The choroid plexus (ChP) is the principal source of cerebrospinal fluid (CSF), which has accepted roles as a fluid cushion and a sink for nervous system waste in vertebrates. Various animal models have provided insight into how the ChP–CSF system develops and matures. In addition, recent studies have uncovered new, active roles for this dynamic system in the regulation of neural stem cells, critical periods and the overall health of the nervous system. Together, these findings have brought about a paradigm shift in our understanding of brain development and health, and have stimulated new initiatives for the treatment of neurological disease.

The genetic basis of Lewy body dementia (LBD) is not well understood. Here, we performed whole-genome sequencing in large cohorts of LBD cases and neurologically healthy controls to study the genetic architecture of this understudied form of dementia and to generate a resource for the scientific community. Genome-wide association analysis identified five independent risk loci, whereas genome-wide gene-aggregation tests implicated mutations in the gene GBA . Genetic risk scores demonstrate that LBD shares risk profiles and pathways with Alzheimer’s disease and Parkinson’s disease, providing a deeper molecular understanding of the complex genetic architecture of this age-related neurodegenerative condition.

POU proteins have been shown to transcriptionally active cell-specific genes and to participate in the determination of cell fate. It is therefore thought that these proteins function in development through the stable activation of genes that define specific developmental pathways. Evidence is provided here for an alternative mode of action. The primary structure of SCIP, a POU protein expressed by developing Schwann cells of the peripheral nervous system, was deduced and SCIP activity was studied. Both in normal development and in response to nerve transection, SCIP expression was transiently activated only during the period of rapid cell division that separates the premyelinating and myelinating phases of Schwann cell differentiation. In cotransfection assays, SCIP acted as a transcriptional repressor of myelin-specific genes.

The monogenic and monoallelic expression of only one out of >1000 mouse olfactory receptor (ORs) genes requires the formation of large heterochromatic chromatin domains that sequester the OR gene clusters. Within these domains, intergenic transcriptional enhancers evade heterochromatic silencing and converge into interchromosomal hubs that assemble over the transcriptionally active OR. The significance of this nuclear organization in OR choice remains elusive. Here, we show that transcription factors Lhx2 and Ebf specify OR enhancers by binding in a functionally cooperative fashion to stereotypically spaced motifs that defy heterochromatin. Specific displacement of Lhx2 and Ebf from OR enhancers resulted in pervasive, long-range, and trans downregulation of OR transcription, whereas pre-assembly of a multi-enhancer hub increased the frequency of OR choice in cis. Our data provide genetic support for the requirement and sufficiency of interchromosomal interactions in singular OR choice and generate general regulatory principles for stochastic, mutually exclusive gene expression programs.

A sheet of choroid plexus epithelial cells extends into each cerebral ventricle and secretes signaling factors into the CSF. To evaluate whether differences in the CSF proteome across ventricles arise, in part, from regional differences in choroid plexus gene expression, we defined the transcriptome of lateral ventricle (telencephalic) versus fourth ventricle (hindbrain) choroid plexus. We find that positional identities of mouse, macaque, and human choroid plexi derive from gene expression domains that parallel their axial tissues of origin. We then show that molecular heterogeneity between telencephalic and hindbrain choroid plexi contributes to region-specific, age-dependent protein secretion in vitro. Transcriptome analysis of FACS-purified choroid plexus epithelial cells also predicts their cell-type-specific secretome. Spatial domains with distinct protein expression profiles were observed within each choroid plexus. We propose that regional differences between choroid plexi contribute to dynamic signaling gradients across the mammalian cerebroventricular system.

Why the cerebral cortex folds in some mammals but not in others has long fascinated and mystified neurobiologists. Over the past century-especially the past decade-researchers have used theory and experiment to support different folding mechanisms such as tissue buckling from mechanical stress, axon tethering, localized proliferation, and external constraints. In this review, we synthesize these mechanisms into a unifying framework and introduce a hitherto unappreciated mechanism, the radial intercalation of new neurons at the top of the cortical plate, as a likely proximate force for tangential expansion that then leads to cortical folding. The interplay between radial intercalation and various biasing factors, such as local variations in proliferation rate and connectivity, can explain the formation of both random and stereotypically positioned folds.

All the higher mental and cognitive functions unique to humans depend on the neocortex ('new' cortex, referring to its relatively recent appearance in evolution), which is divided into discrete areas that subserve distinct functions, such as language, movement and sensation. With a few notable exceptions, all neocortical areas have six layers of neurons and a remarkably similar thickness and overall cell density, despite subtle differences in their cellular architecture. Furthermore, all neocortical areas are formed over roughly the same time period during development and provide little hint at early developmental stages of the rich functional diversity that becomes apparent as development comes to an end. How these areas are formed has long fascinated developmental neuroscientists, because the formation of new cortical areas, with the attendant appearance of new cortical functions, is what must have driven the evolution of mammalian behavior.

SummaryTransplantation of neural stem cells (NSCs) can improve cognition in animal models of Alzheimer's disease (AD). However, AD is a protracted disorder, and prior studies have examined only short-term effects. We therefore used an immune-deficient model of AD (Rag-5xfAD mice) to examine long-term transplantation of human NSCs (StemCells Inc.; HuCNS-SCs). Five months after transplantation, HuCNS-SCs had engrafted and migrated throughout the hippocampus and exhibited no differences in survival or migration in response to β-amyloid pathology. Despite robust engraftment, HuCNS-SCs failed to terminally differentiate and over a quarter of the animals exhibited ectopic human cell clusters within the lateral ventricle. Unlike prior short-term experiments with research-grade HuCNS-SCs, we also found no evidence of improved cognition, no changes in brain-derived neurotrophic factor, and no increase in synaptic density. These data, while disappointing, reinforce the notion that individual human NSC lines need to be carefully assessed for efficacy and safety in appropriate long-term models.