Project description:We identified a subgroup of patient-derived glioblastoma (GBM) cells that express high levels of the neurogenic transcription factor, ASCL1, which predicts response to pharmacological inhibition of the Notch signaling pathway. Treatment of ASCL1hi GBM cells with a Notch signaling inhibitor induced a change in cell fate from neoplastic to neuronal. Importantly, acquisition of the neuronal fate was accompanied by a reduction in tumorigenic potential. Loss of ASCL1 in GBM cells rendered cells no longer responsive to Notch signaling inhibition and we determined ASCL1 is required for the competency of GBM cells to undergo neuronal differentiation. Enforced ASCL1 expression directed GBM cells towards a neuronal cell fate reminiscent of terminal differentiation. RNA-seq analysis of GBM cells treated with the Notch signaling inhibitor reveals neuronal target gene activation is associated with increased stoichiometric levels of ASCL1, suggesting threshold levels of ASCL1 in GBM cells governs neuronal differentiation. We demonstrate that neoplastic cells which retain expression of key neurogenic programs can have their fates redirected towards terminal differentiation. Directed fate specification to neuronal cell types by exploiting latent neurogenic programs may be a strategy to treat a subset of GBM patients. Our findings therefore highlight the potential of differentiation therapy for a subset of molecularly defined GBMs.
Project description:Geminin is a small nucleoprotein that neuralizes ectoderm in the Xenopus embryo. Geminin promotes neural fate acquisition of mouse embryonic stem cells: Geminin knockdown during neural fate acquisition decreased expression of neural precursor cell markers (Pax6, Sox1), while increasing expression of Pitx2, Lefty1 and Cited2, genes involved in formation of the mouse node. Here we differentiated mouse embryonic stem cells into embryoid bodies to study Geminin's ability to repress primitive streak mesendoderm fate acquisition. We used microarrays to define the sets of genes that are regulated by Geminin during cell fate acquisition in embryoid bodies, using Dox-inducible Geminin knockdown or overexpression mouse embryonic stem cell lines. ES cell lines for Geminin over-expression (GemOE) were treated without or with Dox from day 3 to day 5 of EB differentiation and were collected on days 4 or 5 for microarray analysis. Gem knockdown (KD) ES cell lines were treated without or with Dox from day 0 to day 4 of EB differentiation and were collected on day 4 for microarray analysis.
Project description:Geminin is a small nucleoprotein that neuralizes ectoderm in the Xenopus embryo. Geminin promotes neural fate acquisition of mouse embryonic stem cells: Geminin knockdown during neural fate acquisition decreased expression of neural precursor cell markers (Pax6, Sox1), while increasing expression of Pitx2, Lefty1 and Cited2, genes involved in formation of the mouse node. Here we differentiated mouse embryonic stem cells into embryoid bodies to study Geminin's ability to repress primitive streak mesendoderm fate acquisition. We used microarrays to define the sets of genes that are regulated by Geminin during cell fate acquisition in embryoid bodies, using Dox-inducible Geminin knockdown or overexpression mouse embryonic stem cell lines.
Project description:Formation of the complex vertebrate nervous system begins when pluripotent cells of the early embryo are directed to acquire a neural fate. Although cell intrinsic controls play an important role in this process, the molecular nature of this regulation is not well defined. Here we assessed the role for Geminin, a nuclear protein expressed in embryonic cells, in neural fate acquisition from mouse embryonic stem (ES) cells. While Geminin knockdown does not affect the ability of ES cells to maintain or exit pluripotency, we found that it significantly impairs their ability to acquire a neural fate. Conversely, Geminin overexpression promotes neural gene expression, even in the presence of growth factor signaling that antagonizes neural transcriptional responses. These data demonstrate that Geminin’s activity contributes to mammalian neural cell fate acquisition. We investigated the mechanistic basis of this phenomenon and found that Geminin maintains a hyperacetylated and open chromatin conformation at neural genes. Interestingly, recombinant Geminin protein also rapidly alters chromatin acetylation and accessibility even when Geminin is combined with nuclear extract and chromatin in vitro. These findings define a novel activity for Geminin in regulation of chromatin structure. Together, these data support a role for Geminin as a cell intrinsic regulator of neural fate acquisition that promotes expression of neural genes by regulating chromatin accessibility and histone acetylation. Mouse embryonic stem cells were differentiated for two days in N2B27 medium, with or without Doxycycline-inducible shRNAmir knockdown of Geminin and compared by microarray. Three independent experiments were conducted, using two different mouse embryonic stem cell lines for Doxycycline-inducible knockdown of Geminin. The two ES lines express unique shRNAmir sequences targeting Geminin (shRNAmir #9 and #11) to control for off-target effects.
Project description:The establishment of neuronal diversity in the developing cerebral cortex is currently the focus of much attention. How progenitors that seemingly display limited diversity end up in producing a vast array of neurons remains a puzzling question. The prevailing model that recently emerged suggests that temporal maturation of progenitors in the dorsal pallium is a key driver in the diversification of neuronal output. However, temporal constrains are unlikely to account for all diversity across pallial domains, especially in the ventral and lateral aspects where neurons that will later belong to the olfactory cortex, claustrum and amygdala significantly differ from their neocortical counterparts born at the same time. In this study, we implemented single-cell RNAseq to sample the diversity of progenitors and neurons along the dorso-ventral axis of the pallium. We first identified neuronal types, mapped them on the tissue and performed genetic tracing to determine their ontogenic origin. We then investigated progenitor diversity and extensively characterized genes with variable expression along the dorso-ventral axis. We further identified those subjected to temporal vs spatial regulations. Finally, we reconstructed the developmental trajectories followed by ventral and dorsal pallial neurons to identify gene waves specific of each lineage. Our data suggest a model in which discrete neuronal fate acquisition from a continuous gradient of progenitors results from probabilistic mechanisms with a strong bias imposed on progenitors by both spatial information and temporal maturation.