TAR syndrome is inherited in an autosomal recessive manner and is due to changes in the gene RBM8A (1q21.1). Compound inheritance of one RBM8A null allele and one RBM8A partial loss-of-function allele cause TAR syndrome. For the majority of individuals with TAR syndrome, the null allele is a total RBM8A gene deletion, as part of a recurring deletion of chromosome 1q21.1 that removes RBM8A as well as several other genes. Two partial loss-of-function RBM8A alleles have been described: a c.-21G>A nucleotide change in the 5’UTR and a c.67+32G>C nucleotide change in the first intron. These two nucleotide changes lower RBM8A transcription in vitro (Albers et al., 2012).
TAR clinical testing requires a comprehensive strategy to detect large deletions and RBM8A sequence variants. The 1q21.1 TAR deletion is mediated by segmental duplications and varies in size from ~200 kilobases (kb) to more than 2 Megabases (Mb); thus, high-resolution array Comparative Genome Hybridization (aCGH) is the most appropriate method to detect 1q21.1 deletions. RBM8A sequence variants are best detected with Sanger sequencing. The comprehensive TAR Syndrome Panel (Test Code: XM060) includes 1q21.1 deletion/duplication analysis by high-resolution aCGH and full RBM8A gene sequence analysis. Comprehensive TAR testing can provide confirmation of a clinical diagnosis and carrier testing for family members. This test is one of the two components of the TAR panel that may be ordered as a stand-alone test (1q21.1 deletion/duplication, test code CC061). Sequencing analysis only for the RBM8A gene is available also (Test Code: MS061).
- Confirmation of a clinical diagnosis of TAR syndrome
- Carrier testing in adults with a family history of TAR syndrome.
Please note that a "backbone" of probes across the entire genome are included on the array for analytical and quality control purposes. Rarely, off-target copy number variants causative of disease may be identified that may or may not be related to the patient's phenotype. Only known pathogenic off-target copy number variants will be reported. Off-target copy number variants of unknown clinical significance will not be reported.
Submit only 1 of the following specimen types
Type: Whole Blood
In EDTA (purple top) AND sodium heparin (green top) tubes:
Infants (Children (>2 years): 3-5 ml in both tubes
Older Children & Adults: 7-10 ml in both tubes
Specimen Collection and Shipping: Ship sample at room temperature for receipt at EGL within 24 hours of collection. Do not refrigerate or freeze.
- Custom diagnostic mutation analysis (Test Code: KM or DKMDD) is available to family members for mutations identified by sequencing.
- TAR Panel - includes RBM8A sequencing and 1q21.1 deletion/duplication testing (Test Code: XM060)
- Full gene sequence analysis of the RBM8A gene is available to test for point mutations and low-frequency SNPs in the 5’UTR and first intron (Test Code: MS061).