Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Gene profiling within the orexin-producing neurons

ABSTRACT: Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness and attacks of muscle atonia triggered by strong emotions (cataplexy). The best biological marker of narcolepsy is orexin deficiency with dramatic loss in hypothalamic orexin-producing neurons. Together with a tight HLA and T-cell receptor alpha(5) association, narcolepsy is believed to be autoimmune although all attempts to prove it have failed.To characterize orexin specific peptides we produced a transgenic mouse model to access to the orexin neurons transcription profile. We generated BAC-based transgenic mice by replacing the orexin coding sequence by a flag-tagged poly(A) binding protein (Pabp1) cDNA sequence. The basis of this construct is to take advantage of the ability of Pabp1 to bind to the poly(A) tails of mRNAs in vivo. Thus mRNAs from orexin cells are expected to be enriched by cross-linking them to the flag-tagged PABP and then co-immunoprecipitating this complex with a specific anti-flag monoclonal antibody. Keywords: cell type comparison Comparison between immunoprecipitated (IP) mRNA (n=9) and whole brain (WB) RNA (n=9) from BAC-based transgenic mice

ORGANISM(S): Mus musculus

SUBMITTER: Tafti Mehdi

PROVIDER: E-GEOD-17617 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Our computational analyses of sequencing depth and the discovery rates of sequence elements in the 3M-bM-^@M-^YUTR strongly demonstrate that interrogation of the 3M-bM-^@M-^YUTRome in specific tissues and cell types across development will greatly expand the identification of new 3M-bM-^@M-^YUTR isoforms and the sequence elements therein. Therefore, we will generate and sequence the 3M-bM-^@M-^YUTRs from the cell types isolated from the developing germline, mature germ cells, and early embryogenesis. In addition, we will identify the 3M-bM-^@M-^YUTRs for the transcripts isolated from the major somatic tissues during late- and post-embryonic development. Based on our sequencing estimates, we anticipate that the tissue-specific interrogation of the 3M-bM-^@M-^YUTRome will reveal a far greater diversity of novel 3M-bM-^@M-^YUTR isoform expression that is masked in the whole-worm 3M-bM-^@M-^YUTRome sequence data. Using the transgenic myo-3::PABP strain, we have generated polyA-captured libraries for late embryos and across the major stages of post-embryonic development for the muscle transcriptome. We propose to generate these polyA-captured libraries for transcripts expressed in the other major tissues across development. PolyA-captured libraries will be generated for deep sequencing following the tissue-specific isolation of mRNAs by PABP pulldowns (the PABP immunoprecipitations will take advantage of a FLAG epitope which is fused to PABP in all of the transgenic strains). We propose to validate the expression of tissue- specific transcripts by qPCR for select transcripts known to be expressed in those particular tissues. In addition, following the strategy we have employed for the large-scale polyA-captured libraries from muscle, we will perform quality checks for 3M-JM-< end capture by manually sequencing ~60 clones isolated from each library. Once we have obtained the deep sequencing data, we will analyze all of the sequence reads using the bioinformatics pipeline that we established for the whole-worm polyA- captured sequences (Mangone et al., 2010). Four samples representing gravid, L2, L3, and L4 developmental stages were analyzed.

Project description:The molecular mechanism(s) leading to Purkinje neuron loss in the neurodegenerative disorder Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) are limited by the complex morphology of this cell type. Purkinje neurons are notoriously difficult to isolate and maintain in culture presenting considerable difficultly to identify molecular changes in response to riboCGG repeat-containing mRNA that induces neurotoxicity in FXTAS. Several studies have uncovered a number of RNA binding proteins involved in translation that aberrantly interact with the toxic RNA; however, whether these interactions alter the translational profile of cells has not been investigated. Here we employ bacTRAP translational profiling to demonstrate that Purkinje neurons ectopically expressing 90 CGG repeats exhibit a dramatic change in their translational profile even prior to the onset of riboCGG-induced phenotypes. This approach identified nearly 500 transcripts that are differentially associated with ribosomes in r(CGG)90-expressing mice. Functional annotation cluster analysis revealed broad ontologies enriched in the r(CGG)90 list, including RNA binding and response to stress. Intriguingly, a transcript for the Tardbp gene, implicated in a number of other neurodegenerative disorders, exhibits altered association with ribosomes in the presence of r(CGG)90 repeats. We therefore tested and showed that reduced association of Tardbp mRNA with the ribosomes results in a loss of TDP-43 protein expression in r(CGG)90–expressing Purkinje neurons. Furthermore, we showed that TDP-43 could modulate the rCGG repeat-mediated toxicity in a Drosophila model that we developed previously. These findings together suggest translational dysregulation may be an underlying mechanism of riboCGG-induced neurotoxicity and provide insight into the pathogenicity of FXTASBAC-trap studies of Purkinje cels in normal and mutant mice Looking for cell type specific gene expression differences caused by mutation in FMR1 using BAC-Trap RNA capture assay. A cutoff value of 4.5 for mean probe_set mean across all 18 hybridizations was used to determine a cutoff for expression in Purkinje cells. This 16040 corresponded to a mean value of at least 3.4323 in the 4week time point. L7CGG90Fmr1:Pcp2 BAC (r(CGG)90 BAC) and wild-type:L7/Pcp2 BAC (WT BAC) transgenic mice used in this study have a 50% C57B6 and 50% FVB genetic background and were derived from the same parents by crossing L7CGG90Fmr1 heterozygote transgenics (100% C57B6 background) with L7/Pcp2eEGFPL10a BAC homozygous transgenics (100% FVB background). All mice reported were F1 progeny and were therefore hemizygous for one or both transgenes. Littermate wild-type mice were used for all experiments whenever possible.

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Gene profiling within the orexin-producing neurons

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