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Mohr-Tranebjaerg syndrome (MTS) is a rare X-linked recessive neurodegenerative disorder caused by mutations in the Translocase of Inner Mitochondrial Membrane 8A (TIMM8A) gene, which encodes TIMM8a, a protein localized to the mitochondrial intermembrane space (IMS). The pathophysiology of MTS remains poorly understood. To investigate the molecular mechanisms underlying MTS, we established induced pluripotent stem cells (iPSCs) from a male MTS patient carrying a novel TIMM8A mutation (c.225-229del, p.Q75fs95*), referred to as MTS-iPSCs. To generate an isogenic control, we introduced the same mutation into healthy control iPSCs (CTRL-iPSCs) using the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9 (CRISPR/Cas9), resulting in mutant iPSCs (MUT-iPSCs). We differentiated the three iPSC lines into neurons and evaluated their mitochondrial function and neuronal development. Both MTS- and MUT-iPSCs exhibited impaired neuronal differentiation, characterized by smaller somata, fewer branches, and shorter neurites in iPSC-derived neurons. Additionally, these neurons showed increased susceptibility to apoptosis under stress conditions, as indicated by elevated levels of cytochrome c and cleaved caspase-3. Mitochondrial function analysis revealed reduced protein levels and activity of complex IV, diminished ATP synthesis, and increased reactive oxygen species (ROS) generation in MTS- and MUT-neurons. Furthermore, transmission electron microscopy revealed mitochondrial fragmentation in MTS-neurons. RNA sequencing identified differentially expressed genes (DEGs) involved in axonogenesis, synaptic activity, and apoptosis-related pathways. Among these DEGs, coiled-coil-helix-coiled-coil-helix domain-containing 2 (CHCHD2), which encodes a mitochondrial IMS protein essential for mitochondrial homeostasis, was significantly downregulated in MTS-neurons. Western blot analysis confirmed decreased CHCHD2 protein levels in both MTS- and MUT-neurons. Overexpression of CHCHD2 rescued mitochondrial dysfunction and promoted neurite elongation in MTS-neurons, suggesting that CHCHD2 acts as a downstream effector of TIMM8a in the pathogenesis of MTS. In summary, loss-of-function of TIMM8a leads to a downstream reduction in CHCHD2 levels, collectively impairing neurogenesis by disrupting mitochondrial homeostasis. TIMM8a mutation (p.Q75fs95*) leads to mitochondrial dysfunction and neuronal defects in iPSC-derived neurons from patient with Mohr-Tranebjaerg syndrome, which are rescued by overexpression of CHCHD2. TIMM8a translocase of inner mitochondrial membrane 8a, CHCHD2 coiled-coil-helix-coiled-coil-helix domain-containing protein 2, MTS Mohr–Tranebjaerg syndrome, I mitochondrial complex I, II mitochondrial complex II, III mitochondrial complex III, IV mitochondrial complex IV, Q coenzyme Q10, Cyt c cytochrome c.

Human induced pluripotent stem cells and their differentiation into cardiac myocytes (hiPSC-CMs) provides a unique and valuable platform for studies of cardiac muscle structure–function. This includes studies centered on disease etiology, drug development, and for potential clinical applications in heart regeneration/repair. Ultimately, for these applications to achieve success, a thorough assessment and physiological advancement of the structure and function of hiPSC-CMs is required. HiPSC-CMs are well noted for their immature and sub-physiological cardiac muscle state, and this represents a major hurdle for the field. To address this roadblock, we have developed a hiPSC-CMs (?-MHC dominant) experimental platform focused on directed physiological enhancement of the sarcomere, the functional unit of cardiac muscle. We focus here on the myosin heavy chain (MyHC) protein isoform profile, the molecular motor of the heart, which is essential to cardiac physiological performance. We hypothesized that inducing increased expression of ?-MyHC in ?-MyHC dominant hiPSC-CMs would enhance contractile performance of hiPSC-CMs. To test this hypothesis, we used gene editing with an inducible ?-MyHC expression cassette into isogeneic hiPSC-CMs, and separately by gene transfer, and then investigated the direct effects of increased ?-MyHC expression on hiPSC-CMs contractility and relaxation function. Data show improved cardiac functional parameters in hiPSC-CMs induced with ?-MyHC. Positive inotropy and relaxation was evident in comparison to ?-MyHC dominant isogenic controls both at baseline and during pacing induced stress. This approach should facilitate studies of hiPSC-CMs disease modeling and drug screening, as well as advancing fundamental aspects of cardiac function parameters for the optimization of future cardiac regeneration, repair and re-muscularization applications.

