Pediatric frequent relapsing nephrotic syndrome with multiple cerebral infarctions accompanied by patent foramen ovale and cerebral venous sinus thrombosis: a case report.

BACKGROUND: Idiopathic nephrotic syndrome (NS) presents as a hypercoagulable state, of which thromboembolism (TE) is a well-known life-threatening complication. Although TE is more likely to occur in venous vessels than arterial vessels, arterial TE is important because it may cause after-effects, including tissue necrosis and cerebral infarction (CI); therefore, prompt diagnosis and appropriate treatment are required. We report a pediatric NS case with multiple CIs. CASE PRESENTATION: A 14-year-7-month-old Japanese girl was diagnosed with frequent relapsing NS, accompanied by headache and disturbance of consciousness during the second relapse. Brain magnetic resonance imaging (MRI) and four-dimensional computed tomography revealed multiple CIs, vasogenic edema, and cerebral venous sinus thrombosis (CVST). The patient had no underlying thrombophilia other than hypercoagulability due to NS and prednisolone (PSL), and no cardiac arrhythmia; however, a right-to-left shunt through the patent foramen ovale (PFO) was observed with the Valsalva maneuver by echocardiography. Therefore, we assumed that a potential cause of multiple CIs might be an embolic stroke, caused by thrombosis formed from a hypercoagulable state due to NS and PSL treatment and reached through PFO. Antiplatelet and anticoagulant therapies were administered for TE. She was treated with PSL and mycophenolate mofetil (MMF) for NS. Rituximab (RTX) was administered to prevent NS relapse after complete remission (CR). She underwent transcatheter PFO closure at age 14 years and 9 months because we considered that the right-to-left shunt through the PFO would be one of the risks for recurrent cerebral embolism when NS relapses. One year after the onset of CIs, an MRI indicated that the CVST had resolved, leaving no neurological sequelae due to CI; therefore, anticoagulant therapy was discontinued. And then she has been in CR for NS with only MMF therapy. CONCLUSIONS: CI is a serious complication in patients with NS. The pathogenesis of multiple CIs is various, including right-to-left shunt through PFO, in addition to the hypercoagulability due to NS. It is important to investigate and manage underlying risks such as PFO, besides preventing the relapses of NS by aggressive treatments using MMF and RTX, in patients with NS.

Bartter Syndrome Type 1 Due to Novel SLC12A1 Mutations Associated With Pseudohypoparathyroidism Type II.

Bartter syndrome type 1 is caused by mutations in the solute carrier family 12 member 1 (SLC12A1), encoding the sodium-potassium-chloride cotransporter-2 (NKCC2). In addition to causing renal salt-losing tubulopathy, SLC12A1 mutations are known to cause nephrocalcinosis due to hypercalciuria, as well as failure to thrive associated with abnormal calcium and phosphorus homeostasis. We report a now 7-year-old Japanese girl with polyuria, hyponatremia, hypokalemia, and metabolic alkalosis, in whom compound heterozygous novel SLC12A1 mutations were identified. Elevated parathyroid hormone (PTH) levels were consistently noted after the age of 1 year in conjunction with gradually declining serum calcium and increasing serum phosphorus levels. To confirm suspected PTH-resistance, Ellsworth Howard tests were performed at the ages of 6 years 8 months and 6 years 10 months in the absence or presence of ibuprofen, respectively. Urinary adenosine 3',5'-cyclic monophosphate excretion increased on both occasions in response to PTH(1-34) infusion suggesting pseudohypoparathyroidism type II. However, only during treatment with ibuprofen did PTH induce an almost normal phosphaturic response. The nonsteroidal anti-inflammatory drugs thus enhanced growth velocity, alleviated hypercalciuria, and increased PTH-stimulated urinary phosphorus excretion without significantly affecting renal function.

Involvement of GLCCI1 in mouse spermatogenesis.

