Secondary Publication: Proposal for Points of Consideration for Pluripotent Stem Cell Culture.

Human pluripotent stem cells, such as human embryonic stem cells and human induced pluripotent stem cells, are used in basic research and various applied fields, including drug discovery and regenerative medicine. Stem cell technologies have developed rapidly in recent years, and the supply of culture materials has improved. This has facilitated the culture of human pluripotent stem cells and has enabled an increasing number of researchers and bioengineers to access this technology. At the same time, it is a challenge to share the basic concepts and techniques of this technology among researchers and technicians to ensure the reproducibility of research results. Human pluripotent stem cells differ from conventional somatic cells in many aspects, and many points need to be considered in their handling, even for those experienced in cell culture. Therefore, we have prepared this proposal, "Points of Consideration for Pluripotent Stem Cell Culture," to promote the effective use of human pluripotent stem cells. This proposal includes seven items to be considered and practices to be confirmed before using human pluripotent stem cells. These are laws/guidelines and consent/material transfer agreements, diversity of pluripotent stem cells, culture materials, thawing procedure, media exchange and cell passaging, freezing procedure, and culture management. We aim for the concept of these points of consideration to be shared by researchers and technicians involved in the cell culture of pluripotent stem cells. In this way, we hope the reliability of research using pluripotent stem cells can be improved, and cell culture technology will advance.

A disease-specific iPS cell resource for studying rare and intractable diseases.

BACKGROUND: Disease-specific induced pluripotent stem cells (iPSCs) are useful tools for pathological analysis and diagnosis of rare diseases. Given the limited available resources, banking such disease-derived iPSCs and promoting their widespread use would be a promising approach for untangling the mysteries of rare diseases. Herein, we comprehensively established iPSCs from patients with designated intractable diseases in Japan and evaluated their properties to enrich rare disease iPSC resources. METHODS: Patients with designated intractable diseases were recruited for the study and blood samples were collected after written informed consent was obtained from the patients or their guardians. From the obtained samples, iPSCs were established using the episomal method. The established iPSCs were deposited in a cell bank. RESULTS: We established 1,532 iPSC clones from 259 patients with 139 designated intractable diseases. The efficiency of iPSC establishment did not vary based on age and sex. Most iPSC clones originated from non-T and non-B hematopoietic cells. All iPSC clones expressed key transcription factors, OCT3/4 (range 0.27-1.51; mean 0.79) and NANOG (range 0.15-3.03; mean 1.00), relative to the reference 201B7 iPSC clone. CONCLUSIONS: These newly established iPSCs are readily available to the researchers and can prove to be a useful resource for research on rare intractable diseases.

iPS cells from Chediak-Higashi syndrome patients recapitulate the giant granules in myeloid cells.

BACKGROUND: Chediak-Higashi syndrome (CHS) is a congenital disease characterized by immunodeficiency, hemophagocytic lymphohistiocytosis, oculocutaneous albinism, and neurological symptoms. The presence of giant granules in peripheral blood leukocytes is an important hallmark of CHS. Here we prepared induced pluripotent stem cells (iPSCs) from CHS patients (CHS-iPSCs) and differentiated them into hematopoietic cells to model the disease phenotypes. METHODS: Fibroblasts were obtained from two CHS patients and then reprogrammed into iPSCs. The iPSCs were differentiated into myeloid cells; the size of the cytosolic granules was quantified by May-Grunwald Giemsa staining and myeloperoxidase staining. RESULTS: Two clones of iPSCs were established from each patient. The differentiation efficiency to CD33+ CD45+ myeloid cells was not significantly different in CHS-iPSCs compared with control iPSCs, but significantly larger granules were observed. CONCLUSIONS: We succeeded in reproducing a characteristic cellular phenotype, giant granules in myeloid cells, using CHS-iPSCs, demonstrating that iPSCs can be used to model the pathogenesis of CHS patients.

