Cerebrospinal fluid liquid biopsy for detecting somatic mosaicism in brain

Zimeng Ye, Zac Chatterton, Jahnvi Pflueger, John A Damiano, Lara McQuillan, Anthony Simon Harvey, Stephen Malone, Hongdo Do, Wirginia Maixner, Amy Schneider, Bernadette Nolan, Martin Wood, Wei Shern Lee, Greta Gillies, Kate Pope, Michael Wilson, Paul J Lockhart, Alexander Dobrovic, Ingrid E Scheffer, Melanie BahloRichard J Leventer, Ryan Lister, Samuel F Berkovic, Michael S Hildebrand

Research output: Contribution to journalArticle

Abstract

Brain somatic mutations are an increasingly recognized cause of epilepsy, brain malformations and autism spectrum disorders and may be a hidden cause of other neurodevelopmental and neurodegenerative disorders. At present, brain mosaicism can be detected only in the rare situations of autopsy or brain biopsy. Liquid biopsy using cell-free DNA derived from cerebrospinal fluid has detected somatic mutations in malignant brain tumours. Here, we asked if cerebrospinal fluid liquid biopsy can be used to detect somatic mosaicism in non-malignant brain diseases. First, we reliably quantified cerebrospinal fluid cell-free DNA in 28 patients with focal epilepsy and 28 controls using droplet digital PCR. Then, in three patients we identified somatic mutations in cerebrospinal fluid: in one patient with subcortical band heterotopia the LIS1 p. Lys64* variant at 9.4% frequency; in a second patient with focal cortical dysplasia the TSC1 p. Phe581His*6 variant at 7.8% frequency; and in a third patient with ganglioglioma the BRAF p. Val600Glu variant at 3.2% frequency. To determine if cerebrospinal fluid cell-free DNA was brain-derived, whole-genome bisulphite sequencing was performed and brain-specific DNA methylation patterns were found to be significantly enriched (P = 0.03). Our proof of principle study shows that cerebrospinal fluid liquid biopsy is valuable in investigating mosaic neurological disorders where brain tissue is unavailable.

Original languageEnglish
Article numberfcaa235
JournalBrain communications
Volume3
Issue number1
DOIs
Publication statusPublished - 2021

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