Biology subjects

George, A. J.

Publications and source records attributed to George, A. J..

8 recordsLinked to original sources

bioRxiv2025

Neuropathic pain drives time-dependent reorganization of corticostriatal circuits

Chronic pain fundamentally alters sensorimotor integration and motivated behaviors, yet the neural mechanisms underlying this transition remain poorly understood. The striatum, composed of dopamine receptor type 1 (D1)- and type 2 (D2)-expressing spiny projection neurons (SPN), integrates cortical sensory and motor inputs to coordinate movement and motivation, making it a critical candidate for mediating pain-induced behavioral adaptations. Although spinal and cortical pain circuits are well-characterized in limited phases of pain, how corticostriatal pathways and distinct striatal cell populations contribute to the transition from acute to chronic pain states remains unclear. Here we show that neuropathic pain, after spared nerve injury in mice, produces temporally distinct, cell-type-specific changes in striatal SPN activity and corticostriatal plasticity that evolve across acute to chronic pain phases. D1 SPNs exhibit smaller amplitude and slower calcium signals during acute pain stages that persist through early chronic phases, while D2 SPNs show delayed response timing during later chronic stages, but also stimulus-specific alterations in neural activity throughout acute and chronic pain states. Critically, primary somatosensory cortex inputs to D2 SPNs develop depressing synapses specifically during intermediate chronic pain phases ([~]25 days post-injury) that disappear during more severe chronic stages (>3 months), suggesting a failed compensatory mechanism. These findings reveal that striatal circuits undergo dynamic, time-dependent reorganization after peripheral injury, with D1 and D2 pathways contributing distinct temporal signatures to pain-related behavior. The identification of critical windows of striatal plasticity provides new targets for therapeutic interventions that could prevent or reverse chronic pain states by modulating specific corticostriatal circuits during vulnerable transition periods.

neuroscience↗

bioRxiv2025

Novel RNA Polymerase I and Cyclin Dependent Kinase combination therapy for the treatment of aggressive Acute Myeloid Leukemia.

Despite advances in therapy, specific subtypes Acute Myeloid Leukaemia (AML) remains largely incurable. The first-in-class RNA Polymerase I (Pol I) inhibitor, CX-5461, has demonstrated promising activity in both haematological malignancies and solid tumours by selectively inhibiting ribosome biogenesis to induce nucleolar stress, a critical vulnerability in rapidly proliferating cancer cells. CX-5461 has undergone clinical trials for the treatment of both solid and haematological malignancies, and 2nd generation Pol I inhibitor PMR-116 has also entered clinical trials, underscoring the translational potential of drugs that target RNA Polymerase I. To enhance the therapeutic efficacy of Pol I inhibition and prevent the emergence of resistance, we conducted a cell line-based unbiased screen of FDA-approved drugs to identify compounds that might synergise with CX-5461. This screen revealed that the pan-CDK inhibitors Dinaciclib and Flavopiridol enhance nucleolar stress pathway (NSP) activation and are strong candidates for combinatorial therapy with CX-5461. Further analysis showed that the combination of CX-5461 and Dinaciclib acts synergistically across a genetically diverse panel of human AML cell lines. This synergy is dependent on an intact NSP, with both agents independently stabilising p53, but with distinct phenotypic outcomes: Dinaciclib induces rapid apoptosis, whereas CX-5461 primarily enforces cell cycle arrest. This functional complementarity results in efficient tumour cell clearance and likely accounts for the delayed onset of therapy resistance. Importantly, combination treatment with CX-5461 and Dinaciclib significantly improved survival in murine models of AML and reduced colony formation in primary human AML samples. Together these findings provide preclinical evidence for a novel combination treatment strategy that leverages nucleolar stress and cell cycle control to enhance treatment outcomes in AML, paving the way for clinical translation of Pol I-CDK co-targeting therapies.

cancer biology↗

bioRxiv2025

The novel RNA polymerase I transcription inhibitor PMR-116 exploits a critical therapeutic vulnerability in a broad-spectrum of high MYC malignancies.

