DNA methylation and demethylation have been proposed to play an important role in somatic cell reprogramming. Here, we demonstrate that the DNA hydroxylase Tet1 facilitates pluripotent stem cell induction by promoting Oct4 demethylation and reactivation. Moreover, Tet1 (T) can replace Oct4 and initiate somatic cell reprogramming in conjunction with Sox2 (S), Klf4 (K), and c-Myc (M). We established an efficient TSKM secondary reprogramming system and used it to characterize the dynamic profiles of 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), and gene expression during reprogramming. Our analysis revealed that both 5mC and 5hmC modifications increased at an intermediate stage of the process, correlating with a transition in the transcriptional profile. We also found that 5hmC enrichment is involved in the demethylation and reactivation of genes and regulatory regions that are important for pluripotency. Our data indicate that changes in DNA methylation and hydroxymethylation play important roles in genome-wide epigenetic remodeling during reprogramming.

No abstract

Calcium-dependent cell adhesion molecules (cadherins) are involved in maintaining the epithelial structure of a number oftissues including the mammary gland. In breast and other tumor types. loss of E-cadherin expression has been seen in high grade tumors and correlates with increased invasiveness. Here we show high levels of expression of N-cadherin in the most invasive breast cancer cell lines which was inversely correlated with their expression of E-cadherin. A stromal cell line also expressed N-cadherin in accordance with its fibroblastic morphology. N-cadherin localized to areas of cell-cell contact in all cells that expressed it. Calcium-dependent intercellular adhesion of N-cadherin-expressing breast cancer and stro-ma1 cells was specifically inhibited by an anti N-cadherin monoclonal antibody. In addition, N-cadherin promoted the interaction of invasive breast cancer cells with mammary stromal cells; in contrast, E-cadherin expressing cell lines did not co-aggregate with stromal cells. The combined results suggest a functional role for N-cadherin in cohesion of breast tumor cells which, in addition promotes their interaction with the surrounding stromal cells. thereby facilitating invasion and metastasis.

No abstract