br Conclusions br Materials and

Conclusions
Materials and methods
Acknowledgments This work was supported by funds from the Alliance of Cardiovascular Researchers. We would also like to give special thanks and express our gratitude to Drs. Edward Newsome, Ernest Chiu, and David Jansen for their valuable contributions to this study. We also thank Anita Kadala for her great assistance in editing the manuscript. In addition, we would also like to acknowledge Tulane\'s Cancer Center for providing us with the flow cytometry facilities.
Introduction
Results
Discussion
Methods
Role of Funding Source This research was supported by a grant from the Canadian Institutes for Health Research (MOP 82726) to RM. Studentships were provided by NSERC (SKW), EndMS (RK), and Hotchkiss Brain Institute (JG). The authors have no conflict of interest.
Acknowledgments
Introduction In vivo, neuro-epithelial (NE) mitotic inhibitors are the primary progenitors of the central nervous system and symmetrically divide to expand the developing neocortex (Gotz and Huttner, 2005). The complex spatial and temporal differentiation of NE into the neural tube instructed by a complex set of signaling molecules, has been extensively characterized in model organisms, such as mouse and chick (Ishibashi, 2004). Human neural development is comparatively less characterized due to inaccessibility of tissues and lack of an experimental model. Human embryonic stem cells (hESCs) can serve as a model experimental system to study human neurulation events (Nat et al., 2007; Fasano et al., 2010; Pankratz et al., 2007). The proliferation and differentiation of stem and progenitor cells lies at the heart of many human diseases, such as cancer (Reya et al., 2001), and is also of fundamental importance to the development of cell replacement therapies for diseases such as Parkinson\'s and Alzheimer\'s, as well as spinal cord injury and is already used widely for some lineages, such as in bone marrow transplantation (Krause et al., 2001). The underlying mechanisms of proliferation and differentiation are complex and some aspects have recently been defined. One key aspect of proliferation/differentiation is cell polarity (Matter et al., 2005). The role of polarity in proliferation/differentiation has been well characterized in the developing neural system of model organisms (Farkas and Huttner, 2008). Neuroepithelial cells are polarized along their apical-basal axis and cleavage along this plane determines symmetric or asymmetric cell division. Initially the NE cell population increases greatly during the neural plate stage through symmetric cell divisions, however; after closure of the neural tube, NE cells start to divide asymmetrically, concomitant with a reduction in the size of their apical membrane. Several studies define the critical role of polarity in maintaining NE cells in a stem/progenitor state (Rasin et al., 2007; Konno et al., 2008). The Flemming body (i.e. midbody) is a ring like structure that forms between dividing cells and is inherited by only one cell during cytokinesis (Zhao et al., 2006). It has been demonstrated that the apical membranes of symmetrically dividing mouse neuroepithelial cells (stem/progenitor cells) are reduced to half after the transition to asymmetrically dividing, neuron-generating cells (differentiated). This reduction of the apical membrane is accomplished through release of the midbody after cellular divisions, along with extraneous membrane components, into the developing ventricle (Marzesco et al., 2005). The mitotic kinesin-like protein (MKLP-1) has been shown to be required for formation of the midbody in mammalian cells, as well as being required for cytokinesis (Liu and Erikson, 2007; Deavours and Walker, 1999; Matuliene and Kuriyama, 2002; Kuriyama et al., 2002), for these reasons we used MKLP to label midbody particles. hESC neural differentiation protocols have been extensively developed and characterized by many groups, and the protocols range from long term differentiations using stromal feeders and exogenous factors, such as BMP4 (Nat et al., 2007; Pankratz et al., 2007; Dhara et al., 2008; Schulz et al., 2003) to a short term protocol (Bajpai et al., 2009; Curchoe et al., 2010; Cimadamore et al., 2009), previously characterized by our group, that can yield multi-potent neural stem cells that could be appropriate for use in cell based therapies due to the elimination of animal components and expensive exogenous factors.