An Infant Diagnosed With 22q11.2 Deletion Syndrome Following Frequent Apneic Attacks.

22q11.2 deletion syndrome (DS) is a microdeletion syndrome that pediatricians may encounter. It has a distinctive presentation and is often diagnosed based on a few characteristic symptoms. However, 22q11.2 DS with apnea as the initial symptom has never been reported. In this report, we describe the case of a one-month-old infant diagnosed with 22q11.2 DS due to apneic attacks. Early diagnosis of 22q11.2 DS is crucial because it enables appropriate intervention.

Post-renal Biopsy Retroperitoneal Haematoma Accompanied by Decreased Coagulation Factor XIII Levels in Immunoglobulin A Nephropathy.

Post-biopsy bleeding is the primary complication of renal biopsy. Retroperitoneal haematoma is a rare but severe bleeding complication; it commonly occurs among patients who have risk factors or vascular lesions. The bleeding risks in patients with immunoglobulin A (IgA) nephropathy (IgAN) have been discussed in the literature, but clinical data are lacking. Here, we report a case of a post-biopsy retroperitoneal haematoma accompanied by decreased coagulation factor XIII (FXIII) in a patient with IgAN. A 14-year-old male patient with haematuria and proteinuria but no bleeding or family history of bleeding underwent pre-renal biopsy evaluation that showed no coagulation abnormalities. He underwent percutaneous renal biopsy, and the histopathological diagnosis was IgAN. Five days after the biopsy, he presented with delayed bleeding from a retroperitoneal haematoma. During the workup for undiagnosed haemorrhagic diatheses, a mildly decreased FXIII level was discovered. This result suggested the possibility of bleeding complications associated with decreased FXIII. Some bleeding diatheses, including FXIII deficiency, cannot be evaluated in routine pre-biopsy coagulation tests. Mild FXIII deficiency can increase the risk of post-biopsy bleeding complications. Therefore, physicians should consider unevaluated haemorrhagic diatheses when a patient presents with major bleeding complications or delayed bleeding following renal biopsy without any known risk factors or vascular lesions.

A case of right hypodysplastic kidney and ectopic ureter associated with bicornuate uterus in a prepubertal girl.

Congenital anomalies of the kidney and urinary tract (CAKUT) are frequently associated with Mullerian anomalies. This can be explained by the fact that Mullerian duct elongation depends on the preformed Wolffian duct during embryogenesis. While CAKUT such as unilateral renal agenesis and multicystic dysplastic kidney are commonly identified prenatally by routine ultrasound, the diagnosis of Mullerian anomalies is often delayed, increasing the risk of complications such as endometriosis or pelvic inflammatory disease. Herein, we report a case of a premenarchal girl who had initially been diagnosed with right multicystic dysplastic kidney. She presented with continuous urinary incontinence at 4 years old and further evaluation by contrast-enhanced computed tomography, cystoscopy, colposcopy, ureterography, and hysterosalpingography led to the final diagnosis of right hypodysplastic kidney and ectopic ureter associated with bicornuate uterus. A strong family history of uterine malformations prompted the examination of the uterus. Genetic testing was suggested but the family declined. She is planned to be referred to a gynecologist at puberty for further assessment. The recognition and screening rate of concurrent Mullerian anomalies in CAKUT patients varies between institutions. Screening for Mullerian anomalies in prediagnosed CAKUT girls may enable to provide timely counseling and to prevent gynecological complications.

Urinary extracellular vesicles signature for diagnosis of kidney disease.

Congenital disorders characterized by the quantitative and qualitative reduction in the number of functional nephrons are the primary cause of chronic kidney disease (CKD) in children. We aimed to describe the alteration of urinary extracellular vesicles (uEVs) associated with decreased renal function during childhood. By nanoparticle tracking analysis and quantitative proteomics, we identified differentially expressed proteins in uEVs in bilateral renal hypoplasia, which is characterized by a congenitally reduced number of nephrons. This expression signature of uEVs reflected decreased renal function in CKD patients by congenital anomalies of the kidney and urinary tract or ciliopathy. As a proof-of-concept, we constructed a prototype ELISA system that enabled the isolation of uEVs and quantitation of expression of molecules representing the signature. The system identified decreased renal function even in its early stage. The uEVs signature could pave the way for non-invasive methods that can complement existing testing methods for diagnosing kidney diseases.

An infant with X-linked anhidrotic ectodermal dysplasia with immunodeficiency presenting with Pneumocystis pneumonia: A case report.