Investigation of the molecular causes underlying physical abnormalities in Diamond-Blackfan anemia patients with RPL5 haploinsufficiency.

Diamond-Blackfan anemia (DBA) is a genetic disorder caused by mutations in genes encoding ribosomal proteins and characterized by erythroid aplasia and various physical abnormalities. Although accumulating evidence suggests that defective ribosome biogenesis leads to p53-mediated apoptosis in erythroid progenitor cells, little is known regarding the underlying causes of the physical abnormalities. In this study, we established induced pluripotent stem cells from a DBA patient with RPL5 haploinsufficiency. These cells retained the ability to differentiate into osteoblasts and chondrocytes. However, RPL5 haploinsufficiency impaired the production of mucins and increased apoptosis in differentiated chondrocytes. Increased expression of the pro-apoptotic genes BAX and CASP9 further indicated that RPL5 haploinsufficiency triggered p53-mediated apoptosis in chondrocytes. Murine double minute 2 (MDM2), the primary negative regulator of p53, plays a crucial role in erythroid aplasia in DBA patient. We found the phosphorylation level of MDM2 was significantly decreased in RPL5 haploinsufficient chondrocytes. In stark contrast, we found no evidence that RPL5 haploinsufficiency impaired osteogenesis. Collectively, our data support a model in which RPL5 haploinsufficiency specifically induces p53-mediated apoptosis in chondrocytes through MDM2 inhibition, which leads to physical abnormalities in DBA patients.

Generation of two human induced pluripotent stem cell lines derived from two X-linked adrenoleukodystrophy patients with ABCD1 mutations.

Adrenoleukodystrophy (ALD) is an X-linked genetic disorder, characterized by demyelination in the central nervous system and adrenal insufficiency. Human induced pluripotent stem cell (hiPSC) lines derived from two Japanese male patients with ALD were generated from skin fibroblasts using retroviral vectors. The generated hiPSC lines showed self-renewal and pluripotency, and carried either a missense or a nonsense mutation in ABCD1 gene. Since the molecular pathogenesis caused by ABCD1 dysfunction remains unclear, these cell resources provide useful tools to establish disease models and to develop new therapies for X-ALD.

Deterioration of phagocytosis in induced pluripotent stem cell-derived retinal pigment epithelial cells established from patients with retinitis pigmentosa carrying Mer tyrosine kinase mutations.

Retinitis pigmentosa (RP) is an incurable retinal degenerative disease with an unknown mechanism of disease progression. Mer tyrosine kinase (MERTK), which encodes a receptor of the Tyro3/Axl/Mer family of tyrosine kinases, is one of the causal genes of RP. MERTK is reportedly expressed in the retinal pigment epithelium (RPE) and is essential for phagocytosis of the photoreceptor outer segment. Here, we established induced pluripotent stem cells (iPSC) from patients with RP having homozygous or compound heterozygous mutations in MERTK, and from healthy subjects; the RP patient- and healthy control-derived iPSCs were differentiated into RPE cells. Although cytoskeleton staining suggested that polarity may have been disturbed mildly, there were no apparent morphological differences between the diseased and normal RPE cells. The internalization of photoreceptor outer segments in diseased iPSC-RPE cells was significantly lower than that in normal iPSC-RPE cells. This in vitro disease model may be useful for elucidating the mechanisms of disease progression and screening treatments for the disease.

In Vitro Disease Modeling of Hermansky-Pudlak Syndrome Type 2 Using Human Induced Pluripotent Stem Cell-Derived Alveolar Organoids.

