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Saliva-Based Triple-Primed PCR as a Non-Invasive Tool for Detecting NOTCH2NLC GGC Repeat Expansions in NIID
Background:
NOTCH2NLC-related neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disorder caused by abnormal expansions of GGC repeats in the NOTCH2NLC gene. Traditional genetic testing relies on blood samples, which can be invasive. This study investigated the feasibility of using non-invasive saliva samples for detecting GGC repeat expansions in NIID patients.
Methods:
Twenty-four NIID patients and twenty-one controls were enrolled. DNA was extracted from both blood and saliva samples using standard protocols. GGC repeat expansions were detected using triple-primed PCR (TP-PCR), followed by capillary electrophoresis to determine the repeat sizes.
Results:
All NIID patients exhibited characteristic saw-tooth peaks indicative of GGC expansions in both saliva and blood tests, while control samples showed no such patterns. Saliva and blood genetic testing showed compa-rable GGC repeat expansions. Notably, one patient showed inter-tissue discrepancies, suggesting somatic mosaicism.
Conclusions:
Saliva DNA testing offers a reliable, minimally-invasive alternative to blood DNA testing for NIID diagnosis. While tissue-specific mosaicism may cause minor discrepancies, saliva's ease of collection and diagnostic accuracy support its utility in large-scale screening and early intervention strategies.
