Biology subjects

Speed, A.

Publications and source records attributed to Speed, A..

6 recordsLinked to original sources

bioRxiv2026

Mutant KRAS dosage contributes to heterogeneity in lung cancer therapeutic response

Oncogenic KRAS mutations promote tumorigenesis by constitutive activation of multiple, well-characterised signalling pathways. However, there is significant heterogeneity across mutant KRAS tumours in terms of mutation present, mutant allele abundance and downstream signalling strength. It is unclear whether these variations can impact responses to specific therapies. Here, we demonstrate that [~]20% of lung adenocarcinomas (LUAD) show an increase in mutant KRAS dosage (KRASmutant allele fraction > KRASwild-type). Furthermore, we show that KRAS mutant dosage can directly influence clinical outcome and therapeutic susceptibilities in lung cancer. Our findings show that mutant KRAS copy gains specifically affect platinum lung cancer response, promoting resistance to this standard-of-care therapy. Importantly, increases in KRAS mutant dosage are also associated with an increased vulnerability to pS6K inhibition, due to the unique metabolic rewiring of these cells. Together, we show that mutant KRAS dosage contributes to the phenotypic heterogeneity of mutant KRAS NSCLC and that assessment of mutant KRAS content or signalling strength can help optimise treatments strategies for these patients.

cancer biology↗

bioRxiv2023

Raman micro-spectroscopy reveals the spatial distribution of fumarate in cells and tissues.

Aberrantly accumulated metabolites such as fumarate elicit intra- and inter-cellular pro-oncogenic cascades, yet current methods to measure them require sample perturbation or disruption and lack spatio-temporal resolution, limiting our ability to fully characterize their function and distribution in cells and within a tissue. Raman spectroscopy (RS) is a powerful bio-analytical tool that directly characterizes the chemical composition of a sample based solely on the optical fingerprint of vibrational modes. Here, we show for the first time that RS can directly detect fumarate in living cells in vivo and animal tissues ex vivo. Using the observed linear relationship between Raman scattered intensity and fumarate concentration, we demonstrate that RS can distinguish between Fumarate hydratase (Fh1)-deficient and Fh1-proficient cells based on their fumarate concentration. Moreover, RS reveals the spatial compartmentalization of fumarate within cellular organelles: consistent with disruptive methods, in Fh1-deficient cells we observe the highest fumarate concentration (37 {+/-} 19 mM) in the mitochondria, where the TCA cycle operates, followed by the cytoplasm (24 {+/-} 13 mM) and then the nucleus (9 {+/-} 6 mM). Finally, we apply RS to tissues from an inducible mouse model of FH loss in the kidney, demonstrating that RS can accurately classify FH status in these tissues. These results suggest that RS could be adopted as a valuable tool for small molecule metabolic imaging, enabling in situ dynamic evaluation of fumarate compartmentalization.

cell biology↗

bioRxiv2022

HIRA loss transforms FH-deficient cells

Fumarate Hydratase (FH) is a mitochondrial enzyme that catalyses the reversible hydration of fumarate to malate in the TCA cycle. Germline mutations of FH lead to HLRCC, a cancer syndrome characterised by a highly aggressive form of renal cancer(1). Although HLRCC tumours metastasise rapidly, FH-deficient mice develop premalignant cysts in the kidneys, rather than carcinomas (2). How Fh1-deficient cells overcome these tumour suppressive events during transformation is unknown. Here, we perform a genome-wide CRISPR/Cas9 screen to identify genes that, when ablated, enhance the proliferation of Fh1-deficient cells. We found that the depletion of HIRA enhances proliferation and invasion of Fh1-deficient cells in vitro and in vivo. Mechanistically, Hira loss enables the activation of MYC and its target genes, increasing nucleotide metabolism specifically in Fh1-deficient cells, independent of its histone chaperone activity. These results are instrumental for understanding mechanisms of tumorigenesis in HLRCC and the development of targeted treatments for patients.

cancer biology↗

bioRxiv2020

Spatial modulation of dark versus bright stimulus responses in mouse visual cortex

A fundamental task of the visual system is to respond to luminance increments and decrements. In primary visual cortex (V1) of cats and primates, luminance decrements elicit stronger, faster, and more salient neural activity (OFF responses) than luminance increments (ON responses). However, studies of V1 in ferrets and mice show that ON responses may be stronger. These discrepancies may arise from differences in species, experimental conditions, or from measuring responses in single neurons versus populations. Here, we examined OFF versus ON responses across different regions of visual space in both single neurons and populations of mouse V1. We used high-density silicon probes and whole-cell patch-clamp recordings to assess OFF versus ON dominance in local field potential (LFP), single neuron, and membrane potential responses. Across these levels, we found that OFF responses clearly dominated in the central visual field, whereas ON responses were more evident in the periphery. These observations were clearest in LFP and subthreshold membrane potential. Our findings consolidate and resolve prior conflicting results and reveal that retinotopy may provide a common organizing principle for spatially biasing OFF versus ON processing in mammalian visual systems.

neuroscience↗

bioRxiv2019

Diminished cortical excitation during perceptual impairments in a mouse model of autism

Sensory impairments are a core feature of autism spectrum disorder (ASD). These impairments affect visual perception (Robertson and Baron-Cohen, 2017), and have been hypothesized to arise from imbalances in cortical excitatory and inhibitory activity (Rubenstein and Merzenich, 2003; Nelson and Valakh, 2015; Sohal and Rubenstein, 2019); however, there is little direct evidence testing this hypothesis in identified excitatory and inhibitory neurons during impairments of sensory perception. Several recent studies have examined cortical activity in transgenic mouse models of ASD (Goel et al., 2018; Antoine et al., 2019; Lazaro et al., 2019), but have provided conflicting evidence for excitatory versus inhibitory activity deficits. Here, we utilized a genetically relevant mouse model of ASD (CNTNAP2-/- knockout, KO; Arking et al., 2008; Penagarikano et al., 2011) and directly recorded putative excitatory and inhibitory population spiking in primary visual cortex (V1) while measuring visual perceptual behavior (Speed et al., 2019). We found quantitative impairments in the speed, accuracy, and contrast sensitivity of visual perception in KO mice. These impairments were simultaneously associated with elevated inhibitory and diminished excitatory neuron activity evoked by visual stimuli during behavior, along with aberrant 3 - 10 Hz oscillations in superficial cortical layers 2/3 (L2/3). These results establish that perceptual deficits relevant for ASD can arise from diminished sensory activity of excitatory neurons in feedforward layers of cortical circuits.

neuroscience↗

bioRxiv2018

Cortical states control visual spatial perception

Many factors modulate the state of cortical activity, but the importance of cortical states for sensory perception remains debated. We trained mice to detect spatially localized visual stimuli, and simultaneously measured local field potentials and excitatory and inhibitory neuron populations across layers of primary visual cortex (V1). Cortical states with low firing rates and correlations between excitatory neurons, and reduced oscillatory activity in Layer 4, accurately predicted single trials of visual spatial detection behavior. Our results show that cortical states exert strong effects at the initial stage of cortical processing in V1, and play a decisive role for visual spatial behavior in mice.

neuroscience↗