Over the past decade, RNA sequencing (RNA-seq) has become an indispensable tool for transcriptome-wide analysis of differential gene expression and differential splicing of mRNAs. However, as next-generation sequencing technologies have developed, so too has RNA-seq. Now, RNA-seq methods are available for studying many different aspects of RNA biology, including single-cell gene expression, translation (the translatome) and RNA structure (the structurome). Exciting new applications are being explored, such as spatial transcriptomics (spatialomics). Together with new long-read and direct RNA-seq technologies and better computational tools for data analysis, innovations in RNA-seq are contributing to a fuller understanding of RNA biology, from questions…
Pepper is an important vegetable with great economic value and unique biological features. In the past few years, significant development has been made towards understanding the huge complex pepper genome; however, pepper functional genomics has not been well studied. To better understand the pepper gene structure and pepper gene regulation, we conducted full-length mRNA sequencing by PacBio sequencing and obtained 57862 high-quality full-length mRNA sequences derived from 18362 previously annotated and 5769 newly detected genes. New gene models were built that combined the full-length mRNA sequences and corrected approximately 500 fragmented gene models from previous annotations. Based on the full-length…
Although messenger RNAs are key molecules for understanding life, until now, no method has existed to determine the full-length sequence of endogenous mRNAs including their poly(A) tails. Moreover, although non-A nucleotides can be incorporated in poly(A) tails, there also exists no method to accurately sequence them. Here, we present full-length poly(A) and mRNA sequencing (FLAM-seq), a rapid and simple method for high-quality sequencing of entire mRNAs. We report a complementary DNA library preparation method coupled to single-molecule sequencing to perform FLAM-seq. Using human cell lines, brain organoids and Caenorhabditis elegans we show that FLAM-seq delivers high-quality full-length mRNA sequences for…
The carbonic anhydrases (CAs) are a group of enzymes that play an important role in the absorption and transportation of CO2 in Saccharina japonica. They are encoded by a superfamily of genes with seven subtypes that are unrelated in sequence but share conserved function in catalyzing the reversible conversion of CO2 and HCO3-. Here we have characterized the CA members in the transcriptome of S. japonica using Single-molecule real-time (SMRT) sequencing technology. Approximately 9830.4 megabases from 5,028,003 quality subreads were generated, and they were assembled into 326,512 full-length non-chimeric (FLNC) reads, with an average flnc read length of 2181 bp.…
The simultaneous examination of a single cell’s genome and transcriptome presents scientists with a powerful tool to study genetic variability and its effect on gene expression. In this chapter, we describe the library generation method for combined genome and transcriptome sequencing (G&T-seq) originally described by Macaulay et al. (Nat Protoc 11(11):2081-2103, 2016; Nat Methods 12(6):519-522, 2015). This includes some alterations we made to improve robustness of this process for both the novice user and laboratories that want to deploy this method at scale. Using this method, genomic DNA and full-length mRNA from single cells are separated, amplified, and converted into…
The enormous sizes of adhesion G protein-coupled receptors (aGPCRs) go along with complex genomic exon-intron architectures giving rise to multiple mRNA variants. There is a need for a comprehensive catalog of aGPCR variants for proper evaluation of the complex functions of aGPCRs found in structural, in vitro and animal model studies. We used an established bioinformatics pipeline to extract, quantify and visualize mRNA variants of aGPCRs from deeply sequenced transcriptomes. Data analysis showed that aGPCRs have multiple transcription start sites even within introns and that tissue-specific splicing is frequent. On average, 19 significantly expressed transcript variants are derived from a…
Normalization of cDNA is widely used to improve the coverage of rare transcripts in analysis of transcriptomes employing next-generation sequencing. Recently, long-read technology has been emerging as a powerful tool for sequencing and construction of transcriptomes, especially for complex genomes containing highly similar transcripts and transcript-spliced isoforms. Here, we analyzed the transcriptome of sugarcane, with a highly polyploidy plant genome, by PacBio isoform sequencing (Iso-Seq) of two different cDNA library preparations, with and without a normalization step. The results demonstrated that, while the two libraries included many of the same transcripts, many longer transcripts were removed and many new generally…
