Biology subjects

Markovic, S.

Publications and source records attributed to Markovic, S..

4 recordsLinked to original sources

bioRxiv2025

Genome writing to dissect consequences of SVA retrotransposon disease X-Linked Dystonia Parkinsonism

Human retrotransposon insertions are often associated with diseases. In the case of the neurodegenerative X-Linked Dystonia-Parkinsonism disease, a human-specific SINE-VNTR-Alu subfamily F retrotransposon was inserted in intron 32 of the TAF1 gene. Here, we genomically rewrote a portion of the mouse Taf1 allele with the corresponding 78-kb XDP patient derived TAF1 allele. In mESCs, the presence of the intronic SVAs--rather than the hybrid gene structure--reduces hyTAF1 levels. This leads to transcriptional downregulation of genes with TATA box enriched in their promoters and triggering apoptosis. Chromatin and transcriptome profiling revealed that intronic SVAs are actively transcribed, forming barriers that likely impede transcription elongation. In mice, neuronal lineage TAF1 humanization resulted lethality of male progeny within two months. XDP male mice had severe atrophy centered on the striatum--the same affected brain region in XDP patients. Lastly, CRISPRa-mediated activation of hyTAF1 restored mESC viability, suggesting boosting TAF1 transcription as a therapeutic approach.

genetics↗

bioRxiv2023

Axon onset remodeling in response to network activity in mouse cortical neurons

In certain subtypes of pyramidal neurons, axons originate from basal dendrites, resulting in an axon-carrying dendrite branch with unique functional characteristics (AcD cells). The number of AcD cells increases during development, however, it is so far unclear whether neurons remodel their axon emergence throughout their lifetime in response to changes in network activity. To test our hypothesis of such large-scale morphological plasticity, we utilized in vitro and in vivo strategies in mouse primary somatosensory cortex to test whether network activity impacts axon onset. Based on data obtained by immunofluorescence, confocal microscopy and/or live-cell imaging, we show that neurons are indeed capable of changing the onset of their axon origin from somatic to dendritic and vice versa within a few days in vitro and that peripheral whisker manipulation and thus changes in sensory input drives large-scale morphological plasticity in vivo.

neuroscience↗

bioRxiv2022

Resilient CD8+ T cells maintain a high cytotoxic capacity by balancing ROS via ME1 upregulation

Cytotoxic T lymphocytes (CTL) are indispensable in anti-tumor immunity. Although CTLs are prone to exhaustion in patients with advanced cancer, T cell resiliency explains the presence of tumor-reactive CTLs that are less exhausted, capable of cytolytic function, expansion, and rebound in response to immunotherapy to reject metastatic malignances. However, the features of resilient T cells have not been clearly defined. In this report, we demonstrate that peripheral CX3CR1+ CD8+ T cells with low mitochondrial membrane potential rebounded CTL function quickly after radiation therapy in patients with large tumor burden portraying their functional resiliency. Furthermore, CX3CR1+ CD8+ T cell with low, but not high, mitochondrial membrane potential are highly cytotoxic, accumulate less reactive oxygen species (ROS), and express more Malic enzyme 1 (ME1). ME1 overexpression increases ATP production in a glycolysisindependent manner while concurrently curtailing excessive ROS in activated CD8+ T cells; and expands CX3CR1+NKG7+ effector CD8+ T cells with enhanced cytotoxicity. Importantly, transfection of ME1 mRNA promotes tumoricidal activity in CD8+ T cells from patients with advanced cancers. Our study reveals a mechanism used by CTLs to balance excessive ROS via ME1 to maintain a metabolic and functional resiliency. Modification of ME1 expression in CTLs may be a novel method to improve the efficacy of cancer immunotherapy by preventing T cell exhaustion. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/517988v3_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@12e0f36org.highwire.dtl.DTLVardef@e8d412org.highwire.dtl.DTLVardef@1baf57eorg.highwire.dtl.DTLVardef@14b2b43_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LICX3CR1+ and low Dy m identify functional resilient CD8+ T cells. C_LIO_LIResilient CD8+ T cells are highly cytotoxic and have less ROS. C_LIO_LIResilient CD8+ T cells express more ME1 that can balance extra ROS. C_LIO_LIME1 overexpression can promote CTL function of CD8+ T cells. C_LI

immunology↗

bioRxiv2019

EGFR Oncogenes Expressed In Glioblastoma Are Activated As Covalent Dimers And Paradoxically Stimulated By Erlotinib

Mutation of both the intracellular catalytic domain and the extracellular domain of the receptor for epidermal growth factor (EGFR) can drive oncogenicity. Despite clinical success with targeting EGFR catalytic site mutations, no drugs have proven effective in patients expressing allosteric extracellular domain EGFR mutations, including glioblastomas (GBM) where these mutations are highly expressed. We define the molecular mechanism for oncogenic activation of families of extracellular EGFR mutations and reveal how this mechanism renders current generation small molecule ATP-site inhibitors ineffective. We demonstrate that a group of commonly expressed extracellular domain EGFR mutants expressed in GBM is activated by disulfide-bond mediated covalent dimerization, collectively referred to as locked dimerization (LoDi) EGFR oncogenes. Strikingly, small molecules binding to the active kinase conformation (Type I), but not those binding to the inactive kinase conformation (Type II), potently inhibit catalytic site mutants, but induce covalent dimerization and activate LoDi-EGFR oncogenes, manifesting in paradoxical acceleration of proliferation.\n\nSignificanceOur data demonstrate how the locked-dimer mechanism of EGFR oncogenesis has a profound impact on the activity of small molecule inhibitors. This provides a mechanistic understanding for the failure of current generation EGFR inhibitors to effectively treat LoDi-EGFR mutants in GBM, and sets guidelines for discovery of selective LoDi-EGFR inhibitors.

cancer biology↗