By Jacobs K et al. (Research Group Reproduction and Genetics, Vrije Universiteit Brussel)
In this study, the genetic content of 92 individual human cells, including fibroblasts, amniocytes and embryonic stem cells (hESCs) was investigated using single-cell array-based comparative genomic hybridization (aCGH). We find that human somatic and embryonic stem cell cultures show significant fractions of cells carrying unique megabase-scale chromosomal abnormalities, forming genetic mosaics that could not have been detected by conventional cytogenetic methods. Furthermore, fluorescent in situ hybridisation reveals an increased instability of the subtelomeric regions in hESC as compared to somatic cells. This genetic heterogeneity may have an impact on experimental results and, in the case of hESC, on their potential clinical use.