Single-cell individual full-length mtDNA sequencing by iMiGseq uncovers unexpected heteroplasmy shifts in mtDNA editing.

The ontogeny and dynamics of mtDNA heteroplasmy remain unclear due to limitations of current mtDNA sequencing methods. We developed individual Mitochondrial Genome sequencing (iMiGseq) of full-length mtDNA for ultra-sensitive variant detection, complete haplotyping, and unbiased evaluation of heteroplasmy levels, all at the individual mtDNA molecule level. iMiGseq uncovered unappreciated levels of heteroplasmic variants in single cells well below the conventional NGS detection limit and provided accurate quantitation of heteroplasmy level. iMiGseq resolved the complete haplotype of individual mtDNA in single oocytes and revealed genetic linkage of de novo mutations. iMiGseq detected sequential acquisition of detrimental mutations, including large deletions, in defective mtDNA in NARP/Leigh syndrome patient-derived induced pluripotent stem cells. iMiGseq identified unintended heteroplasmy shifts in mitoTALEN editing, while showing no appreciable level of unintended mutations in DdCBE-mediated mtDNA base editing. Therefore, iMiGseq could not only help elucidate the mitochondrial etiology of diseases, but also evaluate the safety of various mtDNA editing strategies.

Hematopoietic Differentiation of Human Pluripotent Stem Cells: HOX and GATA Transcription Factors as Master Regulators.

Numerous human disorders of the blood system would directly or indirectly benefit from therapeutic approaches that reconstitute the hematopoietic system. Hematopoietic stem cells (HSCs), either from matched donors or ex vivo manipulated autologous tissues, are the most used cellular source of cell therapy for a wide range of disorders. Due to the scarcity of matched donors and the difficulty of ex vivo expansion of HSCs, there is a growing interest in harnessing the potential of pluripotent stem cells (PSCs) as a de novo source of HSCs. PSCs make an ideal source of cells for regenerative medicine in general and for treating blood disorders in particular because they could expand indefinitely in culture and differentiate to any cell type in the body. However, advancement in deriving functional HSCs from PSCs has been slow. This is partly due to an incomplete understanding of the molecular mechanisms underlying normal hematopoiesis. In this review, we discuss the latest efforts to generate human PSC (hPSC)-derived HSCs capable of long-term engraftment. We review the regulation of the key transcription factors (TFs) in hematopoiesis and hematopoietic differentiation, the Homeobox (HOX) and GATA genes, and the interplay between them and microRNAs. We also propose that precise control of these master regulators during the course of hematopoietic differentiation is key to achieving functional hPSC-derived HSCs.

Release of taurine and glutamate contributes to cell volume regulation in human retinal Müller cells: differences in modulation by calcium.

Neuronal activity in the retina generates osmotic gradients that lead to Müller cell swelling, followed by a regulatory volume decrease (RVD) response, partially due to the isoosmotic efflux of KCl and water. However, our previous studies in a human Müller cell line (MIO-M1) demonstrated that an important fraction of RVD may also involve the efflux of organic solutes. We also showed that RVD depends on the swelling-induced Ca2+ release from intracellular stores. Here we investigate the contribution of taurine (Tau) and glutamate (Glu), the most relevant amino acids in Müller cells, to RVD through the volume-regulated anion channel (VRAC), as well as their Ca2+ dependency in MIO-M1 cells. Swelling-induced [3H]Tau/[3H]Glu release was assessed by radiotracer assays and cell volume by fluorescence videomicroscopy. Results showed that cells exhibited an osmosensitive efflux of [3H]Tau and [3H]Glu (Tau > Glu) blunted by VRAC inhibitors 4-(2-butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)-oxybutyric acid and carbenoxolone reducing RVD. Only [3H]Tau efflux was mainly dependent on Ca2+ release from intracellular stores. RVD was unaffected in a Ca2+-free medium, probably due to Ca2+-independent Tau and Glu release, but was reduced by chelating intracellular Ca2+. The inhibition of phosphatidylinositol-3-kinase reduced [3H]Glu efflux but also the Ca2+-insensitive [3H]Tau fraction and decreased RVD, providing evidence of the relevance of this Ca2+-independent pathway. We propose that VRAC-mediated Tau and Glu release has a relevant role in RVD in Müller cells. The observed disparities in Ca2+ influence on amino acid release suggest the presence of VRAC isoforms that may differ in substrate selectivity and regulatory mechanisms, with important implications for retinal physiology. NEW & NOTEWORTHY The mechanisms for cell volume regulation in retinal Müller cells are still unknown. We show that swelling-induced taurine and glutamate release mediated by the volume-regulated anion channel (VRAC) largely contributes the to the regulatory volume decrease response in a human Müller cell line. Interestingly, the hypotonic-induced efflux of these amino acids exhibits disparities in Ca2+-dependent and -independent regulatory mechanisms, which strongly suggests that Müller cells may express different VRAC heteromers formed by the recently discovered leucine-rich repeat containing 8 (LRRC8) proteins.

