Test Code: 6288

Angelman-like Syndrome: SLC9A6 Gene Deletion/Duplication
Test Code: 6288
Turnaround time: 3 weeks

CONDITION DESCRIPTION

Mutations in the gene SLC9A6 (Xq26.3) lead to an X-linked mental retardation syndrome associated with microcephaly, seizures, ataxia, and absent speech. Many identified patients also display a happy demeanor with frequent smiling and spontaneous laughter reminiscent of Angelman syndrome. Affected individuals appear normal at birth, then display deceleration of head growth in the first year of life and a thin body habitus. Seizures typically begin to occur around 1-2 years of age. Many individuals have a happy demeanor with frequent smiling and episodes of unprovoked laughter. There is an absence of expressive language and profound mental retardation, along with ataxia and eye squint. Other possible features include an open mouth with profuse drooling, swallowing difficulties, hyperkinetic movements, and facial features such as a long, narrow face and pointed jaw. The clinical spectrum of features seems to resemble Angelman syndrome in younger patients and Christianson syndrome in older patients. There appears to be range of carrier phenotypes in carrier females, from mental retardation to absence of symptoms.

The SLC9A6 gene encodes the Na+/H+ exchanger protein NHE6. NHE6 is a membrane protein found in early recycling endosomal membranes and transiently associates with the plasma membrane. It is believed to have a role in regulating the lumen pH, and a consequence of NHE6 inactivity could be lowered endosomal pH and decreased monovalent ion content, both of which might affect protein folding and trafficking. The disruption in recycling endosome trafficking is likely to disturb the growth of dendritic spines during long-term potentiation, which is the process involved in memory and learning. Abnormalities in synaptic development and plasticity have also been shown to be involved in the pathogenesis of Angelman syndrome; UB3A is involved in the intracellular protein-processing apparatus at the level of protein ubiquination.

References:

Gilfillan, G. et al. SLC9A6 Mutaitons Cause X-Linked Mental Retardation, Microcephaly, Epliepsy, and Ataxia, a Phenotype Mimicking Angelman Syndrome. Am J Hum Gen 82:1003-1010, 2008.

GENES
SLC9A6

INDICATIONS
This test is indicated for male individuals with an Angelman-like phenotype who have tested negative for 15q11-13 findings and for MECP2 mutations.

METHODOLOGY

DNA isolated from peripheral blood is hybridized to a CGH array to detect deletions and duplications. The targeted CGH array has overlapping probes which cover the entire genomic region.

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.

DETECTION

Detection is limited to duplications and deletions. Array CGH will not detect point mutations or intronic mutations. Results of molecular analysis must interpreted in the context of the patient’s clinical and/or biochemical phenotype.

SPECIMEN REQUIREMENTS

Submit only 1 of the following specimen types
* Preferred specimen type: Whole Blood

Type: Whole Blood
Specimen Requirements:
In EDTA (purple top) or ACD (yellow top) tube: Infants (2 years): 3-5 ml
Older Children & Adults: 5-10 ml

Specimen Collection and Shipping: Refrigerate until time of shipment. Ship sample within 5 days of collection at room temperature with overnight delivery.

Type: Saliva
Specimen Requirements:
OrageneTM Saliva Collection kit (available through CEN4GEN) used according to manufacturer instructions.

Specimen Collection and Shipping: Store sample at room temperature. Ship sample within 5 days of collection at room temperature with overnight delivery.

SPECIAL INSTRUCTIONS

Sequence analysis is required before deletion/duplication analysis by targeted CGH array. If sequencing is performed by another third party provider, please submit a copy of the sequencing report with the test requisition. Please submit copies of previous test results (i.e. Angelman testing, Rett testing)

RELATED TESTS

• SLC9A6 Full Gene Sequencing (test code: 1072) is also available.
• X-Linked Intellectual Disability panels are available for 30, 60, and 90+ genes.
• Prader-Willi/Angelman Methylation Studies (test code: 2536).
• Rett Syndrome Sequencing of Methyl CpG-Binding Protein (MECP2) Gene (test code: 9801).
• X-Linked Mental Retardation Deletion/Duplication Array CGH.