Multiple conserved regulatory domains promote Fezf2 expression in the developing cerebral cortex.

BackgroundThe genetic programs required for development of the cerebral cortex are under intense investigation. However, non-coding DNA elements that control the expression of developmentally important genes remain poorly defined. Here we investigate the regulation of Fezf2, a transcription factor that is necessary for the generation of deep-layer cortical projection neurons.ResultsUsing a combination of chromatin immunoprecipitation followed by high throughput sequencing (ChIP-seq) we mapped the binding of four deep-layer-enriched transcription factors previously shown to be important for cortical development. Building upon this we characterized the activity of three regulatory regions around the Fezf2 locus at multiple stages throughout corticogenesis. We identified a promoter that was sufficient for expression in the cerebral cortex, and enhancers that drove reporter gene expression in distinct forebrain domains, including progenitor cells and cortical projection neurons.ConclusionsThese results provide insight into the regulatory logic controlling Fezf2 expression and further the understanding of how multiple non-coding regulatory domains can collaborate to control gene expression in vivo

Effect of Ionic Strength on Solvation Geometries in Aqueous Nitrate Ion Solutions

Temperature-dependent infrared spectra of aqueous nitrate solutions with a range of concentrations and ionic strengths are used to determine the effect of ionic strength on the relative stabilities of different solvation geometries in aqueous nitrate ion. The asymmetric stretching absorption band from 1250 to 1450 cm^–1 changes line shape with temperature, allowing two distinct peaks to be fit for each spectrum. Because each peak is assigned based on electronic structure calculations as a proxy to a different solvation motif, van’t Hoff plots provide insight into the thermodynamics of exchange between different solvation geometries. A strong linear trend is seen between increased ionic strength and the magnitude of both the enthalpic and entropic contributions to the solvation geometry stabilities. Electronic structure computations of previously proposed structures in different ionic strengths are performed in the presence of external fields, roughly simulating the impact of ions in solution

Fezf2 Expression Identifies a Multipotent Progenitor for Neocortical Projection Neurons, Astrocytes, and Oligodendrocytes

Progenitor cells in the cerebral cortex sequentially generate distinct classes of projection neurons. Recent work suggests the cortex may contain intrinsically fate-restricted progenitors marked by expression of Cux2. However, the heterogeneity of the neocortical ventricular zone as well as the contribution of lineage-restricted progenitors to the overall cortical neurogenic program remains unclear. Here, we utilize in vivo genetic fate mapping to demonstrate that Fezf2-expressing radial glial cells (RGCs) exist throughout cortical development and sequentially generate all major projection neuron subtypes and glia. Moreover, we show that the vast majority of CUX2⁺ cells in the VZ and SVZ are migrating interneurons derived from the subcortical telencephalon. Examination of the embryonic cortical progenitor population demonstrates that Cux2⁺ RGCs generate both deep- and upper-layer projection neurons. These results identify Fezf2⁺ radial glial cells as a multipotent neocortical progenitor and suggest that the existence, and molecular identity, of laminar-fate-restricted RGCs awaits further investigation

Multiple conserved regulatory domains promote Fezf2 expression in the developing cerebral cortex.

BackgroundThe genetic programs required for development of the cerebral cortex are under intense investigation. However, non-coding DNA elements that control the expression of developmentally important genes remain poorly defined. Here we investigate the regulation of Fezf2, a transcription factor that is necessary for the generation of deep-layer cortical projection neurons.ResultsUsing a combination of chromatin immunoprecipitation followed by high throughput sequencing (ChIP-seq) we mapped the binding of four deep-layer-enriched transcription factors previously shown to be important for cortical development. Building upon this we characterized the activity of three regulatory regions around the Fezf2 locus at multiple stages throughout corticogenesis. We identified a promoter that was sufficient for expression in the cerebral cortex, and enhancers that drove reporter gene expression in distinct forebrain domains, including progenitor cells and cortical projection neurons.ConclusionsThese results provide insight into the regulatory logic controlling Fezf2 expression and further the understanding of how multiple non-coding regulatory domains can collaborate to control gene expression in vivo

Cux2-Positive Radial Glial Cells Generate Diverse Subtypes of Neocortical Projection Neurons and Macroglia

We recently published genetic lineage-tracing experiments using the Fezf2 and Cux2 loci. These experiments demonstrated that at both the clonal and population levels Fezf2(+) RGCs are multipotent and that at the population level Cux2(+) RGCs are multipotent. Here, we extend our work on the lineages of Fezf2(+) and Cux2(+) RGCs. Clonal analysis of E10.5 neocortical progenitors suggests that most, if not all, Cux2(+) and Fezf2(+) RGCs generate diverse projection neuron subtypes located throughout layers 2-6. These results support our previous conclusion that both Fezf2(+) and Cux2(+) RGCs are multipotent neocortical progenitors. This Matters Arising Response paper addresses the Gil-Sanz et al. (2015) Matters Arising paper, published concurrently in Neuron

TBR1 regulates autism risk genes in the developing neocortex

Exome sequencing studies have identified multiple genes harboring de novo loss-of-function (LoF) variants in individuals with autism spectrum disorders (ASD), including TBR1, a master regulator of cortical development. We performed ChIP-seq for TBR1 during mouse cortical neurogenesis and show that TBR1-bound regions are enriched adjacent to ASD genes. ASD genes were also enriched among genes that are differentially expressed in Tbr1 knockouts, which together with the ChIP-seq data, suggests direct transcriptional regulation. Of the nine ASD genes examined, seven were misexpressed in the cortices of Tbr1 knockout mice, including six with increased expression in the deep cortical layers. ASD genes with adjacent cortical TBR1 ChIP-seq peaks also showed unusually low levels of LoF mutations in a reference human population and among Icelanders. We then leveraged TBR1 binding to identify an appealing subset of candidate ASD genes. Our findings highlight a TBR1-regulated network of ASD genes in the developing neocortex that are relatively intolerant to LoF mutations, indicating that these genes may play critical roles in normal cortical development