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Atrial Fibrillation Syndrome via the NPPA Gene

  • Summary and Pricing
  • Clinical Features and Genetics
  • Citations
  • Methods
  • Ordering/Specimens
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TEST METHODS

Sequencing

Test Code TestIndividual Gene PriceCPT Code Copy CPT Codes
2201 NPPA$490.00 81479 Add to Order
Targeted Testing

For ordering targeted known variants, please proceed to our Targeted Variants landing page.

Turnaround Time

The great majority of tests are completed within 18 days.

Clinical Sensitivity

Precise estimates of clinical sensitivity are not available because only a limited number of patients have been reported. Pathogenic NPPA variants, however, appear to be a rare cause of familial atrial fibrillation.

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Clinical Features

Atrial fibrillation is a disorder characterized by an abnormal and often rapid heart rhythm. This condition involves uncoordinated electrical activity in the atria, “irregularly irregular” pattern in ECG and supraventricular tachyarrhythmia, which deteriorates atrial mechanical function. If untreated, atrial fibrillation can lead to a reduction in cardiac output, atrial thrombus formation and increased risk for mortality. Patients with atrial fibrillation can present with dizziness, chest pain, palpitations, shortness of breath, or even syncope (Fuster et al. 2011). Complications of atrial fibrillation can occur at any age, and some people may never experience any health problems. The likelihood of developing arrhythmias increases with age. Atrial fibrillation can be prevented and treated (Van Wagoner et al. 2015).

Genetics

Atrial fibrillation is the most common cardiac arrhythmia disorder, and currently affects nearly 3 million Americans (Naccarelli et al. 2009). Although the incidence of the familial form of atrial fibrillation is unknown, having a family member with atrial fibrillation is associated with a 40% increased risk for the disorder (Lubitz et al. 2010).

Familial atrial fibrillation is a highly heterogeneous disease and is transmitted in an autosomal dominant pattern. There are at least 15 genes associated with familial atrial fibrillation: ABCC9, GJA5, KCNA5, KCND3, KCNE1, KCNE1L, KCNE2, KCNH2, KCNJ2, KCNQ1, NPPA, SCN1B, SCN2B, SCN3B and SCN5A. The majority of genes associated with atrial fibrillation are components of two important ion channels: potassium and sodium. Both loss and gain of function variants can affect the current of the ion channels and change the atrial action potential and refraction period (Tucker et al. 2014). 

Pathogenic variants in NPPA cause familial atrial fibrillation-6 (ATFB6). The Natriuretic Peptide Precursor A (NPPA) gene contains three exons (151 amino acids), encodes the precursor of atrial natriuretic peptide (ANP), and is located at Chr 1p36.21. ANP is a circulating hormone which plays a primary physiological role in the regulation of intravascular blood volume and vascular tone through ANP–cGMP signaling pathway (Vesely et al. 1998). Genetic variants in NPPA could increase the concentration of ANP and shortened atrial action potentials, which potentially enhances susceptibility to atrial fibrillation (Hodgson-Zingman et al. 2008). Most reported variants in NPPA are missense or nonsense variants.

Testing Strategy

NPPA is located on chromosome 1p36.21. Testing involves PCR amplification from genomic DNA and bidirectional Sanger sequencing of the single coding exon and ~20 bp of adjacent noncoding sequences. We will also sequence any single exon (Test #100) in family members of patients with a known mutation or to confirm research results.

Indications for Test

All patients with symptoms suggestive of familial atrial fibrillation are candidates for this test.

Gene

Official Gene Symbol OMIM ID
NPPA 108780
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Atrial Fibrillation, Familial, 6 AD 612201

Related Tests

Name
Comprehensive Cardiac Arrhythmia Sequencing Panel
Familial Atrial Fibrillation Syndrome Sequencing Panel

CONTACTS

Genetic Counselors
Geneticist
Citations
  • Fuster V. et al. 2011. Circulation. 123: e269-367. PubMed ID: 21382897
  • Hodgson-Zingman D.M. et al. 2008. The New England Journal of Medicine. 359: 158-65. PubMed ID: 18614783
  • Lubitz S.A. et al. 2010. Jama. 304: 2263-9. PubMed ID: 21076174
  • Naccarelli G.V. et al. 2009. The American Journal of Cardiology. 104: 1534-9. PubMed ID: 19932788
  • Tucker N.R., Ellinor P.T. 2014. Circulation Research. 114: 1469-82. PubMed ID: 24763465
  • Van Wagoner D.R. et al. 2015. Heart Rhythm  12: e5-e29. PubMed ID: 25460864
  • Vesely D.L. et al. 1998. Circulation. 98: 323-9. PubMed ID: 9711937
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TEST METHODS

Bi-Directional Sanger Sequencing

Test Procedure

Nomenclature for sequence variants was from the Human Genome Variation Society (http://www.hgvs.org).  As required, DNA is extracted from the patient specimen.  PCR is used to amplify the indicated exons plus additional flanking non-coding sequence.  After cleaning of the PCR products, cycle sequencing is carried out using the ABI Big Dye Terminator v.3.0 kit.  Products are resolved by electrophoresis on an ABI 3730xl capillary sequencer.  In most cases, sequencing is performed in both forward and reverse directions; in some cases, sequencing is performed twice in either the forward or reverse directions.  In nearly all cases, the full coding region of each exon as well as 20 bases of non-coding DNA flanking the exon are sequenced.