Improved Proliferative Capacity of NP-Like Cells Derived from Human Mesenchymal Stromal Cells and Neuronal Transdifferentiation by Small Molecules.

Neural progenitors (NP), found in fetal and adult brain, differentiate into neurons potentially able to be used in cell replacement therapies. This approach however, raises technical and ethical problems which limit their potential therapeutic use. Alternately, NPs can be obtained by transdifferentiation of non-neural somatic cells evading these difficulties. Human bone marrow mesenchymal stromal cells (MSCs) are suggested to transdifferentiate into NP-like cells, which however, have a low proliferation capacity. The present study demonstrates the requisite of cell adhesion for proliferation and survival of NP-like cells and re-evaluates some neuronal features after differentiation by standard procedures. Mature neuronal markers, though, were not detected by these procedures. A chemical differentiation approach was used in this study to convert MSCs-derived NP-like cells into neurons by using a cocktail of six molecules, CHIR99021, I-BET151, RepSox, DbcAMP, forskolin and Y-27632, defined after screening combinations of 22 small molecules. Direct transdifferentiation of MSCs into neuronal cells was obtained with the small molecule cocktail, without requiring the NP-like intermediate stage.

Regulatory volume decrease in neural precursor cells: taurine efflux and gene microarray analysis.

BACKGROUND/AIMS: Neural stem/ progenitor cells (NPCs) endure important changes in cell volume during growth, proliferation and migration. As a first approach to know about NPC response to cell volume changes, the Regulatory Volume Decrease (RVD) subsequent to hypotonic swelling was investigated. METHODS: NPCs obtained from the mesencephalon and the subventricular zone of embryonic and adult mice, respectively, were grown and cultured as neurospheres. Cell volume changes were measured by large-angle light-scattering and taurine efflux by [(3)H]-taurine. Expression of genes encoding molecules related to RVD was analysed using a DNA microarray obtained from NPC samples. RESULTS: Embryonic and adult NPCs exposed to osmolarity reduction (H15, H30, H40) exhibited rapid swelling followed by RVD. The magnitude, efficiency and pharmacological profile, of RVD and of [(3)H]-taurine osmosensitive efflux were comparable to those found in cultured brain cells, astrocytes and neurons. The relative expression of genes encoding molecules related to volume regulation, i.e. K(+) and Cl(-) channels, cotransporters, exchangers and aquaporins were identified in NPCs. CONCLUSION: NPCs show the ability to respond to hypotonic-evoked volume changes by adaptative recovery processes, similar to those found in other cultured brain cells. Genes related to molecules involved in RVD were found expressed in NPCs.

Taurine enhances the growth of neural precursors derived from fetal human brain and promotes neuronal specification.

Taurine is present at high concentrations in the fetal brain and is required for optimal brain development. Recent studies have reported that taurine causes increased proliferation of neural stem/progenitor neural cells (neural precursor cells, NPCs) obtained from embryonic and adult rodent brain. The present study is the first to show that taurine markedly increases cell numbers in cultures and neuronal generation from human NPCs (hNPCs). hNPCs obtained from 3 fetal brains (14-15 weeks of gestation) were cultured and expanded as neurospheres, which contained 76.3% nestin-positive cells. Taurine (5-20 mM) increased the number of hNPCs in culture, with maximal effect found at 10 mM and 4 days of culture. The taurine-induced increase ranged from 57 to 188% in the 3 brains examined. Taurine significantly enhanced the percentage of neurons formed from hNPCs under differentiating conditions, with increases ranging from 172 to 480% over controls without taurine. Taurine also increased the cell number and neuronal generation in cultures of the immortalized human cell line ReNcell VM. These results suggest that taurine has a positive influence on hNPC growth and neuronal formation.

