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- Jewish Heritage Test
Detect the presence of the R12L mutation (also called R73L) in the TMEM216 gene.
Polymerase chain reaction (PCR) and primer extension
Joubert syndrome type II (JBTS2, OMIM 608091) is an inherited, autosomal recessive early-onset disorder characterized by the absence or underdeveloped cerebellar vermis-an area of the brain that controls balance and coördination. This "molar tooth sign" can be seen on midbrain MRI. Common clinical findings in infants are abnormal rapid breathing, hypotonia, oculomotor apraxia/nystagmus, mental retardation, and an inability to coordinate voluntary muscle movements. Other findings include polydactyly, low-set ears, small genitalia, high-arched palate, and hepatic fibrosis. The disease has an elevated prevalence in the Ashkenazi Jewish population, with a carrier rate of 1 in 92. When both parents are carriers of JBTS2, there is a 25% chance with each pregnancy of having a child with the disease. Prenatal diagnosis is available.
Molecular genetic testing for JBTS2 encompasses one mutation in the TMEM216 gene (11q13). Testing for the R12L (also called R73L) mutation identifies approximately greater than 99% of JBTS2 carriers in the Ashkenazi Jewish population. The carrier frequency in the non-Ashkenazi Jewish population has not been determined. A negative result decreases the likelihood that this person is a carrier but cannot completely eliminate the possibility. The presence of a rare mutation cannot be ruled out. DNA test results must be combined with the clinical information for the most accurate interpretation.
Whole blood, amniotic fluid, chorionic villus sample (CVS) (Submission of maternal blood is required for fetal testing.), or LabCorp buccal swab kit (Buccal swab collection kit contains instructions for use of a buccal swab.)
7 mL whole blood, 10 mL amniotic fluid, 20 mg CVS, or LabCorp buccal swab kit
3 mL whole blood, 5 mL amniotic fluid, 10 mg CVS, or two buccal swabs
Maintain specimen at room temperature or refrigerate at 4°C
Causes for Rejection
Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab