AbstractBackgroundTMEM106B is a transmembrane protein involved in dendrite morphogenesis and lysosome trafficking. TMEM106B was identified as a susceptibility gene for frontotemporal lobar degeneration with TDP‐43 inclusions (FTLD‐TDP). Brain tissue from patients with FTLD‐TDP showed increased mRNA levels of TMEM106B compared to normal controls (Van Deerlin et al, Nat Genet 2010). Our goal is to study TMEM106B expression levels in other neurodegenerative conditions such as progressive supranuclear palsy (PSP), Alzheimer’s disease (AD) and a well‐established mouse model of entorhinal cortex lesions (ECL).MethodUnilateral electrolytic lesions to the entorhinal cortex were conducted on two‐to‐three months old male C57BL/6j mice by stereotaxic surgery. For sham‐operated animals, the electrode was lowered only 1 mm without current and sacrifices were performed on the same day. All other lesioned mice were sacrificed 2, 7, 14, 21 or 40 days post‐lesion (DPL). Total RNA was extracted from frozen ipsilateral and contralateral hippocampi and expression profiles were measured with the Affymetrix Mouse ClariomTM D Assay. The Mayo Clinic Brain Bank collected RNA samples from temporal cortex and measured gene expression levels using next‐generation RNA sequencing (RNAseq). Results are available for 274 subjects with the following conditions: PSP, N = 84; AD, N = 82; pathological aging (PA), N = 30; and cognitively unimpaired (CU), N = 78.ResultIn the ECL mouse model, ipsilateral Tmem106b expression levels were significantly reduced during the deafferentation phase (DPL2: p = 0.046) and reached maximum levels during the reinnervation phase (DPL14: p = 0.030 and DPL21: p = 0.019), compared to sham‐operated animals. In human temporal cortices, TMEM106B expression increased progressively from CU (10.76±0.62), to PSP (11.25±0.43), PA (12.13±1.27) and finally AD (13.10±0.44) (mean CPM ±SEM). TMEM106B mRNA levels were significantly higher in AD compared to CU (p = 0.002) and PSP (p = 0.003).ConclusionElevated levels of TMEM106B in FTLD‐TDP, AD and during the reinnervation phase of the ECL mouse model suggest an active response to tissue damage that is consistent with compensatory synaptic and terminal remodeling, independently from tau‐mediated pathology. This hypothesis is consistent with TMEM106B levels found in PSP, which is characterized by abundant neurofibrillary tangles that differ in both distribution and composition from those associated with AD.