Activin/Nodal signalling maintains pluripotency by controlling Nanog expression.

The pluripotent status of embryonic stem cells (ESCs) confers upon them the capacity to differentiate into the three primary germ layers, ectoderm, mesoderm and endoderm, from which all the cells of the adult body are derived. An understanding of the mechanisms controlling pluripotency is thus essential for driving the differentiation of human pluripotent cells into cell types useful for clinical applications. The Activin/Nodal signalling pathway is necessary to maintain pluripotency in human ESCs and in mouse epiblast stem cells (EpiSCs), but the molecular mechanisms by which it achieves this effect remain obscure.

Optimising histidine rich peptides for efficient DNA delivery in the presence of serum.

We recently showed that the antibacterial histidine rich amphipathic peptide LAH4 has significant DNA transfection capabilities in the absence of serum. To further understand the transfection process and to develop the peptides for future applications, we have combined a range of biochemical and biophysical techniques, including fluorescence assisted cell sorting and (2)H solid-state NMR, to characterise the initial binding of the peptide/DNA complexes to the cell surface and the subsequent release of the complexes from the endosome in the presence of serum. Our results show that both primary and secondary peptide structure play important roles in both of these processes.

The antibiotic and DNA-transfecting peptide LAH4 selectively associates with, and disorders, anionic lipids in mixed membranes.

The histidine-rich amphipathic peptide LAH4 has antibiotic and DNA delivery capabilities. The peptide has a strong affinity for anionic lipids found in the outer membrane of bacterial membranes. A role for anionic lipids in release of cationic plasmid-containing complexes has been proposed previously, and disruption of membrane asymmetry and presentation of phosphatidylserine (PS) in the membrane outer leaflet is a general feature observed in diseased mammalian cells.