The wide implementation of next-generation sequencing (NGS) technologies has revolutionized the field of medical genetics. However, the short read lengths of currently used sequencing approaches pose a limitation for identification of structural variants, sequencing repetitive regions, phasing alleles and distinguishing highly homologous genomic regions. These limitations may significantly contribute to the diagnostic gap in patients with genetic disorders who have undergone standard NGS, like whole exome or even genome sequencing. Now, the emerging long-read sequencing (LRS) technologies may offer improvements in the characterization of genetic variation and regions that are difficult to assess with the currently prevailing NGS approaches. LRS…
In this BioConference Live webinar, PacBio CSO Jonas Korlach highlights how multi-kilobase reads from SMRT Sequencing can resolve many of the previously considered ‘difficult-to-sequence’ genomic regions. The long reads also allow phasing of the sequence information along the maternal and paternal alleles, demonstrated by full-length, fully phased HLA class I & II gene sequencing. In addition, characterizing the complex landscape of alternative gene products is currently very difficult with short-read sequencing technologies, and he describes how long-read, full-length mRNA sequencing can be used to describe the diversity of transcript isoforms, with no assembly required. Lastly, in the exciting area of…
Winston Timp from Johns Hopkins University studies the metabolism of hummingbirds, which sustain the highest metabolic rates among all vertebrates. Notably, hummingbirds can switch rapidly between a fuel of lipids to newly ingested sugars. This remarkable metabolism is supported by enzymes which operate at the extreme limit of catalytic efficiency. Understanding the molecular basis of enzymatic action will provide a foundation enabling rational engineering of metabolic circuits in other systems. To do this, Dr. Timp and his team generated a de novo transcriptome of the hummingbird liver using the Iso-Seq method. Characterization of the resulting protein coding sequences provides clues…
Early detection of colorectal cancer (CRC) and its precursor lesions (adenomas) is crucial to reduce mortality rates. The fecal immunochemical test (FIT) is a non-invasive CRC screening test that detects the blood-derived protein hemoglobin. However, FIT sensitivity is suboptimal especially in detection of CRC precursor lesions. As adenoma-to-carcinoma progression is accompanied by alternative splicing, tumor-specific proteins derived from alternatively spliced RNA transcripts might serve as candidate biomarkers for CRC detection.
SMRT Sequencing is a DNA sequencing technology characterized by long read lengths and high consensus accuracy, regardless of the sequence complexity or GC content of the DNA sample. These characteristics can be harnessed to address medically relevant genes, mRNA transcripts, and other genomic features that are otherwise difficult or impossible to resolve. I will describe examples for such new clinical research in diverse areas, including full-length gene sequencing with allelic haplotype phasing, gene/pseudogene discrimination, sequencing extreme DNA contexts, high-resolution pharmacogenomics, biomarker discovery, structural variant resolution, full-length mRNA isoform cataloging, and direct methylation detection.
Tremendous flexibility is maintained in the human proteome via alternative splicing, and cancer genomes often subvert this flexibility to promote survival. Identification and annotation of cancer-specific mRNA isoforms is critical to understanding how mutations in the genome affect the biology of cancer cells. While microarrays and other NGS-based methods have become useful for studying transcriptomes, these technologies yield short, fragmented transcripts that remain a challenge for accurate, complete reconstruction of splice variants. The Iso-Seq method developed at PacBio offers the only solution for direct sequencing of full-length, single-molecule cDNA sequences needed to discover biomarkers for early detection and cancer stratification,…
The PacBio Iso-Seq method produces high-quality, full-length transcripts of up to 10 kb and longer and has been used to annotate many important plant and animal genomes. Here we describe an improved, simplified library workflow and analysis pipeline that reduces library preparation time, RNA input, and cost. The Iso-Seq V2 Express workflow is a one day protocol that requires only ~300 ng of total RNA input while also reducing the number of reverse transcription and amplification steps down to single reactions. Compared with the previous workflow, the Iso-Seq V2 Express workflow increases the percentage of full-length (FL) reads while achieving…
Transcriptome sequencing has proven to be an important tool for understanding the biological changes in cancer genomes including the consequences of structural rearrangements. Short read sequencing has been the method of choice, as the high throughput at low cost allows for transcript quantitation and the detection of even rare transcripts. However, the reads are generally too short to reconstruct complete isoforms. Conversely, long-read approaches can provide unambiguous full-length isoforms, but lower throughput has complicated quantitation and high RNA input requirements has made working with cancer samples challenging. Recently, the COLO 829 cell line was sequenced to 50-fold coverage with PacBio…