Spermatid production is a complex regulatory process in which coordination between hormonal control and apoptosis plays a pivotal role in maintaining a balanced number of sperm cells. Apoptosis in spermatogenesis is controlled by pro-apoptotic and anti-apoptotic molecules. Hormones involved in the apoptotic process during spermatogenesis include gonadotrophins, sex hormones, and glucocorticoid (GC). GC acts broadly as an apoptosis inducer by binding to its receptor (glucocorticoid receptor: GR) during organ development processes, such as spermatogenesis. However, the downstream pathway induced in GC-GR signaling and the apoptotic process during spermatogenesis remains poorly understood. We reported previously that GC induces full-length glucocorticoid-induced transcript 1 (GLCCI1-long), which functions as an anti-apoptotic mediator in thymic T cell development. Here, we demonstrate that mature murine testis expresses a novel isoform of GLCCI1 protein (GLCCI1-short) in addition to GLCCI1-long. We demonstrate that GLCCI1-long is expressed in spermatocytes along with GR. In contrast, GLCCI1-short is primarily expressed in spermatids where GR is absent; instead, the estrogen receptor is expressed. GLCCI1-short also binds to LC8, which is a known mediator of the anti-apoptotic effect of GLCCI1-long. A luciferase reporter assay revealed that ß-estradiol treatment synergistically increased Glcci1-short promotor-driven luciferase activity in Erα-overexpressing cells. Together with the evidence that the conversion of testosterone to estrogen is preceded by aromatase expression in spermatids, we hypothesize that estrogen induces GLCCI1-short, which, in turn, may function as a novel anti-apoptotic mediator in mature murine testis.

A Novel Mouse Model of Idiopathic Nephrotic Syndrome Induced by Immunization with the Podocyte Protein Crb2.

BACKGROUND: The cause of podocyte injury in idiopathic nephrotic syndrome (INS) remains unknown. Although recent evidence points to the role of B cells and autoimmunity, the lack of animal models mediated by autoimmunity limits further research. We aimed to establish a mouse model mimicking human INS by immunizing mice with Crb2, a transmembrane protein expressed at the podocyte foot process. METHODS: C3H/HeN mice were immunized with the recombinant extracellular domain of mouse Crb2. Serum anti-Crb2 antibody, urine protein-to-creatinine ratio, and kidney histology were studied. For signaling studies, a Crb2-expressing mouse podocyte line was incubated with anti-Crb2 antibody. RESULTS: Serum anti-Crb2 autoantibodies and significant proteinuria were detected 4 weeks after the first immunization. The proteinuria reached nephrotic range at 9-13 weeks and persisted up to 29 weeks. Initial kidney histology resembled minimal change disease in humans, and immunofluorescence staining showed delicate punctate IgG staining in the glomerulus, which colocalized with Crb2 at the podocyte foot process. A subset of mice developed features resembling FSGS after 18 weeks. In glomeruli of immunized mice and in Crb2-expressing podocytes incubated with anti-Crb2 antibody, phosphorylation of ezrin, which connects Crb2 to the cytoskeleton, increased, accompanied by altered Crb2 localization and actin distribution. CONCLUSION: The results highlight the causative role of anti-Crb2 autoantibody in podocyte injury in mice. Crb2 immunization could be a useful model to study the immunologic pathogenesis of human INS, and may support the role of autoimmunity against podocyte proteins in INS.

Progression of PTH Resistance in Autosomal Dominant Pseudohypoparathyroidism Type Ib Due to Maternal STX16 Deletions.

CONTEXT: Maternally inherited STX16 deletions that cause loss of methylation at GNAS exon A/B and thereby reduce Gsα expression are the most frequent cause of autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP1B). Early identification of these disease-causing variants in the children of affected and unaffected female carriers would prompt treatment with calcium and calcitriol once parathyroid hormone (PTH) levels increase, thereby preventing hypocalcemia and associated complications. OBJECTIVE: This study aimed to determine when PTH and calcium abnormalities develop after birth if a STX16 deletion is inherited maternally. METHODS: Forty-four children of affected (n = 7) or unaffected (n = 7) females with a STX16 deletion were investigated for the presence of these variants. If a deletion was identified, measurement of PTH, calcium, phosphate, and thyrotropin (TSH) was advised. RESULTS: The STX16 deletion that causes AD-PHP1B was identified in 25 children. Pretreatment laboratory results were available for 19 of those cases. Elevated PTH levels were detected by 2 years of age, and these were progressively higher if laboratory testing was first performed after establishing the genetic defect later in life. Total serum calcium levels remained within normal limits until about 5 years of age. TSH levels showed no consistent rise over time. CONCLUSION: Establishing whether a STX16 deletion is inherited from a female carrier of a disease-causing variant rapidly establishes the diagnosis of AD-PHP1B. Several years before overt hypocalcemia developed, PTH levels increased, thereby establishing the onset of PTH resistance. Our findings provide diagnostic guidance and when treatment with calcium and calcitriol should be considered in order to prevent hypocalcemia and associated sequelae.