Ribosome biogenesis (RiBi) is a key determinant of cell growth and proliferation and is highly elevated in cancer due to the activation by oncogenes such as MYC. First-generation RiBi inhibitor CX-5461, while demonstrating clinical potential for cancer treatment, also induces DNA damage through off-target inhibition of TOP2 and potentially other mechanisms, bringing into question RiBi as a target for cancer therapy. In this study, we test second-generation RiBi inhibitor, PMR-116. PMR-116 exhibits improved drug-like properties compared to first-generation RiBi inhibitors and has robust anti-tumour activity in the absence of global DNA damage signalling in a broad range of pre-clinical models of haematologic and solid cancers, particularly in malignancies where MYC is either the driver of disease or is elevated. Thus, our work demonstrates that RiBi is a genuine target for cancer therapy and highlights the potential to exploit a critical therapeutic vulnerability in high-MYC human cancers with dismal therapeutic outcomes. Statement of significanceDespite the development of new cancer therapies, most advanced malignancies remain incurable. We demonstrate that PMR-116, a second-generation RiBi inhibitor, has robust therapeutic efficacy in preclinical models of cancer, offering great promise to treat a broad spectrum of human solid and haematologic malignancies, especially where MYC is a driver.

cancer biology↗

bioRxiv2024

Chitin synthase targeting antifungal agents for Mucormycosis (Black fungus disease) caused by Rhizopus delemar - An in-silico study

Mucormycosis, a severe fungal infection caused by Mucorales fungi, particularly Rhizopus delemar, has prompted the development of new and more potent antifungal drugs due to the emergence of drug-resistant strains. Currently used drugs are known to be toxic to human cells also, which is a major drawback in their administration. Antifungal drugs commercially under use and their structurally modified analogues along with 30 plants reported with antifungal activity from IMPPAT database, totalling 229 compounds, were screened against the best modelled structure of Chitin Synthase, a key target enzyme of Rhizopus delemar by in-silico molecular docking studies. Computerized methods to assess absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles was employed to further filter key lead drug candidates from among the docked ligands that could act as potential antifungal medications. Modified structures of Posaconazole, Nikkomycin and Isavuconazole were found to give better docking results than compared to the original drugs, though they failed to comply with ADMET parameters. Among the phytochemicals, 1-nonacosanol displayed binding affinity (highest LibDock score) greater than the synthetic drugs and their derivatives, though it too failed to comply with ADMET parameters. The phytochemical Dihydrocapsaicin was found to be the best compound that satisfied all the parameters such as ADMET, TOPKAT, Lipinskis and Vebers rule along with good binding affinity. All in all, this novel study paves a way to investigate the interaction of Chitin Synthase inhibitors at molecular level to achieve an alternative solution with less toxic effects to treat Mucormycosis.

bioinformatics↗

bioRxiv2024

Role of Posterior Medial Thalamus in the Modulation of Striatal Circuitry and Choice Behavior

The posterior medial (POm) thalamus is heavily interconnected with sensory and motor circuitry and is likely involved in behavioral modulation and sensorimotor integration. POm provides axonal projections to the dorsal striatum, a hotspot of sensorimotor processing, yet the role of POm-striatal projections has remained undetermined. Using optogenetics with slice electrophysiology, we found that POm provides robust synaptic input to direct and indirect pathway striatal spiny projection neurons (D1- and D2-SPNs, respectively) and parvalbumin-expressing fast spiking interneurons (PVs). During the performance of a whisker-based tactile discrimination task, POm-striatal projections displayed learning-related activation correlating with anticipatory, but not reward-related, pupil dilation. Inhibition of POm-striatal axons across learning caused slower reaction times and an increase in the number of training sessions for expert performance. Our data indicate that POm-striatal inputs provide a behaviorally relevant arousal-related signal, which may prime striatal circuitry for efficient integration of subsequent choice-related inputs.

neuroscience↗

bioRxiv2021

The E3 ubiquitin ligase RNF216/TRIAD3 is a central regulator of the hypothalamic-pituitary-gonadal axis

