title: Alkaline Phosphatase-Positive Immortal Mouse Embryo Fibroblasts Are Cells in a Transitional Reprogramming State Induced to Face Environmental Stresses.
abstract: In this study, we report that immortal mouse embryonic fibroblasts (I-MEFs) have a baseline level of cells positive for alkaline phosphatase (AP(+)) staining. Environmental stresses, including long-lasting growth in the absence of expansion and treatment with drugs, enhance the frequency of AP(+) I-MEFs. By adapting fast red AP staining to the sorting procedure, we separated AP(+) and AP(-) I-MEFs and demonstrated that the differentially expressed genes are consistent with a reprogrammed phenotype. In particular, we found that sestrin 1 is upregulated in AP(+) I-MEFs. We focused on this gene and demonstrated that increased sestrin 1 expression is accompanied by the growth of I-MEFs in the absence of expansion and occurs before the formation of AP(+) I-MEFs. Together with sestrin 1 upregulation, we found that AP(+) I-MEFs accumulated in the G1 phase of the cell cycle, suggesting that the two events are causally related. Accordingly, we found that silencing sestrin 1 expression reduced the frequency and G1 accumulation of AP(+) I-MEFs. Taken together, our data suggested that I-MEFs stressed by environmental changes acquire the AP(+) phenotype and achieve a quiescent state characterized by a new transcriptional network.
authors.affiliation: Institute of Clinical Physiology (IFC), CNR, Pisa, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Evangelista
authors.affiliation: Laboratory of Integrative Systems Medicine (LISM), CNR, Pisa, Italy.
authors.forename: Mariama El
authors.initials: ME
authors.lastname: Baroudi
authors.affiliation: Institute of Clinical Physiology (IFC), CNR, Pisa, Italy.; Tuscan Tumor Institute (ITT), Firenze, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Rizzo
authors.affiliation: Oncogenomics Unit, Core Research Laboratory (CRL), Tuscan Tumor Institute (ITT), Pisa, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Tuccoli
authors.affiliation: Institute of Clinical Physiology (IFC), CNR, Pisa, Italy.; Oncogenomics Unit, Core Research Laboratory (CRL), Tuscan Tumor Institute (ITT), Pisa, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Poliseno
authors.affiliation: Laboratory of Integrative Systems Medicine (LISM), CNR, Pisa, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Pellegrini
authors.affiliation: Institute of Clinical Physiology (IFC), CNR, Pisa, Italy.; Tuscan Tumor Institute (ITT), Firenze, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rainaldi
keywords: alkaline phosphatases; cell cycle; immortal mouse embryonic fibroblasts; sestrin 1