Gene expression profiling during early embryonic and stem cells neural differentiation

Abstract

Embryonic stem (ES) cells are characterized by the capacity to differentiate into any cell type and by their ability to self-renewal. Available methods to promote ES cell differentiation towards neural lineages attempt to replicate, in different ways, the multistep process of embryonic neural development. The steps involved in the in vitro acquisition of a neural fate are very similar to the events that happen during embryonic development. In both system, the neuroectoderm is specified by the presence of FGF and BMP and Wnt/²-catenin inhibitors. After the neuroectoderm induction, the embryonic neural ectoderm gives rise to the neural tube. Likewise, the ES cells undergoing neural differentiation arrange themselves into rosettes structures that simulates the morphogenesis of the fused neural tube. Both structures present polarity defined by the presence of apical protein complex. Notch pathway controls the balance between proliferation and differentiation of the neural tube neuroprogenitors, as well as the establishment and maintenance of rosettes. Despite the similarities in both systems, the current protocols for ES cell differentiation do not mirror perfectly neural development and the efficiency of neural differentiation is variable depending on the methodology applied. We highlight the importance to compare the neurogenesis process in both systems in order to contribute to the optimization of the neural differentiation protocol. In this context, the identification and characterization of novel transcription factors capable of regulating neurogenesis is essential for our understanding of the mechanisms underlying neuronal differentiation. A transcriptomic analysis through RNA-Seq experiments of the chicken neural tube at stage HH18 and embryonic day 6 embryos identified neural-specific genes potentially involved with the development process. Beyond that, among the transcription factors expressed in the neural tube is Scratch. Chicken Scratch2 (cScratch2) is an evolutionarily conserved transcription factor expressed in early postmitotic neural progenitors of the chick embryonic neural tube that has been described to play a role for proper neural development. In this project we aim to trace a parallel between neural differentiation in ES cells and in embryonic development, and we will also investigate the expression dynamics of potential early neural differentiation genes in embryo and in vitro and characterize in differentiating ES cells the expression pattern of Scratch2. (AU)