RNAseq: A widely used technique for genome-wide expression analysis

Abstract

Transcriptomics is the high-throughput study of the transcript profile of the genome produced under specific circumstances or in a particular cell. Two contemporary techniques, microarrays and RNA-seq, are widely used for transcriptome studies. Microarrays techniques were developed in the 1990s, where thousands of DNA fragments (probs) were immobilized on a solid support and hybridized with complementary target sequences in the organism of interest. It is a powerful tool for quantifying the expression level of many genes within particular mRNA samples. It is widely used to study disease diagnosis, drug discovery and development, toxicological research, immunological studies, microbial detection and identification, comparative genomics, determination of virulence factors affected by various conditions, etc. However, it has many applications in research and diagnosis and has certain limitations. Microarray only identifies sequences whose probes are present on the array chip. Therefore, availability of genome sequence information to prepare the probes is a prerequisite for microarray study. Apart from that, quantifying the expression of low-abundance genes remains challenging in microarrays. These limitations led to inventions of new simple and cost effective techniques for transcriptome studies.