A growing body of clinical literature has described neurodevelopmental delays in infants with chronic prenatal opioid exposure and withdrawal. Despite this, the mechanism of how opioids impact the developing brain remains unknown. Here, we developed an in vitro model of prenatal morphine exposure and withdrawal using healthy human induced pluripotent stem cell (iPSC)-derived midbrain neural progenitors in monolayer. To optimize our model, we identified that a longer neural induction and regional patterning period increases expression of canonical opioid receptors mu and kappa in midbrain neural progenitors compared to a shorter protocol (OPRM1, two-tailed t-test, p =? 0.004; OPRK1, p =? 0.0003). Next, we showed that the midbrain neural progenitors derived from a longer iPSC neural induction also have scant toll-like receptor 4 (TLR4) expression, a key player in neonatal opioid withdrawal syndrome pathophysiology. During morphine withdrawal, differentiating neural progenitors experience cyclic adenosine monophosphate overshoot compared to cell exposed to vehicle (p =? 0.0496) and morphine exposure conditions (p, =? 0.0136, 1-way ANOVA). Finally, we showed that morphine exposure and withdrawal alters proportions of differentiated progenitor cell fates (2-way ANOVA, F =? 16.05, p <? 0.0001). Chronic morphine exposure increased proportions of nestin positive progenitors (p =? 0.0094), and decreased proportions of neuronal nuclear antigen positive neurons (NEUN) (p =? 0.0047) compared to those exposed to vehicle. Morphine withdrawal decreased proportions of glial fibrillary acidic protein positive cells of astrocytic lineage (p =? 0.044), and increased proportions of NEUN-positive neurons (p <? 0.0001) compared to those exposed to morphine only. Applications of this paradigm include mechanistic studies underscoring neural progenitor cell fate commitments in early neurodevelopment during morphine exposure and withdrawal.

Human-induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) represent a promising and renewable cell source for therapeutic applications. A systematic evaluation of the immunological properties and engraftment potential of iMSCs generated from urine-derived iPSCs is lacking, which has impeded their broader application. In this study, we differentiated urine-derived iPSCs into iMSCs and assessed their fundamental MSC characteristics, immunogenicity, immunomodulatory capacity and in vivo engraftment. Compared to umbilical cord-derived MSCs (UCMSCs), iMSCs demonstrated an enhanced proliferative capacity, a higher level of regenerative gene expression, and lower immunogenicity, strengthening resistance to apoptosis induced by allogeneic peripheral blood mononuclear cells (PBMCs) and the NK-92 cell line. In addition, iMSCs exhibited a diminished ability to inhibit T cell proliferation and activation compared with UCMSCs. Transcriptomic analyses further revealed the decreased expression of immune regulatory factors in iMSCs. After transfusion into mouse models, iMSCs engrafted in the lungs, liver, and spleen and exhibited the ability to migrate to tumor tissues. Our results indicated that iMSCs generated from urine-derived iPSCs have a significant replicative capacity, low immunogenicity and unique immunomodulatory properties, and hence offer obvious advantages in immune privilege and allogenic therapeutic application prospects.

Becker muscular dystrophy (BMD) is caused by in-frame mutations in dystrophin gene, leading to progressive muscle weakness, and cardiac and respiratory complications. Currently, there is no cure. We have recently identified the importance of poly-ubiquitination in regulating dystrophin stability through the binding of lncRNA H19 to the dystrophin C-terminal zinc-finger domain (ZNF), inhibiting TRIM63-mediated poly-ubiquitination. We also demonstrated that BMD mutations lead to conformational changes in ZNF domain, reduced lncRNA H19 binding and increased dystrophin ubiquitination. Here we used BMD iPSCs to investigate the in vitro myogenic potential of BMD myogenic cells, as well as in vitro and in vivo studies to evaluate the therapeutic efficacy of three candidate molecules targeting dystrophin ubiquitination pathway. In vitro assays indicated significant deficiencies in myogenic cell differentiation of BMD iPSCs, including reduced proliferation, cell-cycle arrest, increased apoptosis, senescence, and membrane damage, and impaired myotube formation. In vivo engraftment demonstrated significant improvement in BMD iPSC myogenic cell survival and dystrophin expression in the animals treated with two molecules: a TRIM63 inhibitor and an ?-synuclein aggregation inhibitor. These findings provide promising evidence for the potential therapeutic efficacy of these ubiquitination pathway inhibitors to improve muscle progenitor cell survival and dystrophin expression in BMD patients. Graphical abstract Regulation of dystrophin stability via poly-ubiquitination is crucial in Becker muscular dystrophy (BMD). BMD mutations impair lncRNA H19 binding, increasing dystrophin ubiquitination. Darabi and colleagues’ studies, using BMD iPSCs and in vivo models, demonstrate that inhibiting TRIM63 or ?-synuclein aggregation improves myogenic cell survival and dystrophin expression, suggesting promising therapeutic avenues for BMD.

