Project description:Our previous study demonstrates that ClC-Kb chloride channel deficiency in Bartter syndrome (BS) type 3 not only impairs transport activity but also affects the development of the thick ascending limbs (TALs) and possibly distal convoluted tubules (DCTs). This developmental defect is important to the pathogenesis of BS, with unknown underlying mechanisms. This study investigated the cellular effects of ClC-Kb deficiency and explored potential therapeutic strategies addressing these effects. We isolated TALs and DCTs from Clc-k2(ClC-Kb mouse ortholog)-knockout (Clc-k2-/-) and wild-type mice for multi-omics analyses. The results revealed differential regulations involving cell cycle, cell proliferation, mitochondrial respiration, and metabolism. In vitro studies showed that Clc-k2-/- TALs proliferated less efficiently than wild-type cells, exhibited a G2/M cell cycle delay, had reduced mitochondrial mass and oxidative phosphorylation alongside the suppressed glycolysis and fatty acid oxidation. A gain-of-function D561A mutation in with-no-lysine kinase 4 (WNK4), known to stimulate transepithelial salt transport and mitochondrial biogenesis in TALs/DCTs, significantly restored the salt transport in Clc-k2-/- TALs/DCTs and improved the phenotype of BS. Alternatively, overexpressing Pgc1α, a master activator of mitochondrial biogenesis, also alleviated the disease severity in Clc-k2-/- mice. These findings provide insights into the molecular mechanisms of BS type 3 and suggest novel therapeutic approaches.
Project description:The pathogenesis of Bartter syndrome (BS) has long been attributed to decreased NaCl reabsorption in the thick ascending limb of Henle’s loop (TAL). By studying Clc-k2 (mouse ortholog of ClC-Kb)-knockout (Clc-k2-/-) mice, we recently uncovered an additional mechanism in which loss of transport function induces TAL hypoplasia, exacerbating the severity of BS. Here, we further investigated this mechanism. TALs and distal convoluted tubules (DCTs) isolated from Clc-k2-/- and wild-type mice were used for transcriptome, proteomics, and cell cycle and proliferation assays. Mitochondrial morphology and function were studied using electron microscopy and mitochondrial respiration assays. Our results revealed impairments in cell proliferation, S-to-G2/M cell cycle transition, mitochondrial biogenesis, oxidative phosphorylation, glycolysis, and fatty acid oxidation in Clc-k2-/- TALs and DCTs. Increasing transport activity by introducing a gain-of-function with-no-lysine 4 (Wnk4) mutation in Clc-k2-/- mice restored all the abovementioned impairments and improved medulla maturation and phenotype. Transgenic overexpression of Pgc1α, a master activator of mitochondrial biogenesis, in Clc-k2-/- mice also alleviated mitochondrial dysfunction and phenotype. These findings support the hypothesis that mitochondrial hypofunction resulting from decreased transport activity contributes to cell cycle arrest and tubular hypoplasia in BS. Targeting mitochondria early in life could be a potential therapeutic approach for BS.
Project description:Genomic DNA from 189 wild type Col x CLC, 191 msh2 Col x CLC or 187 msh2 Col x Ler F2 individuals was extracted using CTAB and used to generate sequencing libraries as described (Serra et al 2018 PNAS). Sequencing data was analysed to identify crossovers as previously reported, using the TIGER pipeline (Rowan et al., 2015 G3).
Project description:Two molecular subgroups of MF-iCC were identified based on differentially expressed genes between MF-iCC with a cholangiolocellular carcinoma (CLC) component and those without a CLC component.
Project description:ClC-2 is a broadly expressed Cl- channel of the CLC family of Cl- channels and transporters which is abundantly expressed in brain. Here it was proposed to participate in lowering the cytoplasmic Cl- concentration of neurons, a process that establishes an inhibitory response to the neurotransmitters GABA and glycine (Staley et al., 1996). Heterozygous mutations in CLCN2 (the gene encoding ClC-2) were recently reported in a few patients with three clinically distinct forms of epilepsy (Haug et al, 2003). However, the disruption of ClC-2 in mice (ClC-2 KO mouse) did not entail epilepsy (Bösl et al., 2001; Nehrke et al., 2002) but myelin vacuolation in fiber tracts of the central nervous system. We used a gene expression profiling of the ClC-2 KO mouse in brain to identify possible disease mechanism which cause the observed myelin phenotype. As these myelin vacuolation became apparent in the fiber tracts of ClC-2 KO cerebellum at P28 and increased with age, we analysed the cerebellum of ClC-2 KO mice at different postnatal ages, before (P14) and after (P35) the KO cerebellum has been affected by myelin vacuolation.
Project description:The ubiquitous CLC membrane transporters are the only transporter family known to exchange anions for cations. Despite extensive study, there is no model to completely explain the 2:1 Cl‒/H+ stoichiometric exchange mechanism. Here, we provide such a model. Using CLC-ec1, a bacterial homolog that has served as a paradigm for the family, we determined cryo-EM structures at pH 7, pH 4.5, and pH 3. Molecular dynamics simulations of the pH-3 structure reveal critical steps in the transport mechanism, including release of Cl- ions to the extracellular side, opening of the inner gate, and water wires that facilitate H+ transport. Water wires are observed frequently in both the canonical H+-transport pathway and in the Cl- pathway, where they had not been previously reported. We propose that tight coupling of Cl‒/H+ transport is maintained (uncoupled H+ transport is avoided) because H+ transfer from the water wires to the catalytic glutamate is favored only when Cl‒ is also present in the pathway . Mutations that weaken Cl‒ binding without changing the pathway structure exhibit functional properties consistent with this model.
Project description:Lysosomal dysfunction is considered pathogenic in Alzheimer Disease (AD). Loss of Presenilin-1(PSEN1) function causing early onset AD impedes acidification via defective vATPase V0a1 subunit delivery to lysosomes. We report that isoproterenol and related β2-adrenergic agonists re-acidify lysosomes in PSEN1 KO cells and fibroblasts from PSEN1 familial AD(FAD) patients, restores lysosomal calcium homeostasis and proteolysis, and reverses impaired autophagy flux. We identify a novel rescue mechanism involving PKA-mediated facilitated delivery of ClC-7 to lysosomes, which stimulates chloride influx and reverses markedly lowered Cl- content of PSEN1 KO lysosomes. Notably, PSEN1 loss-of-function impedes ER-to-lysosome delivery of ClC-7, thus accounting for lysosomal Cl- deficits that compound pH deficits due to deficient vATPase function. Transcriptomics of PSEN1-deficient cells reveal strongly down-regulated ER-to-lysosome transport pathways and reversibility by isoproterenol. Our findings uncover a broadened PSEN1 role in lysosomal ion homeostasis and novel pH modulation of lysosomes through β-adrenergic regulation of ClC-7, which can be therapeutically modulated.
Project description:Identifying crossover locations in Arabidopsis thaliana wild type Col x CLC, msh2 Col x CLC and msh2 Col x Ler F2 populations using genotyping by sequencing.
Project description:To investigate drug-induced epigenetic resistance in AML, the K562 cell line was selected due to its responsiveness to anthracyclines and its ease of genetic manipulation. Daunorubicin (DNR) was chosen as a model drug because of its pivotal role in AML treatment. DNR treatment of K562 cells induced expression of all three ALDH1 isoforms. To explore the activation of cis-regulatory elements, ChIP-Seq with H3K27Ac was performed on K562 cells treated or not with DNR for 18 hours.