Embryonic Stem Cells from a Mouse Down Syndrome Model Have Impaired Proliferation and Increased Oxidative Stress.

Abstract

Despite the fact that Down syndrome is the most common chromosomal birth defect, the pathogenesis of this disorder is still poorly understood. To develop a model for studying both the effects of this trisomy in pluripotent cells and the pathogenesis of this disorder in vitro, we recently established mouse embryonic stem cell (mESC) lines from a mouse Down syndrome model that carries the complex chromosomal rearrangement Rb(12.Ts171665Dn)2Cje. This chromosomal abnormality results in triplication of at least 6 Mb of proximal chromosome 17 and 13.9 Mb of distal chromosome 16. The triplicated region of 16 is syntenic with human chromosome 21 and confers many of the phenotypic features of Down syndrome. For mESC derivation, 50 blastocysts generated from trisomic females, which transmit this chromosomal abnormality to roughly half of their oocytes, were subjected to a standard derivation protocol using mESC culture medium supplemented with the MAP kinase/ERK kinase inhibitor PD98059. There was a significantly reduced derivation efficiency for trisomic relative to disomic lines (94% were disomic, n=17). Spectral karyotyping and chromosomal counts of the one trisomic and 2 disomic lines revealed over 60% of nuclei were diploid, and there were no unexpected structural chromosomal aberrations. Evaluation of the transcriptomes of these 3 lines using Illumina Mouse WG-6 arrays revealed that 69% of 115 evaluated genes from triplicated regions were overexpressed in the trisomic line relative to disomic lines with an average fold increase of 1.12. The trisomic line was also found to have a significantly slower rate of proliferation, larger average cell size and increased intracellular oxidative stress. Of note, superoxide dismutase-1 (Sod1), a gene in the triplicated region and implicated in the increased oxidative stress in Down syndrome individuals, was overexpressed by 1.54 fold in trisomic cells. This report describes the first trisomic embryonic stem cell line to be generated from this particular mouse model for Down syndrome. Furthermore, it reveals that many of the triplicated genes are overexpressed in trisomic cells at this early developmental stage, and these perturbations in gene expression have profound effects on cellular physiology. This research was supported by NCRR grant 3 P40 RR001183-32S1. (platform)