Whole Exome Sequencing

What is Whole Exome Sequencing?

Whole exome sequencing (WES) is the process of screening protein coding regions (exons) and their surrounding intronic regions in ~21,000 genes of the human genome and reporting disease-causing changes in these regions.

The coding region represents 2% of the human genome, but contains about 85% of disease-causing mutations. While most genetic tests until recently screened only a single gene or a few genes thought to be associated with disease, WES tests screen thousands of genes simultaneously.

This makes WES one of the most effective methods for identifying complex genetic problems. With whole exome sequence analysis, all exons in the human genome are subjected to sequence analysis and it is of great importance in making a definitive diagnosis of the disease, especially for patients with no clinical diagnosis.

Who should undergo whole exome sequence analysis?

Complex cases that cannot be differentiated with clinical findings,
First-line tests are chromosome analysis or array CGH in cases where the analysis is inconclusive,
Diagnosis of genetically and phenotypically heterogeneous groups of disorders (if the same disease is caused by multiple genes or if the same phenotypic findings are observed in several diseases),
Families who have a sick child and are planning a new pregnancy,
Recurrent history of infants with multiple congenital anomalies and cases without reliable clinical information,
If there is no clinic compatible with a specific single gene disease, exome sequencing is recommended for families.

What percentage of patients presenting with whole exome sequencing (WES) can we diagnose?

In 2018 studies*, it was reported that the diagnostic success of whole exome sequencing analysis was 34% in trio analysis (mother-father-child) and 26% in single analysis. This rate varies depending on the type of disease being studied, whether trio analysis is used or not, and the inheritance pattern of the selected disease.

*Nick Dragojlovic et al. GENETICS in MEDICINE,2018

What are the Limitations of Whole Exome Sequencing?

One of the issues to be considered in sample selection for exome sequencing is the expected mutation type as well as the inheritance pattern of the disease. Large translocations, copy number changes, mitochondrial genome mutations, epigenetic factors, mosaic mutations, uniparental dizomy, GC-rich region repeats, nucleotide repeat diseases and mutations expected in genes with very similar pseudogenes cannot be detected by exome sequencing. For copy number variations, special bioinformatics interfaces or algorithms can be used.

Why Should I Have Whole Exome Sequencing Analysis Performed at Private Ankara Genetic Diseases Diagnosis Center?

Report Format Easily Understandable by Clinicians,
Fast and Reliable Result,
Affordable Cost,
Powerful Bioinformatics,
We report the incidental mutations we found in 59 genes belonging to 26 diseases that are recommended to be reported by ACMG (American College of Medical Genetics and Genomics),
A center licensed by the Ministry of Health and regularly inspected.

Triple (Trio) or Single Whole Exome Sequencing Analysis, Which Test Should I Have?

Trio analysis has a much higher diagnosis rate than single whole exome sequencing analysis (approximately 34% vs. 26%). This is due to the possibility to analyze according to inheritance pattern (autosomal recessive, autosomal dominant, X-linked inheritance) in trio analysis. In addition, in order to identify de novo mutations, a trio analysis including mother-father-child samples is required. However, single whole exome sequencing analysis is recommended for patients who cannot have trio analysis for economic reasons or in cases where the clinical diagnosis is very strong.

I want to have WES performed on my patient, what should I do?

The patient is referred to the Private Ankara Genetic Diseases Diagnostic Center. Here, a detailed clinical history is taken by genetic specialists and the patient's physical examination and dysmorphic examination findings are recorded. A family tree including at least 3 generations of the family is drawn. Patient consent for the test to be performed and a blood sample for the test is taken.

If the patient is unable to come to our center;

Detailed patient consent is obtained for the whole exome sequencing procedure.
Clinical history, physical examination findings and 3-generation pedigree of the patient are drawn. It must be stated whether there is another individual with similar findings in the family and whether there is kinship between the parents.
The patient's blood sample taken in 2 EDTA tubes, patient consent and clinical information are delivered to my center as soon as possible.

What is the Procedure Flow in Whole Exome Sequencing?

Peripheral venous blood sample of the patient is taken.
DNA isolation is performed from the blood sample
The samples are sequenced with the Next Generation DNA Sequencing Device.
The patient's data are subjected to biopharmaceutical analysis and responsible mutations are identified.
A clinical report of the patient is prepared by geneticists and the patient's

WES Testi Neden Yapılır?

WES Testi, genetik hastalıkların teşhisinde önemli bir araçtır çünkü genetik hastalıklara neden olan çok sayıda geni aynı anda analiz edebilir. Bu, genetik hastalıkların teşhisini hızlandırabilir ve daha önce teşhis edilemeyen hastalar için yanıtlar sağlayabilir.

WES Testi Ankara

Özel Ankara Genetik Laboratuvarı, WES teknolojisi ile genetik hastalıkların teşhisinde öncü bir rol oynar. Laboratuvarımız, genetik testlerin doğru ve zamanında yapılmasını sağlayarak, hastaların ve ailelerinin gereksiz stres ve belirsizlikten kaçınmalarına yardımcı olur. Ayrıca, laboratuvarımızın genetik danışmanları, test sonuçlarını anlamak ve ne anlama geldiğini öğrenmek için hastalar ve aileleriyle birlikte çalışır.

Gen havuzumuz, genetik çeşitliliğimizin bir göstergesidir ve genetik hastalıkların teşhisi ve tedavisinde önemli olmaktadır. Gen havuzumuz, genetik hastalıkların teşhisinde kullanılan genetik testlerin doğruluğunu ve etkinliğini belirler. WES, gen havuzumuzdaki genetik çeşitliliği analiz ederek, genetik hastalıkların teşhisi ve tedavisinde önemli bir araç olabilir.

Laboratuvarımız, hızlı ve kaliteli genetik test sonuçları sağlayarak, hastaların ve ailelerinin gereksiz stres ve belirsizlikten kaçınmalarına yardımcı olur. Her zaman en güncel ve doğru bilgi için bir sağlık profesyoneli ile görüşmek en iyisidir.

Tüm Egzom Sekanslama (Whole Exome Sequencing - WES),genetik bilgilerimizin büyük bir bölümünü içeren 20.000'den fazla genin (ve bunların çok sayıda eksonlarının) genetik bilgilerini tek bir testte inceleyebilir. Bu, genetik hastalıkların teşhisinde önemli bir araçtır çünkü genetik hastalıklara neden olan çok sayıda geni aynı anda analiz edebilir.

Örnek türü olarak genellikle kan örneği kullanılır. Ancak bazı durumlarda, özellikle prenatal testlerde, amniyotik sıvı veya koryon villus örneği gibi diğer örnek türleri de kullanılabilir.

Wes Testi Sonucu

WES Testi sonuçların alınması genellikle 6-10 hafta (2-3 ay) içinde verilmektedir. Bu süre, laboratuvarın iş yüküne, testin karmaşıklığına ve diğer faktörlere bağlı olarak değişebilir. Ancak genel olarak, WES sonuçlarının alınması genellikle 1.5 ila 2 ay arasında sürer.