Rational design of eukaryotic riboswitches that up-regulate IRES-mediated translation initiation with high switching efficiency through a kinetic trapping mechanism in vitro.

In general, riboswitches functioning through a cotranscriptional kinetic trapping mechanism (kt-riboswitches) show higher switching efficiencies in response to practical concentrations of their ligand molecules than eq-riboswitches, which function by an equilibrium mechanism. However, the former have been much more difficult to design due to their more complex mechanism. We here successfully developed a rational strategy for constructing eukaryotic kt-riboswitches that ligand-dependently enhance translation initiation mediated by an internal ribosome entry site (IRES). This was achieved both by utilizing some predicted structural features of a highly efficient bacterial kt-riboswitch identified through screening and by completely decoupling an aptamer domain from the IRES. Three kt-riboswitches optimized through this strategy, each responding to a different ligand, exhibited three- to sevenfold higher induction ratios (up to ∼90) than previously optimized eq-riboswitches regulating the same IRES-mediated translation in wheat germ extract. Because the IRES used functions well in various eukaryotic expression systems, these types of kt-riboswitches are expected to serve as major eukaryotic gene regulators based on RNA. In addition, the present strategy could be applied to the rational construction of other types of kt-riboswitches, including those functioning in bacterial expression systems.

Lifelong cardiovascular care in Turner syndrome: two cases with review of literature.

Cardiovascular disease is one of the most important complications in girls and women with Turner syndrome (TS). Although the latest international guideline provides useful suggestions for the management of cardiovascular diseases in TS, some unknown cardiac conditions warrant physicians' attention and awareness. Here, we have reported two adult cases wherein significant cardiovascular diseases were detected during the transition period. The first case patient was diagnosed with aortic crank deformity and left subclavian artery aneurysm at 14 years based on the report of cardiac catheterization, computed tomography angiography, and cardiac magnetic resonance imaging, which had remained undetected by annual evaluations using transthoracic echocardiography (TTE). This case emphasizes the importance of cardiac reevaluation during the transition period. The second case patient was diagnosed with moderate mitral valve regurgitation (MR) due to mitral valve prolapse at 18 years through TTE, although the first evaluation at 7 years by TTE detected slight MR without any clinical concerns. The condition however progressed to severe MR at 28 years, requiring mitral valvuloplasty. MR is the most common valve disease worldwide, which makes it challenging to comprehend whether the condition is a complication. However, the condition requiring surgery at this age is extremely rare, which implies the possibility of early progression. Because almost all literature on cardiovascular complications in TS is cross-sectional, further information about longitudinal cardiovascular conditions is vital for optimal care for girls and women with TS. The two cases reported in this article provide significant information for improving lifelong cardiovascular health issues in TS.

Three KINSSHIP syndrome patients with mosaic and germline AFF3 variants.

AFF3 at 2q11.2 encodes the nuclear transcriptional activator AF4/FMR2 Family Member 3. AFF3 constitutes super elongation complex like 3, which plays a role in promoting the expression of genes involved in neurogenesis and development. The degron motif in AFF3 with nine highly conserved amino acids is recognized by E3 ubiquitin ligase to induce protein degradation. Recently, AFF3 missense variants in this region and variants featuring deletion including this region were identified and shown to cause KINSSHIP syndrome. In this study, we identified two novel and one previously reported missense variants in the degron of AFF3 in three unrelated Japanese patients. Notably, two of these three variants exhibited mosaicism in the examined tissues. This study suggests that mosaic variants also cause KINSSHIP syndrome, showing various phenotypes.

First phase 1 clinical study of olaparib in pediatric patients with refractory solid tumors.