Lack of GNAS Remethylation During Oogenesis May Be a Cause of Sporadic Pseudohypoparathyroidism Type Ib.

CONTEXT: Pseudohypoparathyroidism type Ib (PHP1B) is characterized by hypocalcemia and hyperphosphatemia due to parathyroid hormone resistance in the proximal renal tubules. Maternal pathogenic STX16/GNAS variants leading to maternal epigenetic GNAS changes impair expression of the stimulatory G protein alpha-subunit (Gsα) thereby causing autosomal dominant PHP1B. In contrast, genetic defects responsible for sporadic PHP1B (sporPHP1B) remain mostly unknown. OBJECTIVE: Determine whether PHP1B encountered after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) causes GNAS remethylation defects similar to those in sporPHP1B. DESIGN: Retrospective analysis. RESULTS: Nine among 36 sporPHP1B patients investigated since 2000, all with loss of methylation (LOM) at the 3 maternal GNAS differentially methylated regions (DMRs) and gain of methylation at the paternal NESP DMR, had been conceived through IVF or ICSI. Besides abnormal GNAS methylation, IVF/ICSI PHP1B cases revealed no additional imprinting defects. Three of these PHP1B patients have dizygotic twins, and 4 have IVF/ICSI-conceived siblings, all with normal GNAS methylation; 2 unaffected younger siblings were conceived naturally. CONCLUSION: Sporadic and IVF/ICSI-conceived PHP1B patients revealed indistinguishable epigenetic changes at all 4 GNAS DMRs, thus suggesting a similar underlying disease mechanism. Given that remethylation at the 3 maternal DMRs occurs during oogenesis, male factors are unlikely to cause LOM postfertilization. Instead, at least some of the sporPHP1B variants could be caused by a defect or defects in an oocyte-expressed gene that is required for fertility and for re-establishing maternal GNAS methylation imprints. It remains uncertain, however, whether the lack of GNAS remethylation alone and the resulting reduction in Gsα expression is sufficient to impair oocyte maturation.

A Distinct Variant of Pseudohypoparathyroidism (PHP) First Characterized Some 41 Years Ago Is Caused by the 3-kbSTX16 Deletion.

In 1980, Farfel and colleagues (NEJM, 1980;303:237-42) provided first evidence for two distinct variants of pseudohypoparathyroidism (PHP) that present with hypocalcemia and impaired parathyroid hormone (PTH)-stimulated urinary cAMP and phosphate excretion, either in the presence or absence of Albright's hereditary osteodystrophy (AHO). An "abnormal allele" and an "unexpressed allele" were considered as underlying defects, predictions that turned out to be correct for both forms of PHP. Patients affected by the first variant (now referred to as PHP1A) were later shown to be carriers of inactivating mutations involving the maternal GNAS exons encoding Gsα. Patients affected by the second variant (now referred to as PHP1B) were shown in the current study to carry a maternal 3-kb STX16 deletion, the most frequent cause of autosomal dominant PHP1B, which is associated with loss of methylation at GNAS exon A/B that reduces or abolishes maternal Gsα expression. However, the distinct maternal mutations leading to either PHP1A or PHP1B are disease-causing only because paternal Gsα expression in the proximal renal tubules is silenced, ie, "unexpressed." Our findings resolve at the molecular level carefully conducted investigations reported some 41 years ago that had provided first clues for the existence of two distinct PHP variants. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Preferential Maternal Transmission of STX16-GNAS Mutations Responsible for Autosomal Dominant Pseudohypoparathyroidism Type Ib (PHP1B): Another Example of Transmission Ratio Distortion.

