Effect of Aid deletion on the global gene expression iPS cells

It has been shown that DNA demethylation has a pivotal role in the generation of induced pluripotent stem (iPS) cells. However, the underlying mechanism is still unclear. Previous reports indicated that activation-induced cytidine deaminase (Aid) is involved in DNA demethylation in several developmental processes and cell fusion-mediated reprogramming. Based on the reports, we hypothesized that Aid may be involved in DNA demethylation during the iPS cell generation. In this study, we examined the function of Aid in iPS cell generation using Aid knockout (Aid-/-) mice expressing a GFP reporter under the control of a pluripotent stem cell marker, Nanog. By the introduction of Oct3/4, Sox2, Klf4 and c-Myc, Nanog-GFP positive iPS cells could be generated from the fibroblasts and primary B cells of Aid-/- mice. The Aid-/- iPS cells showed normal proliferation and gave rise to chimeras, indicating their capacity for self-renewal and pluripotency. Microarray analysis demonstrated that the global gene expression of Aid-/- iPS cells was similar to that of Aid+/+ iPS cells. Aid+/+ and Aid-/- iPS colonies were generated from Aid+/+ and Aid-/- MEFs and picked up mechanically. The clones were passaged four times on feeder cells and two times on gelatin-coated dishes to exclude the contamination of feeder cells. Subsequently, the RNA was isolated. Six Aid+/+ iPS cell clones and six Aid-/- iPS cell clones were compared by microarray. Samples from Aid+/+ and Aid-/-iPS cells