Frontotemporal Dementia (FTD) - PGRN Gene

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FRONTOTEMPORAL DEMENTIA (FTD) - PGRN GENE

Gene Symbol: PGRN

Chromosomal Locus: 17q21

Protein: Progranulin
 
Pseudonyms: Ubiquitin-positive Frontotemporal Dementia, FTD-PGRN, Granulin, GRN
 
TURNAROUND TIME: 4 weeks
   
TESTING METHODOLOGY:
Polymerase chain reaction (PCR) followed by sequencing all 12 exons (coding and splicing regions) of the PGRN gene.
 
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 regular next day air (No Saturday delivery; store specimen at 4°C 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. However, frontotemporal dementia (FTD) is the second most common form of dementia. 50-70% of FTD is a result of the PGRN gene. In the remainder, (20-50%), the defective gene is MAPT.
 
Inheritance: Autosomal dominant.
 
Disease Characteristics: Behavioral and personality changes leading to cognitive decline, dementia and motor abnormalities. PGRN-related FTD is distinct by the fact that there are ubiquitin-associated inclusions rather than the tau deposits associated with MAPT.
 
Molecular Genetic Mechanism: A variety of mutations have been cited throughout the entire gene.
 
Related Tests: MAPT Complete Gene
 
Clinical Sensitivity: GRN mutations are present in 5-10% of all FTD and in 25% of familial FTD, the assay will detect 90% of those mutations.
 
Analytical Sensitivity: 99%.
 
Test Limitations: Mutations that are not in the coding sequence of the PGRN gene will not be detected. Rare diagnostic errors can occur due to primer / 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 - FTD Lobar Degeneration: www.omim.org/entry/607485
Genetics Home Reference: www.ghr.nlm.nih.gov/gene/GRN