Icahn School of Medicine at Mount Sinai
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Genetic Testing Lab

Test Catalog Molecular Genetics Laboratory Joubert Syndrome

Joubert Syndrome

Test Description:
Joubert syndrome (JBTS) is an autosomal recessive set of disorders characterized by a specific midhindbrain malformation, hypotonia, cerebellar ataxia, and developmental delay. The most prominent characteristic of JBTS is the molar tooth sign in brain MRIs: deep interpeduncular fossa, thick, elongated superior cerebellar peduncles and cerebellar vermis hypoplasia. In the Ashkenazi Jewish population, a founder mutation p.R12L in the gene TMEM216 was identified for JBTS Type 2. The carrier frequency for this mutation in the Ashkenazi Jewish population is estimated to be 1 in 110. Since this is the only mutation reported for JBTS2 in this population, the carrier detection rate is estimated to be at least 95%. Carrier screening for JBTS2 may be considered for individuals of Eastern European (Ashkenazi) Jewish ancestry before or during pregnancy.

Full gene sequencing is available for reproductive partners of known mutation carriers. Prenatal diagnosis is also available. Prior to ordering prenatal testing, please contact our laboratory at 212-241-7518 to discuss.

References:
1. Edvardson, S. et al. Joubert syndrome 2 (JBTS2) in Ashkenazi Jews is associated with a TMEM216 mutation. Am J Hum Genet 86, 93-7 (2010).
2. Keeler, L.C. et al. Linkage analysis in families with Joubert syndrome plus oculo-renal involvement identifies the CORS2 locus on chromosome 11p12-q13.3. Am J Hum Genet 73, 656-62 (2003).

Specimen Requirements:
Post-natal
: Two 5-10 mL tubes of anticoagulated blood in EDTA (lavender top) or two 5-10 mL tubes of anticoagulated blood in ACD (yellow top).

Prenatal: 

  • Chorionic Villi: 5-10 mg in conical tube with sterile saline OR transport media
  • Amniotic Fluid: 10 ml in conical tube
  • Cultured Cells: two confluent T-25 flasks

Additionally, please send:

  • 5-10 ml maternal blood in EDTA (lavender top) required to perform MCC studies on all prenatal samples and in case maternal confirmation studies are necessary
  • 5-10 ml paternal blood in EDTA (lavender top) in case paternal confirmation studies are necessary

Shipping: Send at room temperature.

Turnaround Time: 10-14 days

CPT Code: 81400

Consent and Requisition Forms: Carrier Screening Requisition and Consent [PDF]

Additional Information: Expanded Ashkenazi Jewish Carrier Screening Brochure [PDF]

Related Tests: Ashkenazi Jewish Carrier Test Panel

Prior to ordering prenatal testing, please contact our laboratory at 212-241-7518 to discuss.