New Antibody-Free Mass Spectrometry-Based Quantification Reveals That C9ORF72 Long Protein Isoform Is Reduced in the Frontal Cortex of Hexanucleotide-Repeat Expansion Carriers

Frontotemporal dementia (FTD) is a fatal neurodegenerative disease characterized by behavioral and language disorders. The main genetic cause of FTD is an intronic hexanucleotide repeat expansion (G4C2)n in the C9ORF72 gene. A loss of function of the C9ORF72 protein associated with the allele-specific reduction of C9ORF72 expression is postulated to contribute to the disease pathogenesis. To better understand the contribution of the loss of function to the disease mechanism, we need to determine precisely the level of reduction in C9ORF72 long and short isoforms in brain tissue from patients with C9ORF72 mutations. In this study, we developed a sensitive and robust mass spectrometry (MS) method for quantifying C9ORF72 isoform levels in human brain tissue without requiring antibody or affinity reagent. An optimized workflow based on surfactant-aided protein extraction and pellet digestion was established for optimal recovery of the two isoforms in brain samples. Signature peptides, common or specific to the isoforms, were targeted in brain extracts by multiplex MS through the parallel reaction monitoring mode on a Quadrupole–Orbitrap high resolution mass spectrometer. The assay was successfully validated and subsequently applied to frontal cortex brain samples from a cohort of FTD patients with C9ORF72 mutations and neurologically normal controls without mutations. We showed that the C9ORF72 short isoform in the frontal cortices is below detection threshold in all tested individuals and the C9ORF72 long isoform is significantly decreased in C9ORF72 mutation carriers

Clinicopathological characteristics of ROS1- and RET-rearranged NSCLC in caucasian patients. Data from a cohort of 713 non-squamous NSCLC lacking KRAS/EGFR/HER2/BRAF/PIK3CA/ALK alterations

International audienceTargeted therapies have substantially changed the management of non-small cell lung cancer (NSCLC) patients with driver oncogenes. Given the high frequency, and aberrations were the first to be detected and paved the way for tyrosine kinase inhibitor (TKI) treatments. Other kinases such as and more recently have emerged as promising targets, and ROS1 and RET TKIs are already available for precision medicine. We screened a large cohort of 713 Caucasian non-squamous NSCLC patients lacking ///// aberrations for and rearrangements using fluorescence hybridization to determine the frequency and clinicopathological characteristics of ROS1- and RET-positive patients. Frequencies of and rearrangements were 2.1% and 2.52%, respectively. Contrary to common belief, both and rearrangements were detected in patients with a history of smoking, and the -positive patients were not younger than the negative patients. Moreover, but not rearrangement was associated with the female gender. Nearly half of the -rearranged patients were successfully treated with ROS1 TKIs. In contrast, only 5/18 RET-positive patients received off-label RET TKIs. Two patients had stable disease, and three experienced disease progression. In addition to the 18 RET-positive cases, 10 showed isolated 5' signals. The clinical relevance is unknown but if the frequency is confirmed by other groups, the question whether these patients are eligible to TKIs will arise. More potent RET TKIs are under development and may improve the response rate in RET-positive patients. Therefore, we recommend the routine implementation of RET testing in non-squamous NSCLC patients, including those with a history of smoking

Clinico-pathological and epigenetic heterogeneity of diffuse gliomas with FGFR3::TACC3 fusion

Abstract Background Gliomas with FGFR3::TACC3 fusion mainly occur in adults, display pathological features of glioblastomas (GB) and are usually classified as glioblastoma, IDH-wildtype. However, cases demonstrating pathological features of low-grade glioma (LGG) lead to difficulties in classification and clinical management. We report a series of 8 GB and 14 LGG with FGFR3:TACC3 fusion in order to better characterize them. Methods Centralized pathological examination, search for TERT promoter mutation and DNA-methylation profiling were performed in all cases. Search for prognostic factors was done by the Kaplan–Meir method. Results TERT promoter mutation was recorded in all GB and 6/14 LGG. Among the 7 cases with a methylation score > 0.9 in the classifier (v12.5), 2 were classified as glioblastoma, 4 as ganglioglioma (GG) and 1 as dysembryoplastic neuroepithelial tumor (DNET). t-SNE analysis showed that the 22 cases clustered into three groups: one included 12 cases close to glioblastoma, IDH-wildtype methylation class (MC), 5 cases each clustered with GG or DNET MC but none with PLNTY MC. Unsupervised clustering analysis revealed four groups, two of them being clearly distinct: 5 cases shared age ( 40), pathological features of glioblastoma, and were TERT-mutated. Relevant factors associated with a better prognosis were age < 40 and lack of TERT promoter mutation. Conclusion Among gliomas with FGFR3::TACC3 fusion, age, TERT promoter mutation, pathological features, DNA-methylation profiling and fusion subtype are of interest to determine patients’ risk

