Prolonged culture of human embryonic stem cells (hESCs) can lead to adaptation and the acquisition of chromosomal abnormalities, underscoring the need for rigorous genetic analysis of these cells. Here we report the highest-resolution study of hESCs to date using an Affymetrix SNP 6.0 array containing 906,600 probes for single nucleotide polymorphisms (SNPs) and 946,000 probes for copy number variations (CNVs). Analysis of 17 different hESC lines maintained in different laboratories identified 843 CNVs of 50 kb-3 Mb in size. We identified, on average, 24% of the loss of heterozygosity (LOH) sites and 66% of the CNVs changed in culture between early and late passages of the same lines. Thirty percent of the genes detected within CNV sites had altered expression compared to samples with normal copy number states, of which 44% were functionally linked to cancer. Furthermore, LOH of the q arm of chromosome 16, which has not been observed previously in hESCs, was detected.
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We are grateful to everyone who has taken care of sample collection and handling: T. Golan-Lev, A. Urrutikoetxea-Uriguen, S. Haupt, P. Koch, I. Laufenberg, B. Ley, A. Hampl, M. Vodinska, K. Koudelkova, S. Ström, F. Holm, A.-M. Strömberg, C. Olsson, M. Mikkola, S. Vuoristo, P. Junni and M. Hakkarainen. We especially acknowledge M. Linja, T. Heinonen and the Finnish DNA Microarray Centre for their excellent technical assistance. We acknowledge the Turku Graduate School of Biomedical Sciences. This study is supported by funding for the ESTOOLS consortium under the Sixth Research Framework Programme of the European Union, Juvenile Diabetes Research Foundation, The Academy of Finland and the Finnish Cancer Organizations, The Improving Outcomes Guidance Trust, The Ministry of Education, Youth, and Sport of the Czech Republic, Ida Montin Foundation, The Academy of Finland, projects no. 129657 (Finnish Centre of Excellence program 2006-11) and no. 134117 and the Medical Research Council, UK.