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Walker-Warburg Syndrome via the B3GNT1(B4GAT1) Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
B4GAT1 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
9053B4GAT181479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

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.


Genetic Counselors


  • Angela Gruber, PhD

Clinical Features and Genetics

Clinical Features

Walker-Warburg syndrome (WWS) is a genetically heterogeneous congenital muscular dystrophy in which many causative genes have been previously identified. Each of these genes is believed to be involved in post translational modification of the sarcolemma-spanning protein alpha dystroglycan (ADG). Loss of function of any of these genes results in hypoglycosylation of ADG and reduced binding of ADG to the basal lamina through laminin (Barresi and Campbell 2006). WWS is the most severe form of ADG-related congenital muscular dystrophy, presenting with profound hypotonia, defective neuronal migration and associated structural brain and eye abnormalities. CNS findings include cobblestone lissencephaly, cerebellar malformations, microophthalmia and cataracts. Patients have profound mental retardation and typically die in the first year of life. Muscle biopsies demonstrate a dystrophic process and markedly reduced or absent staining with antibodies to the glycolepitope of ADG. Mutations in a newly discovered gene, B3GNT1(B4GAT1), have been found to be causative for WWS in two families. Functional studies in human cells and a model system confirmed pathogenicity of two missense variants found in one of the families (Buysse et al. 2013). Unexpectedly, both missense variants were in the homozygous state in affected family members. Clinical features of affected individuals included hypotonia, hydrocephalus, Dandy–Walker malformation, and retinal dysplasia. Serum CpK levels were greatly elevated and brain imaging showed cobblestone lissencepahly. Affected individuals from the second family presented with severe WWS including occipital encephalocele, anencephaly, and agenesis of the optic nerve (Shaheen et al. 2013).


B4GAT1-related congenital muscular dystrophy is inherited as an autosomal recessive disorder. In the first family described, two missense variants of conserved amino acids were found to segregate with disease and parents were shown to be heterozygous for both (Buysse et al. 2013). The second reported family was found to segregate a homozygous truncating mutation (Shaheen et al. 2013). B4GAT1 encodes a transmembrane protein that has a glycosyltransferase domain, although enzymatic activity has not yet been demonstrated. Pathogenic variants in B4GAT1 reported to date include amino acid substitutions and a frame-shifting truncating mutation (http://www.LOVD.nl/B3GNT1).

Clinical Sensitivity - Sequencing with CNV PGxome

Too few cases with confirmed mutations in the B4GAT1 gene have been reported to arrive at an estimate of clinical or analytical sensitivity.

Testing Strategy

This test provides full coverage of all coding exons of the B4GAT1 gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

Individuals with severe cobblestone lissencephaly and other symptoms consistent with Walker-Warburg syndrome. Individuals with immunofluorescence results demonstrating hypoglycosylation of ADG in muscle. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in B4GAT1.


Official Gene Symbol OMIM ID
B4GAT1 605517
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


  • Barresi R, Campbell K. 2006. Dystroglycan: from biosynthesis to pathogenesis of human disease. J. Cell Sci. 119:199-207. PubMed ID: 16410545
  • Buysse K, Riemersma M, Powell G, Reeuwijk J van, Chitayat D, Roscioli T, Kamsteeg E-J, Elzen C van den, Beusekom E van, Blaser S, Babul-Hirji R, Halliday W, et al. 2013. Missense mutations in -1,3-N-acetylglucosaminyltransferase 1 (B3GNT1) cause Walker-Warburg syndrome. Human Molecular Genetics 22: 1746–1754. PubMed ID: 23359570
  • Leiden Open Variations Database.
  • Shaheen R, Faqeih E, Ansari S, Alkuraya FS. 2013. A truncating mutation in B3GNT1 causes severe Walker–Warburg syndrome. neurogenetics. PubMed ID: 23877401


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

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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View Ordering Instructions

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2) Select Additional Test Options

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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