WES-Routine - CB-Gene

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WES-Routine Testing Service

Definition

The whole exome refers to the collection of all protein-coding regions (i.e., exons) in the human genome. Although exons only account for approximately 1%-2% of the entire genome, approximately 85% of known disease-associated genetic variants occur in this region.

WES-Routine testing, also known as routine whole exome testing, utilizes high-throughput sequencing technology to perform large-scale, parallel sequencing of all exon regions in an individual's genome. Its core purpose is to quickly and accurately identify genetic variants associated with genetic diseases, cancer, drug response, and other conditions, providing precise genetic evidence for disease diagnosis, prevention, and treatment.

Principle

The WES-Routine technology is based on the combination of "target sequence capture" and "high-throughput sequencing."

1. Target Region Capture: First, probes (i.e., "bait") designed to be specifically complementary to exon regions are hybridized with fragmented genomic DNA. These probes act like magnets, precisely attracting all exon sequences. Non-exon regions (introns, intergenic regions, etc.) are then eluted through a technical process, enriching and purifying the exome DNA.

2. High-throughput sequencing: The enriched exome DNA library is subjected to massively parallel sequencing on a high-throughput sequencing platform (such as Illumina NovaSeq). This technology can generate billions of short sequence reads in a single run, achieving ultra-deep coverage and read access of the target region.

3. Bioinformatics analysis: The resulting massive sequencing data is compared to the human reference genome to identify single-base variants (SNVs) and small insertions and deletions (InDels). These variants are then filtered, annotated, and interpreted using specialized bioinformatics algorithms and databases, ultimately identifying candidate variants that may be pathogenic.

Workflow: From Sample to Report

A standard WES-Routine testing service typically includes the following steps:

Sample Collection and DNA Extraction

A peripheral venous blood or saliva sample is collected from the patient and high-quality, high-molecular-weight genomic DNA is extracted.

Library Construction and Target Capture

The DNA is fragmented and sequencing adapters are added to construct a sequencing library. An exon capture panel is then used to specifically enrich the exon regions in the library.

High-Throughput Sequencing

The captured library is sequenced to ensure sufficient sequencing depth (typically >100x on average) in the target region to ensure detection accuracy and sensitivity.

Data Analysis and Interpretation

*Primary Analysis: The raw sequencing data is converted into base sequences.

*Secondary Analysis: The sequences are aligned with the reference genome to identify variants.

*Advanced Analysis and Interpretation: This is the core step. Using population frequency databases (such as gnomAD), pathogenicity databases (such as ClinVar and OMIM), and protein function prediction software, the vast number of variants is filtered through multiple layers. Ultimately, professional clinical molecular geneticists, combined with the patient's clinical phenotype, assess and interpret the pathogenicity of the selected variants.

Report Generation and Genetic Counseling

A detailed, easy-to-understand clinical test report is generated, clearly listing the pathogenic or likely pathogenic variants found and providing an explanation of their clinical significance. Typically, the testing agency will provide or recommend professional genetic counseling, where the counselor will interpret the report results with the patient or physician and discuss their health and family implications.

Sample Submission Process

Consultation and Appointment

Contact the testing agency and understand the requirements.

Sample Collection

Collect samples according to the sample type requirements.

① Blood Sample: This is the most common sample type. Typically, 2-5 mL of venous blood is collected using EDTA-anticoagulant tubes (typically those with purple caps). Avoid using heparin-anticoagulant tubes, as heparin may inhibit subsequent PCR reactions. After collection, if it cannot be shipped immediately, it should be temporarily refrigerated at 4°C (short-term) or frozen at -20°C/-80°C (long-term), but repeated freezing and thawing should be avoided.

② Tissue Sample: Fresh tissue generally requires 50-200mg (about the size of a grain of rice). After collection, it is best to rinse with pre-chilled saline and snap-freeze in liquid nitrogen as soon as possible, then store at -80°C for transportation.

③ Saliva or Oral Swab: When collecting saliva, it is important to collect as many oral mucosal cells as possible, typically >1ml. Oral swabs require multiple, vigorous scrapings of the inner oral cavity to obtain a sufficient number of cells. These samples can generally be stored and transported at room temperature or 4°C for the short term.

④ Extracted gDNA: If extracting DNA yourself, the required amount is typically 1μg-2μg or higher, with a concentration of ≥50 ng/μL. The purity index OD260/280 should be between 1.8-2.0, and the DNA should be free of degradation and contamination (such as protein or RNA residues). Store at -20°C or -80°C. Ensure sufficient dry ice is used during transportation.

Sample Shipping

① Initial Sample Processing and Storage

② Standard Packaging: Use sturdy containers to prevent breakage during transportation. Cryogenic samples (such as blood, tissue, and DNA) must be transported with sufficient dry ice, ensuring that the dry ice has not completely evaporated upon delivery to the testing facility. Sample tubes should ideally be sealed with Parafilm, and the outer packaging should clearly indicate the sample information.

③ Select a reliable logistics provider and ensure express delivery with tracking.

Sample Receipt and Quality Inspection

Check sample quantity, quality, and integrity.

Report Issuance

If quality inspection fails: Replace or resample as required.

Service Cycle

Advantages

Cost-effectiveness

A single test covers the exon regions of approximately 20,000 genes, significantly reducing the cost of testing a large number of genes individually and resulting in extremely high efficiency.

High diagnostic yield

Particularly suitable for diseases with complex and heterogeneous phenotypes, it eliminates the need to pre-guess suspected genes, thus avoiding test failures and delays caused by incorrect guesses.

Discovery of new genes

It not only detects variants in known disease-causing genes but also has the potential to discover entirely new disease-causing genes, thus advancing medical advancements.

Data re-minability

The data generated by a single sequencing run is a permanent electronic archive. As scientific research and genetic understanding deepen, the original data can be reanalyzed, potentially uncovering new clues to disease, thus avoiding repeated testing.

Comprehensiveness

It avoids potential design omissions in targeted panels and provides the most comprehensive exon-wide screening.

Application Scenarios

WES-Routine has a wide range of applications, primarily including:

Diagnosis of difficult and rare diseases: For patients with complex, nonspecific, or difficult-to-diagnose clinical presentations, WES is a first-line tool for identifying the cause, significantly shortening the diagnostic journey.

Hereditary Cancer Risk Assessment: Screening for germline mutations associated with hereditary cancer syndromes (such as Lynch syndrome and hereditary breast and ovarian cancer syndrome) provides risk assessment and early intervention options for patients and their families.

Neuropsychiatric Disorders: Used to investigate the causes of conditions such as autism spectrum disorder, intellectual disability, epilepsy, and hereditary peripheral neuropathy.

Cardiovascular Disease: Identifying causative genes for hereditary cardiomyopathies, arrhythmias, and familial hypercholesterolemia.

Pharmacogenomics: Analyzing genetic variants involved in drug metabolism, transport, and targets to guide clinical drug selection and dose adjustment, achieving personalized medication.

Scientific Research: Large-scale cohort studies, exploration of disease molecular mechanisms, and discovery of novel pathogenic genes.

The WES-Routine whole-exome sequencing service, with its comprehensiveness, efficiency, and affordability, has become an indispensable component of modern precision medicine. Like a highly effective "genomic detective," it penetrates the very code of life, providing a powerful scientific tool for solving the mysteries of disease and safeguarding individual health. With the continuous advancement of sequencing technology and the increasing strength of its interpretation capabilities, the WES-Routine will undoubtedly play an even more crucial role in future disease prevention, diagnosis, and treatment.

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