Coordinated activities of EZH2 and EZH1 are essential for neurogenesis

Polycomb group proteins (PcG) are well known by their function in the regulation of developmental processes. PcG mediated regulation of genetic programs required for proper development are triggered by EZH2 H3K27 methyltransferase activity. EZH1 can partially substitute EZH2 activity. However, unlike EZH2, EZH1 is presence in differentiated and adult tissues suggesting additional biological functions. Here we show that EZH2 is predominantly expressed in neural stem cells being essential for neural stem cells self renewal and homeostasis. There, it controls the transcriptional state of cell cycle regulators, such as CIP1. But it is also necessary to regulate genes involved in surveillance and neuroepithelial polarity. In contrast, EZH1 expression is more abundant in differentiated cells within the spinal cord and its downregulation unables neural stem cells to differentiate. All together our data reveal a complementary but non-redundant role of EZH2 and EZH1 in neurogenesis. In order to understand how EZH2 might regulate neurogenesis in chick embryo spinal cord cells we performed a transcriptional profiling of flow cytometry purified GFP+ neuroblasts from shRNA-EZH2 or shRNA-Control electroporated neural tubes. Specifically, electroporated embryos were dissected out 48h after electroporation and trypsinized for 5-10 min in 0.5% Trypsin-EDTA (Sigma). Trypsinization was stopped by 20% horse serum in PBS-0.1% glucose solution. GFP+ cells from cell suspension were sorted by flow cytometry using a MoFlo flow cytometer (DakoCytomation, Fort Collins, CO). mRNA from GFP positive cells from dissected shRNA-control or shRNA-EZH2 electroporated neural tubes was extracted by TRIZOL (Invitrogen) protocol with 2 l of pellet paint co-precipitant (Novagene). Then, RNA was processed to hybridization on Affymetrix microarrays.