Kazuhiro Ohkubo

Moyamoya disease susceptibility gene RNF213 links inflammatory and angiogenic signals in endothelial cells

Moyamoya disease (MMD) is a cerebrovascular disorder characterized by occlusive lesions of the circle of Willis. To date, both environmental and genetic factors have been implicated for pathogenesis of MMD. Allelic variations in RNF213 are known to confer the risk of MMD; however, functional roles of RNF213 remain to be largely elusive. We herein report that pro-inflammatory cytokines, IFNG and TNFA, synergistically activated transcription of RNF213 both in vitro and in vivo. Using various chemical inhibitors, we found that AKT and PKR pathways contributed to the transcriptional activation of RNF213. Transcriptome-wide analysis and subsequent validation with quantitative PCR supported that endogenous expression of cell cycle-promoting genes were significantly decreased with knockdown of RNF213 in cultured endothelial cells. Consistently, these cells showed less proliferative and less angiogenic profiles. Chemical inhibitors for AKT (LY294002) and PKR (C16) disrupted their angiogenic potentials, suggesting that RNF213 and its upstream pathways cooperatively organize the process of angiogenesis. Furthermore, RNF213 down-regulated expressions of matrix metalloproteases in endothelial cells, but not in fibroblasts or other cell types. Altogether, our data illustrate that RNF213 plays unique roles in endothelial cells for proper gene expressions in response to inflammatory signals from environments.

Neuroendocrine phenotypes in a boy with 5q14 deletion syndrome implicate the regulatory roles of myocyte-specific enhancer factor 2C in the postnatal hypothalamus.

The 5q14.3 deletion syndrome is a rare chromosomal disorder characterized by moderate to severe intellectual disability, seizures and dysmorphic features. We report a 14-year-old boy with 5q14.3 deletion syndrome who carried a heterozygous deletion of the myocyte-specific enhancer factor 2c (MEF2C) gene. In addition to the typical neurodevelopmental features of 5q14.3 deletion syndrome, he showed recurrent hypoglycemia, appetite loss and hypothermia. Hormonal loading tests using insulin, arginine and growth hormone-releasing factor revealed that growth hormone was insufficiently released into serum in response to these stimuli, thus disclosing the hypothalamic dysfunction in the present case. To uncover the biological roles of MEF2C in the hypothalamus, we studied its expression in the postnatal mouse brain. Notably, neuropeptide Y (NPY)-positive interneurons in the hypothalamic arcuate nuclei highly expressed MEF2C. In contrast, the Rett syndrome-associated protein, Methyl-CpG binding Protein 2 (MECP2) was barely expressed in these neurons. MEF2C knockdown or overexpression experiments using Neuro2a cells revealed that MEF2C activated the endogenous transcription of NPY. Conversely, siRNA-mediated knockdown of MECP2 led to derepression of the Npy gene. These data support the concept that MEF2C and MECP2 share common molecular pathways regulating the homeostatic expression of NPY in the adult hypothalamus. We propose that individuals with 5q14.3 deletion syndrome may exhibit neuroendocrine phenotypes through the functional loss of MEF2C in the postnatal hypothalamus.

Hyperinsulinemic hypoglycemia in Beckwith–Wiedemann, Sotos, and Kabuki syndromes: A nationwide survey in Japan

Beckwith–Wiedemann syndrome (BWS) is a congenital overgrowth syndrome that is occasionally associated with hyperinsulinemic hypoglycemia (HH) in the neonatal period. Sotos syndrome (SS) and Kabuki syndrome (KS) are other malformation syndromes that may be complicated with HH, however, the detailed clinical characteristics of HH accompanied with these syndromes remain unclear. We herein conducted a nationwide questionnaire survey in Japan. We sent a primary questionnaire concerning the clinical experience for these syndromes to 347 perinatal care institutions. As a result, 222 departments or hospitals returned the questionnaires and the total numbers of BWS, SS, and KS patients were 113, 88, and 51, respectively. We sent a secondary questionnaire to 31 institutions where patients with these syndromes presented with HH during infancy. The secondary questionnaires were returned from the institutions and the numbers of patients were 16 for BWS, 9 for SS, and 3 for KS, respectively. Then, we compared the clinical characteristics of infants suffering from transient HH with and without these dysmorphic syndromes. As a result, BWS, SS, and KS patients showed significantly larger body size, lower Apgar scores, higher insulin levels at HH, and shorter durations of HH than non‐dysmorphic infants with transient HH. We propose that a careful observation for the signs of HH, even if not specific to the syndromes, is important for the diagnosis of patients with BWS, SS, and KS in the postnatal period.

The signal transducer and activator of transcription 5B gene polymorphism contributes to the cholesterol metabolism in Japanese children with growth hormone deficiency

Background and aims  GH plays a significant role in the lipid metabolism. In this study, we focused on the JAK2 – signal transducer and activator of the transcription 5 (STAT5) pathway, which transmit the signals from the GH receptor, and selected the STAT5A/B gene as a candidate for the regulation of lipid metabolism in GH deficiency (GHD).

Hypothyroidism and levothyroxine-responsive liver dysfunction in a patient with ring chromosome 18 syndrome.

