Autosomal Dominant Nocturnal Frontal Lobe Epilepsy via the CHRNB2 Gene
- Summary and Pricing
- Clinical Features and Genetics
|Test Code||Test||Individual Gene Price||CPT Code Copy CPT Codes|
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The great majority of tests are completed within 18 days.
CHRNB2 encodes a neuronally expressed beta-subunit of the nicotinic acetylcholine receptor (nAChR). The nAChRs belong to a super-family of ligand-gated ion channels. All of the reported ADNFLE-associated CHRNB2 variants are missense mutations and most are located within the transmembrane domain of the receptor. Highly conserved residues within the transmembrane domain dictate the ligand-specificity and activity of the receptor. Reported mutations in CHRNB2 are gain of function mutations, resulting in an increased sensitivity of neuronal nAChRs to the agonist acetylcholine (Phillips et al. Am J Hum Genet. 68(1):225-231, 2001). It is hypothesized that increased nAchR activity underlies the epilepsy phenotype associated with CHRNB2 mutations.
Indications for Test
|Official Gene Symbol||OMIM ID|
|Autosomal Dominant Nocturnal Frontal Lobe Epilepsy via the CHRNA4 Gene|
|Familial Focal Epilepsy with Variable Foci via the DEPDC5 Gene|
- Genetic Counselor Team - email@example.com
- Li Fan, MD, PhD, FCCMG, FACMG - firstname.lastname@example.org
- Kurahashi H, Hirose S. 2012. Autosomal Dominant Nocturnal Frontal Lobe Epilepsy. In: Pagon RA, Adam MP, Ardinger HH, Bird TD, Dolan CR, Fong C-T, Smith RJ, and Stephens K, editors. GeneReviews(®), Seattle (WA): University of Washington, Seattle. PubMed ID: 20301348
- Ottman R. et al. 2010. Epilepsia 51:655-70. PubMed ID: 20100225
- Phillips HA, Favre I, Kirkpatrick M, Zuberi SM, Goudie D, Heron SE, Scheffer IE, Sutherland GR, Berkovic SF, Bertrand D. 2001. CHRNB2 Is the Second Acetylcholine Receptor Subunit Associated with Autosomal Dominant Nocturnal Frontal Lobe Epilepsy. The American Journal of Human Genetics 68: 225–231. PubMed ID: 11104662
- Steinlein, O.K. et al. (2012). "Mutations in familial nocturnal frontal lobe epilepsy might be associated with distinct neurological phenotypes." Seizure 21(2):118:123. PubMed ID: 22036597
Bi-Directional Sanger Sequencing
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.
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).
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.
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.
- 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.
(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.
(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.
(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.