It has been challenging to generate in vitro models of alveolar lung diseases, as the stable culture of alveolar type 2 (AT2) cells has been difficult. Methods of generating and expanding AT2 cells derived from induced pluripotent stem cells (iPSCs) have been established and are expected to be applicable to disease modeling. Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by dysfunction of lysosome-related organelles, such as lamellar bodies (LBs), in AT2 cells. From an HPS type 2 (HPS2) patient, we established disease-specific iPSCs (HPS2-iPSCs) and their gene-corrected counterparts. By live cell imaging, the LB dynamics were visualized and altered distribution, enlargement, and impaired secretion of LBs were demonstrated in HPS2-iPSC-derived AT2 cells. These findings provide insight into the AT2 dysfunction in HPS patients and support the potential use of human iPSC-derived AT2 cells for future research on alveolar lung diseases.

Pluripotent Stem Cell Model of Nakajo-Nishimura Syndrome Untangles Proinflammatory Pathways Mediated by Oxidative Stress.

Nakajo-Nishimura syndrome (NNS) is an immunoproteasome-associated autoinflammatory disorder caused by a mutation of the PSMB8 gene. Although dysfunction of the immunoproteasome causes various cellular stresses attributed to the overproduction of inflammatory cytokines and chemokines in NNS, the underlying mechanisms of the autoinflammation are still largely unknown. To investigate and understand the mechanisms and signal pathways in NNS, we established a panel of isogenic pluripotent stem cell (PSC) lines with PSMB8 mutation. Activity of the immunoproteasome in PSMB8-mutant PSC-derived myeloid cell lines (MT-MLs) was reduced even without stimulation compared with non-mutant-MLs. In addition, MT-MLs showed an overproduction of inflammatory cytokines and chemokines, with elevated reactive oxygen species (ROS) and phosphorylated p38 MAPK levels. Treatment with p38 MAPK inhibitor and antioxidants decreased the abnormal production of cytokines and chemokines. The current PSC model revealed a specific ROS-mediated inflammatory pathway, providing a platform for the discovery of alternative therapeutic options for NNS and related immunoproteasome disorders.

Reduction of lipid accumulation rescues Bietti's crystalline dystrophy phenotypes.

Bietti's crystalline dystrophy (BCD) is an intractable and progressive chorioretinal degenerative disease caused by mutations in the CYP4V2 gene, resulting in blindness in most patients. Although we and others have shown that retinal pigment epithelium (RPE) cells are primarily impaired in patients with BCD, the underlying mechanisms of RPE cell damage are still unclear because we lack access to appropriate disease models and to lesion-affected cells from patients with BCD. Here, we generated human RPE cells from induced pluripotent stem cells (iPSCs) derived from patients with BCD carrying a CYP4V2 mutation and successfully established an in vitro model of BCD, i.e., BCD patient-specific iPSC-RPE cells. In this model, RPE cells showed degenerative changes of vacuolated cytoplasm similar to those in postmortem specimens from patients with BCD. BCD iPSC-RPE cells exhibited lysosomal dysfunction and impairment of autophagy flux, followed by cell death. Lipidomic analyses revealed the accumulation of glucosylceramide and free cholesterol in BCD-affected cells. Notably, we found that reducing free cholesterol by cyclodextrins or δ-tocopherol in RPE cells rescued BCD phenotypes, whereas glucosylceramide reduction did not affect the BCD phenotype. Our data provide evidence that reducing intracellular free cholesterol may have therapeutic efficacy in patients with BCD.

Human AK2 links intracellular bioenergetic redistribution to the fate of hematopoietic progenitors.

AK2 is an adenylate phosphotransferase that localizes at the intermembrane spaces of the mitochondria, and its mutations cause a severe combined immunodeficiency with neutrophil maturation arrest named reticular dysgenesis (RD). Although the dysfunction of hematopoietic stem cells (HSCs) has been implicated, earlier developmental events that affect the fate of HSCs and/or hematopoietic progenitors have not been reported. Here, we used RD-patient-derived induced pluripotent stem cells (iPSCs) as a model of AK2-deficient human cells. Hematopoietic differentiation from RD-iPSCs was profoundly impaired. RD-iPSC-derived hemoangiogenic progenitor cells (HAPCs) showed decreased ATP distribution in the nucleus and altered global transcriptional profiles. Thus, AK2 has a stage-specific role in maintaining the ATP supply to the nucleus during hematopoietic differentiation, which affects the transcriptional profiles necessary for controlling the fate of multipotential HAPCs. Our data suggest that maintaining the appropriate energy level of each organelle by the intracellular redistribution of ATP is important for controlling the fate of progenitor cells.

