Project description:Long-read RNA sequencing (RNA-seq) is a powerful technology for transcriptome analysis, but the relatively low throughput of current long-read sequencing platforms limits transcript coverage. We present TEQUILA-seq, a versatile, easy-to-implement, and low-cost method for targeted long-read RNA-seq. TEQUILA-seq can be broadly used for targeted sequencing of full-length transcripts in diverse biomedical research settings.
Project description:Background RNA sequencing (RNA-seq) is a powerful technique for identifying and quantifying transcription and splicing events, both known and novel. However, given its recent development and the proliferation of library construction methods, understanding the bias it introduces is incomplete but critical to realizing its value. Results Here we present a method, in vitro transcription sequencing (IVT-seq), for identifying and assessing the technical biases in RNA-seq library generation and sequencing at scale. We created a pool of > 1000 in vitro transcribed (IVT) RNAs from a full-length human cDNA library and sequenced them with poly-A and total RNA-seq, the most common protocols. Because each cDNA is full length and we show IVT is incredibly processive, each base in each transcript should be equivalently represented. However, with common RNA-seq applications and platforms, we find ~50% of transcripts have > 2-fold and ~10% have > 10-fold differences in within-transcript sequence coverage. Strikingly, we also find > 6% of transcripts have regions of high, unpredictable sequencing coverage, where the same transcript varies dramatically in coverage between samples, confounding accurate determination of their expression. To get at causal factors, we used a combination of experimental and computational approaches to show that rRNA depletion is responsible for the most significant variability in coverage and that several sequence determinants also strongly influence representation. Conclusions In sum, these results show the utility of IVT-seq in promoting better understanding of bias introduced by RNA-seq and suggest caution in its interpretation. Furthermore, we find that rRNA-depletion is responsible for substantial, unappreciated biases in coverage. Perhaps most importantly, these coverage biases introduced during library preparation suggest exon level expression analysis may be inadvisable. 5 rRNA-depleted samples with duplicates, 1 polyA selected, 1 total RNA, and 1 plasmid library all without replicates.
Project description:Total RNA was isolated from mouse Asxl2-/- and WT LK cells following standard protocol with TRIZol reagent (Life Technologies) followed by RNA library preparation with the Illumina TruSeq strand-specific mRNA sample preparation system. All RNA-seq libraries were sequenced with a read length of single-end 75bp using the Illumina NextSeq 500, and final of over 45 million reads per sample.
Project description:Background: Whole exome sequencing (WES) has been proven to serve as a valuable basis for various applications such as variant calling and copy number variation (CNV) analyses. For those analyses the read coverage should be optimally balanced throughout protein coding regions at sufficient read depth. Unfortunately, WES is known for its uneven coverage within coding regions due to GC-rich regions or off-target enrichment. Results: In order to examine the irregularities of WES within genes, we applied Agilent SureSelectXT exome capture on human samples and sequenced these via Illumina in 2x101 paired-end mode. As we suspected the sequenced insert length to be crucial in the uneven coverage of exome captured samples, we sheared 12 genomic DNA samples to two different DNA insert size lengths, namely 130 and 170 bp. Interestingly, although mean coverages of target regions were clearly higher in samples of 130 bp insert length, the level of evenness was more pronounced in 170 bp samples. Moreover, merging overlapping paired-end reads revealed a positive effect on evenness indicating overlapping reads as another reason for the unevenness. In addition, mutation analysis on a subset of the samples was performed. In these isogenic subclones almost twofold mutations were failed in the 130 bp samples when compared to the 170 bp samples. Visual inspection of the discarded mutation sites exposed low coverages at the sites embedded in high amplitudes of coverage depth in the affected region. Conclusions: Producing longer insert reads could be a good strategy to achieve better uniform read coverage in coding regions and hereby enhancing the effective sequencing yield to provide an improved basis for further variant calling and CNV analyses.
Project description:Calcium is a universal second messenger molecule which plays a significant role in several biological processes. Presence of calcium sensors (calmodulins) and calcium-dependent protein kinases in Plasmodium species suggests an important role of calcium-dependent signaling pathways in the regulation of cellular processes in the malaria parasites. Evidence for the transcriptional response of control Plasmodium falciparum asexual blood stages not treated with the calcium ionophores, A23187 and ionomycin has been presented here.
Project description:This SuperSeries is composed of the following subset Series: GSE33795: P. falciparum (lab strain 3d7) schizonts untreated control vs P. falciparum (lab strain 3d7) reference RNA pool GSE33796: P. falciparum (lab strain 3d7) schizonts treated with ionomycin vs P. falciparum (lab strain 3d7) reference RNA pool GSE33797: P. falciparum (lab strain 3d7) schizonts treated with A23187 vs P. falciparum (lab strain 3d7) reference RNA pool Refer to individual Series
Project description:Calcium is a universal second messenger molecule which plays a significant role in several biological processes. Presence of calcium sensors (calmodulins) and calcium-dependent protein kinases in Plasmodium species suggests an important role of calcium-dependent signaling pathways in the regulation of cellular processes in the malaria parasites. Evidence for the transcriptional response of Plasmodium falciparum asexual blood stages to the well-known calcium ionophore A23187 has been presented here.