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.
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).
Amniotic Fluid: 10 ml in conical tube
Cultured Cells: two confluent T-25 flasks
Additionally, please send:
5-10 ml paternal blood in EDTA (lavender top) in case paternal confirmation studies are necessary
Forms and Brochures
Carrier Screening Requisition and Consent [PDF]
Expanded Ashkenazi Jewish Carrier Screening Brochure [PDF]
Ashkenazi Jewish Carrier Screening Panel