Analytical Validity

As of March 2016, we compared 17.37 Mb of Sanger DNA sequence generated at PreventionGenetics to NextGen sequence generated in other labs. We detected only 4 errors in our Sanger sequences, and these were all due to allele dropout during PCR. For Proficiency Testing, both external and internal, in the 12 years of our lab operation we have Sanger sequenced roughly 8,800 PCR amplicons. Only one error has been identified, and this was due to sequence analysis error.

Our Sanger sequencing is capable of detecting virtually all nucleotide substitutions within the PCR amplicons. Similarly, we detect essentially all heterozygous or homozygous deletions within the amplicons. Homozygous deletions which overlap one or more PCR primer annealing sites are detectable as PCR failure. Heterozygous deletions which overlap one or more PCR primer annealing sites are usually not detected (see Analytical Limitations). All heterozygous insertions within the amplicons up to about 100 nucleotides in length appear to be detectable. Larger heterozygous insertions may not be detected. All homozygous insertions within the amplicons up to about 300 nucleotides in length appear to be detectable. Larger homozygous insertions may masquerade as homozygous deletions (PCR failure).

Analytical Limitations

In exons where our sequencing did not reveal any variation between the two alleles, we cannot be certain that we were able to PCR amplify both of the patient’s alleles. Occasionally, a patient may carry an allele which does not amplify, due for example to a deletion or a large insertion. In these cases, the report contains no information about the second allele.

Similarly, our sequencing tests have almost no power to detect duplications, triplications, etc. of the gene sequences.

In most cases, only the indicated exons and roughly 20 bp of flanking non-coding sequence on each side are analyzed. Test reports contain little or no information about other portions of the gene, including many regulatory regions.

In nearly all cases, we are unable to determine the phase of sequence variants. In particular, when we find two likely causative mutations for recessive disorders, we cannot be certain that the mutations are on different alleles.

Our ability to detect minor sequence variants, due for example to somatic mosaicism is limited. Sequence variants that are present in less than 50% of the patient’s nucleated cells may not be detected.

Runs of mononucleotide repeats (eg (A)n or (T)n) with n >8 in the reference sequence are generally not analyzed because of strand slippage during PCR and cycle sequencing.

Unless otherwise indicated, the sequence data that we report are based on DNA isolated from a specific tissue (usually leukocytes). Test reports contain no information about gene sequences in other tissues.

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Ordering Options


myPrevent - Online Ordering
  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
REQUISITION FORM
  • The first four pages of the requisition form must accompany all specimens.
  • Billing information is on the third and fourth pages.
  • Specimen and shipping instructions are listed on the fifth and sixth pages.
  • All testing must be ordered by a qualified healthcare provider.

SPECIMEN TYPES
WHOLE BLOOD

(Delivery accepted Monday - Saturday)

  • Collect 3-5 ml (5 ml preferred) of whole blood in EDTA (purple top tube) or ACD (yellow top tube). For Test #500-DNA Banking only, collect 10-20 ml of whole blood.
  • For small babies, we require a minimum of 1 ml of blood.
  • Only one blood tube is required for multiple tests.
  • Ship blood tubes at room temperature in an insulated container. Do not freeze blood.
  • During hot weather, include a frozen ice pack in the shipping container. Place a paper towel or other thin material between the ice pack and the blood tube.
  • In cold weather, include an unfrozen ice pack in the shipping container as insulation.
  • At room temperature, blood specimen is good for up to 48 hours.
  • If refrigerated, blood specimen is good for up to one week.
  • Label the tube with the patient name, date of birth and/or ID number.

DNA

(Delivery accepted Monday - Saturday)

  • NextGen Sequencing Tests: Send in screw cap tube at least 10 µg of purified DNA at a concentration of at least 50 µg/ml
  • Sanger Sequencing Tests: Send in a screw cap tube at least 15 µg of purified DNA at a concentration of at least 20 µg/ml. For tests involving the sequencing of more than three genes, send an additional 5 µg DNA per gene. DNA may be shipped at room temperature.
  • Deletion/Duplication via aCGH: Send in screw cap tube at least 1 µg of purified DNA at a concentration of at least 100 µg/ml.
  • Whole-Genome Chromosomal Microarray: Collect at least 5 µg of DNA in TE (10 mM Tris-cl pH 8.0, 1mM EDTA), dissolved in 200 µl at a concentration of at least 100 ng/ul (indicate concentration on tube label). DNA extracted using a column-based method (Qiagen) or bead-based technology is preferred.

CELL CULTURE

(Delivery accepted Monday - Thursday)

  • PreventionGenetics should be notified in advance of arrival of a cell culture.
  • Ship at least two T25 flasks of confluent cells.
  • Label the flasks with the patient name, date of birth, and/or ID number.
  • We do not culture cells.