An open-source, automated, and cost-effective platform for COVID-19 diagnosis and rapid portable genomic surveillance using nanopore sequencing.

The COVID-19 pandemic, caused by SARS-CoV-2, has emphasized the necessity for scalable diagnostic workflows using locally produced reagents and basic laboratory equipment with minimal dependence on global supply chains. We introduce an open-source automated platform for high-throughput RNA extraction and pathogen diagnosis, which uses reagents almost entirely produced in-house. This platform integrates our methods for self-manufacturing magnetic nanoparticles and qRT-PCR reagents-both of which have received regulatory approval for clinical use-with an in-house, open-source robotic extraction protocol. It also incorporates our "Nanopore Sequencing of Isothermal Rapid Viral Amplification for Near Real-time Analysis" (NIRVANA) technology, designed for tracking SARS-CoV-2 mutations and variants. The platform exhibits high reproducibility and consistency without cross-contamination, and its limit of detection, sensitivity, and specificity are comparable to commercial assays. Automated NIRVANA effectively identifies circulating SARS-CoV-2 variants. Our in-house, cost-effective reagents, automated diagnostic workflows, and portable genomic surveillance strategies provide a scalable and rapid solution for COVID-19 diagnosis and variant tracking, essential for current and future pandemic responses.

Influence of WNK3 on intracellular chloride concentration and volume regulation in HEK293 cells.

The involvement of WNK3 (with no lysine [K] kinase) in cell volume regulation evoked by anisotonic conditions was investigated in two modified stable lines of HEK293 cells: WNK3+, overexpressing WNK3 and WNK3-KD expressing a kinase inactive by a punctual mutation (D294A) at the catalytic site. This different WNK3 functional expression modified intracellular Cl(-) concentration with the following profile: WNK3+ > control > WNK3-KD cells. Stimulated with 15% hypotonic solutions, WNK3+ cells showed less efficient RVD (13.1%), lower Cl(-) efflux and decreased (94.5%) KCC activity. WNK3-KD cells showed 30.1% more efficient RVD, larger Cl(-) efflux and 5-fold higher KCC activity, increased since the isotonic condition. Volume-sensitive Cl(-) currents were similar in controls, WNK3+ cells, and WNK3-KD cells. Taurine efflux was not evoked at H15%. These results show a WNK3 influence on RVD in HEK293 cells via increasing KCC activity. Hypertonic medium induced cell shrinkage and RVI. In both WNK3+ and WNK3-KD cells, RVI and NKCC activity were increased, in WNK3+ cells presumably by enhanced NKCC phosphorylation, and in WNK3-KD cells via the [Cl(-)](i) reduction induced by the higher KCC activity in characteristic of these cells. These results support the role of WNK3 in modulation of intracellular Cl(-) concentration, in RVD, and indirectly on RVI, via its effects on KCC and NKCC activity. WNK3 in HEK293 cells is expressed as puncta at the intercellular junctions and diffusely at the cytosol, while the inactive kinase was found concentrated at the Golgi area. Cells with inactive WNK3 exhibited a marked change of cell phenotype.

NIRVANA for Simultaneous Detection and Mutation Surveillance of SARS-CoV-2 and Co-infections of Multiple Respiratory Viruses.

Detection and mutation surveillance of SARS-CoV-2 are crucial for combating the COVID-19 pandemic. Here we describe a lab-based method for multiplex isothermal amplification-based sequencing and real-time analysis of multiple viral genomes. It can simultaneously detect SARS-CoV-2, influenza A, human adenovirus, and human coronavirus and monitor mutations for up to 96 samples in real time. The method proved to be rapid and sensitive (limit of detection: 29 viral RNA copies/µL of extracted nucleic acid) in detecting SARS-CoV-2 in clinical samples. We expect it to offer a promising solution for rapid field-deployable detection and mutational surveillance of pandemic viruses.