Microglia play a pivotal role in neurodegenerative disease pathogenesis, but the mechanisms underlying microglia dysfunction and toxicity remain to be elucidated. To investigate the effect of neurodegenerative disease-linked genes on the intrinsic properties of microglia, we studied microglia-like cells derived from human induced pluripotent stem cells (iPSCs), termed iMGs, harboring mutations in profilin-1 (PFN1) that are causative for amyotrophic lateral sclerosis (ALS). ALS-PFN1 iMGs exhibited evidence of lipid dysmetabolism, autophagy dysregulation and deficient phagocytosis, a canonical microglia function. Mutant PFN1 also displayed enhanced binding affinity for PI3P, a critical signaling molecule involved in autophagic and endocytic processing. Our cumulative data implicate a gain-of-toxic function for mutant PFN1 within the autophagic and endo-lysosomal pathways, as administration of rapamycin rescued phagocytic dysfunction in ALS-PFN1 iMGs. These outcomes demonstrate the utility of iMGs for neurodegenerative disease research and implicate microglial vesicular degradation pathways in the pathogenesis of these disorders. Mutations in profilin 1 (PFN1), which modulates actin dynamics, are associated with ALS. Here the authors show that expression of ALS-PFN1 is sufficient to induce deficits in human microglia-like cells, including impaired phagocytosis and lipid metabolism, and that gain-of-function interactions between ALS-PFN1 and PI3P may underlie these deficits.

SUMMARY Resident cardiac macrophages are critical mediators of cardiac function. Despite their known importance to cardiac electrophysiology and tissue maintenance, there are currently no stem-cell-derived models of human engineered cardiac tissues (hECTs) that include resident macrophages. In this study, we made an induced pluripotent stem cell (iPSC)-derived hECT model with a resident population of macrophages (iM0) to better recapitulate the native myocardium and characterized their impact on tissue function. Macrophage retention within the hECTs was confirmed via immunofluorescence after 28 days of cultivation. The inclusion of iM0s significantly impacted hECT function, increasing contractile force production. A potential mechanism underlying these changes was revealed by the interrogation of calcium signaling, which demonstrated the modulation of ?-adrenergic signaling in +iM0 hECTs. Collectively, these findings demonstrate that macrophages significantly enhance cardiac function in iPSC-derived hECT models, emphasizing the need to further explore their contributions not only in healthy hECT models but also in the contexts of disease and injury. In brief Lock and Graney et al. develop a human engineered cardiac tissue with an incorporated iPSC-derived macrophage population to better mimic the complex cell landscape of the native myocardium. Macrophage inclusion leads to increased contractile function of the tissue, which is attributed to macrophage stimulation of the cardiomyocyte ?-adrenergic signaling pathway. Graphical Abstract

SummaryCytoplasmic mislocalization and aggregation of the RNA-binding protein TDP-43 is a pathological hallmark of the motor neuron (MN) disease amyotrophic lateral sclerosis (ALS). Furthermore, while mutations in TARDBP (encoding TDP-43) have been associated with ALS, the pathogenic consequences of these mutations remain poorly understood. Using CRISPR-Cas9, we engineered two homozygous knock-in induced pluripotent stem cell lines carrying mutations in TARDBP encoding TDP-43A382T and TDP-43G348C, two common yet understudied ALS TDP-43 variants. Motor neurons (MNs) differentiated from knock-in iPSCs had normal viability and displayed no significant changes in TDP-43 subcellular localization, phosphorylation, solubility, or aggregation compared with isogenic control MNs. However, our results highlight synaptic impairments in both TDP-43A382T and TDP-43G348C MN cultures, as reflected in synapse abnormalities and alterations in spontaneous neuronal activity. Collectively, our findings suggest that MN dysfunction may precede the occurrence of TDP-43 pathology and neurodegeneration in ALS and further implicate synaptic and excitability defects in the pathobiology of this disease. Graphical abstract Highlights•Mutant MNs maintain viability but are more vulnerable to cellular stress•Mutant MNs do not show TDP-43 pathology•TDP-43 variants lead to a progressive decline in spontaneous neuronal activity•Functional impairments are accompanied by abnormal synaptic marker expression Molecular neuroscience; Cellular neuroscience

AbstractA basic assumption underlying induced pluripotent stem cell (iPSC) models of neurodegeneration is that disease-relevant pathologies present in brain tissue are also represented in donor-matched cells differentiated from iPSCs. However, few studies have tested this hypothesis in matched iPSCs and neuropathologically characterized donated brain tissues. To address this, we assessed iPSC-neuron production of ?-amyloid (A?) A?40, A?42, and A?43 in 24 iPSC lines matched to donor brains with primary neuropathologic diagnoses of sporadic AD (sAD), familial AD (fAD), control, and other neurodegenerative disorders. Our results demonstrate a positive correlation between A?43 production by fAD iPSC-neurons and A?43 accumulation in matched brain tissues but do not reveal a substantial correlation in soluble A? species between control or sAD iPSC-neurons and matched brains. However, we found that the ApoE4 genotype is associated with increased A? production by AD iPSC-neurons. Pathologic tau phosphorylation was found to be increased in AD and fAD iPSC-neurons compared to controls and positively correlated with the relative abundance of longer-length A? species produced by these cells. Taken together, our results demonstrate that sAD-predisposing genetic factors influence iPSC-neuron phenotypes and that these cells are capturing disease-relevant and patient-specific components of the amyloid cascade.

