Osmotic modulation of chromatin impacts on efficiency and kinetics of cell fate modulation

Abstract

Chromatin structure is a major regulator of transcription and gene expression. Herein we explore the use of osmotic modulation to modify the chromatin structure and reprogram gene expression. In this study we use the extracellular osmotic pressure as a chromatin structure and transcriptional modulator. Hyposmotic modulation promotes chromatin loosening and induces changes in RNA polymerase II (Pol II) activity. The chromatin decondensation opens space for higher amounts of DNA engaged RNA Pol II. Hyposmotic modulation constitutes an alternative route to manipulate cell fate decisions. This technology was tested in model protocols of induced pluripotency and transdifferentiation in cells growing in suspension and adherent to substrates, CD34+ umbilical-cord-blood (UCB), fibroblasts and B-cells. The efficiency and kinetics of these cell fate modulation processes were improved by transient hyposmotic modulation of the cell environment.

Mapping interfacial hydration in ETS-family transcription factor complexes with DNA: a chimeric approach

“…We analyzed gene expression data in murine macrophages and found that target genes for PU.1 are significantly over-represented in osmotically responsive genes ( 25 ). Recently, hypo -osmotic stress in K562 leukemic cells was reported to drive PU.1 binding to promoter sites in significant excess over Ets-1 ( 29 ), in agreement with their osmotic profiles in binding experiments. The differential interfacial hydration in DNA binding therefore also appears to establish the two ETS members’ roles in cellular response to physiologic osmotic stress.…”

TEA-seq: a trimodal assay for integrated single cell measurement of transcription, epitopes, and chromatin accessibility

“…1, 2a ). Hypotonic lysis conditions used in these protocols may also be a biophysical stressor to the native chromatin state, as previously observed 15 . To reduce perturbation of chromatin, we performed cell membrane permeabilization under isotonic conditions to allow access to the nuclear DNA without isolating nuclei through hypotonic lysis.…”

Optical quantification of intracellular mass density and cell mechanics in 3D mechanical confinement

“…Indeed, it was recently reported that inhibition of chromatin condensation in HeLa cells on 2D substrates results in a reduction of RI and r, while inducing chromatin condensation results in the opposite effect. 28 It has been widely reported that external osmotic pressure modulates chromatin structure and aberrations [67][68][69] and more recently intracellular mass density. 15 In addition, it was shown that cancer cells under mechanical compression, actively efflux ions to decrease their intracellular tonicity in order to improve their chances of survival.…”