In situ monitoring reveals cellular environmental instabilities in human pluripotent stem cell culture.

Mammalian cell cultures are a keystone resource in biomedical research, but the results of published experiments often suffer from reproducibility challenges. This has led to a focus on the influence of cell culture conditions on cellular responses and reproducibility of experimental findings. Here, we perform frequent in situ monitoring of dissolved O2 and CO2 with optical sensor spots and contemporaneous evaluation of cell proliferation and medium pH in standard batch cultures of three widely used human somatic and pluripotent stem cell lines. We collate data from the literature to demonstrate that standard cell cultures consistently exhibit environmental instability, indicating that this may be a pervasive issue affecting experimental findings. Our results show that in vitro cell cultures consistently undergo large departures of environmental parameters during standard batch culture. These findings should catalyze further efforts to increase the relevance of experimental results to the in vivo physiology and enhance reproducibility.

Wiskott-Aldrich syndrome protein forms nuclear condensates and regulates alternative splicing.

The diverse functions of WASP, the deficiency of which causes Wiskott-Aldrich syndrome (WAS), remain poorly defined. We generated three isogenic WAS models using patient induced pluripotent stem cells and genome editing. These models recapitulated WAS phenotypes and revealed that WASP deficiency causes an upregulation of numerous RNA splicing factors and widespread altered splicing. Loss of WASP binding to splicing factor gene promoters frequently leads to aberrant epigenetic activation. WASP interacts with dozens of nuclear speckle constituents and constrains SRSF2 mobility. Using an optogenetic system, we showed that WASP forms phase-separated condensates that encompasses SRSF2, nascent RNA and active Pol II. The role of WASP in gene body condensates is corroborated by ChIPseq and RIPseq. Together our data reveal that WASP is a nexus regulator of RNA splicing that controls the transcription of splicing factors epigenetically and the dynamics of the splicing machinery through liquid-liquid phase separation.

Structure of the full-length human Pannexin1 channel and insights into its role in pyroptosis.

Pannexin1 (PANX1) is a large-pore ATP efflux channel with a broad distribution, which allows the exchange of molecules and ions smaller than 1 kDa between the cytoplasm and extracellular space. In this study, we show that in human macrophages PANX1 expression is upregulated by diverse stimuli that promote pyroptosis, which is reminiscent of the previously reported lipopolysaccharide-induced upregulation of PANX1 during inflammasome activation. To further elucidate the function of PANX1, we propose the full-length human Pannexin1 (hPANX1) model through cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulation studies, establishing hPANX1 as a homo-heptamer and revealing that both the N-termini and C-termini protrude deeply into the channel pore funnel. MD simulations also elucidate key energetic features governing the channel that lay a foundation to understand the channel gating mechanism. Structural analyses, functional characterizations, and computational studies support the current hPANX1-MD model, suggesting the potential role of hPANX1 in pyroptosis during immune responses.

Simultaneous detection and mutation surveillance of SARS-CoV-2 and multiple respiratory viruses by rapid field-deployable sequencing.

BACKGROUND: Strategies for monitoring the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are crucial for combating the pandemic. Detection and mutation surveillance of SARS-CoV-2 and other respiratory viruses require separate and complex workflows that rely on highly specialized facilities, personnel, and reagents. To date, no method can rapidly diagnose multiple viral infections and determine variants in a high-throughput manner. METHODS: We describe a method for multiplex isothermal amplification-based sequencing and real-time analysis of multiple viral genomes, termed nanopore sequencing of isothermal rapid viral amplification for near real-time analysis (NIRVANA). It can simultaneously detect SARS-CoV-2, influenza A, human adenovirus, and human coronavirus and monitor mutations for up to 96 samples in real time. FINDINGS: NIRVANA showed high sensitivity and specificity for SARS-CoV-2 in 70 clinical samples with a detection limit of 20 viral RNA copies per µL of extracted nucleic acid. It also detected the influenza A co-infection in two samples. The variant analysis results of SARS-CoV-2-positive samples mirror the epidemiology of coronavirus disease 2019 (COVID-19). Additionally, NIRVANA could simultaneously detect SARS-CoV-2 and pepper mild mottle virus (PMMoV) (an omnipresent virus and water-quality indicator) in municipal wastewater samples. CONCLUSIONS: NIRVANA provides high-confidence detection of both SARS-CoV-2 and other respiratory viruses and mutation surveillance of SARS-CoV-2 on the fly. We expect it to offer a promising solution for rapid field-deployable detection and mutational surveillance of pandemic viruses. FUNDING: M.L. is supported by KAUST Office of Sponsored Research (BAS/1/1080-01). This work is supported by KAUST Competitive Research Grant (URF/1/3412-01-01; M.L. and J.C.I.B.) and Universidad Catolica San Antonio de Murcia (J.C.I.B.). A.M.H. is supported by Saudi Ministry of Education (project 436).

