Clinical performance of a novel chemiluminescent enzyme immunoassay for FGF23.

INTRODUCTION: Measurement of fibroblast growth factor 23 (FGF23) has been reported to be clinically useful for the differential diagnosis of chronic hypophosphatemia. However, assays for research use only are available in Japan. Thus, the objective of this study was to examine the clinical utility of a novel and automated chemiluminescent enzyme immunoassay for the measurement of FGF23. MATERIALS AND METHODS: Participants were recruited from July 2015 to January 2017 at six facilities in Japan. Thirty-eight patients with X-linked hypophosphatemic rickets (XLH 15 males, 23 females, age 0-66 years), five patients with tumour-induced osteomalacia (TIO 3 males, 2 females, age 60-73 years), and twenty-two patients with hypophosphatemia (11 males, 11 females, age 1-75 years) caused due to other factors participated in this study. RESULTS: With the clinical cut-off value of FGF23 at 30.0 pg/mL indicated in the Diagnostic Guideline of Rickets/Osteomalacia in Japan, the sensitivity and specificity of FGF23-related hypophosphatemic rickets/osteomalacia without vitamin D deficiency (disease group-1) were 100% and 81.8%, respectively, which distinguished it from non-FGF23-related hypophosphatemia (disease group-2). Furthermore, the diagnostic sensitivity of FGF23-related hypophosphatemia with vitamin D deficiency remained at 100%. Among the four patients with FGF23 levels ≥ 30.0 pg/mL in disease group-2, two patients with relatively higher FGF23 values were suspected to have genuine FGF23-related hypophosphatemia, due to the ectopic production of FGF23 in pulmonary and prostate small cell carcinomas. CONCLUSION: The novel FGF23 assay tested in this study is useful for the differential diagnosis of hypophosphatemic rickets/osteomalacia in a clinical setting.

Robust and highly efficient hiPSC generation from patient non-mobilized peripheral blood-derived CD34+ cells using the auto-erasable Sendai virus vector.

BACKGROUND: Disease modeling with patient-derived induced pluripotent stem cells (iPSCs) is a powerful tool for elucidating the mechanisms underlying disease pathogenesis and developing safe and effective treatments. Patient peripheral blood (PB) cells are used for iPSC generation in many cases since they can be collected with minimum invasiveness. To derive iPSCs that lack immunoreceptor gene rearrangements, hematopoietic stem and progenitor cells (HSPCs) are often targeted as the reprogramming source. However, the current protocols generally require HSPC mobilization and/or ex vivo expansion owing to their sparsity at the steady state and low reprogramming efficiencies, making the overall procedure costly, laborious, and time-consuming. METHODS: We have established a highly efficient method for generating iPSCs from non-mobilized PB-derived CD34+ HSPCs. The source PB mononuclear cells were obtained from 1 healthy donor and 15 patients and were kept frozen until the scheduled iPSC generation. CD34+ HSPC enrichment was done using immunomagnetic beads, with no ex vivo expansion culture. To reprogram the CD34+-rich cells to pluripotency, the Sendai virus vector SeVdp-302L was used to transfer four transcription factors: KLF4, OCT4, SOX2, and c-MYC. In this iPSC generation series, the reprogramming efficiencies, success rates of iPSC line establishment, and progression time were recorded. After generating the iPSC frozen stocks, the cell recovery and their residual transgenes, karyotypes, T cell receptor gene rearrangement, pluripotency markers, and differentiation capability were examined. RESULTS: We succeeded in establishing 223 iPSC lines with high reprogramming efficiencies from 15 patients with 8 different disease types. Our method allowed the rapid appearance of primary colonies (~ 8 days), all of which were expandable under feeder-free conditions, enabling robust establishment steps with less workload. After thawing, the established iPSC lines were verified to be pluripotency marker-positive and of non-T cell origin. A majority of the iPSC lines were confirmed to be transgene-free, with normal karyotypes. Their trilineage differentiation capability was also verified in a defined in vitro assay. CONCLUSION: This robust and highly efficient method enables the rapid and cost-effective establishment of transgene-free iPSC lines from a small volume of PB, thus facilitating the biobanking of patient-derived iPSCs and their use for the modeling of various diseases.

