Pluripotent stem cell-derived somatic stem cells as tool to study the role of microRNAs in early human neural development.

The in vitro differentiation of human pluripotent stem cells represents a convenient approach to generate large numbers of neural cells for basic and translational research. We recently described the derivation of homogeneous populations of long-term self-renewing neuroepithelial-like stem cells from human pluripotent stem cells (lt-NES® cells). These cells constitute a suitable source of neural stem cells for in vitro modelling of early human neural development. Recent evidence demonstrates that microRNAs are important regulators of stem cells and nervous system development. Studies in several model organisms suggest that microRNAs contribute to different stages of neurogenesis - from progenitor self-renewal to survival and function of differentiated neurons. However, the understanding of the impact of microRNA-based regulation in human neural development is still at its dawn. Here, we give an overview on the current state of microRNA biology in stem cells and neural development and examine the role of the neural-associated miR-124, miR- 125b and miR-9/9* in human lt-NES® cells. We show that overexpression of miR-124, as well as overexpression of miR-125b, impair lt-NES® cell self-renewal and induce differentiation into neurons. Overexpression of the miR-9/9* locus also impairs self-renewal of lt-NES® cells and supports their commitment to neuronal differentiation. A detailed examination revealed that overexpression of miR-9 promotes differentiation, while overexpression of miR-9* affects both proliferation and differentiation of lt-NES® cells. This work provides insights into the regulation of early human neuroepithelial cells by microRNAs and highlights the potential of controlling differentiation of human stem cells by modulating the expression of selected microRNAs.