A Robust, Safe, and Scalable Magnetic Nanoparticle Workflow for RNA Extraction of Pathogens from Clinical and Wastewater Samples.

Molecular diagnosis and surveillance of pathogens such as SARS-CoV-2 depend on nucleic acid isolation. Pandemics at the scale of COVID-19 can cause a global shortage of proprietary commercial reagents and BSL-2 laboratories to safely perform testing. Therefore, alternative solutions are urgently needed to address these challenges. An open-source method, magnetic-nanoparticle-aided viral RNA isolation from contagious samples (MAVRICS), built upon readily available reagents, and easily assembled in any basically equipped laboratory, is thus developed. The performance of MAVRICS is evaluated using validated pathogen detection assays and real-world and contrived samples. Unlike conventional methods, MAVRICS works directly in samples inactivated in phenol-chloroform (e.g., TRIzol), thus allowing infectious samples to be handled safely without biocontainment facilities. MAVRICS allows wastewater biomass immobilized on membranes to be directly inactivated and lysed in TRIzol followed by RNA extraction by magnetic nanoparticles, thereby greatly reducing biohazard risk and simplifying processing procedures. Using 39 COVID-19 patient samples and two wastewater samples, it is shown that MAVRICS rivals commercial kits in detection of SARS-CoV-2, influenza viruses, and respiratory syncytial virus. Therefore, MAVRICS is safe, fast, and scalable. It is field-deployable with minimal equipment requirements and could become an enabling technology for widespread testing and wastewater monitoring of diverse pathogens.

Quick and Easy Assembly of a One-Step qRT-PCR Kit for COVID-19 Diagnostics Using In-House Enzymes.

One-step reverse-transcription quantitative polymerase chain reaction (qRT-PCR) is the most widely applied method for COVID-19 diagnostics. Notwithstanding the facts that one-step qRT-PCR is well suited for the diagnosis of COVID-19 and that there are many commercially available one-step qRT-PCR kits in the market, their high cost and unavailability due to airport closures and shipment restriction became a major bottleneck that had driven the desire to produce the key components of such kits locally. Here, we provide a simple, economical, and powerful one-step qRT-PCR kit based on patent-free, specifically tailored versions of Moloney murine leukemia virus reverse transcriptase and Thermus aquaticus DNA polymerase and termed R3T (Rapid Research Response Team) one-step qRT-PCR. We also demonstrate the robustness of our enzyme production strategies and provide the optimal reaction conditions for their efficient augmentation in a one-step approach. Our kit was routinely able to reliably detect as low as 10 copies of the synthetic RNAs of SARS-CoV-2. More importantly, our kit successfully detected COVID-19 in clinical samples of broad viral titers with similar reliability and selectivity to that of the Invitrogen SuperScript III Platinum One-step qRT-PCR and TaqPath one-step RT-qPCR kits. Overall, our kit has shown robust performance in both laboratory settings and the Saudi Ministry of Health-approved testing facility.

Functional expression and subcellular localization of the taurine transporter TauT in murine neural precursors.

