Early Infantile Epileptic Encephalopathy-15 and Intellectual Disability via the ST3GAL3 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 | |
|---|---|---|---|---|---|
| 4253 | ST3GAL3 | 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
Early infantile epileptic encephalopathy-15 (EIEE15) is an infantile onset disorder defined by seizures and intellectual disability. Seizures present at around 6 months of age usually as spasms involving the limbs (Edvardson et al. 2013). EEG recording reveals hypsarrhythmia (Edvardson et al. 2013). Seizures may worsen with age and progress to Lennox-Gastout or West syndromes. Developmental delay is noted during infancy and precedes seizure onset; no significant developmental regression has been reported. Intellectual disability in EIEE15 patients ranges from mild to profound (Edvardson et al. 2013; Hu et al. 2011). Metabolic tests, cerebral spinal fluid assays, skin biopsy, and MRI were all normal in EIEE15 patients.
Genetics
EIEE15 is inherited in an autosomal recessive manner and is caused by variants in the ST3GAL3 gene. All reported pathogenic ST3GAL3 variants are missense variants (Edvardson et al. 2013; Hu et al. 2011). The ST3GAL3 gene encodes the beta-galactoside-alpha2,3- sialyltransferase-III protein. ST3GAL3 transfers sialic acid epitopes to glycoproteins. Normally, ST3GAL3 is localized to the Golgi where it modifies target proteins. In vitro experiments studying pathogenic ST3GAL3 variants demonstrated that mutant ST3GAL3 localization is restricted to the endoplasmic reticulum (ER), suggesting that ST3GAL3 is spatially separated from its protein targets in these patients (Hu et al. 2011). Another in vitro study showed loss of ST3GAL3 enzyme function as a result of a mutation within the active site (Edvardson et al. 2013). Reduced or absent ST3GAL3-mediated sialylation in the brain is believed to underlie the phenotype of EIEE15 patients.
Clinical Sensitivity - Sequencing with CNV PG-Select
No large scale sequencing studies have been conducted to determine the frequency of ST3GAL3 variants in patients with epilepsy or intellectual disability. Analytical sensitivity should be high because all mutations reported are detectable by sequencing.
Testing Strategy
This test provides full coverage of all coding exons of the ST3GAL3 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.
Indications for Test
ST3GAL3 testing should be considered in patients with EIEE15 or non-syndromic intellectual disability with suspected autosomal recessive inheritance. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in ST3GAL3.
ST3GAL3 testing should be considered in patients with EIEE15 or non-syndromic intellectual disability with suspected autosomal recessive inheritance. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in ST3GAL3.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| ST3GAL3 | 606494 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Diseases
| Name | Inheritance | OMIM ID |
|---|---|---|
| Epileptic Encephalopathy, Early Infantile, 15 | AR | 615006 |
| Mental Retardation, Autosomal Recessive 12 | AR | 611090 |
Citations
- Edvardson S, Baumann A-M, Mühlenhoff M, Stephan O, Kuss AW, Shaag A, He L, Zenvirt S, Tanzi R, Gerardy-Schahn R, Elpeleg O. 2013. West syndrome caused by ST3Gal-III deficiency: ST3GAL3 Mutation Causes West Syndrome. Epilepsia 54: e24–e27. PubMed ID: 23252400
- Hu H, Eggers K, Chen W, Garshasbi M, Motazacker MM, Wrogemann K, Kahrizi K, Tzschach A, Hosseini M, Bahman I, Hucho T, Mühlenhoff M, et al. 2011. ST3GAL3 Mutations Impair the Development of Higher Cognitive Functions. The American Journal of Human Genetics 89: 407–414. PubMed ID: 21907012
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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2) Select Additional Test Options
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