Neuroanatomically precise, genome-wide maps of transcript distributions are critical resources to complement genomic sequence data and to correlate functional and genetic brain architecture. Here we describe the generation and analysis of a transcriptional atlas of the adult human brain, comprising extensive histological analysis and comprehensive microarray profiling of ~900 neuroanatomically precise subdivisions in two individuals. Transcriptional regulation varies enormously by anatomical location, with different regions and their constituent cell types displaying robust molecular signatures that are highly conserved between individuals. Analysis of differential gene expression and gene co-expression relationships demonstrates that brain-wide variation strongly reflects the distributions of major cell classes such as neurons, oligodendrocytes, astrocytes and microglia. Local neighbourhood relationships between fine anatomical subdivisions are associated with discrete neuronal subtypes and genes involved with synaptic transmission. The neocortex displays a relatively homogeneous transcriptional pattern, but with distinct features associated selectively with primary sensorimotor cortices and with enriched frontal lobe expression. Notably, the spatial topography of the neocortex is strongly reflected in its molecular topography— the closer two cortical regions, the more similar their transcriptomes. This freely accessible online data resource forms a high-resolution transcriptional baseline for neurogenetic studies of normal and abnormal human brain function.

Implementation of amyloid biomarkers in clinical practice would be accelerated if such biomarkers could be measured in blood. We analyzed plasma levels of Aβ42 and Aβ40 in a cohort of 719 individuals (the Swedish BioFINDER study), including patients with subjective cognitive decline (SCD), mild cognitive impairment (MCI), Alzheimer’s disease (AD) dementia and cognitively healthy elderly, using a ultrasensitive immunoassay (Simoa platform). There were weak positive correlations between plasma and cerebrospinal fluid (CSF) levels for both Aβ42 and Aβ40, and negative correlations between plasma Aβ42 and neocortical amyloid deposition (measured with PET). Plasma levels of Aβ42 and Aβ40 were reduced in AD dementia compared with all other diagnostic groups. However, during the preclinical or prodromal AD stages (i.e. in amyloid positive controls, SCD and MCI) plasma concentration of Aβ42 was just moderately decreased whereas Aβ40 levels were unchanged. Higher plasma (but not CSF) levels of Aβ were associated with white matter lesions, cerebral microbleeds, hypertension, diabetes and ischemic heart disease. In summary, plasma Aβ is overtly decreased during the dementia stage of AD indicating that prominent changes in Aβ metabolism occur later in the periphery compared to the brain. Further, increased levels of Aβ in plasma are associated with vascular disease.

Neuronal development requires highly coordinated regulation of the cytoskeleton within the developing axon. This dynamic regulation manifests itself in axonal branching, turning, and pathfinding, presynaptic differentiation, and growth cone collapse and extension. Semaphorin 3A (Sema3A), a secreted guidance cue that primarily acts to repel axons from inappropriate targets, induces cytoskeletal rearrangements that results in growth cone collapse 1 . These effects require intra-axonal mRNA translation. Here we show that transcripts for RhoA, a small GTPase that regulates the actin cytoskeleton, are localized to developing axons and growth cones, and this localization is mediated by an axonal targeting element located in the RhoA 3'UTR. Sema3A induces intra-axonal translation of RhoA mRNA and this local translation of RhoA is necessary and sufficient for Sema3A-mediated growth cone collapse. These studies indicate that local RhoA translation regulates the neuronal cytoskeleton and identify a novel mechanism for the regulation of RhoA signaling.Studies using Xenopus retinal axons demonstrated that cytoskeletal regulation of the growth cone by Sema3A requires intra-axonal, or "local", mRNA translation 2 . Sema3A treatment results in increased protein synthesis in growth cones as evidenced by metabolic labeling experiments and by phosphorylation of elongation factor 4E-BP1 2 . These effects occur within minutes of Sema3A application 2 . Furthermore, Sema3A-mediated growth cone collapse is blocked by ribosomal inhibitors. The mRNA translation that is required for Sema3A-mediated growth cone collapse occurs in the axon, as both Sema3A-induced collapse and inhibition of this collapse by ribosomal inhibitors is preserved in axons that are severed from their cell bodies 2 .To determine if intra-axonal mRNA translation is required for Sema3A signaling in mammalian neurons, we examined Sema3A-mediated growth cone collapse in embryonic rat dorsal root ganglia (DRG) explant cultures 3 -5 . To eliminate the possibility that the effects of Sema3A were mediated through somatic translation, axons were severed from their cell bodies 2 ( Supplementary Fig. 1a). Treatment of severed axons with Sema3A for 60 min resulted in an increase in collapsed growth cones from 17 ± 1.3% to 75 ± 2.8 % ( Supplementary Fig. 1b, c, g). This effect was blocked by pretreatment of axons with either cycloheximide or anisomycin ( Supplementary Fig. 1d-f), both of which are ribosomal inhibitors. Pretreatment of these cultures with rapamycin, an inhibitor of cap-dependent translation 6 , also blocked Sema3A-mediated growth cone collapse. Together, these data indicate that the requirement forCorrespondence and requests for materials should be addressed to S.R.J. (e-mail:srj2003@med.cornell.edu).. * These authors contributed equally to this work.Supplementary Information accompanies the paper on Nature's website (http://www.nature.com). Competing interests statementThe authors declare that they have no competing financial interests. Supplementary ...

