uses. For basic scientists, these cells will be a more amenable tool to understand gene function, as it is easier to manipulate a gene when it is present in only one copy. While therapeutic applications are far off, these cells are a perfect match to the egg donor and thus should not be recognized as foreign by the immune system if they can be harnessed for cell-based treatments. This work was supported in part by NYSTEM award C026184 to Dr. Egli.
Sagi I, Chia G, Golan-Lev T, Peretz M, Weissbein U, Sui L, Sauer MV, Yanuka O, Egli D, Benvenisty N. Derivation and differentiation of haploid human embryonic stem cells. Nature. 2016 Mar 16, 532(7595).