Cerebrospinal Fluid TDP-43 in Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis Patients with and without the C9ORF72 Hexanucleotide Expansion

BACKGROUND TDP-43 is the main protein component of ubiquitinated inclusions in a subgroup of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) patients. The C9ORF72 hexanucleotide expansion is one of the main mutations associated with TDP-43 pathology in FTLD and ALS. Our aim was to analyze cerebrospinal fluid (CSF) TDP-43 levels and Alzheimer's disease biomarkers in FTLD and ALS patients and to test whether the C9ORF72 expansion carrier status affects these variables. METHODS The patient cohort consisted of 90 clinically well-characterized FTLD (n = 69) and ALS (n = 21) patients. There were 30 patients with the C9ORF72 expansion and 60 patients without the expansion. CSF TDP-43, AΒ1-42, t-tau, and phospho-tau levels were measured using commercial ELISA kits. RESULTS There was no difference in CSF TDP-43 levels between the C9ORF72 expansion carriers and the noncarriers. CSF TDP-43 levels were higher in ALS patients than in FTLD patients, and this finding was independent of the C9ORF72 expansion carrier status. Males had significantly higher TDP-43 levels than females (p = 0.008 in the total cohort). CONCLUSION CSF TDP-43 does not seem to distinguish the C9ORF72 expansion carriers from noncarriers. However, higher CSF TDP-43 levels were detected in ALS than in FTLD, which might be an indicator of a more rapid progression of TDP-43 pathology in ALS.