Pluripotent stem cell models of Blau syndrome reveal an IFN-γ-dependent inflammatory response in macrophages.

BACKGROUND: Blau syndrome, or early-onset sarcoidosis, is a juvenile-onset systemic granulomatosis associated with a mutation in nucleotide-binding oligomerization domain 2 (NOD2). The underlying mechanisms of Blau syndrome leading to autoinflammation are still unclear, and there is currently no effective specific treatment for Blau syndrome. OBJECTIVES: To elucidate the mechanisms of autoinflammation in patients with Blau syndrome, we sought to clarify the relation between disease-associated mutant NOD2 and the inflammatory response in human samples. METHODS: Blau syndrome-specific induced pluripotent stem cell (iPSC) lines were established. The disease-associated NOD2 mutation of iPSCs was corrected by using a CRISPR-Cas9 system to precisely evaluate the in vitro phenotype of iPSC-derived cells. We also introduced the same NOD2 mutation into a control iPSC line. These isogenic iPSCs were then differentiated into monocytic cell lineages, and the statuses of nuclear factor κB pathway and proinflammatory cytokine secretion were investigated. RESULTS: IFN-γ acted as a priming signal through upregulation of NOD2. In iPSC-derived macrophages with mutant NOD2, IFN-γ treatment induced ligand-independent nuclear factor κB activation and proinflammatory cytokine production. RNA sequencing analysis revealed distinct transcriptional profiles of mutant macrophages both before and after IFN-γ treatment. Patient-derived macrophages demonstrated a similar IFN-γ-dependent inflammatory response. CONCLUSIONS: Our data support the significance of ligand-independent autoinflammation in the pathophysiology of Blau syndrome. Our comprehensive isogenic disease-specific iPSC panel provides a useful platform for probing therapeutic and diagnostic clues for the treatment of patients with Blau syndrome.

Insulin-producing cells derived from 'induced pluripotent stem cells' of patients with fulminant type 1 diabetes: Vulnerability to cytokine insults and increased expression of apoptosis-related genes.

AIMS/INTRODUCTION: The present study was carried out to generate induced pluripotent stem cells (iPSCs) from patients with fulminant type 1 diabetes, and evaluate the cytokine-induced apoptotic reactions of ß-like insulin-producing cells differentiated from the iPSCs. MATERIALS AND METHODS: iPSCs were generated from fibroblasts of patients with fulminant type 1 diabetes by inducing six reprogramming factors. Insulin-producing cells were differentiated from the iPSCs in vitro. The proportion of cleaved caspase-3-positive or terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling-positive cells among insulin (INS)-positive cells derived from fulminant type 1 diabetes iPSC and control human iPSC lines was evaluated under treatment with tumor necrosis factor-α, interleukin-1ß and interferon-γ. Ribonucleic acid sequencing was carried out to compare gene expressions in INS-positive cells derived from fulminant type 1 diabetes iPSC and control human iPSC lines. RESULTS: Two iPSC clones were established from each of three patients with fulminant type 1 diabetes. The differentiation of insulin-producing cells from fulminant type 1 diabetes iPSC was confirmed by immunofluorescence analysis and KCl-induced C-peptide secretion. After treatment with pro-inflammatory cytokines, these INS-positive cells showed higher expression of cleaved caspase-3 than those derived from control human iPSCs. Altered expression levels of several apoptosis-related genes were observed in INS-positive cells derived from the fulminant type 1 diabetes iPSCs by ribonucleic acid sequencing. CONCLUSIONS: We generated iPSCs from patients with fulminant type 1 diabetes and differentiated them into insulin-producing cells. This in vitro disease model can be used to elucidate the disease mechanisms of fulminant type 1 diabetes.