Taurine addition to cultured embryonic neural precursor cells (NPC) significantly increased cell proliferation [Hernández-Benítez et al., 2010]. The medium used for NPC growing and proliferation is a fetal serum-free medium, and therefore, NPC become taurine depleted. Addition of taurine to the cultured medium fully replenished the cell taurine pool, suggesting the functional expression of a taurine transporter (TauT) in these cells. In the present study, TauT in NPC was functionally characterized and its protein expression and the subcellular distribution of immunoreactivity were determined. ³H-taurine uptake in NPC could be separated into a non-saturable component and a Na(+)/Cl⁻-dependent, saturable component. The saturable component showed an apparent 2:1:1 Na(+)/Cl⁻/taurine stoichiometry, a V(max) of 0.39 ± 0.04 nmol/mg protein/min, and a K(m) of 21.7 ± 2.6 µM. TauT in NPC was strongly inhibited by hypotaurine and ß-alanine (92 and 79%, respectively) and reduced (71%) by γ-aminobutyric acid. TauT protein is expressed in NPC as a single band of about 70 kDa. Essentially all (98.8%) of the neurosphere-forming cells were positive to TauT immunoreactivity. Immunolocalization visualized by confocal microscopy localized TauT predominantly at the cell membrane. TauT was also found at the cytosol and only occasionally at the nuclear membrane. This study represents the first characterization of TauT in NPC.

Taurine stimulates proliferation of mice embryonic cultured neural progenitor cells.

Taurine is present in high levels in fetal brain which decrease in the adult, suggesting its role in brain development. In some regions of taurine deficient animals cells show defective migration and the presence of numerous mitotic figures, suggesting a delay in cell proliferation. To know more about the role of taurine in the developing brain cells, the present study investigated whether taurine is a factor involved in proliferation or/and viability of neural progenitor cells (NPC). NPC were obtained from 13.5-days mice embryos mesencephalon, and cultured during 4-5 days to form neurospheres in the presence of EGF plus FGFb (EGF/FGF) or EGF alone. Mesencephalon taurine content (349 mmoles/kg protein) was lost in NPC and recovered after addition of 10 mM taurine to the culture. Neurospheres-forming NPC were over 94% nestin-positive. Taurine increased 38.6% and 43.2% the number of NPC formed in EGF/FGF or EGF conditions, respectively. In secondary neurospheres this increase was 24.6% and 62.1%, in EGF/FGF or EGF cultures respectively. Correspondingly neurospheres size was increased by taurine but neurospheres number was not enhanced. Taurine significantly increased the number of BrdU-positive cells, without affecting cell viability, suggesting proliferation as the mechanism responsible for taurine action increasing NPC. Taurine seems unable to increase the number of beta-III-tubulin-positive cells differentiated from neurospheres after serum addition, and rather an increase in astrocytes was observed. These results point to taurine as a trophic factor contributing to optimize NPC proliferation.

Neuronal Transdifferentiation Potential of Human Mesenchymal Stem Cells from Neonatal and Adult Sources by a Small Molecule Cocktail.

Human mesenchymal stem cells (MSCs) are good candidates for brain cell replacement strategies and have already been used as adjuvant treatments in neurological disorders. MSCs can be obtained from many different sources, and the present study compares the potential of neuronal transdifferentiation in MSCs from adult and neonatal sources (Wharton's jelly (WhJ), dental pulp (DP), periodontal ligament (PDL), gingival tissue (GT), dermis (SK), placenta (PLAC), and umbilical cord blood (UCB)) with a protocol previously tested in bone marrow- (BM-) MSCs consisting of a cocktail of six small molecules: I-BET151, CHIR99021, forskolin, RepSox, Y-27632, and dbcAMP (ICFRYA). Neuronal morphology and the presence of cells positive for neuronal markers (TUJ1 and MAP2) were considered attributes of neuronal induction. The ICFRYA cocktail did not induce neuronal features in WhJ-MSCs, and these features were only partial in the MSCs from dental tissues, SK-MSCs, and PLAC-MSCs. The best response was found in UCB-MSCs, which was comparable to the response of BM-MSCs. The addition of neurotrophic factors to the ICFRYA cocktail significantly increased the number of cells with complex neuron-like morphology and increased the number of cells positive for mature neuronal markers in BM- and UCB-MSCs. The neuronal cells generated from UCB-MSCs and BM-MSCs showed increased reactivity of the neuronal genes TUJ1, MAP2, NF-H, NCAM, ND1, TAU, ENO2, GABA, and NeuN as well as down- and upregulation of MSC and neuronal genes, respectively. The present study showed marked differences between the MSCs from different sources in response to the transdifferentiation protocol used here. These results may contribute to identifying the best source of MSCs for potential cell replacement therapies.