Pneumocystis jirovecii pneumonia associated with primary immunodeficiency should be considered in infants with slowly progressing cyanosis, even without fever or respiratory symptoms. Genetic counseling is crucial for incontinentia pigmenti families in advance of pregnancy because lethal infections can occur before the diagnosis of X-linked anhidrotic ectodermal dysplasia with immunodeficiency.

A case of 17q12 deletion syndrome that presented antenatally with markedly enlarged kidneys and clinically mimicked autosomal recessive polycystic kidney disease.

The gene encoding hepatocyte nuclear factor 1ß (HNF1B), a transcription factor involved in the development of the kidney and other organs, is located on chromosome 17q12. Heterozygous deletions of chromosome 17q12, which involve 15 genes including HNF1B, are known as 17q12 deletion syndrome and are a common cause of congenital anomalies of the kidneys and urinary tract (CAKUT) and may also present as a multisystem disorder. Autosomal recessive polycystic kidney disease (ARPKD), on the other hand, is a severe form of polycystic kidney disease caused by mutations in PKHD1 (polycystic kidney and hepatic disease 1). It is important to differentiate between these two diseases because they differ significantly in inheritance patterns, renal prognosis, and extrarenal manifestations. Here we report a case of 17q12 deletion syndrome that clinically mimicked ARPKD in which genetic testing was essential for appropriate genetic counseling and monitoring of possible extrarenal manifestations. The patient presented antenatally with markedly enlarged kidneys and showed bilaterally hyperechoic kidneys with poor corticomedullary differentiation and multiple cysts on ultrasonography. There was no family history of renal disease. ARPKD was clinically suspected and genetic testing was performed to confirm diagnosis, resulting in an unexpected finding of 17q12 deletion including HNF1B. While some research has been done to identify patients that should be tested for HNF1B anomalies, this case illustrates the difficulty of recognizing HNF1B-related disease and the importance of genetic testing in appropriately managing CAKUT cases.

A cellular model of albumin endocytosis uncovers a link between membrane and nuclear proteins.

Cubilin (CUBN) and amnionless (AMN), expressed in kidney and intestine, form a multiligand receptor complex called CUBAM that plays a crucial role in albumin absorption. To date, the mechanism of albumin endocytosis mediated by CUBAM remains to be elucidated. Here, we describe a quantitative assay to evaluate albumin uptake by CUBAM using cells expressing full-length CUBN and elucidate the crucial roles of the C-terminal part of CUBN and the endocytosis signal motifs of AMN in albumin endocytosis. We also demonstrate that nuclear valosin-containing protein-like 2 (NVL2), an interacting protein of AMN, is involved in this process. Although NVL2 was mainly localized in the nucleolus in cells without AMN expression, it was translocated to the extranuclear compartment when coexpressed with AMN. NVL2 knockdown significantly impaired internalization of the CUBN-albumin complex in cultured cells, demonstrating an involvement of NVL2 in endocytic regulation. These findings uncover a link between membrane and nucleolar proteins that is involved in endocytic processes.

Incomplete cryptic splicing by an intronic mutation of OCRL in patients with partial phenotypes of Lowe syndrome.

Mutations of OCRL cause Lowe syndrome, which is characterised by congenital cataracts, infantile hypotonia with mental retardation, and renal tubular dysfunction and Dent-2 disease, which only affects the kidney. While few patients with an intermediate phenotype between these diseases have been reported, the mechanism underlying variability in the phenotype is unclear. We identified an intronic mutation, c.2257-5G>A, in intron 20 of OCRL in an older brother with atypical Lowe syndrome without eye involvement and a younger brother with renal phenotype alone. This mutation created a splice acceptor motif that was accompanied by a cryptic premature termination codon at the junction of exons 20 and 21. The mutation caused incomplete alternative splicing, which created a small amount of wild-type transcript and a relatively large amount of alternatively spliced transcript with a premature termination codon. In the patients' cells, the alternatively spliced transcript was degraded by nonsense-mediated decay and the wild-type transcript was significantly decreased, but not completely depleted. These findings imply that an intronic mutation creating an incomplete alternative splicing acceptor site results in a relatively low level of wild-type OCRL mRNA expression, leading to partial phenotypes of Lowe syndrome.

Rituximab-induced serum sickness in a 6-year-old boy with steroid-dependent nephrotic syndrome.