RNF216/TRIAD3 is an E3 ligase that ubiquitinates substrates in the nervous system. Recessive mutations in RNF216/TRIAD3 cause Gordon Holmes syndrome (GHS), where hypogonadotropic hypogonadism is a core phenotype. However, the functions of RNF216/TRIAD3 within the neuroendocrine system are not well-understood. Here, we used the CRISPR-Cas9 system to knock out Rnf216/Triad3 in GT1-7 cells, a GnRH immortalized cell line derived from mouse hypothalamus. Rnf216/Triad3 knockout cells had decreased steady state Gnrh and reduced calcium transient frequency. To address functions of RNF216/TRIAD3 in vivo, we generated a Rnf216/Triad3 constitutive knockout (KO) mouse. KO mice of both sexes showed reductions in GnRH and soma size. Furthermore, KO mice exhibited sex-specific phenotypes with males showing gonadal impairment and derangements in gonadotropin release compared to KO females, which only had irregular estrous cyclicity. Our work shows that dysfunction of RNF216/TRIAD3 affects the HPG axis in a sex-dependent manner, implicating sex-specific therapeutic interventions for GHS. HighlightsO_LIRnf216/Triad3 controls Gnrh and intrinsic hypothalamic cell activity C_LIO_LIRnf216/Triad3 knockout male mice have greater reproductive impairments than females C_LIO_LIRnf216/Triad3 controls the HPG axis at multiple levels C_LI

neuroscience↗

bioRxiv2021

Nuclear stabilisation of p53 requires a functional nucleolar surveillance pathway

The nucleolar surveillance pathway (NSP) monitors nucleolar fidelity and responds to nucleolar stresses (i.e., inactivation of ribosome biogenesis) by mediating the inhibitory binding of ribosomal proteins (RPs) to mouse double minute 2 homolog (MDM2), a nuclear-localised E3 ubiquitin ligase, which results in p53 accumulation. Inappropriate activation of the NSP has been implicated in the pathogenesis of collection of human diseases termed "ribosomopathies", while drugs that selectively activate the NSP are now in trials for cancer. Despite the clinical significance, the precise molecular mechanism(s) regulating the NSP remain poorly understood. Using genome-wide loss of function screens, we demonstrate the ribosome biogenesis (RiBi) axis as the most potent class of genes whose disruption stabilises p53. Furthermore, we identified a novel suite of genes critical for the NSP, including a novel mammalian protein implicated in 5S ribonucleoprotein particle (5S-RNP) biogenesis, HEATR3. By selectively disabling the NSP, we unexpectedly demonstrate that a functional NSP is required for the ability of all nuclear acting stresses tested, including DNA damage, to robustly induce p53 accumulation. Together, our data demonstrates that the NSP has evolved as the dominant central integrator of stresses that regulate nuclear p53 abundance, thus ensuring RiBi is hardwired to cellular proliferative capacity.

cell biology↗

bioRxiv2020

Cohesin mutations are synthetic lethal with stimulation of WNT signaling

Mutations in genes encoding subunits of the cohesin complex are common in several cancers, but may also expose druggable vulnerabilities. We generated isogenic MCF10A cell lines with deletion mutations of genes encoding cohesin subunits SMC3, RAD21 and STAG2 and screened for synthetic lethality with 3,009 FDA-approved compounds. The screen identified several compounds that interfere with transcription, DNA damage repair and the cell cycle. Unexpectedly, one of the top hits was a GSK3 inhibitor, an agonist of Wnt signaling. We show that sensitivity to GSK3 inhibition is likely due to stabilization of {beta}-catenin in cohesin mutant cells, and that Wnt-responsive gene expression is highly sensitized in STAG2-mutant CMK leukemia cells. Moreover, Wnt activity is enhanced in zebrafish mutant for cohesin subunit rad21. Our results suggest that cohesin mutations could progress oncogenesis by enhancing Wnt signaling, and that targeting the Wnt pathway may represent a novel therapeutic strategy for cohesin mutant cancers.

cancer biology↗