Preferential transmission of a genetic mutation to the next generation, referred to as transmission ratio distortion (TRD), is well established for several dominant disorders, but underlying mechanisms remain undefined. Recently, TRD was reported for patients affected by pseudohypoparathyroidism type Ia or pseudopseudohypoparathyroidism. To determine whether TRD is observed also for autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP1B), we analyzed kindreds with the frequent 3-kb STX16 deletion or other STX16/GNAS mutations. If inherited from a female, these genetic defects lead to loss-of-methylation at exon A/B alone or at all three differentially methylated regions (DMR), resulting in parathyroid hormone (PTH)-resistant hypocalcemia and hyperphosphatemia and possibly resistance to other hormones. In total, we investigated 212 children born to 80 females who are unaffected carriers of a STX16/GNAS mutation (n = 47) or affected by PHP1B (n = 33). Of these offspring, 134 (63.2%) had inherited the genetic defect (p = .00012). TRD was indistinguishable for mothers with a STX16/GNAS mutation on their paternal (unaffected carriers) or maternal allele (affected). The mechanisms favoring transmission of the mutant allele remain undefined but are likely to include abnormalities in oocyte maturation. Search for mutations in available descendants of males revealed marginally significant evidence for TRD (p = .038), but these analyses are less reliable because many more offspring of males than females with a STX16/GNAS mutation were lost to follow-up (31 of 98 versus 6 of 218). This difference in follow-up is probably related to the fact that inheritance of a mutation from a male does not have clinical implications, whereas inheritance from an affected or unaffected female results in PHP1B. Lastly, affected PHP1B females had fewer descendants than unaffected carriers, but it remains unclear whether abnormal oocyte development or impaired actions of reproductive hormones are responsible. Our findings highlight previously not recognized aspects of AD-PHP1B that are likely to have implications for genetic testing and counseling. © 2020 American Society for Bone and Mineral Research (ASBMR).

GLCCI1 is a novel protector against glucocorticoid-induced apoptosis in T cells.

Glucocorticoids (GCs) potently induce T-cell apoptosis in a GC receptor (GR)-dependent manner and are used to control lymphocyte function in clinical practice. However, its downstream pathways remain controversial. Here, we showed that GC-induced transcript 1 (GLCCI1) is a novel downstream molecule of the GC-GR cascade that acts as an antiapoptotic mediator in thymic T cells. GLCCI1 was highly phosphorylated and colocalized with microtubules in GLCCI1-transfected human embryonic kidney QBI293A cells. GR-dependent up-regulation of GLCCI1 was associated with GC-induced proapoptotic events in a cultured thymocyte cell line. However, GLCCI1 knockdown in a thymocyte cell line led to apoptosis. Consistently, transgenic mice overexpressing human GLCCI1 displayed enlarged thymi that consisted of larger numbers of thymocytes. Further molecular characterization showed that GLCCI1 bound to both dynein light chain LC8-type 1 (LC8) and its functional kinase, p21-protein activated kinase 1 (PAK1), thereby inhibiting the kinase activity of PAK1 toward LC8 phosphorylation, a crucial event in apoptotic signaling. GLCCI1 induction facilitated LC8 dimer formation and reduced Bim expression. Thus, GLCCI1 is a candidate factor involved in apoptosis regulation of thymic T cells.-Kiuchi, Z., Nishibori, Y., Kutsuna, S., Kotani, M., Hada, I., Kimura, T., Fukutomi, T., Fukuhara, D., Ito-Nitta, N., Kudo, A., Takata, T., Ishigaki, Y., Tomosugi, N., Tanaka, H., Matsushima, S., Ogasawara, S., Hirayama, Y., Takematsu, H., Yan, K. GLCCI1 is a novel protector against glucocorticoid-induced apoptosis in T cells.

USP40 gene knockdown disrupts glomerular permeability in zebrafish.

Unbiased transcriptome profiling and functional genomics approaches have identified ubiquitin-specific protease 40 (USP40) as a highly specific glomerular transcript. This gene product remains uncharacterized, and its biological function is completely unknown. Here, we showed that mouse and rat glomeruli exhibit specific expression of the USP40 protein, which migrated at 150 kDa and was exclusively localized in the podocyte cytoplasm of the adult kidney. Double-labeling immunofluorescence staining and confocal microscopy analysis of fetal and neonate kidney samples revealed that USP40 was also expressed in the vasculature, including in glomerular endothelial cells at the premature stage. USP40 in cultured glomerular endothelial cells and podocytes was specifically localized to the intermediate filament protein nestin. In glomerular endothelial cells, immunoprecipitation confirmed actual protein-protein binding of USP40 with nestin, and USP40-small-interfering RNA transfection revealed significant reduction of nestin. In a rat model of minimal-change nephrotic syndrome, USP40 expression was apparently reduced, which was also associated with the reduction of nestin. Zebrafish morphants lacking Usp40 exhibited disorganized glomeruli with the reduction of the cell junction in the endothelium and foot process effacement in the podocytes. Permeability studies in these zebrafish morphants demonstrated a disruption of the selective glomerular permeability filter. These data indicate that USP40/Usp40 is a novel protein that might play a crucial role in glomerulogenesis and the glomerular integrity after birth through the modulation of intermediate filament protein homeostasis.