Rei Nishimura

Heterozygous nonsense mutations near the C‐terminal region of IGF1R in two patients with small‐for‐gestational‐age‐related short stature

The type I insulin‐like growth factor I receptor (IGF1R) plays an important role in growth. We aimed to evaluate the detailed mechanism underlying the effect of IGF1R on human growth.

Familial short stature is associated with a novel dominant‐negative heterozygous insulin‐like growth factor 1 receptor (IGF1R) mutation

Type-1 insulin-like growth factor receptor (IGF1R) plays a critical role in foetal and postnatal growth. Several heterozygous IGF1R mutations cause small-for-gestational-age (SGA) short stature. Here, we describe a family with severe SGA short stature, carrying a heterozygous missense mutation in the tyrosine kinase domain of IGF1R. The patient was a 9-year-old Japanese girl, the first child of her parents. The mother was born at 40 weeks of gestation, with a birth weight of 2200 g ( 2 2 SD), and had severe short stature [height: 137 cm ( 4 0 SD)]. The patient was born at 37 weeks of gestation, with a birth weight of 2175 g ( 1 5 SD) and a birth height of 42 5 cm ( 2 5 SD). Other than her short stature, she was healthy. The delayed mental development of both the patient and her mother had not been noted before this study. At 6 years of age, the patient’s height was 100 4 cm ( 3 0 SD), and the head circumference was 45 1 cm ( 2 1 SD). Her actual bone age was 5 8 years. The IGF1 serum level was 344 ng/mL (+3 3 SD). At 5 years of age, results from both GH stimulation with insulin and arginine (peak values: 13 and 10 6 ng/mL, respectively) and a 75-g oral glucose tolerance test revealed that the patient had normal glucose levels. GH treatment (0 25 mg/kg/week) was started when the patient was 6 years of age. The GH dose was increased to 0 32 mg/kg/

Increased IRS2 mRNA Expression in SGA Neonates: PCR Analysis of Insulin/IGF Signaling in Cord Blood

Context: Hypoglycemia is the most common metabolic problem among small-for-gestational-age (SGA) neonates. However, the pathological mechanism and insulin/ insulin-like growth factor (IGF) signaling axis in neonates remain unknown. Objective: To determine the insulin/IGF axis in neonates, we analyzed the messenger RNA (mRNA) expression of insulin/IGF signaling in fetal umbilical cord blood. Setting: The Perinatal Medical Center of Tottori University Hospital. Participants: Fifty-two [42 appropriate-for-gestational-age (AGA) and 10 SGA] neonates. Interventions: Immediately collected cord blood was placed into a PAXgene Blood RNA Tube. Total RNA from the blood was purified using reagents provided in the PAXgene Blood RNA Kit within 4 days, and reverse transcription polymerase chain reaction (PCR) was performed. Main Outcome Measure: Quantitative real-time PCR analysis was applied to evaluate the mRNA expression of insulin receptor (INSR), IGF-I receptor (IGF1R), insulin receptor substrate 1 (IRS1), IRS2, and glucose transporters (SLC2A2 and SLC2A4). β-Actin was used as a control gene. Results: Serum glucose and IGF-I levels in SGA neonates were significantly lower. The cord serum insulin levels were similar between AGA and SGA neonates. The IRS2 mRNA expression was significantly higher in SGA than in AGA neonates (P < 0.05). The IRS2 mRNA expression was significantly higher in hypoglycemic SGA neonates than in normoglycemic SGA neonates. Conclusions: We determined that intrauterine growth restriction induces increased IRS2 mRNA expression in cord blood, without hyperinsulinemia. The increased expression of IRS2 mRNA might be associated with abnormal glucose metabolism in SGA neonates. Our findings might lead to the elucidation of abnormal glucose metabolism in SGA neonates.