Better understanding of the earliest molecular pathologies of all neurodegenerative diseases is expected to improve human therapeutics. We investigated the earliest molecular pathology of spinocerebellar ataxia type 1 (SCA1), a rare familial neurodegenerative disease that primarily induces death and dysfunction of cerebellum Purkinje cells. Extensive prior studies have identified involvement of transcription or RNA-splicing factors in the molecular pathology of SCA1. However, the regulatory network of SCA1 pathology, especially central regulators of the earliest developmental stages and inflammatory events, remains incompletely understood. Here, we elucidated the earliest developmental pathology of SCA1 using originally developed dynamic molecular network analyses of sequentially acquired RNA-seq data during differentiation of SCA1 patient-derived induced pluripotent stem cells (iPSCs) to Purkinje cells. Dynamic molecular network analysis implicated histone genes and cytokine-relevant immune response genes at the earliest stages of development, and revealed relevance of ISG15 to the following degradation and accumulation of mutant ataxin-1 in Purkinje cells of SCA1 model mice and human patients. Molecular changes in neurodegeneration occur much earlier than previously expected. In this study, dynamic molecular network analysis of iPSC differentiation uncovers a temporal pathway from histone to ISG15 with the earliest molecular changes of SCA1.

IntroductionEmerging biotechnologies are increasingly being explored for food production, including the development of cell-cultivated meat. Conventional approaches typically rely on satellite cell (SC) biopsies, which present challenges in scalability. Bovine induced pluripotent stem cells (biPSCs) represent a promising alternative due to their capacity for self-renewal and developmental plasticity.MethodsThis study utilized both lentiviral (integrating) and episomal (non-integrating) reprogramming strategies to generate biPSCs suitable for myogenic differentiation. Bovine fetal fibroblasts (bFFs) were reprogrammed using episomal vectors pMaster K and pCXB-EBNA1, leading to the emergence of putative iPSC colonies 13 days post-nucleofection. A clonal line, bFF-iPSCs pMK, was selected for further analysis.ResultsThe bFF-iPSCs pMK line expressed key pluripotency markers including alkaline phosphatase (AP), OCT4, SOX2, and NANOG, and was stably maintained for over 33 passages, although episomal plasmids remained detectable. in vitro myogenic differentiation was assessed by comparing this line to a previously established lentiviral reprogrammed line (bFF-iPSCs mOSKM). Both lines exhibited downregulation of pluripotency markers and upregulation of the early myogenic marker PAX3. By day 30, the bFF-iPSCs pMK line formed elongated, multinucleated cells characteristic of myotubes and displayed a corresponding gene expression profile.DiscussionThese results provide new insights into bovine in vitro myogenesis and its application in cultured meat production. While promising, the study also highlights the difficulty in achieving complete myogenic differentiation, indicating a need for further optimization of differentiation protocols. Graphical abstract

ObjectiveThyroid hormone (TH) action is mediated by thyroid hormone receptor (THR) isoforms. While THR?1 is likely the main isoform expressed in liver, its role in human hepatocytes is not fully understood.MethodsTo elucidate the role of THR?1 action in human hepatocytes we used CRISPR/Cas9 editing to knock out THR?1 in induced pluripotent stem cells (iPSC). Following directed differentiation to the hepatic lineage, iPSC-derived hepatocytes were then interrogated to determine the role of THR?1 in ligand-independent and -dependent functions.ResultsWe found that the loss of THR?1 promoted alterations in proliferation rate and metabolic pathways regulated by T3, including gluconeogenesis, lipid oxidation, fatty acid synthesis, and fatty acid uptake. We observed that key genes involved in liver metabolism are regulated through both T3 ligand-dependent and -independent THR?1 signaling mechanisms. Finally, we demonstrate that following THR?1 knockout, several key metabolic genes remain T3 responsive suggesting they are THR? targets.ConclusionsThese results highlight that iPSC-derived hepatocytes are an effective platform to study mechanisms regulating TH signaling in human hepatocytes. Graphical abstractImage 1 Highlights•THR?1 is essential for T3 effects in human iPSC-derived hepatocytes (iHEPs).•THR?1 knockout reduces iPSC and progenitor cell proliferative capacity.•T3 regulates key genes involved in lipid and carbohydrate metabolism through THR?1.•THR?1 plays a strong ligand-independent role.