[Rickets/Osteomalacia. Vitamin D dependency.]

Vitamin D dependency is caused by inborn error in the process of vitamin D metabolism or action. It is classified to vitamin D-dependent rickets type 1 which shows defective 1,25(OH)2D production, and vitamin D-dependent rickets type 2 which shows end-organ unresponsiveness to 1,25(OH)2D. Recent advance in the molecular analysis of these diseases revealed variety in the presentation and in the inheritance patterns. Molecular diagnosis would be preferable for adequate diagnosis and therapy.

Functional analyses of a novel missense and other mutations of the vitamin D receptor in association with alopecia.

Hereditary 1,25-dihydroxyvitamin D-resistant rickets (HVDRR) is a rare disorder, caused by bialellic mutations of the vitamin D receptor (VDR) gene, sometimes associated with alopecia. The aim of this study is to elucidate the mechanism of functional disruption of a novel mutation, detected in a patient with HVDRR, comparing to other mutations with or without alopecia. The patient was a 2-year-old girl with alopecia, who was clinically diagnosed as HVDRR. Genetic analysis revealed a novel homozygous mutation, S360P, located in ligand binding domain (LBD). The mutation was predicted as not disease causing by Polyphen2 and SIFT. But the transcriptional activity of S360P was disrupted as well as other reported mutations, Q152X (located in the hinge lesion), and R274L, H305Q (located in LBD). Following assays revealed no ligand binding affinity, no interaction with cofactors or RXR and no functioning of nuclear localization signals. Our results provide an additional evidence for the previous findings suggesting that DNA binding by the VDR/RXR heterodimer is essential for the function of the VDR in hair development. In conclusion, we identified a novel missense mutation of VDR causing HVDRR with alopecia. Functional analyses revealed that the single amino acid substitution could disrupt the function of the protein.

Steroid-resistant nephrotic syndrome as the initial presentation of nail-patella syndrome: a case of a de novo LMX1B mutation.

BACKGROUND: Nail-patella syndrome (NPS) is an autosomal dominant disorder caused by mutations in the LMX1B gene and is characterized by nail dysplasia, skeletal abnormalities, and nephropathy. We herein report a case of steroid-resistant nephrotic syndrome (SRNS) prior to overt orthopedic symptoms in a patient with NPS. CASE PRESENTATION: A 24-year-old woman presented to our hospital with knee pain. She had poorly developed nails, hypoplastic patellas, dislocation of the elbows, and iliac horns in the pelvis. At the age of 7, she developed nephrotic syndrome and was diagnosed with primary focal segmental glomerulosclerosis by renal biopsy. She received long-term corticosteroid therapy with no obvious response. Her clinical course and orthopedic manifestations indicated NPS, and a genetic analysis showed a de novo mutation in the LMX1B gene (c.819 + 1G > A). Nephropathy in this case was considered to be associated with NPS. Therefore, we discontinued corticosteroids without the exacerbation of nephrotic syndrome. CONCLUSIONS: Patients with NPS may develop nephrotic syndrome prior to overt orthopedic symptoms and only show non-specific findings in renal biopsy at an early stage of NPS nephropathy. Hereditary nephrotic syndrome, often presenting as childhood-onset SRNS, may also be difficult to diagnose in patients with the following conditions: renal symptoms prior to overt extrarenal symptoms, de novo mutations, and non-specific findings in renal biopsy. Therefore, in the management of SRNS in children, we need to reconsider the possibility of hereditary diseases such as NPS even without a family history.

Spectrum of LMX1B mutations: from nail-patella syndrome to isolated nephropathy.

