Project description:Within just a few years single cell RNA sequencing has become a frequently used standard method in many research fWithin just a few years single cell RNA sequencing has become a frequently used standard method in many research facilities worldwide. Declining sequencing costs and further refinements of the available protocols will pave the way for previously unimaginable prospects, up to single cell transcriptomic maps of entire organisms. The sample collection process can constitute a severe bottleneck in scRNA-seq experiments especially for solid tissues. Lengthy dissociation protocols are not uncommon to obtain sufficient amounts of starting material and can lead to significant changes in the gene expression profiles of cells. Preservation of the transcriptome prior to single cell dissociation can overcome this setback. Here we present an extensive performance analysis of glyoxal as an alternative fixative for scRNA-seq application. High numbers of transcripts and genes were recovered from glyoxal-fixed cells subjected to Drop-seq methodology with the best performance in Drosophila cells. While glyoxal fixation in Drosophila Kc167 and human HEK 293T cells revealed transcriptome data similar to the unfixed condition, reduced library complexity was observed for the human sample. We found the integrity of Drosophila intestinal tissue maintained following glyoxal fixation, while dissociation of the fixed tissue allowed sufficient cell isolation. In conclusion, we present glyoxal as a well-suited fixative for Drosophila samples that allows high-quality single cell transcriptomic analysis and successful intestinal tissue disaggregationcilities worldwide. Declining sequencing costs and further refinements of the available protocols will pave the way for previously unimaginable prospects, up to single cell transcriptomic maps of entire organisms. The sample collection process can constitute a severe bottleneck in scRNA-seq experiments especially for solid tissues. Lengthy dissociation protocols are not uncommon to obtain sufficient amounts of starting material and can lead to significant changes in the gene expression profiles of cells. Preservation of the transcriptome prior to single cell dissociation can overcome this setback. Here we present an extensive performance analysis of glyoxal as an alternative fixative for scRNA-seq application. High numbers of transcripts and genes were recovered from glyoxal-fixed cells subjected to Drop-seq methodology with the best performance in Drosophila cells. While glyoxal fixation in Drosophila and human cells revealed transcriptome data similar to the unfixed condition, reduced library complexity was observed for the human sample and might require further protocol optimization. We found the integrity of Drosophila intestinal tissue maintained following glyoxal fixation, while dissociation of the fixed tissue allowed sufficient cell isolation. In conclusion, we present glyoxal as a well-suited fixative for Drosophila samples that allows high-quality single cell transcriptomic analysis and successful intestinal tissue disaggregation.
Project description:Mammalian development is an intricate process regulated by multiple gene isoforms and their epigenetic states, which are yet undefined. Using integrative massive parallel sequencing and bioinformatics approach, we built genome-wide inventory of transcript variants, their promoters and histone modification states during normal development, using mouse cerebellum as model system. The data we integrated consists of 29,589 (4,792 novel) promoters that transcribe 61,525 (12,796 novel) distinct mRNAs, corresponding to 14,508 protein-coding and 9,862 non-coding genes. While 68% of the multi-transcript genes exhibit alternative splicing, 78% use alternative transcriptional events that are regulated during cerebellar development through H3K4me3 and H3K27me3. The data presented highlight the magnitude of alternative promoters and transcriptional termination as major source of transcriptome diversity along with alternative splicing. We also show that alternative promoters differentially activated during normal cerebellar development are aberrantly used in medulloblastoma, emphasizing the importance of studying gene regulation and function at the isoform-level. Study of transcriptome diversity in cerebellar development. We performed mRNA-seq and ChIP-seq experiments. mRNA-seq were performed on total RNA isolated from two P0, P5, P15 and adult cerebellum using 10 microgram of total RNA as the starting material for sequencing library prep. For each stage, mRNA-seq data was obtained from two lanes of a flowcell. For ChIP-seq experiments, solubilized chromatin was prepared by pooling multiple cerebellum tissues (3-18) and then ChIP-enriched DNA (using anti-RNAP II, anti-H3K4me3, anti-H3K27me3, or negative control IgG antibodies) were isolated. 10 microgram of ChIP-enriched DNA was used to prepare the ChIP-seq library for sequencing in a single lane.
Project description:Establishing the functional roles of genetic variants remains a significant challenge in the post-genomic era. Here, we present a method, allele-specific alternative mRNA processing (ASARP), to identify genetically influenced mRNA processing events using transcriptome sequencing (RNA-Seq) data. The method examines RNA-Seq data at both single nucleotide and whole-gene/isoform levels to identify allele-specific expression (ASE) and existence of allele-specific regulation of mRNA processing. We applied the methods to data obtained from the human glioblastoma cell line U87MG and primary breast cancer tissues and found that 26M-bM-^@M-^S45% of all genes with sufficient read coverage demonstrated ASE, with significant overlap between the two cell types. Our methods predicted potential mechanisms underlying ASE due to regulations affecting either whole-gene-level expression or alternative mRNA processing, including alternative splicing, alternative polyadenylation and alternative transcriptional initiation. Allele-specific alternative splicing and alternative polyadenylation may explain ASE in hundreds of genes in each cell type. Reporter studies following these predictions identified the causal single nucleotide variants (SNVs) for several allele-specific alternative splicing events. Finally, many genes identified in our study were also reported as disease/phenotype-associated genes in genome-wide association studies. Future applications of our approach may provide ample insights for a better understanding of the genetic basis of gene regulation underlying phenotypic diversity and disease mechanisms. Examine allele-specific gene expression and alternative RNA processing in U87MG cell line