Rituximab (RTX) is a murine-human chimeric monoclonal antibody against CD20 that has been proven effective for preventing relapse in frequently-relapsing or steroid-dependent nephrotic syndrome (NS). Serum sickness, a type-3 hypersensitivity reaction resulting from injection of foreign proteins, has been reported in patients treated with RTX. Herein, we describe a case of RTX-induced serum sickness (RISS) in a 6-year-old boy with steroid-dependent NS. He presented to the hospital with fever and polyarthralgia at 10 days after his fourth dose of RTX. Although he was started on empiric intravenous antibiotics, there was no evidence of septic arthritis and his symptoms resolved over the course of 4 days. He was diagnosed with RISS based on the chronology of RTX administration and the acute-onset self-limiting course of the polyarthritis. His serum human anti-chimeric antibody (HACA) level on day 53 exceeded the limit of quantification (5000 ng/mL). The pathogenesis of RISS and the role of HACAs remain unclear. It is important for clinicians to recognize RISS, because further infusions of RTX may cause more severe reactions in patients with a history of RISS.

Amnionless-mediated glycosylation is crucial for cell surface targeting of cubilin in renal and intestinal cells.

Mutations in either cubilin (CUBN) or amnionless (AMN) genes cause Imerslund-Gräsbeck syndrome (IGS), a hereditary disease characterised by anaemia attributed to selective intestinal malabsorption of cobalamin and low-molecular weight proteinuria. Although cubilin protein does not have a transmembrane segment, it functions as a multi-ligand receptor by binding to the transmembrane protein, amnionless. We established a system to quantitatively analyse membrane targeting of the protein complex in cultured renal and intestinal cells and analysed the pathogenic mechanisms of mutations found in IGS patients. A novel CUBN mutation, several previously reported CUBN missense mutations and all previously reported AMN missense mutations resulted in endoplasmic reticulum (ER) retention and completely inhibited amnionless-dependent plasma membrane expression of cubilin. The ER retention of cubilin and amnionless was confirmed in renal proximal tubular cells of a patient with IGS. Notably, the interaction between cubilin and amnionless was not sufficient, but amnionless-mediated glycosylation of cubilin was necessary for their surface expression. Quantitative mass spectrometry and mutagenesis demonstrated that N-linked glycosylation of at least 4 residues of cubilin protein was required for its surface targeting. These results delineated the molecular mechanisms of membrane trafficking of cubilin in renal and intestinal cells.

Harnessing membrane trafficking to promote cancer spreading and invasion: The case of RAB2A.

How cancer disseminates and metastasizes remains an outstanding open question. Emerging evidence indicates that membrane trafficking is frequently harnessed by tumors of epithelial origin to acquire a mesenchymal program of invasiveness. However, the critical molecular hubs used by cancer cells this context have only began to be elucidated. Here, we discussed the results of a recent phenotypic screening that led to the identification of the small GTPase RAB2A, not previously involved in cancer dissemination, as pivotal for the acquisition of pericellular proteolysis, cell dissemination and distant metastatic spreading of human breast cancer. At the cellular levels, RAB2A controls both canonical polarized Golgi-to-Plasma membrane trafficking of the junctional protein E-cadherin, and post-endocytic trafficking of the membrane-bound metalloprotease, MT1-MMP. This finding reveals an unexpected plasticity in the control of diverse trafficking routes exerted by RAB2A through canonical (Golgi stacking) and non-canonical (late endosome recycling) functional interactions, contributing to break established membrane trafficking dogma on the rigorous molecular distinction between polarized Golgi and post endocytic routes. Finally, they suggest that epithelial cancers may specifically select for those molecules that enable them to control multiple trafficking routes, in turn essential for the regulation of activities necessary for acquisition of mesenchymal traits.

Altered expression of Crb2 in podocytes expands a variation of CRB2 mutations in steroid-resistant nephrotic syndrome.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is a genetically heterogeneous disorder for which more than 25 single-gene hereditary causes have been identified. METHODS: Whole exome sequencing was performed in a 3-year-old girl with SRNS. We analyzed the expression of Crb2 and slit diaphragm molecules in the patient's glomeruli, and compared it with that of controls or other nephrotic patients. RESULTS: Whole-exome analysis identified novel compound heterozygous mutations in exons 10 and 12 of CRB2 (p.Trp1086ArgfsX64 and p.Asn1184Thr, each from different parents; Asn1184 within extracellular 15th EGF repeat domain). Renal pathology showed focal segmental glomerulosclerosis with effaced podocyte foot processes in a small area, with significantly decreased Crb2 expression. Molecules critical for slit diaphragm were well-expressed in this patient's podocytes. Crb2 expression was not altered in the other patients with congenital nephrotic syndrome with NPHS1 mutations. CONCLUSIONS: These findings demonstrate that Crb2 abnormalities caused by these mutations are the mechanism of steroid-resistant NS. Although CRB2 mutations previously found in SRNS patients have been clustered within the extracellular tenth EGF-like domain of this protein, the present results expand the variation of CRB2 mutations that cause SRNS.

