Gene Expression Analysis Using RNA-Seq

Revealing DNA sequences is vital for all branches of biological sciences. Next-Generation Sequencing (NGS) is a different approach in this area so that it has created a great evolution in biology science and covers various aspects of genome, transcriptome, epigenome and metagenome-level studies. NGS is considered as a high-performance method for genomic and transcriptomic information analysis in comparison with traditional methods due to providing good genomic coverage, determining each single pairs of bases and eliminating the first generation sequencing disadvantages (Sanger sequencing). Use of NGS has begun since 2005 and 2006, after the commercialization of various apparatus companies such as ABI/SOLiD Illumina, Science Roch/454Life, and Solexa to study the transcriptome of the model and non-model organisms. Recently, RNA sequencing is used widely to identify genes associated with growth and development processes and their expression patterns in response to a variety of biological and non-biological stresses, in various organs and growth stages in different organisms. It helps scientists to determine the amounts of gene expression, differentiation of different isoforms of genes, detection of gene fusions and characterization of small RNA as well as alternative splicing events, duplicate elements, exon of genes, new transcripts, UTRs, SNPs, and somatic mutations. The RNA-seq method typically consists of providing suitable biological samples, isolation of total RNA, enrichment of non-ribosomal RNAs, conversion of RNA to cDNA, construction of a fragment library, selecting size and adding linkers and sequencing on high-throughput sequencing platform, alignment, and assembly of the reads and downstream analysis.