A novel frameshift mutation in NR3C2 leads to decreased expression of mineralocorticoid receptor: a family with renal pseudohypoaldosteronism type 1

Pseudohypoaldosteronism type 1 (PHA1) is a rare genetic disease characterized by resistance to aldosterone, and the renal form of PHA1 is associated with heterozygous inactivating mutations in NR3C2, which encodes mineralocorticoid receptor (MR). Here we report a case of renal PHA1 due to a novel frameshift mutation in NR3C2. A 10-day-old Japanese male infant, born at 39 weeks gestation (birth weight, 2,946 g), was admitted to our hospital because of lethargy and vomiting, with a 6.7% weight loss since birth. Laboratory test results were: Na+, 132 mEq/L; K+, 6.6 mEq/L; Cl+, 93 mEq/L. Both plasma aldosterone level and plasma renin activity were markedly elevated at diagnosis, 2,940 ng/dL (normal range: 26.9-75.8 ng/dL) and 560 ng/mL/h (normal range 3.66-12.05 ng/mL/h), respectively. Direct sequence analysis of NR3C2 revealed a novel heterozygous mutation (c.3252delC) in the patient and his father. The mutation causes a frameshift starting at amino acid I 963 within the C terminal ligand-binding domain of MR and results in a putative abnormal stop codon at amino acid 994, with an extension of 10 amino acids compared to normal MR. We performed cell culture experiments to determine the levels of mutant NR3C2 mRNA and MR, and evaluate the effects of the mutation on MR response to aldosterone. The mutation decreased the expression of MR, but not NR3C2 mRNA, and led to decreased MR function, with no dominant negative effect. These results provide important information about MR function and NR3C2 mutation in PHA1.

Cholesterol ester storage disease with a novel LIPA mutation (L264P) that presented massive hepatomegaly: A case report

Cholesterol ester storage disease (CESD) is an autosomal recessive disorder caused by deficient lysosomal acid lipase (LAL) activity, resulting in cholesteryl ester (CE) accumulation. CESD patients have liver disease associated with mixed dyslipidemia leading to liver failure. We here report the case of an 11‐year‐old male CESD patient with a novel mutation who had the chief complaint of massive hepatomegaly. The patients liver reached to his pelvis, and his spleen was 2 cm below the costal margin. The patient had elevated serum liver enzymes and mixed dyslipidemia. The liver biopsy tissue showed characteristic CESD pathology, which included microvesicular steatosis, mild fibrosis and foamy macrophages. Electron microscopy showed a remnant cleft of CE crystals, and dried blood spot testing showed reduced LAL activity. We identified compound heterozygous mutations in the LIPA gene in this patient, namely, c.607G>C and c.791T>C. The former mutation was previously reported only in a Japanese patient, whereas the latter mutation is novel. The findings of this study suggest that LIPA gene mutations in Japanese CESD patients are different from those in Western patients. Although CESD is rare, it is likely that many patients are unrecognized or misdiagnosed, and thus the possibility of CESD should be considered in patients with hepatosplenomegaly and dyslipidemia.

A rare CYP 21 mutation (p.E431K) induced deactivation of CYP 21A2 and resulted in congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is caused by mutations in the CYP21A2 gene. The residual enzyme activity is strongly associated with the phenotype. We describe a rare case of CAH with a rare CYP21A2 mutation. The patient was a one-year-old Japanese boy. At 16 days old, he was referred to our hospital because of elevated serum 17-OH-progesterone (17-OHP) levels in neonatal screening. The compound heterozygous mutations (IVS2-13 A/C>G, and p.E431K) in CYP21A2 were identified at 2 months old, and we diagnosed non-classical CAH, since he did not have significant physical signs (pigmentation and salt-wasting). However, his body weight decreased, and his serum 17-OHP level (99.5 ng/mL) was elevated at 3 months old. Steroid replacement therapy was started at 3 months old. Our patients clinical course resembled simple virilizing (SV) CAH, but classification was difficult because the patient showed increased renin activity indicating an aldosterone deficiency, and late onset of symptoms. While the IVS 2-13 A/C>G mutation is common in the classical form of CAH, p.E431K is a rare point mutation. Functional analysis revealed that the residual enzyme activity of p.E431L was 5.08±2.55% for 17-OHP and 4.12±2.37% for progesterone, which is consistent with SV CAH. p.E431 is localized in the L-helix near the heme-binding site. The mutation might interfere with heme binding, leading to deactivation of CYP21A2. This report showed that CYP21A2 p.E431 has an important effect on enzyme activity.