BACKGROUND: The survival of patients with high-risk, refractory, relapsed, or metastatic solid tumors remains dismal. A poly(ADP-ribose) polymerase (PARP) inhibitor could be effective for the treatment of pediatric solid tumors with defective homologous recombination. METHODS: This open-label, multicenter phase 1 clinical trial evaluated the safety, tolerability, and efficacy of olaparib, a PARP inhibitor, in pediatric patients with refractory solid tumors to recommend a dose for Phase 2 trials. Olaparib (62.5, 125, and 187.5 mg/m2 twice daily) was administered orally every day (1 cycle = 28 days) using a standard 3 + 3 dose-escalation design. Patients aged 3-18 years with recurrent pediatric solid tumors were eligible. Pharmacokinetic and pharmacodynamic analyses were performed. RESULTS: Fifteen patients were enrolled and received olaparib monotherapy, which was well tolerated. The recommended phase 2 dose for daily administration was 187.5 mg/m2 twice daily. Pharmacokinetics were dose proportional. The area under the concentration-time curve from 0 to 12 h and the peak plasma concentration for 187.5 mg/m2 twice daily in children were comparable to previous data obtained in a 200-mg, twice-daily cohort and lower than those in the 300-mg twice-daily cohort in adults. Pharmacodynamic studies demonstrated substantial inhibition of PARP activity. Two partial responses were observed in patients with Wilms tumor and neuroblastoma. CONCLUSIONS: This report is the first clinical trial to describe the use of a PARP inhibitor as monotherapy in children. Olaparib was well tolerated, with preliminary antitumor responses observed in DNA damage response-defective pediatric tumors. LAY SUMMARY: This Phase 1 trial evaluated the efficacy and safety of olaparib in patients with refractory childhood solid tumors. Olaparib was well tolerated, achieving objective response in 2/15 patients. The DNA damage response was attenuated in nearly one-half of advanced neuroblastoma patients, demonstrating the utility of the PARP inhibitor. The results support further investigation of olaparib as a new treatment for DNA damage-response or repair-defective pediatric cancers.

A risk-stratified therapy for infants with acute lymphoblastic leukemia: a report from the JPLSG MLL-10 trial.

The prognosis for infants with acute lymphoblastic leukemia (ALL), particularly those with KMT2A gene rearrangement (KMT2A-r), is dismal. Continuous efforts have been made in Japan to investigate the role of hematopoietic stem cell transplantation (HSCT) for infants with KMT2A-r ALL, but improvement in outcome was modest. In the Japanese Pediatric Leukemia/Lymphoma Study Group MLL-10 trial, infants with ALL were stratified into 3 risk groups (low risk [LR], intermediate risk [IR], and high risk [HR]) according to KMT2A status, age, and presence of central nervous system leukemia. Children's Oncology Group AALL0631 modified chemotherapy with the addition of high-dose cytarabine in early intensification was introduced to KMT2A-r patients, and the option of HSCT was restricted to HR patients only. The role of minimal residual disease (MRD) was also evaluated. Ninety eligible infants were stratified into LR (n = 15), IR (n = 19), or HR (n = 56) risk groups. The 3-year event-free survival (EFS) rate for patients with KMT2A-r ALL (IR + HR) was 66.2% (standard error [SE], 5.6%), and for those with germline KMT2A (KMT2A-g) ALL (LR), the 3-year EFS rate was 93.3% (SE, 6.4%). The 3-year EFS rate was 94.4% (SE, 5.4%) for IR patients and 56.6% (SE, 6.8%) for HR patients. In multivariable analysis, female sex and MRD ≥0.01% at the end of early consolidation were significant factors for poor prognosis. Risk stratification and introduction of intensive chemotherapy in this study were effective and were able to eliminate HSCT for a subset of infants with KMT2A-r ALL. Early clearance of MRD seems to have translated into favorable outcomes and should be incorporated into risk stratifications in future trials. This trial was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as #UMIN000004801.

Eukaryotic artificial ON-riboswitches that respond efficiently to mid-sized short peptides.

We chose two types of mid-sized Arg-rich peptides (Rev-pep and Tat-pep) as ligands and used their aptamers to construct efficient eukaryotic ON-riboswitches (ligand-dependently upregulating riboswitches). Due to the aptamers' high affinities, the best Rev-pep-responsive and Tat-pep-responsive riboswitches obtained showed much higher switching efficiencies at low ligand concentrations than small ligand-responsive ON-riboswitches in the same mechanism. In addition, despite the high sequence similarity of Rev-pep and Tat-pep, the two best riboswitches were almost insensitive to each other's peptide ligand. Considering the high responsiveness and specificity along with the versatility of the expression platform used and the applicability of Arg-rich peptides, this orthogonal pair of riboswitches would be widely useful eukaryotic gene regulators or biosensors.

Postchemotherapy immune status in infants with acute lymphoblastic leukemia: A report from the JPLSG MLL-10 trial.

