Biology subjects

Schmitt, R.

Publications and source records attributed to Schmitt, R..

3 recordsLinked to original sources

bioRxiv2026

Cyst-type epithelial heterogeneity shapes therapeutic responsiveness in ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) exhibits substantial interpatient variability in disease course and therapeutic response, but the cellular basis for this variability remains poorly understood. Here, we combine single-nucleus RNA sequencing of human cyst epithelia with machine learning-based histological analysis of >1,800 cysts to resolve three epithelial cyst types--proximal tubule-like, collecting duct-like, and mixed. These cyst types display distinct injury states, metabolic programs, and stromal microenvironments, including a mixed-cyst niche enriched for CCL2-associated inflammatory signaling. Expression of key therapeutic targets was highly cell-type specific with CFTR enriched in proximal-like epithelia, whereas AVPR2 expression was confined to AQP2-positive collecting duct-like cells. Cyst-type composition varied widely across patients and in an orthologous mouse model (Pkd1RC/RC) in which the burden of AQP2-positive cysts correlated with responsiveness to tolvaptan. These findings identify cyst-type heterogeneity as a major determinant of molecular pathway activation and predictability of therapeutic response in ADPKD.

molecular biology↗

bioRxiv2021

Transcriptome Analysis of Chloride Intracellular Channel Knockdown in Drosophila Identifies Oxidation-Reduction Function as Possible Mechanism of Altered Sensitivity to Ethanol Sedation

Chloride intracellular channels (CLICs) are a unique family of evolutionarily conserved metamorphic proteins, switching between stable conformations based on redox conditions. CLICs have been implicated in a wide variety biological processes including ion channel activity, apoptosis, membrane trafficking, and enzymatic oxidoreductase activity. Understanding the molecular mechanisms by which CLICs engage in these activities is an area of active research. Here, the sole Drosophila melanogaster ortholog, Clic, was targeted for RNAi knockdown to identify genes and biological processes associated with Clic expression. Clic knockdown had a substantial impact on global transcription, altering expression of over 9% of transcribed Drosophila genes. Overrepresentation analysis of differentially expressed genes identified enrichment of 23 Gene Ontology terms including Cytoplasmic Translation, Oxidation-Reduction Process, Heme Binding, Membrane, Cell Junction, and Nucleolus. The top term, Cytoplasmic Translation, was enriched almost exclusively with downregulated genes. Drosophila Clic and vertebrate ortholog Clic4 have previously been tied to ethanol sensitivity and ethanol-regulated expression. Clic knockdown-responsive genes from the present study were found to overlap significantly with gene sets from 4 independently published studies related to ethanol exposure and sensitivity in Drosophila. Bioinformatic analysis of genes shared between these studies revealed an enrichment of genes related to amino acid metabolism, protein processing, oxidation-reduction processes, and lipid particles among others. To determine whether the modulation of ethanol sensitivity by Clic may be related to co-regulated oxidation-reduction processes, we evaluated the effect of hyperoxia on ethanol sedation in Clic knockdown flies. Consistent with previous findings, Clic knockdown reduced acute ethanol sedation sensitivity in flies housed under nomoxia. However, this effect was reversed by exposure to hyperoxia, suggesting a common set of molecular-genetic mechanism may modulate each of these processes. This study suggests that Drosophila Clic has a major influence on regulation of oxidative stress signaling and that this function overlaps with the molecular mechanisms of acute ethanol sensitivity in the fly.

neuroscience↗

bioRxiv2020

IDH1 Mutations Induce Organelle Defects Via Dysregulated Phospholipids

Cytosolic IDH1 enzyme plays a key, but currently unexplored, role in lipid biosynthesis. Using Raman imaging microscopy, we identified heterogeneous lipid profiles in cellular organelles attributed uniquely to IDH1 mutations. Via organelle lipidomics, we found an increase in saturated and monounsaturated fatty acids in the endoplasmic reticulum of IDH1mut cells compared with IDHWT glioma. We showed that these fatty acids incorporate into phospholipids and induce organelle dysfunctions, with prominent dilation of Golgi apparatus, which can be restored by transient knockdown of stearyl-CoA desaturase or inhibition of D-2-hydroxyglutarate (D-2HG) formation. We validated these findings using tissue from patients with glioma. Oleic acid addition led to increased sensitivity to apoptosis of IDH1mut cells compared with IDHWT. Addition of D-2HG to U251WT cells lead in increased ER and Golgi apparatus dilation. Collectively, these studies provide clinically relevant insights into the functional link between IDH1mut-induced lipid alterations and organelle dysfunction, with therapeutic implications. SignificanceGliomas are devastating tumors, with the most aggressive form--glioblastoma multiforme-- correlated with a mean patient survival of 14.5 months. No curative treatment exists to date. Low-grade glioma (LGG) with the isocitrate dehydrogenase 1 (IDH1) mutation, R132H, provides a survival benefit to patients. Understanding the unique metabolic profile of IDH1mut could provide clues regarding its association with longer survival and information about therapeutic targets. Herein, we identified lipid imbalances in organelles, generated by IDHmut in cells and patient tissue, that were responsible for Golgi dilation and that correlated with increased survival. Addition of oleic acid, which tilted the balance towards elevated levels of monounsaturated fatty acids produced IDH1mut-specific cellular apoptosis. HighlightsO_LISingle-organelle omics revealed unique alterations in lipid metabolism due to IDH1-mutations. C_LIO_LIIDH mutation leads to organelle-wide structural defects. C_LIO_LIIDH1 mutation leads to increased monounsaturated fatty acids levels in glioma cells and oligodendroglioma patient samples. C_LIO_LILipid alterations affect the membrane integrity of the Golgi apparatus. C_LIO_LIIncreased D-2HG induced SCD expression and elevated monounsaturated fatty acids C_LIO_LITilting the balance toward more-abundant monounsaturated fatty acids leads to specific IDH1mut glioma apoptosis. C_LI

cancer biology↗