Project description:High-throughput sequencing (HTS) has become a powerful tool for the detection of and sequence characterization of microRNAs (miRNA) and other small RNAs (sRNA). Unfortunately, the use of HTS data to determine the relative quantity of different miRNAs in a sample has been shown to be inconsistent with quantitative PCR and Northern Blot results. Several recent studies have concluded that the major contributor to this inconsistency is bias introduced during the construction of sRNA libraries for HTS and that the bias is primarily derived from the adaptor ligation steps; specifically where single stranded adaptors are sequentially ligated to the 3' and 5'-end of sRNAs using T4 RNA ligases. In this study we investigated the effects of ligation bias by using a pool of randomized ligation substrates, defined mixtures of miRNA sequences and several combinations of adaptors in HTS library construction. We show that like the 3' adaptor ligation step, the 5' adaptor ligation is also biased, not because of primary sequence, but instead due to secondary structures of the two ligation substrates. We find that multiple secondary structural factors influence final representation in HTS results. Our results provide insight about the nature of ligation bias and allowed us to design adaptors that reduce ligation bias and produce HTS results that more accurately reflect the actual concentrations of miRNAs in the defined starting material. 28 samples were sequenced and the libraries were made using various synthetic oligo mixtures and adaptor combinations
Project description:High-throughput sequencing (HTS) has become a powerful tool for the detection of and sequence characterization of microRNAs (miRNA) and other small RNAs (sRNA). Unfortunately, the use of HTS data to determine the relative quantity of different miRNAs in a sample has been shown to be inconsistent with quantitative PCR and Northern Blot results. Several recent studies have concluded that the major contributor to this inconsistency is bias introduced during the construction of sRNA libraries for HTS and that the bias is primarily derived from the adaptor ligation steps; specifically where single stranded adaptors are sequentially ligated to the 3' and 5'-end of sRNAs using T4 RNA ligases. In this study we investigated the effects of ligation bias by using a pool of randomized ligation substrates, defined mixtures of miRNA sequences and several combinations of adaptors in HTS library construction. We show that like the 3' adaptor ligation step, the 5' adaptor ligation is also biased, not because of primary sequence, but instead due to secondary structures of the two ligation substrates. We find that multiple secondary structural factors influence final representation in HTS results. Our results provide insight about the nature of ligation bias and allowed us to design adaptors that reduce ligation bias and produce HTS results that more accurately reflect the actual concentrations of miRNAs in the defined starting material.
Project description:The ligation step in RNA sequencing library generation is a known source of bias. We present the first comparison of the standard duplex adaptor protocol supplied by Life Technologies for use on the Ion Torrent PGM with an alternate single adaptor approach involving CircLigase (CircLig). We also investigate whether using the thermostable ligase Methanobacterium thermoautotrophicum RNA ligase K97A (Mth K97A) for the initial ligation step in the CircLigase protocol reduces bias. A pool of small RNA fragments of known composition was converted into a sequencing library using one of three protocols and sequenced on an Ion Torrent PGM. The single adaptor CircLigase-based approach significantly reduces, but does not eliminate, bias in Ion Torrent data. Using Mth K97A as part of the CircLig method does not further reduce bias.
Project description:One method of directional cloning of fragmented mRNA is based on single strand RNA ligation, for which ligation bias occurrs if the adapters have single sequences. The sequencing bias affects the mRNA quantification and subsequently the differential expression analysis. High definition (HD) adapters [Sorefan et al 2012, Xu et al 2015] can be used to diminish the cloning bias during library construction. HD adapters and standard illumina adapters were used to construct mRNA-seq libraries for a side by side comparison.
Project description:Most of small RNA library construction methods are based on RNA ligases, which prefer to join the molecules (small RNAs and adapters) that can anneal to each other and form a ligase favoured structure. Different platforms for next generation sequencing use different adapter sequences, causing the cloning bias. Adapters with degenerated nucleotides at the ligating ends (High Definition, HD adapters) were developed to reduce the cloning bias. However, above 90% of the cloning products is adapter dimer when the current available commercial kits and their corresponding protocols are used. Here we adopted and further improved a method demonstrated in a publically available patent (http://www.google.com/patents/WO2011056866A2?cl=en). Using the improved method, we constructed the small RNA libraries by using the total RNA of chondrosarcoma cell line. The adapter dimer was significantly reduced. The small RNA sequences were also analysed.
Project description:Most of small RNA library construction methods are based on RNA ligases, which prefer to join the molecules (small RNAs and adapters) that can anneal to each other and form a ligase favoured structure. Different platforms for next generation sequencing use different adapter sequences, causing the cloning bias. Adapters with degenerated nucleotides at the ligating ends (High Definition, HD adapters) were developed to reduce the cloning bias. However, above 90% of the cloning products is adapter dimer when the current available commercial kits and their corresponding protocols are used. Here we adopted and further improved a method demonstrated in a publically available patent (http://www.google.com/patents/WO2011056866A2?cl=en). Using the improved method, we constructed the small RNA libraries by using the total RNA of Medicago truncatula leaf tissue. The adapter dimer was significantly reduced. The small RNA sequences were also analysed.
Project description:Most of small RNA library construction methods are based on RNA ligases, which prefer to join the molecules (small RNAs and adapters) that can anneal to each other and form a ligase favoured structure. Different platforms for next generation sequencing use different adapter sequences, causing the cloning bias. Adapters with degenerated nucleotides at the ligating ends (High Definition, HD adapters) were developed to reduce the cloning bias. However, above 90% of the cloning products is adapter dimer when the current available commercial kits and their corresponding protocols are used. Here we adopted and further improved a method demonstrated in a publically available patent (http://www.google.com/patents/WO2011056866A2?cl=en). Using the improved method, we constructed the small RNA libraries by using the total RNA of chondrosarcoma cell line. The adapter dimer was significantly reduced. The small RNA sequences were also analysed. The small RNA libraries of cultured chondrosarcoma cell line were constructed by using an improved protocol where high-definition (HD) adapters were used.
Project description:Most of small RNA library construction methods are based on RNA ligases, which prefer to join the molecules (small RNAs and adapters) that can anneal to each other and form a ligase favoured structure. Different platforms for next generation sequencing use different adapter sequences, causing the cloning bias. Adapters with degenerated nucleotides at the ligating ends (High Definition, HD adapters) were developed to reduce the cloning bias. However, above 90% of the cloning products is adapter dimer when the current available commercial kits and their corresponding protocols are used. Here we adopted and further improved a method demonstrated in a publically available patent (http://www.google.com/patents/WO2011056866A2?cl=en). Using the improved method, we constructed the small RNA libraries by using the total RNA of Medicago truncatula leaf tissue. The adapter dimer was significantly reduced. The small RNA sequences were also analysed. The small RNA libraries of medicago truncatula leaves were constructed by using an improved protocol where high-definition (HD) adapters were used.