Biomedical subjects
Kenichi Satomura
Publications and source records attributed to Kenichi Satomura.
EYA1 and SIX1 gene mutations in Japanese patients with branchio-oto-renal (BOR) syndrome and related conditions.
We isolated genomic DNA from 15 patients with branchio-oto-renal (BOR) syndrome or BOR-related conditions. Seven patients had BOR syndrome (two familial and five sporadic), and eight had deafness and renal malformations without branchial fistula (BOR-related conditions). We analyzed all exons and exon-intron boundaries of EYA1 and SIX1 using the polymerase chain reaction (PCR) direct sequencing, and characterized their mutations. In some patients, analysis of mRNA by reverse transcription (RT)-PCR was performed to examine whether the mutation affects the mRNA splicing. We identified five novel disease-causing heterozygous EYA1 mutations in five patients with BOR syndrome (two familial and three sporadic, 5/7=71%), but EYA1 and SIX1 mutations were not detected in the other two patients with BOR syndrome or any of the patients with BOR-related conditions. The detected EYA1 mutations were two nonsense mutations, two splicing acceptor-site mutations, and a point mutation (G>T) of the first base of exon 10. Analysis of mRNA by RT-PCR direct sequencing revealed that the latter point mutation led to the skipping of exon 10. In conclusion, (1) EYA1 mutations are a major cause of BOR syndrome in Japanese, (2) EYA1 and SIX1 mutations were not a major cause of BOR-related conditions, (3) we demonstrated for the first time that the point mutation (G>T) of the first base of the exon in EYA1 gene induced exon skipping.
The role of fibroblast growth factor 23 for hypophosphatemia and abnormal regulation of vitamin D metabolism in patients with McCune-Albright syndrome.
McCune-Albright syndrome (MAS) is sometimes complicated by hypophosphatemia and abnormally low levels of 1,25(OH)(2)D in the presence of hypophosphatemia. Recently, fibroblast growth factor 23 (FGF-23) was reported as a phosphaturic and a causal factor of abnormal vitamin D metabolism. This abnormal phosphate and vitamin D metabolism is well known to be found in oncogenic and X-linked hypophosphatemia. We furthermore reported increased circulating plasma FGF-23 levels in patients with oncogenic and X-linked hypophosphatemia. To determine whether FGF-23 may be involved in the pathogenesis of MAS, we measured plasma FGF-23 levels in six MAS patients. As a control for hypophosphatemia, we also investigated the plasma FGF-23 levels in two patients with hereditary hypophosphatemic rickets with hypercalciuria (HHRH). We also investigated the correlation of plasma FGF-23 levels with serum phosphate and 1,25(OH)(2)D levels after short-term pamidronate therapy in three MAS patients. Plasma FGF-23 levels were significantly increased in patients with MAS compared to normal controls, whereas they were not increased in HHRH patients. Serum phosphate levels of the MAS patients were significantly lower than those observed in normal controls. Plasma FGF-23 levels showed significant negative correlation with serum phosphate concentrations. In three MAS patients, pamidronate therapy decreased plasma FGF-23 levels, which showed significant negative correlation with serum 1,25(OH)(2)D concentrations. These data suggested that FGF-23 is a possible causal factor for hypophosphatemia and abnormal vitamin D metabolism in MAS.
Analysis of NPHS1, NPHS2, ACTN4, and WT1 in Japanese patients with congenital nephrotic syndrome.
BACKGROUND: Congenital nephrotic syndrome (CNS) causes significant renal failure, and is classified into two types: (1) Finnish type; and (2) other, including diffuse mesangial sclerosis. Mutations of NPHS1 and NPHS2, which encode the slit diaphragm components nephrin and podocin, cause CNS and autosomal-recessive familial steroid-resistant nephrotic syndrome, respectively. Most patients with Finnish-type CNS in Europe and the United States have NPHS1 mutations. However, NPHS2 mutations have been detected in some cases. Mutations in ACTN4, encoding alpha-actinin-4, cause an autosomal-dominant focal segmental glomerulosclerosis. alpha-actinin-4 stabilizes the podocyte cytoskeleton structure, connecting with actin filaments. WT1 mutations, causing Wilm's tumor, have been demonstrated in some CNS patients with diffuse mesangial sclerosis. Systematic investigation of genes for CNS in Japan has never been performed. METHODS: To clarify the role of mutations in these four genes, we used polymerase chain reaction (PCR) and direct sequencing to investigate all exons and exon-intron boundaries for these genes in 13 unrelated CNS patients from regional pediatric kidney disease centers in Japan. RESULTS: A novel homozygous nonsense mutation of NPHS1, E246X in exon 7, and a novel homozygous deletion mutation of NPHS1, 2156_2163del in exon 16 were detected in one patient each. A novel homozygous nonsense mutation of NPHS2, R196X in exon 5, was found in one patient, and the same heterozygous nonsense mutation was detected in another. No ACTN4 or WT1 mutations were detected. CONCLUSION: These studies demonstrate that mutation of NPHS1 is not a major cause of CNS in Japanese patients, and that mutation of NPHS2 can be responsible for CNS in this population.
NPHS2 mutations in sporadic steroid-resistant nephrotic syndrome in Japanese children.
