Control of naive and primed pluripotency by the Netrin-1 signalling pathway in rodents and primates. – STEMNET

Pluripotency defines the ability of a stem cell to self-renew and differentiate into ectoderm, endoderm and mesoderm derivatives. In mice, pluripotent stem cells (PSCs) can be captured in two distinct configurations entitled ‘naïve’ and ‘primed’, corresponding to pre- and post-implantation embryos, respectively. Compared to the naïve state, the primed state is a lesser state of pluripotency characterized by fragile self-renewal, genome instability and variable differentiation abilities. In humans and non-human primates (NHPs), conventional PSC lines established from embryos display the characteristic features of primed pluripotency, although they are generated from the early epiblast of the blastocyst, similar to rodent naïve PSCs. Only a handful of human naïve-like PSCs have been generated, and none of them showed self-renewal and genetic stability similar to that of mouse naïve PSCs. Identification and characterization of new signal(s) controlling naïve and primed pluripotency is, therefore, crucial for advancing our understanding of PSC biology and early embryo development. It is also of paramount importance to generate human PSCs with increased self-renewal capabilities and improved genetic stability with the prospect of large-scale clinical applications in regenerative medicine.
The coordinator of the proposal recently identified the axon guidance cue, Netrin-1, and its receptors, Neo1 and Unc5b, as critical regulators of somatic cell reprogramming (Nature Communications 2015) and naïve pluripotency in mice (Nature Cell Biology 2020). The ‘STEMNET’ programme builds on this pioneering work to explore the function of Netrin signalling in regulating naïve and primed pluripotency in both rodents and primates. In the first workpackage (WP), the function of Netrin-1 signalling pathway in regulating primed pluripotency will be explored in mouse PSCs. In the second WP, a study of the dynamics and the interactome of the Netrin-1 signalling members will be conducted in mouse naïve and primed PSCs. In the third WP, the function of the Netrin-1 signalling pathway during the formation of mouse epiblast will be evaluated by performing gain- and loss-of-function approaches. In the fourth WP, the function of Netrin-1 and Netrin-4 signalling in human and rhesus monkey PSC self-renewal will be explored in both primed and naïve states. A common approach across the four WPs is the use of recombinant Netrin-1 as a new factor stimulating self-renewal and maintaining PSC pluripotency.
The ‘STEMNET’ proposal is based on the complementary expertise of four partners in the areas of mouse pluripotency (Coordinator, Partner 1), Netrin biochemistry (Partner 2), mouse embryo development (Partner 3) and primate pluripotency (Partner 4). It will improve our understanding of pluripotent stem cell biology and early development by characterizing a signalling pathway and its ability to govern pluripotency in rodents and primates. This programme may lead to important advances in both basic research and regenerative medicine.