The MLL-10 trial (UMIN000004801) modified a Children's Oncology Group (COG) AALL0631 therapy for infants with KMT2A-rearranged acute lymphoblastic leukemia (ALL). In 2016, one registered case developed secondary immunodeficiency during maintenance therapy and eventually died due to cytomegalovirus infection. Around the same time, fatal secondary immunodeficiencies were reported in five infants with ALL in North America who had received COG-based chemotherapy between 1996 and 2015. Given these cases, we decided to conduct a retrospective study on the postchemotherapy immune status of infants with ALL. A questionnaire collected data on posttreatment immune function, frequency of infections, and supportive care for the 34 infants in the MLL-10 trial. Patients receiving allogeneic hematopoietic stem cell transplantation in first remission were excluded. Responses to the survey were obtained in 28 cases (85%). Most patients were immunocompetent after the completion of chemotherapy (median follow-up duration from the day of chemotherapy completion was 431 days), except for the aforementioned case. There were seven patients with nonsevere viral infection, all of whom recovered. In conclusion, severe chemotherapy-induced immunodeficiency in infants with ALL appears to be rare, but prospective data collection of immune function is necessary to clarify this finding.

Coupled in vitro transcription/translation based on wheat germ extract for efficient expression from PCR-generated templates in short-time batch reactions.

We successfully constructed a coupled in vitro transcription/translation (cIVTT) system based on wheat germ extract (WGE) for efficient expression from PCR-generated DNA templates in short-time (∼3-h) batch reactions. The productivity of this system under optimized conditions was 85 µg (2.8 nmol) per 1 mL of reaction solution (corresponding to 425 µg per 1 mL of WGE), which was about 9-fold higher than that by the conventional batch method using mRNA as a template. The DNA template concentration required for efficient cIVTT was as low as 2.5 nM, which is much lower than those required for other eukaryotic cIVTT systems to maximize their productivity (30-50 nM). The productivity of the present system with a 2.5 nM template was 80-fold and 4-fold higher than that of a commercially available WGE-based cIVTT system with a 2.5 nM and a 40 nM template, respectively. In addition, the present system functioned well in a liposome (i.e., in an artificial cell) without a loss of productivity. Given that WGE-based systems have the advantage of being suitable for the expression of a broad range of proteins, the present cIVTT system is expected to be widely used in future cell-free synthetic biology.

A needle-type micro-sampling device for collecting nanoliter sap sample from plants.

In plant research, measuring the physiological parameters of plants is vital for understanding the behavior and response of plants to changes in the external environment. Plant sap analysis provides an approach for elucidating the physiological condition of plants. However, to facilitate accurate sap analysis, a sampling device capable of collecting sap samples from plants is required. In this paper, a minimally invasive, needle-type micro-sampling device capable of collecting nanoliter (~ 91 nL) quantities of sap from plants is described. The developed micro-sampling system showed great reproducibility (3%) in experiments designed to assess sampling performance. As a proof of concept, sap samples were collected continuously from target plants with the micro-sampling system, and the dynamic changes in potassium ions, plant hormones and sugar levels inside plants were analyzed. The results demonstrated the feasibility of the micro-sampling device and its potential for developing a measurement system for plant research in the future.

Renal morphology and function from childhood to adulthood in Turner syndrome.

BACKGROUND: Turner syndrome (TS) is a chromosomal disorder with various complications, including congenital anomaly of the kidney and urinary tract (CAKUT). However, its renal function remains poorly known. Therefore, this study aimed to evaluate renal function in TS of various ages from childhood to adulthood. METHODS: We retrospectively analyzed 63 patients with TS who visited our hospital between 1989 and 2020, examined their renal morphology, and analyzed renal function by calculating the estimated glomerular filtration rate (eGFR) using formulas applicable for Japanese populations. RESULTS: Renal morphological abnormality was observed in 22 cases (35.0%) (horseshoe kidney, 7 [11.1%]; hydronephrosis, 11 [17.5%]; duplex collecting system, 3 [4.8%]; and single unilateral kidney, 1 [1.6%]). We evaluated the eGFR of 47 subjects aged 2.8-39.3 years and classified them into Group 1 (with CAKUT, n = 15) and Group 2 (without CAKUT, n = 32). The eGFR at the first visit and the final follow-up was not statistically different between these groups. In Group 1 with CAKUT, the eGFR was not significantly different between that at the first visit and that at the final follow-up (p = 0.21). During the observation period (median, 7.9 years), the eGFR of all individuals in both groups gradually decreased with age, but did not fall < 60 mL/min/1.73 m2, which defines chronic kidney disease (CKD). CONCLUSIONS: The renal function of TS remained normal in all cases during our investigation period, and no one developed CKD by the age of 40 years.

Autologous Stem Cell Transplantation for Children With Renal Tumors, and Adults With Wilms Tumor: Retrospective Analysis of the Japanese Transplant Registry Unified Management Program.

