CFTR Gene Mutation Analysis

 

HEREDITY HEALTHCARE AND LIFE SCIENCES

Contact us:

Dr.GopalPurohit

Email: gopal.purohit@hdls.in

Contact number: 7381298980

Website:www.heredity.in

 

 Written by: Sweta Yadav

Introduction:

Cystic fibrosis (CF) is an inherited disease that affects mainly the lungs, pancreas, and sweat glands. It leads to the production of thick, sticky mucus and can cause recurrent respiratory infections and impaired function of the pancreas. The CF gene mutation panel detects the common mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7 to screen for or diagnose CF or to identify carriers of the disease.

Cystic fibrosis is caused by a mutation in each of the two copies of the CFTR gene (one copy from each parent). Both copies (alleles) of this gene pair must be abnormal to cause CF. If only one copy is mutated, the individual is a CF carrier. Carriers do not generally have any CF symptoms, but they can pass their abnormal CF gene copy on to their children.

To detect cystic fibrosis (CF) gene mutations; to screen for or help diagnose CF; to determine whether you are a carrier of a CF genetic mutation and to evaluate the risk of having a baby with CF.

A blood sample drawn from an infant’s heel by collecting a spot of blood onto filter paper; for older children or adults, a blood sample obtained by inserting a needle into a vein in the arm; sometimes a scraping of the inner cheek (buccal swab) or, for prenatal testing, amniotic fluid obtained through amniocentesis or a chorionic villus sample.

In a CF gene mutation panel, the laboratory specifically examines the CFTR gene on each chromosome 7 for the 23 mutations. If the initial panel of mutations demonstrates a single mutation, additional testing for other less common mutations may be indicated if the individual is suspected of having CF.

 

   Some important questions:-

 

ü How is the CF mutation panel used?

The CF mutation panel can be used as part of prenatal testing to determine whether prospective parents are carriers of a CF gene mutation and therefore at risk of passing the gene mutation to future children.In a sequential strategy, the mother is usually tested first. If she is not a carrier, then any child she had would, at most, be a carrier from the father’s side. Using this logic, the father is not tested.

A positive result for the mother should include the recommendation of testing her partner and at risk family members.All individuals with positive results for diagnostic tests or partners who are both identified as carriers should receive genetic counseling. In addition, any individuals who have a family history of CF should be referred for genetic counseling.

CF gene mutation testing can also be used for prenatal diagnosis if both parents are known to be carriers. DNA from amniocentesis and chorionic villus sampling procedures, although somewhat invasive, can be used to test the fetus for the mutations that have been identified in the parents.

 

 

ü When is the test ordered?

 

A CF gene mutation panel may be ordered:

·         When you or your partner are planning to become pregnant

·         During the first trimester of pregnancy or the first prenatal visit

·         When someone has a close relative who has been diagnosed with cystic fibrosis

·         For an infant, soon after birth

·         When a person has had a positive CF screening test such as a sweat chloride conductivity test or IRT test

·         When a person has signs and symptoms of CF, such as:

·         Very salty sweat

·         Frequent respiratory infections, such as bronchitis or pneumonia

·         Wheezing, shortness of breath

·         Persistent diarrhea and/or foul-smelling, bulky, greasy stools

·         Delayed growth or poor weight gain (failure to thrive)

·         Vitamin deficiency, malnutrition

·         Infertility in men

 

ü Does this test detect all genetic causes of cystic fibrosis?

 

No. To date, more than 2,000 different mutations of the CFTR gene that cause cystic fibrosis have been identified, but only a few of the mutations are common. Some laboratories use the standard panel recommended by the American College of Medical Genetics and the American College of Obstetricians and Gynecologists that tests for 23 of the most common mutations. Some laboratories offer expanded panels of up to 100 or more mutations. However, even these will not detect all genetic causes of cystic fibrosis.

 

 

References:

Cystic Fibrosis Foundation. Sweat Testing Procedure and Commonly Asked Questions. [On-line information]. Available online at http://www.cff.org/publications01.htm.

Diagnosing and Treating Cystic Fibrosis. American Lung Association. Available online at http://www.lung.org/lung-health-and-diseases/lung-disease-lookup/cystic-fibrosis/diagnosing-and-treating-cf.html. Accessed on 11/12/16.

Lyon, E. et. Al (2016 October Updated). Cystic Fibrosis – CF. ARUP Consult. Available online at https://arupconsult.com/content/cystic-fibrosis. Accessed on 11/12/16.

Sharma, G. (2016 June 8 Updated). Cystic Fibrosis. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/1001602-overview Accessed on 11/12/16.