RAB2A controls MT1-MMP endocytic and E-cadherin polarized Golgi trafficking to promote invasive breast cancer programs.

The mechanisms of tumor cell dissemination and the contribution of membrane trafficking in this process are poorly understood. Through a functional siRNA screening of human RAB GTPases, we found that RAB2A, a protein essential for ER-to-Golgi transport, is critical in promoting proteolytic activity and 3D invasiveness of breast cancer (BC) cell lines. Remarkably, RAB2A is amplified and elevated in human BC and is a powerful and independent predictor of disease recurrence in BC patients. Mechanistically, RAB2A acts at two independent trafficking steps. Firstly, by interacting with VPS39, a key component of the late endosomal HOPS complex, it controls post-endocytic trafficking of membrane-bound MT1-MMP, an essential metalloprotease for matrix remodeling and invasion. Secondly, it further regulates Golgi transport of E-cadherin, ultimately controlling junctional stability, cell compaction, and tumor invasiveness. Thus, RAB2A is a novel trafficking determinant essential for regulation of a mesenchymal invasive program of BC dissemination.

Epithelial protein lost in neoplasm modulates platelet-derived growth factor-mediated adhesion and motility of mesangial cells.

Mesangial cell migration, regulated by several growth factors, is crucial after glomerulopathy and during glomerular development. Directional migration requires the establishment of a polarized cytoskeletal arrangement, a process regulated by coordinated actin dynamics and focal adhesion turnover at the peripheral ruffles in migrating cells. Here we found high expression of the actin cross-linking protein EPLIN (epithelial protein lost in neoplasm) in mesangial cells. EPLIN was localized in mesangial angles, which consist of actin-containing microfilaments extending underneath the capillary endothelium, where they attach to the glomerular basement membrane. In cultured mesangial cells, EPLIN was localized in peripheral actin bundles at focal adhesions and formed a protein complex with paxillin. The MEK-ERK (extracellular signal-regulated kinase) cascade regulated EPLIN-paxillin interaction and induced translocalization of EPLIN from focal adhesion sites to peripheral ruffles. Knockdown of EPLIN in mesangial cells enhanced platelet-derived growth factor-induced focal adhesion disassembly and cell migration. Furthermore, EPLIN expression was decreased in mesangial proliferative nephritis in rodents and humans in vivo. These results shed light on the coordinated actin remodeling in mesangial cells during restorative remodeling. Thus, changes in expression and localization of cytoskeletal regulators underlie phenotypic changes in mesangial cells in glomerulonephritis.

LMX1B mutation with residual transcriptional activity as a cause of isolated glomerulopathy.

BACKGROUND: Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder caused by LMX1B mutation. In patients with the renal lesions typical of NPS without skeletal or nail findings, it is described as nail-patella-like renal disease (NPLRD). However, the pathogenesis of NPLRD is largely unknown. METHODS: A 6-year-old girl with microscopic haematuria and mild proteinuria was diagnosed with NPLRD because of an aberrantly thickened glomerular basement membrane (GBM) and deposition of Type III collagen in the GBM observed by electron microscopy. Immunohistological analyses of podocyte protein expression were performed on biopsy tissues. Sequence analysis of LMX1B was performed, and the functional consequences of the detected mutation were analysed by luciferase reporter assay. RESULTS: When analysing molecules that are important for podocyte development, maintenance and maturation, CD2AP expression was found to be altered in the podocytes. A novel LMX1B missense mutation (R246Q) was identified. Functional analyses revealed partial but significant impairment of R246Q transcriptional activity. However, no dominant-negative effect of R246Q was detected, which suggests that NPLRD is caused by LMX1B haploinsufficiency. CONCLUSIONS: This is the first report on LMX1B mutation identified in a patient with NPLRD. Residual transcriptional activity would account for normality of the nails and patella in this case. Genetic and pathological analyses of additional cases would clarify the role of LMX1B in glomerulopathy without systemic symptoms, which, together with nephropathy in NPS, can be designated as 'LMX1B nephropathy'.

