Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling by array of rat cortex regions

ABSTRACT: The neocortex of the mammalian brain is comprised by six distinct layers with neuronal subtypes that appear indistinguishable from one cortical area to the next. Correspondingly, global gene expression seems to be almost identical across the cerebral cortex and only a few genes have so far been reported to show regional enrichment in specific cortical areas. In the present study on adult rat brain, we have corroborated the strikingly similar gene expression among cortical areas. However, differential expression analysis has allowed for the identification of 30, 24 and 11 genes enriched in frontomedial -, temporal- or occipital cortex, respectively. A large proportion of these 65 genes appear to be involved in signal transduction, including the ion channel Fxyd6, the neuropeptide Grp and the nuclear receptor Rorb. We also find that the majority of these genes display increased expression levels around birth and show distinct preferences for certain cortical layers and cell types in rodents. Since specific patterns of expression often are linked to equally specialised biological functions, we propose that these cortex sub-region enriched genes are important for proper functioning of the cortical regions in question and may represent interesting candidates for further genetic studies of neuropsychiatric phenotypes.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Christine Stansberg

PROVIDER: E-TABM-1019 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Genome-wide transcriptional profiling allows characterization of the molecular underpinnings of neocortical organization, including cortical areal specialization, laminar cell type diversity and functional anatomy. Microarray analysis of individual cortical layers across sensorimotor and association cortices in rhesus macaque demonstrated robust and specific laminar and areal molecular signatures driven by differential expression of genes associated with specialized neuronal function. Gene expression corresponding with laminar architecture was generally similar across cortical areas, although genes with robust areal patterning were often highly laminar as well, and these patterns were more highly conserved between macaque and human as compared to mouse. Layer 4 of primate primary visual cortex displayed a distinct molecular signature compared to other cortical regions, a specialization not observed in mouse. Overall, transcriptome-based relationships were strongest between proximal layers in a cortical area, and between neighboring areas along the rostrocaudal axis, reflecting in vivo cortical spatial topography and therefore a developmental imprint. Tissue from male and female monkeys (n = 2-3 animals/gender) was collected from anterior cingulate gyrus (ACG), layers 2, 3, 5, 6; orbitofrontal cortex (OFC), layers 2, 3, 5, 6; dorsolateral prefrontal cortex (DLPFC), layers 2-6; primary motor cortex (M1), layers 2, 3, 5, 6; primary somatosensory cortex (S1), layers 2-6; primary auditory cortex (A1), layers 2-6; primary visual cortex (V1), layers 2-6 including 4A, 4B, 4Calpha (4Ca), 4Cbeta (4Cb); secondary visual cortex (V2), layers 2-6; middle temporal area (MT), layers 2-6; temporal area (TE), layers 2-6; hippocampus, CA1, CA2, CA3, dentate gyrus (DG); and dorsal lateral geniculate nucleus (LGN), magnocellular, parvocellular and koniocellular divisions. Due to the limited number of samples that could be amplified concurrently, amplifications were performed in 3 batches (batches A-C, containing 102, 119 and 10 experimental samples, respectively). To control for batch effects, common RNA pool control samples were amplified and hybridized in each batch. These included LCM extracted hippocampus CA3 samples from the current study and a whole rhesus brain RNA pool (Biochain). These control samples were hybridized in 6 replicates in batch A and B and in 3 replicates in batch C (3 replicates per 96 well plate).

Project description:Despite the well-established role of the frontal and posterior peri-sylvian cortices in many facets of human-cognitive specializations, including language, little is known about the developmental patterning of these regions in human brain. We performed a genome-wide analysis of human cerebral patterning during mid-gestation, a critical epoch in cortical regionalization. A total of 345 genes were identified as differentially expressed (DE) between superior temporal gyrus (STG) and the remaining cerebral cortex (CTX). GO categories representing transcription factors were enriched in STG, while cell-adhesion and extracellular matrix molecules, were enriched in the other cortical regions. Q-PCR or in situ hybridization were performed to validate differential expression in a subset of 32 genes, most of which were confirmed. LIM domain binding 1 (LDB1), which we show to be enriched in the STG, is a recently identified interactor of LIM domain only 4 (LMO4), a gene known to be involved in the asymmetric pattering of the peri-sylvian region in the developing human brain. Protocadherin 17 (PCDH17), a neuronal cell adhesion molecule, was highly enriched in focal regions of the human prefrontal cortex. Contactin Associated Protein-Like 2 (CNTNAP2), in which mutations are known to cause autism, epilepsy and language delay, showed a remarkable pattern of anterior enriched expression in cortical regions important for human higher cognition. Importantly, a similar pattern was not observed in the mouse or rat. These data highlight the importance of expression analysis of human brain and the utility of cross-species comparisons of gene expression. Genes identified here provide a foundation for understanding molecular aspects of human-cognitive specializations and disorders that disrupt them. Experiment Overall Design: Fresh frozen human mid-gestation brains were obtained from the NICHD Brain and Tissue Bank for Developmental Disorders (University of Maryland, Baltimore, MD). After separation of the two hemispheres, tissue from STG was extracted. RNA from STG and remaining CTX was hybridized on both Agilent G4110A arrays (n=8) and Affymetrix HGU133A arrays (n=17).

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Transcription profiling by array of rat cortex regions

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