BACKGROUND: Almost all pediatric patients with renal tumors are diagnosed with nephroblastoma (Wilms tumor), clear cell sarcoma, or malignant rhabdoid tumor. The choice of treatment is important for relapsed and refractory patients with nephroblastoma. Furthermore, clear cell sarcoma of the kidney (CCSK) and malignant rhabdoid tumor of the kidney (MRTK) have a poor prognosis compared with nephroblastoma. Thus, stem cell transplantation (SCT) is sometimes selected to treat these tumors. PATIENTS AND METHODS: The authors targeted a total of 84 patients with nephroblastoma, CCSK, and MRTK who underwent a first autologous SCT between 1992 and 2014, and were registered in the Japanese Transplant Registry Unified Management Program system. The authors retrospectively analyzed the SCT data for survival rate. RESULTS: Five-year overall survival rates for nephroblastoma, CCSK, and MRTK were 72.4%±6.3%, 46.8%±13.8%, and 36.4%±14.5%, respectively. The event-free survival rates at 5 years were 64.9%±6.7%, 35.7%±12.8%, and 27.3%±13.4%, respectively. The relapse rates at 5 years were 25.3%±11.4%, 46.2%±28.4%, and 60.0%±43.1%, respectively. CONCLUSION: Although the survival rate for nephroblastoma was relatively high, those of CCSK and MRTK were poor.

Four stay-sutures method: a simplified hand-sewn purse-string suture in laparoscopic circular-stapled esophagojejunostomy.

Laparoscopic esophagojejunostomy is a challenging procedure because of its technical difficulty. We herein report a new method involving circular-stapled anastomosis using a hand-sewn suture with four stay-sutures and evaluate its outcomes. Esophagojejunostomy using this method was performed in 36 consecutive patients with clinical stage I gastric cancer at the authors' institutions. The key feature of our procedure was the placement of four full-thickness stay-sutures to anchor the esophageal stump prior to the hand-sewn purse-string suture. The median operation time and mean anvil fixation time were 315.5 and 21.9 min, respectively. The mortality rate was 0%, although anastomotic leakage following esophagojejunostomy was observed in 1 patient (2.8%), and anastomotic stenosis was observed in another patient (2.8%). Intracorporeal esophagojejunostomy using the four stay-sutures method appears to be safe and feasible. We believe that this method enables hand-sewn purse-string suturing to be performed more easily.

Mutation of the start codon to enhance Cripavirus internal ribosome entry site-mediated translation in a wheat germ extract.

Wheat germ extract (WGE) is one of the most widely used eukaryotic cell-free translation systems for easy synthesis of a broad range of proteins merely by adding template mRNAs. Its productivity has thus far been improved by removing translational inhibitors from the extract and stabilizing the template with terminal protectors. Nonetheless, there remains room for increasing the yield by designing a terminally protected template with higher susceptibility to translation. Given the fact that a 5' terminal protector is a strong inhibitor of the canonical translation, we herein focused on Cripavirus internal ribosome entry sites (IRESes), which allow for a unique translation initiation from a non-AUG start codon without the help of any initiation factors. We mutated their start codons to enhance the IRES-mediated translation efficiency in WGE. One of the mutants showed considerably higher efficiency, 3-4-fold higher than that of its wild type, and also 3-4-fold higher than the canonical translation efficiency by an IRES-free mRNA having one of the most effective canonical-translation enhancers. Because this mutated IRES is compatible with different types of genes and terminal protectors, we expect it will be widely used to synthesize proteins in WGE.

In vitro selection of a 3' terminal short protector that stabilizes transcripts to improve the translation efficiency in a wheat germ extract.

Wheat cell-free expression systems based on wheat germ extract (WGE) enable us to briefly synthesize various types of proteins in vitro merely by exogenously adding their mRNA templates. Moreover, it is possible to produce larger amounts of protein by thoroughly removing the endosperm, which contains many translation inhibitors, including ribonucleases (RNases). However, because small amounts of RNases are also present even in an endosperm-free, high-quality WGE (hqWGE), the in-vitro transcribed mRNA is rapidly degraded. In particular, 3' exonucleases have been considered as the major RNases that degrade mRNA. We thus herein performed in vitro selection to find an effective, short 3' protector sequence from a random RNA pool. The selected sequences stabilized in vitro transcripts in the hqWGE more effectively than the previously reported, longer 3' protectors did. In addition, when one of these 3' protectors was minimized and then fused to mRNA, the translation efficiency increased 5-6-fold in the hqWGE, mainly due to the mRNA stabilization.

Canonical translation-modulating OFF-riboswitches with a single aptamer binding to a small molecule that function in a higher eukaryotic cell-free expression system.

We have found that OFF-riboswitches that ligand-dependently downregulate the canonical translation in a higher eukaryotic expression system (wheat germ extract) can be easily created by inserting a single aptamer into the 5' untranslated region (UTR) of mRNA, even if its ligand is as small as theophylline. The key is the position of the inserted aptamer: the 5' end (+0 position) is much better than other positions for inhibiting canonical translation with the aptamer-ligand complex. The data showed that ribosome loading is suppressed by a rigid structure in the 5' end, and this suppression is dependent on the structure's stability but not on its size. Although this preference of aptamer insertion point contradicts the results in a lower eukaryote, it accords with the fact that the 5'-end structural hindrance is more effective for blocking the ribosome in higher eukaryotes. Therefore, the present type of OFF-riboswitch would function in various higher eukaryotic expression systems.

OsPIN2, which encodes a member of the auxin efflux carrier proteins, is involved in root elongation growth and lateral root formation patterns via the regulation of auxin distribution in rice.

Auxin flow is important for different root developmental processes such as root formation, emergence, elongation and gravitropism. However, the detailed information about the mechanisms regulating the auxin flow is less well understood in rice. We characterized the auxin transport-related mutants, Ospin-formed2-1 (Ospin2-1) and Ospin2-2, which exhibited curly root phenotypes and altered lateral root formation patterns in rice. The OsPIN2 gene encodes a member of the auxin efflux carrier proteins that possibly regulates the basipetal auxin flow from the root tip toward the root elongation zone. According to DR5-driven GUS expression, there is an asymmetric auxin distribution in the mutants that corresponded with the asymmetric cell elongation pattern in the mutant root tip. Auxin transport inhibitor, N-1-naphthylphthalamic acid and Ospin2-1 Osiaa13 double mutant rescued the curly root phenotype indicating that this phenotype results from a defect in proper auxin distribution. The typical curly root phenotype was not observed when Ospin2-1 was grown in distilled water as an alternative to tap water, although higher auxin levels were found at the root tip region of the mutant than that of the wild-type. Therefore, the lateral root formation zone in the mutant was shifted basipetally compared with the wild-type. These results reflect that an altered auxin flow in the root tip region is responsible for root elongation growth and lateral root formation patterns in rice.

Secondary bone/soft tissue sarcoma in childhood cancer survivors: a nationwide hospital-based case-series study in Japan.

BACKGROUND: Secondary cancer is the most life-threatening late effect of childhood cancer. We investigated the clinical features of secondary bone/soft tissue sarcoma among childhood cancer survivors (CCSs). METHODS: We conducted a retrospective case-series study of 10 069 CCSs newly diagnosed with cancer between 1980 and 2009 across 15 Japanese hospitals. Twenty-one cases of pathologically diagnosed secondary bone/soft tissue sarcoma were selected, and the respective clinical courses were determined using additional questionnaires. RESULTS: The primary cancers included retinoblastoma (n = 7), acute lymphoblastic leukemia (n = 5), lymphoma (n = 5), osteosarcoma (n = 1), rhabdomyosarcoma (n = 1), brain tumor (n = 1) and Langerhans cell histiocytosis (n = 1). The median age at the primary cancer diagnosis was 2.9 years, and the male-to-female ratio was 16:5. The histological classifications of the secondary sarcoma included osteosarcoma (n = 10), malignant peripheral nerve sheath tumor (n = 4), rhabdomyosarcoma (n = 3), Ewing's sarcoma (n = 3) and primitive neuroectodermal tumor (n = 1). The median latency period to the secondary sarcoma was 10.2 years. Significant risk factors for secondary sarcoma in the multivariate Cox regression model included a history of retinoblastoma as the primary cancer (hazard ratio [HR], 20.9; 95% confidence interval [CI], 5.70-76.5) and autologous stem cell transplantation (SCT) (HR, 2.56; 95% CI, 1.08-6.03). Seventeen CCSs with secondary sarcoma underwent radiation, and nine, hematopoietic SCT. Twelve CCSs with secondary sarcoma achieved disease-free survival, while CCSs with hematological cancer or relapsed primary cancer who developed secondary sarcoma had the worst prognoses. CONCLUSION: The prognoses of CCSs with secondary sarcoma may depend on the primary cancer or prior relapse of primary cancer.

Effects of Magnesium Oxide on the Serum Duloxetine Concentration and Antidepressant-Like Effects of Duloxetine in Rats.

Duloxetine is a serotonin/noradrenaline reuptake inhibitor that is used as an antidepressant. However, it is known to cause constipation as a side effect. Magnesium compounds, such as magnesium oxide and magnesium hydroxide aqueous solution, are often combined with duloxetine to ameliorate the constipation caused by duloxetine. However, there is concern that these magnesium compounds might alter the effects of duloxetine via physicochemical interactions. In this study, we attempted to clarify the interactions that take place between duloxetine and magnesium oxide using in vivo and in vitro experiments. We evaluated the influence of magnesium oxide on in vitro duloxetine concentrations using HPLC. In addition, we examined the in vivo antidepressant-like effects and serum concentrations of duloxetine in rats. In the in vitro experiment, the duloxetine concentration was significantly decreased by co-treatment with magnesium oxide. In the in vivo experiment, the antidepressant-like effects of duloxetine were not affected by the combined oral administration of magnesium oxide and a duloxetine formulation although the serum duloxetine level was significantly decreased. However, the antidepressant-like effects of a duloxetine reagent were significantly attenuated by the co-administration of magnesium oxide. These results suggest that duloxetine and magnesium oxide directly interact and that such interactions affect the absorption and antidepressant-like effects of duloxetine.

Secondary cancer after a childhood cancer diagnosis: viewpoints considering primary cancer.

BACKGROUNDS: Multidisciplinary therapy has increased the risk of subsequent late effects, but detailed analyses on secondary cancers in childhood cancer survivors (CCSs) are limited in Asian countries. METHODS: This was a retrospective cohort study comprising 10,069 CCSs who were diagnosed between 1980 and 2009 across 15 Japanese hospitals. We conducted secondary analyses to estimate the incidence of secondary cancer according to each primary malignancy and to elucidate the association between primary and secondary cancers. We also explored the risk factors for the development of secondary cancer in each independent primary malignancy. RESULTS: The cumulative incidence of secondary cancer at 20 years varied among primary cancers: hematological malignancy, 3.1% (95% CI 2.2-4.3); retinoblastoma, 6.6% (95% CI 1.5-16.8); pediatric solid tumor, 2.5% (95% CI 1.3-4.2); brain tumors, 5.2% (95% CI 1.7-11.8) bone/soft tissue sarcoma, 5.2% (95% CI 2.3-10.1); and others, 3.3% (95% CI 1.6-6.0) (p = 0.015). The cumulative incidence of secondary cancers is highest in those with osteosarcoma (13.1%) followed by those with hepatoblastoma (8.4%) and retinoblastoma (6.6%). Close association between the primary and secondary cancer diagnoses was found. The risk factors for secondary cancer development depended on the primary cancer, but autologous/allogeneic stem cell transplantation was a relatively common risk factor. CONCLUSION: The cumulative incidence of secondary cancer varied among primary cancers. The primary cancer was closely associated with the secondary cancer but stem cell transplantation was a common risk factor for secondary cancers among CCSs.

TALEN-mediated single-base-pair editing identification of an intergenic mutation upstream of BUB1B as causative of PCS (MVA) syndrome.

Cancer-prone syndrome of premature chromatid separation with mosaic variegated aneuploidy [PCS (MVA) syndrome] is a rare autosomal recessive disorder characterized by constitutional aneuploidy and a high risk of childhood cancer. We previously reported monoallelic mutations in the BUB1B gene (encoding BUBR1) in seven Japanese families with the syndrome. No second mutation was found in the opposite allele of any of the families studied, although a conserved BUB1B haplotype and a decreased transcript were identified. To clarify the molecular pathology of the second allele, we extended our mutational search to a candidate region surrounding BUB1B. A unique single nucleotide substitution, G > A at ss802470619, was identified in an intergenic region 44 kb upstream of a BUB1B transcription start site, which cosegregated with the disorder. To examine whether this is the causal mutation, we designed a transcription activator-like effector nuclease-mediated two-step single-base pair editing strategy and biallelically introduced this substitution into cultured human cells. The cell clones showed reduced BUB1B transcripts, increased PCS frequency, and MVA, which are the hallmarks of the syndrome. We also encountered a case of a Japanese infant with PCS (MVA) syndrome carrying a homozygous single nucleotide substitution at ss802470619. These results suggested that the nucleotide substitution identified was the causal mutation of PCS (MVA) syndrome.