Objective:To test whether plasma tau is altered in Alzheimer disease (AD) and whether it is related to changes in cognition, CSF biomarkers of AD pathology (including β-amyloid [Aβ] and tau), brain atrophy, and brain metabolism.Methods:This was a study of plasma tau in prospectively followed patients with AD (n = 179), patients with mild cognitive impairment (n = 195), and cognitive healthy controls (n = 189) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and cross-sectionally studied patients with AD (n = 61), mild cognitive impairment (n = 212), and subjective cognitive decline (n = 174) and controls (n = 274) from the Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study at Lund University, Sweden. A total of 1284 participants were studied. Associations were tested between plasma tau and diagnosis, CSF biomarkers, MRI measures, 18fluorodeoxyglucose-PET, and cognition.Results:Higher plasma tau was associated with AD dementia, higher CSF tau, and lower CSF Aβ42, but the correlations were weak and differed between ADNI and BioFINDER. Longitudinal analysis in ADNI showed significant associations between plasma tau and worse cognition, more atrophy, and more hypometabolism during follow-up.Conclusions:Plasma tau partly reflects AD pathology, but the overlap between normal aging and AD is large, especially in patients without dementia. Despite group-level differences, these results do not support plasma tau as an AD biomarker in individual people. Future studies may test longitudinal plasma tau measurements in AD.

In many vertebrate and invertebrate cells, inositol 1,4,5-trisphospate production induces a biphasic Ca2+ signal. Mobilization of Ca2+ from internal stores drives the initial burst. The second phase, referred to as storeoperated Ca2+ entry (formerly capacitative Ca2+ entry), occurs when depletion of intracellular Ca2+ pools activates a non-voltage-sensitive plasma membrane Ca2+ conductance. Despite the prevalence of store-operated Ca2+ entry, no vertebrate channel responsible for store-operated Ca2+ entry has been reported. trp (transient receptor potential), a Drosophila gene required in phototransduction, encodes the only known candidate for such a channel throughout phylogeny. In this report, we describe the molecular characterization of a human homolog of trp, TRPCI. TRPC1 (transient receptor potential channel-related protein 1) was 40%o identical to Drosophila TRP over most of the protein and lacked the charged residues in the S4 transmembrane region proposed to be required for the voltage sensor in many voltage-gated ion channels. TRPCI was expressed at the highest levels in the fetal brain and in the adult heart, brain, testis, and ovaries. Evidence is also presented that TRPC1 represents the archetype of a family of related human proteins. Several signaling mechanisms for store-operated Ca2+ entry have been proposed (for review, see refs. 1, 3-5, 11). In one model, a diffusible messenger is produced or released upon depletion of the intracellular Ca2+ pool, and this messenger then activates the plasma membrane Ca2+ channels (12). A second model suggests that emptying the intracellular Ca2+ stores causes a conformational change in the storage organelle and/or its surface proteins, such as the InsP3 receptor, which is transmitted to plasma membrane Ca2+ channels either by direct coupling or via the cytoskeleton (13,14). Despite the prevalence of store-operated Ca2+ entry, no vertebrate SOC gene has been identified. Elucidation of the mechanism responsible for store-operated Ca2+ entry would be considerably aided by cloning and characterizing the channels.

Availability of genome-scale in situ hybridization data allows systematic analysis of genetic neuroanatomical architecture. Within the hippocampus, electrophysiology and lesion and imaging studies demonstrate functional heterogeneity along the septotemporal axis, although precise underlying circuitry and molecular substrates remain uncharacterized. Application of unbiased statistical component analyses to genome-scale hippocampal gene expression data revealed robust septotemporal molecular heterogeneity, leading to the identification of a large cohort of genes with robust regionalized hippocampal expression. Manual mapping of heterogeneous CA3 pyramidal neuron expression patterns demonstrates an unexpectedly complex molecular parcellation into a relatively coherent set of nine expression domains in the septal/temporal and proximal/distal axes with reciprocal, nonoverlapping boundaries. Unique combinatorial profiles of adhesion molecules within these domains suggest corresponding differential connectivity, which is demonstrated for CA3 projections to the lateral septum using retrograde labeling. This complex, discrete molecular architecture provides a novel paradigm for predicting functional differentiation across the full septotemporal extent of the hippocampus.

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SUMMARY To provide a temporal framework for the genoarchitecture of brain development, in situ hybridization data were generated for embryonic and postnatal mouse brain at 7 developmental stages for ~2100 genes, processed with an automated informatics pipeline and manually annotated. This resource comprises 434,946 images, 7 reference atlases, an ontogenetic ontology, and tools to explore co-expression of genes across neurodevelopment. Gene sets coinciding with developmental phenomena were identified. A temporal shift in the principles governing the molecular organization of the brain was detected, with transient neuromeric, plate-based organization of the brain present at E11.5 and E13.5. Finally, these data provided a transcription factor code that discriminates brain structures and identifies the developmental age of a tissue, providing a foundation for eventual genetic manipulation or tracking of specific brain structures over development. The resource is available as the Allen Developing Mouse Brain Atlas (developingmouse.brain-map.org).