Gene Expression and Transcriptome Sequencing: Basics, Analysis, Advances

Gene expression studies are extremely useful for understanding a broad range of biological, physiological, and molecular responses. The techniques for gene expression reflect differential patterns of gene regulation and have evolved with time from detecting one gene to many genes at a time laterally. Gene expression depends on the spatiotemporal expression in a particular tissue at a given time point and needs critical examination and interpretation. Transcriptome sequencing or RNA-seq using next-generation sequencing (short and long reads) is the most widely deployed technology for accurate quantification of gene expression. According to the biological aim of the experiment, replications, platform, and chemistries, propelling improvement has been demonstrated and documented using RNA-seq in plants, humans, animals, and clinical sciences with respect to gene expression of mRNA, small non-coding, long non-coding RNAs, alternative splice variations, isoform variations, gene fusions, single-nucleotide variants. Integrating transcriptome sequencing with other techniques such as chromatin immunoprecipitation, methylation, genome-wide association studies, manifests insights into genetic and epigenetic regulation. Epi-transcriptome including RNA methylation, modification, and alternative polyadenylation events can also be explored through long-read sequencing. In this chapter, we have presented an account of the basics of gene expression methods, transcriptome sequencing, and the various methodologies involved in the downstream analysis.