Podocin is an integral membrane protein encoded by NPHS2, which is mapped to 1q25-31 and is exclusively expressed in glomerular podocytes. NPHS2 mutations are responsible for autosomal recessive familial steroid-resistant nephrotic syndrome (SRNS) with minor glomerular abnormalities or focal segmental glomerulosclerosis (FSGS), which is characterized by early childhood onset (age less than 6 years) and rapid progression to chronic renal insufficiency. This gene mutation is also responsible for an adolescent/adult onset form of autosomal recessive familial FSGS with heavy proteinuria. It has been demonstrated that sporadic SRNS and heavy proteinuria are also due to NPHS2 gene mutations. We isolated genomic DNA from 36 Japanese children with chronic renal insufficiency caused by SRNS or heavy proteinuria, and analyzed all eight exons and exon-intron boundaries of NPHS2 using the polymerase chain reaction and direct sequencing. The age at onset of disease was 3.9+/-0.5 years. There were 29 patients with SRNS and 7 with heavy proteinuria without nephrotic syndrome at the onset, but all patients developed chronic renal insufficiency 4.6+/-0.8 years after the onset. A new homozygous missense variant of NPHS2, G34E (G101A) in exon 1, was detected in 1 of 36 patients. However, this homozygous variant was also found in 1 of 44 normal controls, suggesting that the mutation is a polymorphism. Two silent variants (T954C and A1038G) in exon 8 of this gene were also identified in some of the patients and normal controls, indicating that the silent variants are also polymorphisms. There was no significant difference in the genotypic and allelic frequencies of T954C and A1038G polymorphisms between the patients and normal controls. In conclusion, NPHS2 gene mutations are not a major cause of chronic renal insufficiency caused by sporadic SRNS or heavy proteinuria in Japanese children.
[A case of Denys-Drash syndrome with prophylactic bilateral nephrectomy].
Denys-Drash syndrome is a rare disorder consisting of pseudohermaphrodism, Wilms' tumor and nephropathy. We describe here a boy with severe hypospadias and undescended testes, who presented with end-stage renal failure at the age of 1 year and 8 months when he was referred to our hospital. Emergency hemodialysis was performed because of oliguria, edema and severe hypertension, and then peritoneal dialysis was started. The findings of the renal biopsy showed diffuse mesangial sclerosis, consistent with the characteristic change in Denys-Drash syndrome. The analysis of WT1 gene revealed a G-to-A point mutation at 1,186 resulting in a change from Asp to Asn at 396 in exon 9. Since he had no urine output and his kidneys were not functional and in addition, patients with this mutation have been reported to have a high risk of Wilms' tumor, bilateral nephrectomy was performed. The removed kidneys showed no malignancies. Since Denys-Drash syndrome is frequently associated with Wilms' tumor, renal biopsy and gene analysis should be performed on male patients with gonadal anomaly, such as hypospadias and/or undescended testes, and proteinuria.
[Glucocorticoid treatment and osteoporosis in children].
Glucocorticoid (GC) -induced osteoporosis is defined as a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone, leading to increased fragility and susceptibility to fracture due to GC excess. The main mechanisms of GC-induced osteoporosis are a decreased bone formation and increased bone absorption. Although diagnosis criteria and recommendations for the prevention and treatment of GC-induced osteoporosis are established in adults, there are no criteria and recommendation for children. Bisphosphonate, the most effective drug for the treatment of GC-induced osteoporosis in adults, is not approved for the treatment of GC-induced osteoporosis in children. And there in no available data that GC-induced osteoporosis would affect the peak bone mass and senile osteoporosis or not. Diagnosis criteria and recommendations for the prevention and treatment of GC-induced osteoporosis should be established in children.
PAX2 gene mutation in a family with isolated renal hypoplasia.
The PAX2 gene encodes a transcription factor that plays a critical role in the development of the urogenital tract, eyes, ears, and central nervous system. Recently, renal hypoplasia was observed to be part of the renal-coloboma syndrome, which is caused by heterozygous mutations of the PAX2 gene. The renal-coloboma syndrome is a rare autosomal dominant syndrome that involves optic nerve colobomas and renal anomalies. For investigation of whether PAX2 mutations occur in patients with isolated renal hypoplasia, patient DNA was analyzed for PAX2 mutations, by using PCR and direct sequencing. The study involved 20 patients with bilateral renal hypoplasia associated with decreased renal function. Heterozygous PAX2 mutations were detected in two patients, i.e., a novel nonsense mutation (C to A transversion at position 1566 in exon 9) in patient 1 and another novel nonsense mutation (C to T transversion at position 1318 in exon 7) in patient 2. The nucleotide changes for patients 1 and 2 directly introduced stop codons, presumably resulting in a message for a truncated PAX2 protein that lacked a partial transactivation domain. An ophthalmologic examination revealed a very mild, asymptomatic coloboma in patient 2, whereas the fundus was normal for patient 1. The mutation cosegregated with the presence of renal hypoplasia in the family of patient 1, appearing de novo in the mother of the patient, which strongly suggests that this mutation was the cause of renal hypoplasia in this family. This study demonstrates for the first time that PAX2 mutations can be responsible for isolated renal hypoplasia.