BACKGROUND Ring chromosome 18 [r18] is a rare constitutional chromosomal aberration syndrome, characterized by dysmorphic face, hypoactivity, short stature, and delayed development. Autoimmune thyroiditis and immunoglobulin (Ig) A deficiency are occasionally associated with chromosome-18 deletion syndromes. SUMMARY Here, we report a 2-year-old male child with r(18) syndrome and a selective IgA deficiency (<1.6 mg/dL, reference range [rr]: 20-149), who developed hypothyroidism and liver dysfunction. Thyroid function tests (thyroid-stimulating hormone [TSH]: 1031 μIU/mL, rr 0.43-4.0; free triiodothyronine: 0.52 pg/mL, rr 2.37-4.65; free thyroxine: 0.11 ng/dL, rr 1.03-2.00) and positive thyroid antibodies (anti-TSH receptor 1.7 IU/L, cut-off index [coi]: <1.0, antithyroid peroxidase 171 IU/mL, coi <0.3, and antithyroglobulin 2.8 IU/mL, coi <0.3) indicated autoimmune hypothyroidism. Elevated levels of aspartate aminotransferase (AST, 240 IU/L, rr 17-39) and alanine aminotransferase (ALT, 315 IU/L, rr 4-23), but negative antibodies against LKM and mitochondrial M2, suggested no autoimmune hepatitis. Transaminase levels became normalized after he was given levothyroxine therapy to achieve the euthyroid state, but they repeatedly became elevated when levothyroxine was inadvertently discontinued (peak AST=409 IU/L; peak ALT=390 IU/L). A maintenance dose of levothyroxine has effectively maintained the euthyroid state and normalized liver function tests despite no immunosuppressive therapy. CONCLUSIONS The r18 patient with autoimmune hypothyroidism and IgA deficiency suffered from idiopathic hepatitis. The liver dysfunction was associated with hypothyroidism that resolved with thyroid hormone treatment. While the former combination has been described, the latter has not. The reason for the development of hepatitis in association with hypothyroidism is unexplained. However, we postulate that it might be related, in ways that are not clear, to the deleted genes of r18.

Effective shunt closure for pulmonary hypertension and liver dysfunction in congenital portosystemic venous shunt

Congenital portosystemic venous shunt (CPSVS) is a rare vascular malformation with a high risk of mortality from pulmonary arterial hypertension (PAH), but the treatment outcome of CPSVS closure remains elusive. Our aim was to investigate the clinical features and establish the optimal management of CPSVS with or without PAH.

Comprehensive screening for monogenic diabetes in 89 Japanese children with insulin-requiring antibody-negative type 1 diabetes

Mutations in causative genes for neonatal diabetes or maturity‐onset diabetes of the young have been identified in multiple patients with autoantibody‐negative type 1 diabetes (T1D).

Vascular pathomechanism in acute encephalopathy with biphasic seizures and late reduced diffusion

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a childhood-onset encephalopathy, but the precise pathophysiology remains unclear. We encountered a child with Moyamoya syndrome and AESD. He exhibited left-predominant stenosis of the middle cerebral artery (MCA), and later developed broad lesions in the left hemisphere, raising the possibility that insufficient blood supply relates to formation of the lesions. To test the hypothesis, we investigated the relationship between MCA volume and lesion extent in seven AESD children without preexisting diseases. The MCA volume and lesion extent were quantified with time of flight images for construction of magnetic resonance angiography and apparent diffusion coefficient maps, respectively. Lateralization indices ([right - left]/[right + left]) of the MCA volume and lesion extent were calculated. We found that the lateralization indices were negatively correlated (r = -0.786, p = .036), that is, when the MCA volume was smaller in one side than the other side, the lesions were likely to develop more extensively in the ipsilateral side than the contralateral side. This indicates the association of insufficient blood supply with the lesions. The present study provides the first observation to suggest the involvement of vascular mechanism in AESD and has potential implications for novel therapeutic approach.

A male case with CDKL5-associated encephalopathy manifesting transient methylmalonic acidemia

Mutations in the X-linked gene CDKL5 cause early-onset epileptic encephalopathy and severe developmental delay. Because this disorder predominantly affects females, the full clinical spectrum of male patients remains elusive. We herein report a 16-year-old boy, who suffered from intractable seizures 20 days after birth. Serial electroencephalograms detected recurrent focal epileptiform discharges from age 4 months, which evolved to hypsarrhythmia later in infancy. Mass-spectrometric analyses revealed increase in urinary excretion of methylmalonic acid without perturbed concentrations of propionic acid, homocystein and methionine. Whole-exome sequencing identified a de novo, truncating mutation in CDKL5 (NM_003159.2:c.419dupA, p.Asn140Lysfs*8). Targeted sequencing excluded concomitant mutations in methylmalonic academia-associated genes. No methylmalonic acidemia has been reported in children with CDKL5 disorder. Extensive analyses on organic acid metabolism for males with CDKL5 mutations will gain more insight into their biochemical profiles in infancy.

Resolution of Hydronephrosis in a Patient With Mucopolysaccharidosis Type II With Enzyme Replacement Therapy

Mucopolysaccharidosis type II (MPS II) is caused by deficiency of lysosomal enzyme iduronate-2-sulfatase. Insufficient activity of the enzyme results in accumulation of glycosaminoglycans leading to progressive multisystem pathologies. MPS II is less likely to be complicated by kidney and urinary tract problems. We report a boy with MPS II, who developed left hydronephrosis. His hydronephrosis improved after starting enzyme replacement therapy. It was suggested that MPS II was closely associated with the pathogenesis of hydronephrosis.