Next Generation Sequencing

Next generation sequencing (NGS) has revolutionized our understanding of biological systems in health and disease, significantly advancing translational and clinical research. NGS empowers researchers and clinicians to study the underlying mechanisms linked to rare genetic disorders, cancer, neonatal and infectious disease (among others) at the DNA level. This innovative method has led to the development of better targeted and personalized diagnostics and therapies.

NGS platforms can sequence millions of DNA fragments in parallel, allowing researchers to sequence everything from specific targeted regions to the entire human genome in one day.¹ NGS, which is also known as deep sequencing or massively parallel sequencing, has also enabled large-scale genomic sequencing that is more beneficial than previous sequencing technologies.

First generation sequencing, also known as Sanger sequencing, had been widely used for 30 years, leading to significant advances in the understanding of the human genome.^1,2 However, NGS surpassed first generation sequencing because of the significant advantages of the NGS method. Improved sensitivity and coverage, cost effectiveness and efficient workflow with faster turnaround time are some of the benefits NGS has over the older sequencing technology.^1,2,3

There are three main steps in the typical NGS workflow.

• Sample preparation - Genomic DNA is extracted from samples, which can include blood, saliva and tissue. The DNA is fragmented into shorter sequences followed by ligation of adapters, then amplification and enrichment.

• Sequencing - The sequencing method is dependent on the platform being utilized. Some methods include pyrosequencing and sequencing by synthesis or ligation. Sequencing by synthesis is one of the most popular technologies because it enables researchers to sequence large amounts of genomic DNA simultaneously at a high sensitivity to detect a wide-range of genetic alterations, including single-nucleotide polymorphisms (SNPs), small insertions and deletions (indels), and structural variants.

• Data Analysis - Bioinformatic tools or data analysis applications are used for quality control, alignment to reference sequence and identification of pathogenic variants.

Depending on the area that researchers wish to focus on, NGS can be used for multiple applications.

• Whole genome sequencing to determine an organism’s complete DNA sequence
• Whole exome sequencing to focus on the coding regions of the genome
  
• Targeted sequencing to study specific genomic regions of interest
  
• Epigenomics to evaluate epigenetic modifications
  
• RNA Sequencing for transcriptome profiling of coding and noncoding regions, identifying genes in specific cell types and determining genetic alterations like gene fusions and single nucleotide variants (SNVs)
• To help unlock the potential of every sample, Roche offers clinicians and researchers an extensive portfolio of products for their NGS needs.