Progressive Myoclonic Epilepsy via the GOSR2 Gene
Summary and Pricing 
Test Method
Sequencing and CNV Detection via NextGen Sequencing using PG-Select Capture Probes| Test Code | Test Copy Genes | Test CPT Code | Gene CPT Codes Copy CPT Code | Base Price | |
|---|---|---|---|---|---|
| 4161 | GOSR2 | 81479 | 81479,81479 | $990 | Order Options and Pricing |
Pricing Comments
Testing run on PG-select capture probes includes CNV analysis for the gene(s) on the panel but does not permit the optional add on of exome-wide CNV analysis. Any of the NGS platforms allow reflex to other clinically relevant genes, up to whole exome or whole genome sequencing depending upon the base platform selected for the initial test.
An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.
This test is also offered via a custom panel (click here) on our exome or genome backbone which permits the optional add on of exome-wide CNV or genome-wide SV analysis.
Turnaround Time
3 weeks on average for standard orders or 2 weeks on average for STAT orders.
Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.
Targeted Testing
For ordering sequencing of targeted known variants, go to our Targeted Variants page.
Clinical Features and Genetics
Clinical Features
Progressive myoclonic epilepsy 6 (EPM6) is a neurological disorder characterized by early onset ataxia and myoclonic seizures. The first symptom of EPM6 is ataxia with onset around 2 years of age. Myoclonic seizures begin in early childhood, and patients exhibit multiple seizure types including: generalized tonic clonic seizures, absence seizures, and drop attacks. Seizures are photosensitive and are worsened by psychological stress and physical movement. EEG reveals generalized spike and wave discharges. Ataxia and myoclonus are progressive with patients becoming wheelchair bound in their early teens. Many EPM6 patients have scoliosis or other skeletal abnormalities. In some patients serum levels of creatine kinase are elevated (median 734 IU), but patients have a normal muscle biopsy (Boisse Lomax et al. 2013; van Egmond et al. 2014). Cognition is preserved, and MRI is largely normal; in one case autopsy revealed slight cerebral atrophy (Corbett et al. 2011). Death typically occurs in the 3rd or 4th decade.
Genetics
EPM6 is inherited in an autosomal recessive manner and is caused by mutations in the GOSR2 gene. A founder mutation, c.430G>T (p.Gly144Trp), exists in the Dutch population (Corbett et al. 2011; Boisse Lomax et al. 2013; van Egmond et al. 2014).
The GOSR2 protein is a member of the Qb-SNARE family of vesicle docking proteins. SNARE complexes form on opposing membranes and aid in membrane fusion in the secretory and endosomal pathways (Xu et al. 2000). The p.Gly144Trp variant alters a conserved residue in the Q-SNARE domain of GOSR2. In vitro studies demonstrate that the p.Gly144Trp mutation disrupts localization of GOSR2 to the Golgi (Corbett et al. 2011). Defects in vesicle trafficking and possibly neurotransmitter release may underlie the epilepsy phenotype of the GOSR2 variant.
Clinical Sensitivity - Sequencing with CNV PG-Select
The pathogenic c.430G>T GOSR2 variant was identified in ~7% (12 of 159) and ~11% (5 of 46) of patients with genetically unresolved diagnoses of PME or PMA; many patients homozygous for the c.430G>T variant were of Dutch or German ancestry (Boisse Lomax et al. 2013; van Egmond et al. 2014).
Testing Strategy
This test provides full coverage of all coding exons of the GOSR2 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.
Indications for Test
GOSR2 sequencing should be considered for patients with a diagnosis of progressive myoclonic epilepsy (PME), progressive myoclonic ataxia (PMA), or Ramsay Hunt syndrome, especially if they are of Dutch ancestry (van Egmond et al. 2014). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in GOSR2.
GOSR2 sequencing should be considered for patients with a diagnosis of progressive myoclonic epilepsy (PME), progressive myoclonic ataxia (PMA), or Ramsay Hunt syndrome, especially if they are of Dutch ancestry (van Egmond et al. 2014). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in GOSR2.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| GOSR2 | 604027 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Epilepsy, Progressive Myoclonic 6 | AR | 614018 |
Citations
- Boisse Lomax L, Bayly MA, Hjalgrim H, Moller RS, Vlaar AM, Aaberg KM, Marquardt I, Gandolfo LC, Willemsen M, Kamsteeg E-J, O’Sullivan JD, Korenke GC, et al. 2013. “North Sea” progressive myoclonus epilepsy: phenotype of subjects with GOSR2 mutation. Brain 136: 1146–1154. PubMed ID: 23449775
- Corbett MA, Schwake M, Bahlo M, Dibbens LM, Lin M, Gandolfo LC, Vears DF, O’Sullivan JD, Robertson T, Bayly MA, Gardner AE, Vlaar AM, et al. 2011. A Mutation in the Golgi Qb-SNARE Gene GOSR2 Causes Progressive Myoclonus Epilepsy with Early Ataxia. The American Journal of Human Genetics 88: 657–663. PubMed ID: 21549339
- van Egmond ME, Verschuuren-Bemelmans CC, Nibbeling EA, Elting JWJ, Sival DA, Brouwer OF, Vries JJ de, Kremer HP, Sinke RJ, Tijssen MA, Koning TJ de. 2014. Ramsay Hunt syndrome: clinical characterization of progressive myoclonus ataxia caused by GOSR2 mutation. Mov. Disord. 29: 139–143. PubMed ID: 24458321
- Xu D, Joglekar AP, Williams AL, Hay JC. 2000. Subunit Structure of a Mammalian ER/Golgi SNARE Complex. Journal of Biological Chemistry 275: 39631–39639. PubMed ID: 11035026
Ordering/Specimens
Ordering Options
We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.
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.
- PGnome sequencing panels can be ordered via the myPrevent portal only at this time.
Requisition Form
- A completed requisition form must accompany all specimens.
- Billing information along with specimen and shipping instructions are within the requisition form.
- All testing must be ordered by a qualified healthcare provider.
For Requisition Forms, visit our Forms page
If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.
Specimen Types
Specimen Requirements and Shipping Details
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ORDER OPTIONS
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