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Chambers, A.

Publications and source records attributed to Chambers, A..

2 recordsLinked to original sources
bioRxiv2022

High-Field Asymmetric Waveform Ion Mobility Spectrometry and Parallel Reaction Monitoring Increases Sensitivity for Clinical Biomarker Quantitation from Formalin-Fixed, Paraffin-Embedded Tumor Biopsies

Mass spectrometry-based targeted proteomics allows objective protein quantitation of clinical biomarkers from a single section of formalin-fixed, paraffin-embedded (FFPE) tumor tissue biopsies. We combined high-field asymmetric waveform ion mobility spectrometry (FAIMS) and parallel reaction monitoring (PRM) to increase assay sensitivity. The modular nature of the FAIMS source allowed direct comparison of the performance of FAIMS-PRM to PRM. Limits of quantitation were determined by spiking synthetic peptides into a human spleen matrix. In addition, 20 clinical samples were analyzed using FAIMS-PRM and the quantitation of HER2 was compared with that obtained with the Ventana immunohistochemistry assay. FAIMS-PRM improved the overall signal-to-noise ratio over that from PRM and increased assay sensitivity in FFPE tissue analysis for four (HER2, EGFR, cMET, and KRAS) of five proteins of clinical interest. FAIMS-PRM enabled sensitive quantitation of basal HER2 expression in breast cancer samples classified as HER2 negative by immunohistochemistry. Furthermore, we determined the degree of FAIMS-dependent background reduction and showed that this correlated with an improved lower limit of quantitation with FAIMS. FAIMS-PRM is anticipated to benefit clinical trials in which multiple biomarker questions must be addressed and the availability of tumor biopsy samples is limited.

cancer biology↗
bioRxiv2021

Mapping vestibular and visual contributions to angular head velocity tuning in the cortex

Neurons that signal the direction and angular velocity of head movements (AHV cells) are critically important to process visual and spatial information. However, it has been challenging to isolate the sensory modality that drives them and to comprehensively map their cortical distribution. To address this, we developed a method that enables rotating awake, head-fixed mice under a two-photon microscope in a visual environment. Starting in layer 2/3 of the retrosplenial cortex, a key area for vision and navigation, we found that a significant fraction of rotation-sensitive neurons report AHV. These tuning properties depend on vestibular input because they persist in darkness and are reduced when replaying visual flow to stationary animals. When mapping the spatial extent, we found AHV cells in all cortical areas that we explored, including motor, somatosensory, visual- and posterior parietal cortex. Notably, the vestibular and visual contributions to AHV are area dependent. Thus, many cortical circuits have access to AHV, enabling a diverse integration with sensorimotor and cognitive information.

neuroscience↗