The mammalian cerebral cortex supports cognitive functions such as sensorimotor integration, memory, and social behaviors. Normal brain function relies on a diverse set of differentiated cell types, including neurons, glia, and vasculature. Here, we have used large-scale single-cell RNA sequencing (RNA-seq) to classify cells in the mouse somatosensory cortex and hippocampal CA1 region. We found 47 molecularly distinct subclasses, comprising all known major cell types in the cortex. We identified numerous marker genes, which allowed alignment with known cell types, morphology, and location. We found a layer I interneuron expressing Pax6 and a distinct postmitotic oligodendrocyte subclass marked by Itpr2. Across the diversity of cortical cell types, transcription factors formed a complex, layered regulatory code, suggesting a mechanism for the maintenance of adult cell type identity.

https://science.sciencemag.org/content/sci/early/2015/02/18/science.aaa1934.full.pdf

Cell types in the mouse cortex and hippocampus revealed by single-cell RNA-seq

The journal of neuroscience : the official journal of the Society for Neuroscience.

The RNA-guided nuclease Cas9 can be reengineered as a programmable transcription factor. However, modest levels of gene activation have limited potential applications. We describe an improved transcriptional regulator obtained through the rational design of a tripartite activator, VP64-p65-Rta (VPR), fused to nuclease-null Cas9. We demonstrate its utility in activating endogenous coding and noncoding genes, targeting several genes simultaneously and stimulating neuronal differentiation of human induced pluripotent stem cells (iPSCs).

/pdf/highly-efficient-cas9-mediated-transcriptional-programming-4bgmi5fouq.pdf

Highly efficient Cas9-mediated transcriptional programming

Transcriptome Engineering with RNA-Targeting Type VI-D CRISPR Effectors

We analyzed genetic data of 47,429 multiple sclerosis (MS) and 68,374 control subjects and established a reference map of the genetic architecture of MS that includes 200 autosomal susceptibility variants outside the major histocompatibility complex (MHC), one chromosome X variant, and 32 variants within the extended MHC. We used an ensemble of methods to prioritize 551 putative susceptibility genes that implicate multiple innate and adaptive pathways distributed across the cellular components of the immune system. Using expression profiles from purified human microglia, we observed enrichment for MS genes in these brain-resident immune cells, suggesting that these may have a role in targeting an autoimmune process to the central nervous system, although MS is most likely initially triggered by perturbation of peripheral immune responses.

/pdf/multiple-sclerosis-genomic-map-implicates-peripheral-immune-3lfthe7auc.pdf

Multiple sclerosis genomic map implicates peripheral immune cells and microglia in susceptibility

Rapid Single-Step Induction of Functional Neurons from Human Pluripotent Stem Cells

How to Make an Active Zone: Unexpected Universal Functional Redundancy between RIMs and RIM-BPs

RIM-BPs Mediate Tight Coupling of Action Potentials to Ca(2+)-Triggered Neurotransmitter Release.

Neuromodulator Signaling Bidirectionally Controls Vesicle Numbers in Human Synapses

Hundreds of L1CAM gene mutations have been shown to be associated with congenital hydrocephalus, severe intellectual disability, aphasia, and motor symptoms. How such mutations impair neuronal function, however, remains unclear. Here, we generated human embryonic stem (ES) cells carrying a conditional L1CAM loss-of-function mutation and produced precisely matching control and L1CAM-deficient neurons from these ES cells. In analyzing two independent conditionally mutant ES cell clones, we found that deletion of L1CAM dramatically impaired axonal elongation and, to a lesser extent, dendritic arborization. Unexpectedly, we also detected an ∼20-50% and ∼20-30% decrease, respectively, in the levels of ankyrinG and ankyrinB protein, and observed that the size and intensity of ankyrinG staining in the axon initial segment was significantly reduced. Overexpression of wild-type L1CAM, but not of the L1CAM point mutants R1166X and S1224L, rescued the decrease in ankyrin levels. Importantly, we found that the L1CAM mutation selectively decreased activity-dependent Na(+)-currents, altered neuronal excitability, and caused impairments in action potential (AP) generation. Thus, our results suggest that the clinical presentations of L1CAM mutations in human patients could be accounted for, at least in part, by cell-autonomous changes in the functional development of neurons, such that neurons are unable to develop normal axons and dendrites and to generate normal APs.

/pdf/conditional-deletion-of-l1cam-in-human-neurons-impairs-both-2cshybwad2.pdf

Claudio Acuna

Papers

Rapid Single-Step Induction of Functional Neurons from Human Pluripotent Stem Cells

How to Make an Active Zone: Unexpected Universal Functional Redundancy between RIMs and RIM-BPs

RIM-BPs Mediate Tight Coupling of Action Potentials to Ca(2+)-Triggered Neurotransmitter Release.

Neuromodulator Signaling Bidirectionally Controls Vesicle Numbers in Human Synapses

Conditional deletion of L1CAM in human neurons impairs both axonal and dendritic arborization and action potential generation