Identification of a High-Frequency Somatic NLRC4 Mutation as a Cause of Autoinflammation by Pluripotent Cell-Based Phenotype Dissection.

OBJECTIVE: To elucidate the genetic background of a patient with neonatal-onset multisystem inflammatory disease (NOMID) with no NLRP3 mutation. METHODS: A Japanese male child diagnosed as having NOMID was studied. The patient did not have any NLRP3 mutation, even as low-frequency mosaicism. We performed whole-exome sequencing on the patient and his parents. Induced pluripotent stem cells (iPSCs) were established from the patient's fibroblasts. The iPSCs were then differentiated into monocyte lineage to evaluate the cytokine profile. RESULTS: We established multiple iPSC clones from a patient with NOMID and incidentally found that the phenotypes of monocytes from iPSC clones were heterogeneous and could be grouped into disease and normal phenotypes. Because each iPSC clone was derived from a single somatic cell, we hypothesized that the patient had somatic mosaicism of an interleukin-1ß-related gene. Whole-exome sequencing of both representative iPSC clones and the patient's blood revealed a novel heterozygous NLRC4 mutation, p.T177A (c.529A>G), as a specific mutation in diseased iPSC clones. Knockout of the NLRC4 gene using the clustered regularly interspaced short palindromic repeat/Cas9 system in a mutant iPSC clone abrogated the pathogenic phenotype. CONCLUSION: Our findings indicate that the patient has somatic mosaicism of a novel NLRC4 mutation. To our knowledge, this is the first case showing that somatic mutation of NLRC4 causes autoinflammatory symptoms compatible with NOMID. The present study demonstrates the significance of prospective genetic screening combined with iPSC-based phenotype dissection for individualized diagnoses.

BMP-SMAD-ID promotes reprogramming to pluripotency by inhibiting p16/INK4A-dependent senescence.

Fibrodysplasia ossificans progressiva (FOP) patients carry a missense mutation in ACVR1 [617G > A (R206H)] that leads to hyperactivation of BMP-SMAD signaling. Contrary to a previous study, here we show that FOP fibroblasts showed an increased efficiency of induced pluripotent stem cell (iPSC) generation. This positive effect was attenuated by inhibitors of BMP-SMAD signaling (Dorsomorphin or LDN1931890) or transducing inhibitory SMADs (SMAD6 or SMAD7). In normal fibroblasts, the efficiency of iPSC generation was enhanced by transducing mutant ACVR1 (617G > A) or SMAD1 or adding BMP4 protein at early times during the reprogramming. In contrast, adding BMP4 at later times decreased iPSC generation. ID genes, transcriptional targets of BMP-SMAD signaling, were critical for iPSC generation. The BMP-SMAD-ID signaling axis suppressed p16/INK4A-mediated cell senescence, a major barrier to reprogramming. These results using patient cells carrying the ACVR1 R206H mutation reveal how cellular signaling and gene expression change during the reprogramming processes.

Identification of MMP1 as a novel risk factor for intracranial aneurysms in ADPKD using iPSC models.

Cardiovascular complications are the leading cause of death in autosomal dominant polycystic kidney disease (ADPKD), and intracranial aneurysm (ICA) causing subarachnoid hemorrhage is among the most serious complications. The diagnostic and therapeutic strategies for ICAs in ADPKD have not been fully established. We here generated induced pluripotent stem cells (iPSCs) from seven ADPKD patients, including four with ICAs. The vascular cells differentiated from ADPKD-iPSCs showed altered Ca(2+) entry and gene expression profiles compared with those of iPSCs from non-ADPKD subjects. We found that the expression level of a metalloenzyme gene, matrix metalloproteinase (MMP) 1, was specifically elevated in iPSC-derived endothelia from ADPKD patients with ICAs. Furthermore, we confirmed the correlation between the serum MMP1 levels and the development of ICAs in 354 ADPKD patients, indicating that high serum MMP1 levels may be a novel risk factor. These results suggest that cellular disease models with ADPKD-specific iPSCs can be used to study the disease mechanisms and to identify novel disease-related molecules or risk factors.

