Kunihiro Hamamoto

ITPKC functional polymorphism associated with Kawasaki disease susceptibility and formation of coronary artery aneurysms

Kawasaki disease is a pediatric systemic vasculitis of unknown etiology for which a genetic influence is suspected. We identified a functional SNP (itpkc_3) in the inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) gene on chromosome 19q13.2 that is significantly associated with Kawasaki disease susceptibility and also with an increased risk of coronary artery lesions in both Japanese and US children. Transfection experiments showed that the C allele of itpkc_3 reduces splicing efficiency of the ITPKC mRNA. ITPKC acts as a negative regulator of T-cell activation through the Ca2+/NFAT signaling pathway, and the C allele may contribute to immune hyper-reactivity in Kawasaki disease. This finding provides new insights into the mechanisms of immune activation in Kawasaki disease and emphasizes the importance of activated T cells in the pathogenesis of this vasculitis.

A genome-wide association study identifies three new risk loci for Kawasaki disease

We performed a genome-wide association study (GWAS) of Kawasaki disease in Japanese subjects using data from 428 individuals with Kawasaki disease (cases) and 3,379 controls genotyped at 473,803 SNPs. We validated the association results in two independent replication panels totaling 754 cases and 947 controls. We observed significant associations in the FAM167A-BLK region at 8p22-23 (rs2254546, P = 8.2 × 10−21), in the human leukocyte antigen (HLA) region at 6p21.3 (rs2857151, P = 4.6 × 10−11) and in the CD40 region at 20q13 (rs4813003, P = 4.8 × 10−8). We also replicated the association of a functional SNP of FCGR2A (rs1801274, P = 1.6 × 10−6) identified in a recently reported GWAS of Kawasaki disease. Our findings provide new insights into the pathogenesis and pathophysiology of Kawasaki disease.

CD40 ligand gene and Kawasaki disease.

Kawasaki disease (KD) is an acute systemic vasculitis syndrome of infants and young children. Although its etiology is largely unknown, epidemiological findings suggest that genetic factors play a role in the pathogenesis of KD. To identify genetic factors, affected sib-pair analysis has been performed. One of the identified peaks was located on the Xq26 region. A recent report of elevated expression of CD40 ligand (CD40L), which maps to Xq26, during the acute-phase KD, and its relationship to the development of coronary artery lesions (CAL) prompted us to screen for polymorphism of CD40L and to study the association of the gene to KD. A newly identified SNP in intron 4 (IVS4+121 A>G) is marginally over-represented in KD patients as compared to controls (109/602, 18.1 vs 111/737, 15.1%). When male KD patients with CAL were analyzed as a patient group, the SNP was significantly more frequent than in controls (15/58, 25.9%, vs 111/737, 15.1%, OR=2.0, 95% CI=1.07–3.66; P=0.030). Interestingly, this variation was extremely rare in a control Caucasian population (1/145, 0.7%). Our results suggest a role of CD40L in the pathogenesis of CAL and might explain the excess of males affected with KD.

Possible Synergic Effect of Angiotensin-I Converting Enzyme Gene Insertion/Deletion Polymorphism and Angiotensin-II Type-1 Receptor 1166A/C Gene Polymorphism on Ischemic Heart Disease in Patients with Kawasaki Disease

ACE I/D and AT1R 1166A/C polymorphisms are considered to comprise individual risk factors for the development of coronary disease. We sought to demonstrate that the ACE I/D and AT1R 1166A/C polymorphisms affect coronary artery stenosis in patients with Kawasaki disease (KD). We examined 147 healthy controls and 281 Japanese children with KD. The patients were further divided into group N (n = 246, no ischemia) and group I (n = 35, severe coronary artery stenosis with myocardial ischemia), and we studied the genotype of ACE I/D and AT1R 1166A/C polymorphisms. We also examined ACE activity in patients with acute KD. We did not detect any prevalent genotypes of the ACE and AT1R polymorphisms between controls and KD patients. However, the prevalence of the D allele in the ACE polymorphism and of the C allele in the AT1R polymorphism tended to be higher in group I than in group N (odds ratios, 2.00 and 2.32, respectively). In addition, the presence of the D and/or C alleles significantly increased the relative risk of developing myocardial ischemia (odds ratio, 2.71; p = 0.038). During the convalescent phase of KD, ACE activity was increased despite significant attenuation during the acute phase. These results suggested that the renin-angiotensin system is associated with the formation of severe coronary artery stenosis and myocardial ischemia.