Nail-patella syndrome (NPS) is an autosomal-dominant disease caused by LMX1B mutations and is characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and iliac horns. Renal involvement is the major determinant of the prognosis for NPS. Patients often present with varying degrees of proteinuria or hematuria, and can occasionally progress to chronic renal failure. Recent genetic analysis has found that some mutations in the homeodomain of LMX1B cause isolated nephropathy without nail, patellar or skeletal abnormality (LMX1B-associated nephropathy). The classic term "nail-patella syndrome" would not represent disease conditions in these cases. This review provides an overview of NPS, and highlights the molecular genetics of NPS nephropathy and LMX1B-associated nephropathy. Our current understanding of LMX1B function in the pathogenesis of NPS and LMX1B-associated nephropathy is also presented, and its downstream regulatory networks discussed. This recent progress provides insights that help to define potential targeted therapeutic strategies for LMX1B-associated diseases.

[Kenny-Caffey syndrome and its related syndromes].

Kenny-Caffey syndrome (KCS) is a very rare dysmorphologic syndrome characterized by proportionate short stature, cortical thickening and medullary stenosis of tubular bones, delayed closure of anterior fontanelle, eye abnormalities, and hypoparathyroidism. Two types of KCS were known: the autosomal recessive form (KCS type 1), which is caused by mutations of the TBCE gene, and the autosomal dominant form (KCS type 2), which is caused by mutations of the FAM111A gene. TBCE mutation also causes hypoparathyroidism-retardation-dysmorphism syndrome, and FAM111A mutation also causes gracile bone dysplasia. These two diseases can be called as KCS-related syndromes. In this article, we review the clinical manifestations of KCS and discuss its related syndromes.

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'.

[Updates on rickets and osteomalacia: vitamin D dependency].

Vitamin D dependency was first termed for patients resembling vitamin D-deficiency but require high doses of vitamin D administration. Now this disease is known to be caused by defective conversion of 25OHD to 1,25 (OH) 2D, which is termed vitamin D-dependent rickets type 1 or 1α-hydroxylase deficiency, or by end-organ unresponsiveness to 1,25 (OH) 2D, which is called vitamin D-dependent rickets type 2 or hereditary vitamin D-resistant rickets. Recent advance in the molecular analysis of these diseases revealed variety in the presentation and in the inheritance patterns. Molecular diagnosis would be preferable for some atypical cases for adequate therapy.

MLL2 and KDM6A mutations in patients with Kabuki syndrome.

Kabuki syndrome is a congenital anomaly syndrome characterized by developmental delay, intellectual disability, specific facial features including long palpebral fissures and ectropion of the lateral third of the lower eyelids, prominent digit pads, and skeletal and visceral abnormalities. Mutations in MLL2 and KDM6A cause Kabuki syndrome. We screened 81 individuals with Kabuki syndrome for mutations in these genes by conventional methods (n = 58) and/or targeted resequencing (n = 45) or whole exome sequencing (n = 5). We identified a mutation in MLL2 or KDM6A in 50 (61.7%) and 5 (6.2%) cases, respectively. Thirty-five MLL2 mutations and two KDM6A mutations were novel. Non-protein truncating-type MLL2 mutations were mainly located around functional domains, while truncating-type mutations were scattered through the entire coding region. The facial features of patients in the MLL2 truncating-type mutation group were typical based on those of the 10 originally reported patients with Kabuki syndrome; those of the other groups were less typical. High arched eyebrows, short fifth finger, and hypotonia in infancy were more frequent in the MLL2 mutation group than in the KDM6A mutation group. Short stature and postnatal growth retardation were observed in all individuals with KDM6A mutations, but in only half of the group with MLL2 mutations.

Supernumerary impacted teeth in a patient with SOX2 anophthalmia syndrome.

SOX2 anophthalmia syndrome characteristically presents as anophthalmia or microphthalmia, with various extraocular symptoms, such as hypogonadotropic hypogonadism, brain anomaly, and esophageal abnormalities. In this report, we describe a patient with SOX2 anophthalmia syndrome complicated with a dental anomaly, multiple supernumerary impacted teeth, and persistence of deciduous teeth. Multiple supernumerary teeth are usually not solitary symptoms, but indicate systemic syndrome such as cleidocranial dysplasia. In odontogenesis, many transcriptional factors, such as BMPs, FGFs, and Wnts, play significant roles and SOX2 is known to interact with some of them. The role of SOX2 in dental development remains unknown, however, multiple supernumerary teeth can be considered as extraocular symptoms of SOX2 anophthalmia syndrome, rather than the coincidence of two rare diseases.

