• Test Code:
    1080
  • Department:
    Molecular Genetics
  • Test Synonyms:
    WDR45 full gene sequencingBPAN sequencingNBIA Sequencing
  • CPT Code(s):
    81479
Background:

Mutations in WDR45 are associated with beta-propeller protein-associated neurodegeneration (BPAN), an X-linked form of neurodegeneration with brain iron accumulation (NBIA). Patients with BPAN have characteristic brain MRI results (including T1 hyperintense and T2 hypointense signals in the substantia nigra), along with global developmental delay in childhood, regression in early adulthood, as well as progressive dystonia, parkinsonism and dementia. Additionally, patients with BPAN have similar phenotypic characteristics to individuals diagnosed with atypical Rett syndrome. If Rett specific mutations are not identified in those patients, WDR45 mutational analysis should be considered. All mutations in WDR45 are suspected to arise de-novo, however due to the X-linked nature of the gene females may have germline or somatic mutations while males will have somatic mutations.

Reasons for Referral:

  • Individuals with characteristic BPAN brain MRI results
  • Individuals identified with developmental delay accompanied by seizures and/or disordered sleep
  • Individuals identified with symptoms of atypical Rett syndrome

Methodology:

Sequencing can be performed by either Sanger Sequencing or Next-Generation Sequencing.

Sanger Sequencing: Sequencing of WDR45 is carried out by amplification of all exons and intron/exon boundaries followed by bi-directional Sanger sequencing. The sensitivity of full gene sequencing is estimated to be approximately 99% for single nucleotide substitutions and small insertions/deletions. All nucleotide changes are analyzed within the context of current databases and literature to predict pathogenicity.

NGS: Next generation sequencing will analyze the exons or coding regions of WDR45 using Illumina NextSeq 500 technology. Samples are prepared using hybridization probes to enrich exonic regions. Promoter, intronic, etc. regions are not assessed on our assay, but may contain variants that impact gene function.

Test reporting follows the ACMG Standards & Guidelines for Clinical Genetics Laboratories, Ultra-Rare Disorders Guidelines, and Interpretation of Sequence Variants Guidelines.

Specimen Requirements:

Blood:  EDTA or ACD (Solution A or B):    

    • Adult: 5 mL
    • Child: 5 mL
    • Infant: 2-3 mL

Saliva: 2 ORAgene Saliva Kit(s) (OGR-500)
Skin Fibroblast: Punch Biopsy, or 2 T-25 confluent flasks
Prenatal:

  • Direct Amniotic Fluid (10-20mL)
  • Direct CVS
  • Cultured Amnio or CVS (2-T25 flasks)

DNA: 1-2µg at a minimum of 50-100ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS)

Notice Regarding Molecular Genetic Testing on CVS or Amniotic Fluid Specimens:

  • Maternal cell rule-out testing will be performed on all prenatal specimens received.Please provide maternal blood in addition to the fetal specimen.Additional charges apply for the maternal cell rule-out test.
  • All genetic testing performed on Direct CVS or Direct Amniotic Fluid specimens will be confirmed on cell cultures prepared by Knight Diagnostic Laboratories.Cell cultures will be prepared from the specimen received.Additional charges apply for confirmatory testing.

For routine testing of blood, saliva and buccal swabs, KDL does NOT accept samples from patients within two (2) weeks of a packed cell/platelet transfusion or within four (4) weeks of a whole blood transfusion.  For extraordinary circumstances, where testing must be performed outside of the above windows, please contact our lab.

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES.  Please include detailed clinical information, including ethnicity, clinical history, and family history.

Test Performed (Days):

Weekly

Turn Around Time:

21 days

Shipment Sensitivity Requirements:

  • Package and ship specimen to remain cold, but not frozen. 
  • Ship via overnight express, using the FedEx priority overnight label provided. 
  • Contact Client Services for shipping kits and instructions at (855) 535-1522.

References:

  1. Haack T, et al. Exome sequencing reveals de novo mutations in WDR45 causing a phenotypically distinct, X-linked dominant form of NBIA. 2012. AM J Hum Genet. 2102 Dec 7;91(6):1144-9.
  2. Hayflick S, et al., BPAN: a new X-linked dominant form of neurodegeneration with brain iron accumulation (NBIA). Brain. 2013; 136(Pt6):1708-17.

Additional Info: