RecN spatially and temporally controls RecA-mediated repair of DNA double-strand breaks.

RecN, a bacterial structural maintenance of chromosomes-like protein, plays an important role in maintaining genomic integrity by facilitating the repair of DNA double-strand breaks (DSBs). However, how RecN-dependent chromosome dynamics are integrated with DSB repair remains unclear. Here, we investigated the dynamics of RecN in response to DNA damage by inducing RecN from the PBAD promoter at different time points. We found that mitomycin C (MMC)-treated ΔrecN cells exhibited nucleoid fragmentation and reduced cell survival; however, when RecN was induced with arabinose in MMC-exposed ΔrecN cells, it increased a level of cell viability to similar extent as WT cells. Furthermore, in MMC-treated ΔrecN cells, arabinose-induced RecN colocalized with RecA in nucleoid gaps between fragmented nucleoids and restored normal nucleoid structures. These results suggest that the aberrant nucleoid structures observed in MMC-treated ΔrecN cells do not represent catastrophic chromosome disruption but rather an interruption of the RecA-mediated process. Thus, RecN can resume DSB repair by stimulating RecA-mediated homologous recombination, even when chromosome integrity is compromised. Our data demonstrate that RecA-mediated presynapsis and synapsis are spatiotemporally separable, wherein RecN is involved in facilitating both processes presumably by orchestrating the dynamics of both RecA and chromosomes, highlighting the essential role of RecN in the repair of DSBs.

N-terminal acetyltransferase NatB regulates Rad51-dependent repair of double-strand breaks in Saccharomyces cerevisiae.

Homologous recombination (HR) is a highly accurate mechanism for repairing DNA double-strand breaks (DSBs) that arise from various genotoxic insults and blocked replication forks. Defects in HR and unscheduled HR can interfere with other cellular processes such as DNA replication and chromosome segregation, leading to genome instability and cell death. Therefore, the HR process has to be tightly controlled. Protein N-terminal acetylation is one of the most common modifications in eukaryotic organisms. Studies in budding yeast implicate a role for NatB acetyltransferase in HR repair, but precisely how this modification regulates HR repair and genome integrity is unknown. In this study, we show that cells lacking NatB, a dimeric complex composed of Nat3 and Mdm2, are sensitive to the DNA alkylating agent methyl methanesulfonate (MMS), and that overexpression of Rad51 suppresses the MMS sensitivity of nat3Δ cells. Nat3-deficient cells have increased levels of Rad52-yellow fluorescent protein foci and fail to repair DSBs after release from MMS exposure. We also found that Nat3 is required for HR-dependent gene conversion and gene targeting. Importantly, we observed that nat3Δ mutation partially suppressed MMS sensitivity in srs2Δ cells and the synthetic sickness of srs2Δ sgs1Δ cells. Altogether, our results indicate that NatB functions upstream of Srs2 to activate the Rad51-dependent HR pathway for DSB repair.

Effectiveness of Plasma Exchange in a Girl With Corticosteroid-Resistant Anti-myelin Oligodendrocyte Glycoprotein-Associated Disease.

The patient was a 6-year-old girl with clinically isolated syndrome-like anti-myelin oligodendrocyte glycoprotein-associated disease (MOG-AD). Methylprednisolone pulse therapy resolved her cerebral lesion, and her visual acuity and field fully recovered after plasma exchange. This is the first case report presenting the therapeutic course in a child with clinically isolated syndrome-like MOG-AD. [J Pediatr Ophthalmol Strabismus. 2023;60(2):e11-e15.].

The Japanese Pediatric Continuous Renal Replacement Therapy (jpCRRT) Registry: Study Protocol.

BACKGROUND: The use of continuous renal replacement therapy (CRRT) in critically ill children is rapidly increasing, but the standard of care has not yet been established and prognosis remains poor. To develop optimal CRRT strategies, we launched a research project generating the Japanese Pediatric CRRT registry, a multicenter registry of CRRT in Japanese pediatric intensive care units (PICUs), to investigate the actual status of CRRT in recent years in PICUs, where data are lacking. METHODS: This manuscript presents a protocol for planning a multicenter prospective registry. As of April 2023, 15 Japanese PICUs are voluntarily participating. Patients enrolled are those <16 years of age who enter the PICUs of the collaborating institutions, require CRRT, and have the guardians' consent. CRRT is defined as anticipated to be required for >24 hours, and CRRT connected to extracorporeal membrane oxygenation is also included. The registry is an online registry system managed by the University Hospital Medical Information Network. The primary outcomes are Pediatric Cerebral Performance Category Scale at PICU discharge and 6 months post-discharge (deaths included), persistent need for dialysis, and PICU readmission within 6 months. The secondary outcomes are adverse events during and immediately after CRRT initiation, and initial circuit life span. CONCLUSIONS: This project will examine the differences in outcomes of CRRT in PICUs in specific patient and treatment groups and will be used to design future interventional studies. We will also aim to establish a platform for a multicenter registry study in Japanese PICUs, considering the current lack of such a platform.

Diploid-associated adaptation to chronic low-dose UV irradiation requires homologous recombination in Saccharomyces cerevisiae.

Ultraviolet-induced DNA lesions impede DNA replication and transcription and are therefore a potential source of genome instability. Here, we performed serial transfer experiments on nucleotide excision repair-deficient (rad14Δ) yeast cells in the presence of chronic low-dose ultraviolet irradiation, focusing on the mechanisms underlying adaptive responses to chronic low-dose ultraviolet irradiation. Our results show that the entire haploid rad14Δ population rapidly becomes diploid during chronic low-dose ultraviolet exposure, and the evolved diploid rad14Δ cells were more chronic low-dose ultraviolet-resistant than haploid cells. Strikingly, single-stranded DNA, but not pyrimidine dimer, accumulation is associated with diploid-dependent fitness in response to chronic low-dose ultraviolet stress, suggesting that efficient repair of single-stranded DNA tracts is beneficial for chronic low-dose ultraviolet tolerance. Consistent with this hypothesis, homologous recombination is essential for the rapid evolutionary adaptation of diploidy, and rad14Δ cells lacking Rad51 recombinase, a key player in homologous recombination, exhibited abnormal cell morphology characterized by multiple RPA-yellow fluorescent protein foci after chronic low-dose ultraviolet exposure. Furthermore, interhomolog recombination is increased in chronic low-dose ultraviolet-exposed rad14Δ diploids, which causes frequent loss of heterozygosity. Thus, our results highlight the importance of homologous recombination in the survival and genomic stability of cells with unrepaired lesions.

Upregulation of OASIS/CREB3L1 in podocytes contributes to the disturbance of kidney homeostasis.

Podocyte injury is involved in the onset and progression of various kidney diseases. We previously demonstrated that the transcription factor, old astrocyte specifically induced substance (OASIS) in myofibroblasts, contributes to kidney fibrosis, as a novel role of OASIS in the kidneys. Importantly, we found that OASIS is also expressed in podocytes; however, the pathophysiological significance of OASIS in podocytes remains unknown. Upon lipopolysaccharide (LPS) treatment, there is an increase in OASIS in murine podocytes. Enhanced serum creatinine levels and tubular injury, but not albuminuria and podocyte injury, are attenuated upon podocyte-restricted OASIS knockout in LPS-treated mice, as well as diabetic mice. The protective effects of podocyte-specific OASIS deficiency on tubular injury are mediated by protein kinase C iota (PRKCI/PKCι), which is negatively regulated by OASIS in podocytes. Furthermore, podocyte-restricted OASIS transgenic mice show tubular injury and tubulointerstitial fibrosis, with severe albuminuria and podocyte degeneration. Finally, there is an increase in OASIS-positive podocytes in the glomeruli of patients with minimal change nephrotic syndrome and diabetic nephropathy. Taken together, OASIS in podocytes contributes to podocyte and/or tubular injury, in part through decreased PRKCI. The induction of OASIS in podocytes is a critical event for the disturbance of kidney homeostasis.

Transcription factor old astrocyte specifically induced substance is a novel regulator of kidney fibrosis.

Prevention of kidney fibrosis is an essential requisite for effective therapy in preventing chronic kidney disease (CKD). Here, we identify Old astrocyte specifically induced substance (OASIS)/cAMP responsive element-binding protein 3-like 1 (CREB3l1), a CREB/ATF family transcription factor, as a candidate profibrotic gene that drives the final common pathological step along the fibrotic pathway in CKD. Although microarray data from diseased patient kidneys and fibrotic mouse model kidneys both exhibit OASIS/Creb3l1 upregulation, the pathophysiological roles of OASIS in CKD remains unknown. Immunohistochemistry revealed that OASIS protein was overexpressed in human fibrotic kidney compared with normal kidney. Moreover, OASIS was upregulated in murine fibrotic kidneys, following unilateral ureteral obstruction (UUO), resulting in an increase in the number of OASIS-expressing pathological myofibroblasts. In vitro assays revealed exogenous TGF-ß1 increased OASIS expression coincident with fibroblast-to-myofibroblast transition and OASIS contributed to TGF-ß1-mediated myofibroblast migration and increased proliferation. Significantly, in vivo kidney fibrosis induced via UUO or ischemia/reperfusion injury was ameliorated by systemic genetic knockout of OASIS, accompanied by reduced myofibroblast proliferation. Microarrays revealed that the transmembrane glycoprotein Bone marrow stromal antigen 2 (Bst2) expression was reduced in OASIS knockout myofibroblasts. Interestingly, a systemic anti-Bst2 blocking antibody approach attenuated kidney fibrosis in normal mice but not in OASIS knockout mice after UUO, signifying Bst2 functions downstream of OASIS. Finally, myofibroblast-restricted OASIS conditional knockouts resulted in resistance to kidney fibrosis. Taken together, OASIS in myofibroblasts promotes kidney fibrosis, at least in part, via increased Bst2 expression. Thus, we have identified and demonstrated that OASIS signaling is a novel regulator of kidney fibrosis.

Immune-complex glomerulonephritis with a membranoproliferative pattern in Frasier syndrome: a case report and review of the literature.

BACKGROUND: Mutations in the Wilms tumor 1 gene cause a spectrum of podocytopathy ranging from diffuse mesangial sclerosis to focal segmental glomerulosclerosis. In a considerable fraction of patients with Wilms tumor 1 mutations, the distinctive histology of immune-complex-type glomerulonephritis has been reported. However, the clinical relevance and etiologic mechanisms remain unknown. CASE PRESENTATION: A 5-year-old child presented with steroid-resistant nephrotic range proteinuria. Initial renal biopsy revealed predominant diffuse mesangial proliferation with a double-contour and coexisting milder changes of focal segmental glomerulosclerosis. Immunofluorescence and electron microscopy revealed a full-house-pattern deposition of immune complexes in the subendothelial and paramesangial areas. Serial biopsies at 6 and 8 years of age revealed that more remarkable changes of focal segmental glomerulosclerosis had developed on top of the initial proliferative glomerulonephritis. Identification of a de novo Wilms tumor 1 splice donor-site mutation in intron 9 (NM_024426.6:c.1447 + 4C > T) and 46,XY-gonadal dysgenesis led to the diagnosis of Frasier syndrome. CONCLUSIONS: Our findings, together with those of others, point to the importance of heterogeneity in clinicopathological phenotypes caused by Wilms tumor 1 mutations and suggest that immune-complex-mediated membranoproliferative glomerulopathy should be considered as a histological variant.

A Pediatric Case of Relapsing-Remitting Multiple Sclerosis Onset following Varicella Zoster Ophthalmicus with Optic Neuritis.

Some epidemiological studies have implied a pathogenetic association between varicella zoster virus (VZV) and multiple sclerosis (MS); this, however, remains controversial. The present report describes a case involving an immunocompetent 10-year-old girl who developed relapsing-remitting MS following the prolonged reactivation of VZV inside the first branch of the trigeminal nerve, exhibiting herpes zoster ophthalmicus with severe optic neuritis. Symptoms related to herpes zoster ophthalmicus and MS appeared consecutively in the 10-week period after the appearance of vesicles. This suggests that the onset of MS was triggered by some mechanism involving VZV reactivation in the first branch of the trigeminal nerve. To the best of our knowledge, this report is the first to describe a relationship between the onset of MS and herpes zoster ophthalmicus. Early diagnosis and aggressive antiviral therapy are important in cases of herpes zoster ophthalmicus to prevent the possible development of MS as well as visual impairment as sequela.

Polycythemia, capillary rarefaction, and focal glomerulosclerosis in two adolescents born extremely low birth weight and premature.

BACKGROUND: Low birthweight infants have a reduced number of nephrons and are at high risk of chronic kidney disease. Preterm birth and/or intrauterine growth restriction (IUGR) may also affect peritubular capillary development, as has been shown in other organs. CASE-DIAGNOSIS/TREATMENT: We report two patients with a history of preterm birth and extremely low birthweight who showed polycythemia and renal capillary rarefaction. Patient 1 and 2, born at 25 weeks of gestation with a birthweight of 728 and 466 g, showed mild proteinuria at age 8 and 6 years, respectively. In addition to increasing proteinuria, hemoglobin levels became elevated towards adolescence and their serum erythropoietin (EPO) was high despite polycythemia. Light microscopic examination of renal biopsy specimens showed glomerular hypertrophy, focal segmental glomerulosclerosis, and only mild tubulointerstitial fibrosis. A decrease in the immunohistochemical staining of CD31 and CD34 endothelial cells in renal biopsy specimens was consistent with peritubular capillary rarefaction. CONCLUSIONS: Since kidney function was almost normal and fibrosis was not severe, we consider that the capillary rarefaction and polycythemia associated with elevated EPO levels were largely attributable to preterm birth and/or IUGR.

Renal complications in 6p duplication syndrome: microarray-based investigation of the candidate gene(s) for the development of congenital anomalies of the kidney and urinary tract (CAKUT) and focal segmental glomerular sclerosis (FSGS).

6p duplication syndrome is a rare chromosomal disorder that frequently manifests renal complications, including proteinuria, hypoplastic kidney, and hydronephrosis. We report a girl with the syndrome, manifesting left hydronephrosis, proteinuria/hematuria, and focal segmental glomerular sclerosis (FSGS) resulting in chronic end-stage renal failure, successfully treated with renal transplantation. Microarray comparative genomic hybridization showed the derivative chromosome 6 to have a 6.4-Mb duplication at 6p25.3-p25.1 with 32 protein-coding genes and a 220-Kb deletion at 6p25.3 with two genes of no possible relation to the renal pathology. Review of the literature shows that variation of renal complications in the syndrome is compatible with congenital anomalies of the kidney and urinary tract (CAKUT). FSGS, observed in another patient with 6p duplication syndrome, could be a non-coincidental complication. FOXC1, located within the 6.4-Mb duplicated region at 6p25.3-p25.2, could be a candidate gene for CAKUT, but its single gene duplication effect would not be sufficient. FSGS would be a primary defect associated with duplicated gene(s) albeit no candidate could be proposed, or might occur in association with CAKUT.

Successful treatment of fulminant Wilson's disease without liver transplantation.

Fulminant Wilson's disease (WD) is life-threatening. The revised WD prognostic index (RWPI) has been used to predict the severity of the disease, with a score ≥11 indicating fatal outcome without liver transplantation (LTx). We here report the case of a 10-year-old female patient with fulminant WD (RWPI, 16) who recovered fully after plasma exchange and continuous hemodiafiltration, followed by treatment with copper chelate agents. To the best of our knowledge, there have been five fulminant WD patients with RWPI ≥ 11 including the present patient, in whom LTx was not done. Based on the therapeutic modalities in these five cases, non-surgical treatment (blood purification and copper chelate agents) may be able to avoid LTx in fulminant WD even with very high RWPI, although preparation for LTx is necessary.

Serial monitoring of Mucorales DNA load in serum samples of a patient with disseminated mucormycosis after allogeneic bone marrow transplantation.

Mucormycosis is a fatal complication in immunocompromised patients, and is additionally difficult to diagnose due to the lack of useful serum biomarkers. Using a quantitative PCR approach, we retrospectively analyzed Mucorales DNA load in sera collected serially from a 3-year-old patient with chronic granulomatous disease, who died of multi-organ failure probably due to dissemination of Rhizomucor pusillus, which was detected from necropsy specimens. Mucorales DNA load was below the detection limit on days 9, 2, and 4 after unrelated bone marrow transplantation. Rhizomucor DNA was first detected on day 14 (1.6 × 10(3) copies/mL), and subsequently fluctuated between 1.3 × 10(3) and 37.2 × 10(3) copies/mL until day 43. Rhizomucor achieved a peak value of 940.0 × 10(3) copies/mL on day 48 the day before death. The detection or fluctuation of Rhizomucor DNA appeared to be associated with corticosteroid dosages or C-reactive protein levels. This specific, noninvasive, and highly quantitative assay may be useful for the early diagnosis of mucormycosis and prediction of disease progression.

A case of adult Dent disease in Japan with advanced chronic kidney disease.

Dent disease is an inherited tubulopathy caused by a mutation in the CLCN5 chloride channel gene. In cases of Dent disease in Japan (Japanese Dent, J-Dent), renal function is generally preserved and rarely progresses to advanced kidney dysfunction. However, the long-term prognosis of J-Dent remains unknown. We report the case of a 32-year-old man with J-Dent who developed advanced kidney dysfunction. Since the age of 3 years, he persistently exhibited proteinuria, and examination of a kidney biopsy specimen indicated focal segmental glomerulosclerosis (FSGS)-like lesions. Repeated corticosteroid treatments were found to be ineffective. After the age of 18 years, the patient was lost to follow-up and treatment was discontinued. The patient presented to our hospital again at the age of 32 years with advanced kidney dysfunction with low-molecular-weight proteinuria (LMWP), along with proximal tubular dysfunction and nephrocalcinosis. The patient's 5-year-old nephew was also found to have LMWP from the age of 7 months. Therefore, Dent disease was suspected and genetic testing in the patient and his nephew revealed a CLCN5 mutation. Our case report suggests that J-Dent may cause advanced kidney dysfunction in adulthood, and, therefore, close collaboration between pediatricians and nephrologists is essential for the early identification of this complication. When male patients exhibit chronic kidney disease (CKD) of unknown etiology along with proximal tubular dysfunction and nephrocalcinosis, Dent disease should be considered. Investigations of undiagnosed adult J-Dent cases and further research on the natural history of J-Dent will help us better understand its clinical characteristics, prognosis, and effective treatment options.

A case of Bardet-Biedl syndrome complicated with intracranial hypertension in a Japanese child.

Bardet-Biedl syndrome (BBS) is a rare heterogeneous autosomal recessive disorder characterized by rod-cone dystrophy, postaxial polydactyly, truncal obesity, hypogonadism, learning disability, and renal anomaly that are caused by ciliary dysfunction. 16 genes have been associated with the BBS phenotype. Although recent pathophysiological studies using animal models have shown that ciliary dysfunction may induce hydrocephalus, there have been no reports of BBS with intracranial hypertension. We here describe a 9-year-old Japanese girl who was diagnosed as having BBS and later received renal transplantation due to chronic renal failure. She also exhibited intracranial hypertension, including papilledema and increased intrathecal pressure (260-300 mmH2O), but her brain magnetic resonance imaging was normal. No genetic abnormalities were detected by DNA chip analysis or exome sequencing. Her papilledema improved following administration of acetazolamide. This is the first report of a case of BBS complicated with intracranial hypertension and its treatment.

Thrombotic microangiopathy due to multiple autoantibodies related to antiphospholipid syndrome.

BACKGROUND: Antiphospholipid syndrome (APS) is a rare disorder in children. More than half of childhood APS occurs as secondary APS complicated by systemic lupus erythematosus (SLE) and other autoimmune diseases. CASE-DIAGNOSIS/TREATMENT: We encountered a boy with SLE who presented with thrombotic microangiopathy (TMA) due to APS. He was initially diagnosed with SLE and treated with methylprednisolone pulse therapy. However, his renal function rapidly deteriorated. Since poikilocytes were detected, we suspected that his condition was complicated by TMA or APS. Urgent plasma exchange, continuous hemodialysis, and intravenous cyclophosphamide saved the patient and his renal failure ameliorated. A renal biopsy performed at the onset of disease showed multiple microvascular thrombi, diffuse mesangiolysis, and cortical necrosis compatible with TMA. He was positive for anticardiolipin antibody, anti-ß2-glycoprotein I antibody, and lupus anticoagulant as well as anti-phosphatidylserine-prothrombin complex IgG antibody (aPS/PT). Anti-a disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) antibody was negative and ADAMTS13 activity was normal. The aPS/PT is thrombogenic and is a newly discovered lupus anticoagulant. CONCLUSIONS: Childhood TMA due to APS has rarely been reported. To the best of our knowledge this is the first report of pediatric TMA due to APS with positive aPS/PT. Physicians need to be aware of aPS/PT in pediatric APS and/or SLE.

Sequential liver-kidney transplantation in a boy with congenital hepatic fibrosis and nephronophthisis from a living donor.

A five-yr-old boy developed chronic liver failure and ESKD because of CHF and juvenile NPHP. He underwent sequential liver and kidney transplantation with a compatible blood type from his father, at five yr, seven months and five yr, 11 months old, respectively. Because the patient was not in ESKD, we initially performed LDLT because of significant portal hypertension. Even after LDLT, his ascites was not ameliorated, and he needed continuous drainage of ascites and daily albumin and gamma globulin infusion. Thereafter, he progressed to ESKD and needed hemodialysis for one month before LDKT. CDC crossmatch for donor B cells in the warm test, FCXM for B cell IgG, and flow PRA for donor class II were positive before LDKT. After pretreatment of three courses of plasma exchange and intravenous gamma globulin, LDKT was performed. Two weeks after LDKT, AIHA concomitant with autoimmune thrombocytopenia, also called Evans syndrome, occurred because of passenger lymphocytes from the donor; however, the patient was successfully treated with intravenous methylprednisolone. Eighteen months have passed since LDKT, and liver and kidney function in both the recipient and donor are normal.