Functional characterization of LMX1B mutations associated with nail-patella syndrome.

Nail-patella syndrome (NPS) is an autosomal dominant disease characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and nephropathy. Recently, it was shown that NPS is the result of heterozygous mutations in the LIM-homeodomain gene, LMX1B. Subsequently, many mutations of the LMX1B gene have been reported in NPS patients. However, functional analyses of the mutant proteins have been performed in only a few mutations. Furthermore, the mechanisms of dominant inheritance in humans have not been established. In the present study, we analyzed the LMX1B gene in three Japanese patients with NPS and identified two novel mutations, 6 nucleotide deletion (Delta246N 247Q) and V242L. These two mutations are located in the homeodomain of LMX1B. Functional analyses of the LMX1B mutants revealed that these mutants had diminished transcriptional activity and had lost DNA binding ability. Furthermore, we demonstrated that each mutant did not manifest a dominant-negative effect on the transcriptional activity of wild-type LMX1B. These results suggested that NPS is caused by loss-of-function mutations of LMX1B, and haploinsufficiency of LMX1B should be the predominant pathogenesis of NPS in humans.

Novel compound heterozygous AIRE mutations in a Japanese patient with APECED.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomal recessive disorder defined by the presence of two of three conditions, namely, Addison's disease, hypoparathyroidism, and mucocutaneous candidiasis. APECED is caused by alteration in a single gene, named the autoimmune regulator (AIRE) gene. We report AIRE gene mutations in a Japanese female with APECED. The patient is a 22-year-old Japanese female who was diagnosed with Addison's disease, hypoparathyroidism, and mucocutaneous candidiasis at age 8 years. Sequence analysis of the AIRE gene revealed novel compound heterozygous mutations. One was 1471 delCinsTT in exon 11 (GenBank accession no. AB006682), which leads to a frameshift and premature truncation of a 502 amino acid protein. The other was a G-->A transition at IVS11+1. Her mother was heterozygous for 1471 delCinsTT and was normal homozygous for IVS11+1. We found novel compound heterozygous mutations in the AIRE gene of a Japanese female with APECED.

Promoter-specific repression of hepatocyte nuclear factor (HNF)-1 beta and HNF-1 alpha transcriptional activity by an HNF-1 beta missense mutant associated with Type 5 maturity-onset diabetes of the young with hepatic and biliary manifestations.

Mutations in the hepatocyte nuclear factor (HNF)-1 beta lead to type 5 maturity-onset diabetes of the young (MODY5). HNF-1 beta forms a homodimer or a heterodimer with HNF-1 alpha and regulates various target genes. HNF-1 beta mutations are rare, and no functional analysis has been performed in conjunction with HNF-1 alpha. HNF-1 beta is expressed in the liver and biliary system and controls liver-specific and bile acid-related genes. Moreover, liver-specific Hnf-1 beta knockout mice present with severe jaundice. However, no patients with HNF-1 beta mutations have biliary manifestations. In this report, we found a novel missense mutation in the HNF-1 beta gene in a patient with neonatal cholestasis and liver dysfunction together with the common features of MODY5. Functional analysis revealed that the mutant HNF-1 beta had diminished transcriptional activity by loss of the DNA binding activity. The mutant had a promoter-specific dominant-negative transcriptional effect on wild-type HNF- and inhibited its DNA binding. Moreover, the mutant had a promoter- and cell-specific transcriptional repressive effect on HNF-1 alpha and a promoter-specific inhibitory effect on HNF-1 alpha DNA binding. From these results, we considered that the different phenotype of patients with HNF-1 beta mutations might be caused by the different HNF-1 beta activity in conjunction with the different repression of HNF-1 alpha activity in selected promoters and tissues.