Role of ASCL1 in human neural development

As a proneural gene, ASCL1 was reported to be important to neurogenesis. To better illustrate the role of ASCL1 in human telencephalon development, we genetically engineered an ASCL1 knockout (KO) hESC line and ASCL1 rescue (RE) hESC line, and then preformed RNA sequencing when WT, KO and RE were differentiated into neural progenitors in vitro. Our results showed that ASCL1 KO hESCs could be regularly maintained in vitro, and could be efficiently specified into neuroectoderm cells and following telencephalic neural progenitors. Remarkably, dorsal progenitors-derived from ASCL1 KO hESCs failed to differentiate into DCX positive neuroblasts. In addition, dorsal and ventral progenitors retained higher expression of VZ/ESVZ genes but had much lower expression of LSVZ genes after KO of ASCL1. Re-introducing of ASCL1 in KO hESCs through a doxycycline (Dox) inducible overexpression system reversed the gene expression changes induced by cortical progenitors with ASCL1 KO. Taken all these together, our results revealed a pivotal role of ASCL1 in both dorsal and ventral telencephalic development by progressing the cycling progenitors within the ESVZ to post-mitotic early born neurons in the LSVZ in human telencephalon. The mRNA of wild type (WT) and ASCL1 knock out (KO) neural progenitors with dorsal and ventral identies, and ASCL1 rescue (RE) dorsal neural progenitors in a background of ASCL1 knock out were extracted with triplicated at Day25 in vitro differentiation and sequenced on an Illumina HiSeq 2500 platform.