Loss of Pluripotency in Human Embryonic Stem Cells Directly Correlates with an Increase in Nuclear Zinc

Abstract

The pluripotency of human embryonic stem cells (hESCs) is important to investigations of early development and to cell replacement therapy, but the mechanism behind pluripotency is incompletely understood. Zinc has been shown to play a key role in differentiation of non-pluripotent cell types, but here its role in hESCs is directly examined. By mapping the distribution of metals in hESCs at high resolution by x-ray fluorescence microprobe (XFM) and by analyzing subcellular metal content, we have found evidence that loss of pluripotency is directly correlated with an increase in nuclear zinc. Zinc elevation not only redefines our understanding of the mechanisms that support pluripotency, but also may act as a biomarker and an intervention point for stem cell differentiation.

Iron distribution through the developmental stages of Medicago truncatula nodules

“…This is consistent with the abundance of zinc-finger domain regulatory proteins in the nucleus and with observations in other eukaryotic cell types. 20 Smaller concentrations of this element were observed in the cell wall/apoplast regions of the cell, where calcium was the most abundant element. This is befitting the role of calcium in neutralizing and crosslinking negative charges, such as those of pectins, in cell walls.…”

Inorganic Signatures of Physiology: The X-Ray Fluorescence Microscopy Revolution

“…In examining the growth of human embryonic stem cells, taking a systems biology approach to examining entire colonies of cells and all the first row transition metals, we also found that the amount of zinc present in cells directly correlated with their differentiation (Wolford, Chishti et al 2010). The images in Figure 1, of stem cells differentiated with retinoic acid, are particularly illustrative.…”

XFM of “Trace Metals” in Cultured Cells: Framing the Picture

“…The "stemness" of the cell is maintained by a balance between proteins that promote differentiation and proteins that maintain pluripotency [2,3]. We have begun to explore whether the nuclear zinc influx that we have observed during differentiation [4] is biologically relevant to the "stemness" of the cell. We have published that mitotic chromosomes exclude zinc [4], suggesting that zinc is excluded from heterochromatin.…”

“…We have begun to explore whether the nuclear zinc influx that we have observed during differentiation [4] is biologically relevant to the "stemness" of the cell. We have published that mitotic chromosomes exclude zinc [4], suggesting that zinc is excluded from heterochromatin. This result calls into question the postulate of zinc binding to histones in condensed chromatin [5,6].…”

“…These cells were fixed and imaged as described in [4]; a commercial antibody for metallothionein (Abcam) was used.…”