Impaired adipogenic capacity in induced pluripotent stem cells from lipodystrophic patients with BSCL2 mutations.

OBJECTIVE: Congenital generalized lipodystrophy (CGL) is an autosomal recessive disorder characterized by marked scarcity of adipose tissue, extreme insulin resistance, hypertriglyceridemia, hepatic steatosis and early-onset diabetes. Mutation of the BSCL2/SEIPIN gene causes the most severe form of CGL. The aim of this study was to generate induced pluripotent stem (iPS) cells from patients with CGL harboring BSCL2/SEIPIN mutations. METHODS: Skin biopsies were obtained from two Japanese patients with CGL harboring different nonsense mutations (E189X and R275X) in BSCL2/SEIPIN. The fibroblasts thus obtained were infected with retroviruses encoding OCT4, SOX2, c-MYC, and KLF4. The generated iPS cells were evaluated for pluripotency by examining the expression of pluripotency markers (alkaline phosphatase, SSEA-4, TRA-1-60, and NANOG) and their ability to differentiate to three germ layers in vitro by forming embryoid bodies, and to form teratomas in vivo. Adipogenic capacity of differentiated BSCL2-iPS cells was determined by oil red O and adipose differentiation-related protein (ADRP) staining. Rescue experiments were also performed using stable expression of wild-type BSCL2. A coimmunoprecipitation assay was conducted to investigate the interaction of SEIPIN with ADRP. RESULTS: iPS cells were generated from fibroblasts of the two patients with CGL. Each of the patient-derived iPS (BSCL2-iPS) clones showed all of the hallmarks of pluripotency and could differentiate into derivatives of all three germ layers in vitro by forming embryoid bodies, and form teratomas after injection into mouse testes. BSCL2-iPS cells maintained the mutations in BSCL2 and lacked intact BSCL2. Upon adipogenic differentiation, BSCL2-iPS cells exhibited marked reduction of lipid droplet formation concomitant with diffuse cytoplasmic distribution of ADRP, compared with iPS cells from healthy individuals. Forced expression of BSCL2 not only rescued the lipid accumulation defects, but also restored cytoplasmic punctate localization of ADRP in BSCL2-iPS cells. Coimmunoprecipitation indicated SEIPIN interacted with ADRP. CONCLUSION: BSCL2-iPS cells that recapitulate the lipodystrophic phenotypes in vitro could provide valuable models with which to study the physiology of lipid accumulation and the pathology of human lipodystrophy. We found that BSCL2 defines the localization of ADRP, which has a role in lipid accumulation and adipogenic differentiation.

Functional analysis of iPSC-derived myocytes from a patient with carnitine palmitoyltransferase II deficiency.

INTRODUCTION: Carnitine palmitoyltransferase II (CPT II) deficiency is an inherited disorder involving ß-oxidation of long-chain fatty acids (FAO), which leads to rhabdomyolysis and subsequent acute renal failure. The detailed mechanisms of disease pathogenesis remain unknown; however, the availability of relevant human cell types for investigation, such as skeletal muscle cells, is limited, and the development of novel disease models is required. METHODS: We generated human induced pluripotent stem cells (hiPSCs) from skin fibroblasts of a Japanese patient with CPT II deficiency. Mature myocytes were differentiated from the patient-derived hiPSCs by introducing myogenic differentiation 1 (MYOD1), the master transcriptional regulator of myocyte differentiation. Using an in vitro acylcarnitine profiling assay, we investigated the effects of a hypolipidemic drug, bezafibrate, and heat stress on mitochondrial FAO in CPT II-deficient myocytes and controls. RESULTS: CPT II-deficient myocytes accumulated more palmitoylcarnitine (C16) than did control myocytes. Heat stress, induced by incubation at 38°C, leads to a robust increase of C16 in CPT II-deficient myocytes, but not in controls. Bezafibrate reduced the amount of C16 in control and CPT II-deficient myocytes. DISCUSSION: In this study, we induced differentiation of CPT II-deficient hiPSCs into mature myocytes in a highly efficient and reproducible manner and recapitulated some aspects of the disease phenotypes of CPT II deficiency in the myocyte disease models. This approach addresses the challenges of modeling the abnormality of FAO in CPT II deficiency using iPSC technology and has the potential to revolutionize translational research in this field.

