Project description:Neocortical circuits consist of stereotypical motifs that must self-assemble during development. Recent evidence suggests the subtype identity of both excitatory projection neurons (PNs) and inhibitory interneurons (INs) is important for this process. We knocked out the transcription factor Satb2 in PNs to induce those of the intratelencephalic (IT)-type to adopt a pyramidal tract (PT)-type identity. Loss of IT-type PNs selectively disrupted the lamination and circuit integration of INs derived from the caudal ganglionic eminence (CGE). Strikingly, reprogrammed PNs demonstrated reduced synaptic targeting of CGE-derived INs relative to controls. In control mice, IT-type PNs targeted neighboring CGE INs while PT-type PNs did not in deep layers, confirming this lineage-dependent motif. Finally, single cell RNA-sequencing revealed that major CGE IN subtypes were conserved after loss of IT PNs, but with differential transcription of synaptic proteins and signaling molecules. Thus, IT-type PNs influence CGE-derived INs in a non-cell autonomous manner during cortical development.
Project description:Gene expression profiling of the medial (MGE), lateral (LGE) and caudal (CGE) ganglionic eminence, and cerebral cortex (CTX) at various embryonic stages (E12.5, E14 and E16).
Project description:In order to assess the quality of alleged PM identifications from Arabidopsis, PM-enriched fractions were compared to PM-depleted fractions using 18O isotopic labeling and mass spectrometry. The two samples submitted are biological replicates. Keywords: Protein Localization via MS
Project description:Many biological processes are controlled by master regulators that activate complex downstream transcriptional and/or posttranslational networks. These networks have been hard to dissect using reverse genetics because of the difficulty of mutating large numbers of binding motifs or phosphorylation sites at different chromosomal loci. Here, we use a novel competitive genome editing (CGE) assay for dissecting the transcriptional network downstream of the master regulatory oncogene MYC. The CGE method is based on precision genome editing using template libraries that either reconstitute the original feature or introduce an altered sequence. Both types of libraries also introduce sequence tags, generating a large number of replicate lineages and enabling direct comparison between cells that carry original and mutant features. By using precision editing and by comparing two populations of edited cells, the CGE method overcomes the two main limitations of CRISPR/Cas9-technology in analyzing the effect of genotype on phenotype: the difficulty of cutting DNA exactly at the intended site, and the decreased cell proliferation caused by the DNA cuts themselves. Importantly, it provides a powerful method for studying subtle effects elicited by mutation of individual transcription factor binding sites. We show here that E-box mutations at several MYC target gene promoters resulted in reduced cellular fitness, demonstrating a direct correlation between MYC-regulated cellular processes and MYC binding, and identifying important transcriptional targets responsible for its functions.
Project description:Proper regulation of the proliferation and differentiation of radial glia (RG), the neural stem cells of the developing cortex, is fundamental for brain growth and organization. In humans, a specialized RG subtype, the outer radial glia (oRG), are abundant and give rise to diverse neuronal and glial progeny. However, the mechanisms regulating oRG development and differentiation are not fully understood. Here we investigated the regulation of oRG expansion and lineage potential by perturbing Leukemia Inhibitory Factor (LIF) signaling in the developing human cortex and in human pluripotent stem cell (PSC)-derived cortical organoids. LIF receptors are specifically expressed in oRG cells during neurogenesis, and, consistent with the previously described role of this cytokine as an activator of stem cell self-renewal, LIF treatment increased the number of oRG cells. Surprisingly, LIF treatment also increased the production of inhibitory interneurons (INs) in the cortex. Comparative transcriptomic analysis suggested that these INs resemble INs produced in the caudal ganglionic eminence (CGE). To test if oRG cells are the progenitors of these CGE-like INs, we isolated oRG cells from primary developing cortex and cultured them for several weeks with and without LIF treatment. We found that CGE-like INs were produced by oRG cells, and their abundance is increased by LIF treatment. Together, these observations suggest that LIF signaling regulates oRG lineage potential and capacity to generate CGE-like INs.
