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Frontotemporal Dementia (FTDP) - MAPT Gene, Exon 10 Only

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Gene Symbol: MAPT   
                                  
Chromosomal Locus: 17q21
 
Protein: Microtubule-Associated Protein Tau  
    
Pseudonyms:  Frontotemporal Dementia with Parkinsonism, Pick disease, FTDP-17,Tauopathy  
   
TURNAROUND TIME:  10 days
  
TESTING METHODOLOGY:    Polymerase chain reaction (PCR) of the MAPT gene followed by sequencing of exon 10 and surrounding intron region, including IVS9 – 10G>T and IVS10 + 29G>A mutations.
 
SPECIMEN REQUIREMENTS:
  • Collect:Prefer two 5ml whole blood EDTA (lavender top) tube. 
  • Min. Collection: 0.7 ml whole blood EDTA.
  • Transport: blood EDTA at Room Temp shipped next day air (No Sat. delivery; store specimen refrigerated and ship Monday).
  • Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
  • Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.        
  • Prenatal testing:Direct: 5ml direct unspun amniotic fluid or 15mg CVS tissue with a backup flask growing. Culture: confluent T25 flask.  Maternal blood sample is required for maternal cell contamination studies.

A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.

Note: Counseling and informed consent are recommended for genetic testing. A consent form is available as a resource but not required.
 
INTERPRETATIVE DATA:
 
Incidence: Unknown.
 
Inheritance: Autosomal dominant.
 
Disease Characteristics: FTDP-17 features include behavioral and personality changes, cognitive decline, dementia and motor abnormalities. MAPT-related FTD is distinct because of tau deposits in the brain and is distinct from GRN gene-related FTDP which results in ubiquitin-associated inclusions in the brain.
 
Molecular Genetic Mechanism:  A variety of mutations have been described throughout the gene.  However, the exon 10 and surrounding intron region is considered a hotspot with an incidence of about 60% of the mutations. Therefore this abbreviated test was designed to examine this region only.
 
PGRN gene

Clinical Sensitivity:  20 - 30% of individuals with a family history of FTDP will have a mutation in the MAPT gene; 60% of those mutations are found in exon 10.
 
Analytical Sensitivity: 99%
 
Test Limitations: Deletions of entire exons or the entire gene are not detected.  Mutations that are not in the coding sequence of the gene will not be detected. Rare diagnostic errors can occur due to primer or probe site mutations or rare polymorphisms.
 
INDICATIONS FOR USE: 
  • To confirm the nature of the dementia in an affected individual and determine inheritance risks.
  • Presymptomatic testing for a known familial mutation.
ADDITIONAL RESOURCES:
OMIM- Frontotemporal Dementia: http://omim.org/entry/600274