Induced pluripotent stem cells from patients with human fibrodysplasia ossificans progressiva show increased mineralization and cartilage formation.

BACKGROUND: Abnormal activation of endochondral bone formation in soft tissues causes significant medical diseases associated with disability and pain. Hyperactive mutations in the bone morphogenetic protein (BMP) type 1 receptor ACVR1 lead to fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder characterized by progressive ossification in soft tissues. However, the specific cellular mechanisms are unclear. In addition, the difficulty obtaining tissue samples from FOP patients and the limitations in mouse models of FOP hamper our ability to dissect the pathogenesis of FOP. METHODS: To address these challenges and develop a "disease model in a dish", we created human induced pluripotent stem cells (iPS cells) derived from normal and FOP dermal fibroblasts by two separate methods, retroviral integration or integration-free episomal vectors. We tested if the ability to contribute to different steps of endochondral bone formation was different in FOP vs. control iPS cells. RESULTS: Remarkably, FOP iPS cells showed increased mineralization and enhanced chondrogenesis in vitro. The mineralization phenotypes could be suppressed with a small-molecule inhibitor of BMP signaling, DMH1. Our results indicate that the FOP ACVR1 R206H mutation favors chondrogenesis and increases mineral deposition in vitro. CONCLUSIONS: Our findings establish a FOP disease cell model for in vitro experimentation and provide a proof-of-concept for using human iPS cell models to understand human skeletal disorders.

The moyamoya disease susceptibility variant RNF213 R4810K (rs112735431) induces genomic instability by mitotic abnormality.

Moyamoya disease (MMD) is a cerebrovascular disease characterized by occlusive lesions in the Circle of Willis. The RNF213 R4810K polymorphism increases susceptibility to MMD. In the present study, we characterized phenotypes caused by overexpression of RNF213 wild type and R4810K variant in the cell cycle to investigate the mechanism of proliferation inhibition. Overexpression of RNF213 R4810K in HeLa cells inhibited cell proliferation and extended the time of mitosis 4-fold. Ablation of spindle checkpoint by depletion of mitotic arrest deficiency 2 (MAD2) did not shorten the time of mitosis. Mitotic morphology in HeLa cells revealed that MAD2 colocalized with RNF213 R4810K. Immunoprecipitation revealed an RNF213/MAD2 complex: R4810K formed a complex with MAD2 more readily than RNF213 wild-type. Desynchronized localization of MAD2 was observed more frequently during mitosis in fibroblasts from patients (n=3, 61.0 ± 8.2%) compared with wild-type subjects (n=6, 13.1 ± 7.7%; p<0.01). Aneuploidy was observed more frequently in fibroblasts (p<0.01) and induced pluripotent stem cells (iPSCs) (p<0.03) from patients than from wild-type subjects. Vascular endothelial cells differentiated from iPSCs (iPSECs) of patients and an unaffected carrier had a longer time from prometaphase to metaphase than those from controls (p<0.05). iPSECs from the patients and unaffected carrier had significantly increased mitotic failure rates compared with controls (p<0.05). Thus, RNF213 R4810K induced mitotic abnormalities and increased risk of genomic instability.