Podocyte expression of nonmuscle myosin heavy chain-IIA decreases in idiopathic nephrotic syndrome, especially in focal segmental glomerulosclerosis.

BACKGROUND: Previous studies have identified significant associations between the development of idiopathic focal segmental glomerulosclerosis (FSGS) and MYH9 encoding nonmuscle myosin heavy chain-IIA (NMMHC-IIA). However, these studies focused only on the linkage of MYH9 polymorphisms and development of FSGS. There have been no reports on pathological changes of NMMHC-IIA in human glomerular diseases. Here we report on the precise localization of NMMHC-IIA in podocytes and changes in NMMHC-IIA expression in pathological states in rats and humans. METHODS: Immunocytochemical (immunofluorescence and immunoelectron microscopy) studies were performed to determine the precise localization of NMMHC-IIA. Expression levels of NMMHC-IIA were investigated in puromycin aminonucleoside (PAN)-treated rats; and expression levels of NMMHC-IIA and other podocyte-related proteins were investigated in glomeruli of patients with idiopathic FSGS and other heavy proteinuric glomerular diseases. RESULTS: NMMHC-IIA was located primarily at the cell body and primary processes of podocytes; this localization is distinct from other podocyte-related molecules causing hereditary FSGS. In PAN-treated rat kidneys, expression levels of NMMHC-IIA in podocytes decreased. Immunohistochemical analysis revealed that expression levels of NMMHC-IIA markedly decreased in idiopathic nephrotic syndrome, especially FSGS, whereas it did not change in other chronic glomerulonephritis showing apparent proteinuria. Changes in NMMHC-IIA expression were observed in glomeruli where expression of nephrin and synaptopodin was maintained. CONCLUSIONS: Considering previous genome-wide association studies and development of FSGS in patients with MYH9 mutations, the characteristic localization of NMMHC-IIA and the specific decrease in NMMHC-IIA expression in idiopathic nephrotic syndrome, especially FSGS, suggest the important role of NMMHC-IIA in the development of FSGS.

SIRPα interacts with nephrin at the podocyte slit diaphragm.

The slit diaphragm (SD) is an intercellular junction between renal glomerular epithelial cells (podocytes) that is essential for permselectivity in glomerular ultrafiltration. The SD components, nephrin and Neph1, assemble a signaling complex in a tyrosine phosphorylation dependent manner, and regulate the unique actin cytoskeleton of podocytes. Mutations in the NPHS1 gene that encodes nephrin cause congenital nephrotic syndrome (CNS), which is characterized by the loss of the SD and massive proteinuria. Recently, we have identified the expression of the transmembrane glycoprotein signal regulatory protein α (SIRPα) at the SD. In the present study, we analyzed the expression of SIRPα in developing kidneys, in kidneys from CNS patients and in proteinuric rat models. The possibility that SIRPα interacts with known SD proteins was also investigated. SIRPα was concentrated at the SD junction during the maturation of intercellular junctions. In the glomeruli of CNS patients carrying mutations in NPHS1, where SD formation is disrupted, the expression of SIRPα as well as Neph1 and nephrin was significantly decreased, indicating that SIRPα is closely associated with the nephrin complex. Indeed, SIRPα formed hetero-oligomers with nephrin in cultured cells and in glomeruli. Furthermore, the cytoplasmic domain of SIRPα was highly phosphorylated in normal glomeruli, and its phosphorylation was dramatically decreased upon podocyte injury in vivo. Thus, SIRPα interacts with nephrin at the SD, and its phosphorylation is dynamically regulated in proteinuric states. Our data provide new molecular insights into the phosphorylation events triggered by podocyte injury.

Pretransplantation combined therapy with plasmapheresis and rituximab in a second living-related kidney transplant pediatric recipient with a very high risk for focal segmental glomerulosclerosis recurrence.

Prophylactic PP can provide some protection against post-transplantation recurrences of FSGS, but it cannot prevent recurrences in all cases. Therefore, new preventive therapies are needed. We report on a 7.9-yr-old girl treated with pretransplantation prophylactic combined therapy consisting of four sessions of PP and one dose of rituximab before a second living-related KTX. The patient had a very high risk of post-transplantation FSGS recurrence because this had occurred after the first KTX. During the 36 months since the second transplantation, she has had no evidence of proteinuria or significant infectious complications. Although our experience is too preliminary to draw any generalizable conclusions, pretransplantation combined therapy with PP and rituximab might be a possible option for the prevention of FSGS recurrence in very high-risk recipients undergoing living-donor KTXs.