Whole exome sequencing

  1. NGS Exome Sequencing

What is whole exome sequencing?

Whole exome sequencing (WES) is a targeted next generation sequencing method that identifies all the protein-coding genes in the genome. It is primarily performed using hybridization capture, a technique that uses 5′ biotin–modified oligonucleotide probes to “capture” the region of interest for sequencing. Focusing on protein-coding exons (and excluding other regions of the genome) can lower the cost and time of sequencing, as exons make up about 1% of the genome. In contrast to their small size contribution to the genome, exons contain 85% of the variants that are associated with disease, so this level of sequencing is often preferred for diagnostic applications [ 1].

Uses of whole exome sequencing

WES is a practical method for mapping variants that are rare in the population, to elucidate complex disorders [2]. It is also a feasible option for population genetics and discovery science, or data mining [3]. WES is particularly useful in oncology research and is currently used for cancer diagnostics [4]. Information gained from WES can provide insight into prognoses and personalized treatment options [5]. WES is most often carried out with hybridization probes rather than amplicons.

Benefits of whole exome sequencing

  • Achieve deep and uniform coverage even across protein-coding regions
  • Integrate with common sequencing platforms
  • More manageable data output (5 GB) for genotyping applications than whole genome sequencing (90 GB)
  • Lower cost and faster analysis than whole genome sequencing

Targeting coding regions

Exome sequencing is invaluable for sequencing only the coding regions of the human genome. With exons representing only about 1% of the genome, it is critical to have an effective method of separating these regions from non-coding DNA to focus on potentially important mutations implicated in disease. The captured material must also be suitable for sequencing to a sufficient depth of coverage for reliable detection of variant alleles.

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Targeted sequencing application guide

This detailed overview walks you through major advances in capture and enrichment technology, types of targeted next generation sequencing, their applications and more.

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Whole exome sequencing workflow

Exome sequencing is a type of targeted next generation sequencing. After genomic material is extracted from the sample, libraries must be prepared. Library prep includes the addition of adapters to identify the samples or molecules in the sample and to help the DNA or RNA adhere to the sequencing apparatus. Exome sequencing specifically enriches or captures the exome before the sequencing step.

Get started with whole exome sequencing

Working in an area that would benefit from exome sequencing? Just starting? See how you can easily improve your workflows and results.

xGen Exome Research Panel

The xGen Exome Research Panel v1.0 consists of 429,826 individually synthesized and quality controlled xGen Lockdown Probes. The Exome Research Panel spans a 39 Mb target region (19,396 genes) of the human genome and covers 51 Mb of end-to-end tiled probe space.

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References

  1. Choi M, Scholl UI, et al. (2009) Genetic diagnosis by whole exome capture and massively parallel DNA sequencing. Proc Natl Acad Sci U S A 106(45): 19096-19101.
  2. Williams HJ, Hurst JR, et al. (2016) The use of whole-exome sequencing to disentangle complex phenotypes. Eur J Hum Genet 24(2): 298–301.
  3. Bamshad MJ, Ng SB, et al. (2011) Exome sequencing as a tool for Mendelian disease gene discovery. Nat Rev Genet 12(11): 745–755.
  4. Kamps R, Brandao RD, et al. (2017) Next-generation sequencing in oncology: genetic diagnosis, risk prediction and cancer classification. Int J Mol Sci 18(2).
  5. Rabbani B, Nakaoka H, et al. (2016) Next generation sequencing: implications in personalized medicine and pharmacogenomics. Mol Biosyst 12(6): 1818–1830.
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