Induction of amyloid-β deposits from serially transmitted, histologically silent, Aβ seeds issued from human brains

International audienceIn humans, iatrogenic transmission of cerebral amyloid-β (Aβ)-amyloidosis is suspected following inoculation of pituitary-derived hormones or dural grafts presumably contaminated with Aβ proteins as well as after cerebral surgeries. Experimentally, intracerebral inoculation of brain homogenate extracts containing misfolded Aβ can seed Aβ deposition in transgenic mouse models of amyloidosis or in non-human primates. The transmission of cerebral Aβ is governed by the host and by the inoculated samples. It is critical to better characterize the propensities of different hosts to develop Aβ deposition after contamination by an Aβ-positive sample as well as to better assess which biological samples can transmit this lesion. Aβ precursor protein (huAPP wt) mice express humanized non-mutated forms of Aβ precursor protein and do not spontaneously develop Aβ or amyloid deposits. We found that inoculation of Aβ-positive brain extracts from Alzheimer patients in these mice leads to a sparse Aβ deposition close to the alveus 18 months post-inoculation. However, it does not induce cortical or hippocampal Aβ deposition. Secondary inoculation of apparently amyloid deposit-free hippocampal extracts from these huAPP wt mice to APP swe /PS1 dE9 mouse models of amyloidosis enhanced Aβ deposition in the alveus 9 months post-inoculation. This suggests that Aβ seeds issued from human brain samples can persist in furtive forms in brain tissues while maintaining their ability to foster Aβ deposition in receptive hosts that overexpress endogenous Aβ. This work emphasizes the need for high-level preventive measures, especially in the context of neurosurgery, to prevent the risk of iatrogenic transmission of Aβ lesions from samples with sparse amyloid markers

Pathological changes induced by Alzheimer’s brain inoculation in amyloid-beta plaque-bearing mice

International audienceAbstract Alzheimer's disease (AD) is characterized by intracerebral accumulations of extracellular amyloid-β (Aβ) plaques and intracellular tau pathology that spread in the brain. Three types of tau lesions occur in the form of neuropil threads, neurofibrillary tangles, and neuritic plaques i.e. tau aggregates within neurites surrounding Aβ deposits. The cascade of events linking these lesions and synaptic or memory impairments are still debated. Intracerebral infusion of human AD brain extracts in Aβ plaque-bearing mice that do not overexpress pathological tau proteins induces tau pathologies following heterotopic seeding of mouse tau protein. There is however little information regarding the downstream events including synaptic or cognitive repercussions of tau pathology induction in these models. In the present study, human AD brain extracts (AD be ) and control-brain extracts (Ctrl be ) were infused into the hippocampus of Aβ plaque-bearing APP swe /PS1 dE9 mice. Memory, synaptic density, as well as Aβ plaque and tau aggregate loads, microgliosis, astrogliosis at the inoculation site and in connected regions (perirhinal/entorhinal cortex) were evaluated 4 and 8 months post-inoculation. AD be inoculation produced the following effects: (i) memory deficit; (ii) increased Aβ plaque deposition in proximity to the inoculation site; (iii) tau pathology induction; (iv) appearance of neuropil threads and neurofibrillary tangles next to the inoculation site with a spreading to connected regions. Neuritic plaque pathology was detected in both AD be - and Ctrl be -inoculated animals but AD be inoculation increased the severity close to and at distance of the inoculation site. (v) Finally, AD be inoculation reduced synaptic density in the vicinity to the inoculation site and in connected regions as the perirhinal/entorhinal cortex. Synaptic impairments were correlated with increased severity of neuritic plaques but not to other tau lesions or Aβ lesions, suggesting that neuritic plaques are a culprit for synaptic loss. Synaptic density was also associated with microglial load. Graphical abstrac