Variations in ORAI1 Gene Associated with Kawasaki Disease

Kawasaki disease (KD; MIM#61175) is a systemic vasculitis syndrome with unknown etiology which predominantly affects infants and children. Recent findings of susceptibility genes for KD suggest possible involvement of the Ca(2+)/NFAT pathway in the pathogenesis of KD. ORAI1 is a Ca(2+) release activated Ca(2+) (CRAC) channel mediating store-operated Ca(2+) entry (SOCE) on the plasma membrane. The gene for ORAI1 is located in chromosome 12q24 where a positive linkage signal was observed in our previous affected sib-pair study of KD. A common non-synonymous single nucleotide polymorphism located within exon 2 of ORAI1 (rs3741596) was significantly associated with KD (P = 0.028 in the discovery sample set (729 KD cases and 1,315 controls), P = 0.0056 in the replication sample set (1,813 KD cases vs. 1,097 controls) and P = 0.00041 in a meta-analysis by the Mantel-Haenszel method). Interestingly, frequency of the risk allele of rs3741596 is more than 20 times higher in Japanese compared to Europeans. We also found a rare 6 base-pair in-frame insertion variant associated with KD (rs141919534; 2,544 KD cases vs. 2,414 controls, P = 0.012). These data indicate that ORAI1 gene variations are associated with KD and may suggest the potential importance of the Ca(2+)/NFAT pathway in the pathogenesis of this disorder.

A case of long QT syndrome with triple gene abnormalities: Digenic mutations in KCNH2 and SCN5A and gene variant in KCNE1

molecular genetic studies have identi-fied 13 different forms of congenital LQTS caused bymutations in the genes of potassium, sodium, and calciumchannels or membrane adaptors. Recent studies also showedthat common candidate gene variants are associated with QTinterval duration in the general population.

Effect of aging on autonomic function in individuals with severe motor and intellectual disabilities

Autonomic nervous function is often abnormally regulated in individuals with severe motor and intellectual disabilities (SMID). In this study, we assessed autonomic nervous function of patients with SMID and determined how it was influenced by age. The study included 21 individuals with SMID and 15 healthy adolescents (control). To determine the effect of aging, the patients with SMID were divided into an older age group (Old) and younger age group (Young). Autonomic nervous function was assessed using power spectral analysis of heart rate variability (HRV) for 24-h Holter electrocardiogram recordings. The low- and high-frequency components (LH and HF) of HRV were calculated. The ratio between LF and HF (LF/HF) was used as an indicator of sympathetic modulation, while HF alone was used as an indicator of parasympathetic modulation. The LH/HF in the control group was higher in the daytime than at nighttime, while HF had an opposite pattern of change. Therefore, circadian rhythms were observed in the control group for both sympathetic and parasympathetic nervous activities. In contrast, the LF/HF in patients with SMID had no circadian rhythm. The HF was higher in the Old SMID group than in the Young group, and it exhibited a circadian rhythm in eight patients in the Old SMID group versus none of the patients in the Young group. These findings suggest that the sympathetic nervous system is suppressed in both old and young patients with SMID. However, while the parasympathetic nervous system is suppressed in younger patients with SMID, it is activated with increasing age.

Scimitar syndrome with an accessory diaphragm and an absent right superior vena cava

An 8-year-old boy with scimitar syndrome, an accessory diaphragm and an absent right superior vena cava, underwent surgery on March 28, 1983. The scimitar vein was separated from an accessory diaphragm and cut just above the right diaphragm where the vein penetrated. The vein was re-implanted into the right lateral portion of the right atrium and a tunnel was made between the atrial septal defect created in the septum and the site of the implanted vein. The accessory diaphragm was not removed because of the lack of compression on the right lung. At cardiopulmonary bypass, venous cannulae were inserted into the persistent left superior vena cava and inferior vena cava. Because of the absence of the right superior vena cava, the right atrium was not fixed by both cavae so that there was difficulty in intracardiac maneuvers. The patient is doing well 32 months after this treatment.

ACE I/D and AT1 1166A/C Polymorphism as a Risk Factor for Coronary Artery Stenosis in Kawasaki Disease

Gene polymorphism is considered to become the individual risk factors for the disease developments. We studied the gene polymorphism of Angiotensin Converting Enzyme(ACE) I/D, and Angiotensin II Receptor1 (AT1) 1166A/C polymorphism in Kawasaki disease patients and examined whether these polymorphism associate with coronary artery stenosis. (Subjects and Methods) 195 Kawasaki disease patients were enrolled in this study. Written informed consents were acquired from all patients. We divided the patients into three groups. Group N (n=122); no coronary artery changes, Group C (n=40); coronary artery dilation and/or stenosis without myocardial ischemia, Group S (n=33); coronary artery stenosis with myocardial ischemia. Genomic DNA specific primers were designed and Polymerase Chain Reaction (PCR) were performed. PCR products were separated on the agarose gel directly (ACE I/D polymorphism), or after the sequence specific restriction enzymes digestion (AT1 1166A/C polymorphism). (Results) We could not detect any significant differences in specific genotypes between the groups. However, when we evaluated the patients whether they possess D allele of ACE I/D polymorphism and/or C allele of AT1 1166A/C polymorphism, the patients who own both ACE polymorphism D allele and AT1 polymorphism C allele were significantly higher in Group S (χ2 test; p<0.05). We concluded the Kawasaki disease patients who have both D allele in ACE I/D polymorphism and C allele in AT1 1166A/C polymorphism are exposed to the higher risk for coronary artery stenosis.