Manatsu Satoh

Characterization of the human nebulette gene: a polymorphism in an actin-binding motif is associated with nonfamilial idiopathic dilated cardiomyopathy.

Abstract. Idiopathic dilated cardiomyopathy (IDC) is characterized by a thin-walled heart with systolic dysfunction of unknown etiology. Because abnormalities in genes for cytoskeletal proteins related to Z-disc function have recently been reported to cause IDC, genomic organization of the gene for nebulette, a novel actin-binding Z-disc protein, was determined and its sequence variations were searched for in Japanese patients with IDC and healthy controls. The nebulette gene consists of 28 exons, and four sequence variations leading to amino acid replacement (Gln187His, Met351Val, Asn654Lys, and Thr728Ala) were identified in the patients. These variations were also found in the healthy controls and hence they were polymorphisms and not disease-specific mutations. Frequencies of Gln187His, Met351Val, and Thr728Ala variants were similar in the patients and controls. However, the frequency of homozygotes for Lys at codon 654, a variant at a relatively conserved residue in an actin-binding motif, was significantly increased in nonfamilial IDC patients (n=106) as compared with healthy control subjects (n=331) (7.54% vs 1.21%, OR=6.25, P=0.002, 95% CI=1.92–20.29), while this association was not found in familial IDC patients (n=24). These observations suggest that the nebulette polymorphism in the actin-binding motif was a novel genetic marker of susceptibility to nonfamilial IDC.

MICA gene polymorphism in Takayasu's arteritis and Buerger's disease

To further clarify the HLA-linked genes susceptible to arterio-vasculitis of unknown etiology, Takayasus arteritis and Buergers disease, polymorphism in the MICA gene, a newly identified gene near the HLA-B gene and expressed in epithelial cell lineage, was investigated. Polymerase chain reaction (PCR)-DNA conformation polymorphism (DCP) analysis and subsequent sequencing of the MICA gene have revealed that there are 5 MICA alleles which are different in the number of a GCT repeat in exon 5: MICA alleles MICA-1.1, -1.2, -1.3 and -1.4 have 9, 6, 5 and 4 GCT repeats, respectively, and MICA-1.5 has 5 GCT repeats with a 1 bp frameshift insertion in the repeat. MICA genotyping data in 81 Japanese patients with Takayasus arteritis, 38 Japanese patients with Buergers disease, and 160 healthy Japanese controls showed that MICA-1.2 and -1.4 were significantly associated with Takayasus arteritis and Buergers disease, respectively. Because MICA-1.2 and -1.4 were in strong linkage disequilibria with HLA-B52 and -B54 in the Japanese populations, respectively, we have compared the odds ratio (OR) of the risk to the diseases for individuals having both or each of the disease-associated MICA and HLA-B alleles. It was found that MICA-1.2 gave a significantly high OR of risk to Takayasus arteritis in the absence of HLA-B52, suggesting that the HLA-linked gene susceptible to Takayasus arteritis is mapped near the MICA gene. In contrast, MICA-1.4 gave a significantly high OR of risk to Buergers disease only in the presence of HLA-B54, suggesting that the HLA-linked gene susceptible to Buergers disease is linked to the HLA-B54-MICA-1.4 haplotype, and may be differently mapped from that to Takayasus arteritis.

Early expression of a malignant phenotype of familial hypertrophic cardiomyopathy associated with a Gly716Arg myosin heavy chain mutation in a Korean family

The clinical course and prognosis of familial hypertrophic cardiomyopathy (HCM) are different according to the type of mutation in the genes for sarcomere proteins. It has been disputed that a mutation, which occurs at a functionally important region in the sarcomere proteins, may increase the penetrance and expressivity of the disease. We searched for a causative mutation in an HCM family, which is characterized by early expression of clinical phenotype, high incidence of sudden death at young ages, and progressive heart failure in adults. Among the 32 family members in 4 generations, 13 were affected; 4 died suddenly before age 16, 2 children have already had full expression of the cardiac hypertrophy, and other adults have either progressive heart failure or poor left ventricular systolic functions. PCR-SSCP (polymerase chain reaction-single strand confirmation polymorphism) analysis of genomic DNAs isolated from peripheral blood leukocytes of the family members identified a Gly716Arg mutation in the cardiac beta-myosin heavy chain gene, which was cosegregated with the clinical phenotype. The mutation is localized near a functionally important site of the myosin heavy chain, the 2 active thiols, which contribute to the adenosine triphosphatase activity of myosin S1. This family provides further evidence that the mutation, which occurs at a functionally important site of the myosin heavy chain, is associated with the high penetrance and early expression of HCM.

Hypertrophic obstructive cardiomyopathy due to a novel T-to-A transition at codon 624 in the β-myosin heavy chain (β-MHC) gene possibly related to the sudden death

Many missense mutations in the beta-myosin heavy chain have been reported in patients with hypertrophic obstructive cardiomyopathy (HOCM). However, the controversy is present whether the mutation accompanying the change of electric charge is related with poorer prognosis. The proband, a 48-year-old female, of the family was diagnosed clinically as HOCM, and a structural analysis of the cardiac beta-MHC gene showed that the proband and her junior daughter had a novel mutation with T to A transition in codon 624 replacing tyrosine with asparagine, which was not present in her husband, elder daughter and son. The probands husband, son and two daughters were healthy except that the ECG of junior daughter (15-year-old) showed complete right bundle branch block. Probands mother died suddenly after the delivery of the proband and the proband also collapsed suddenly. The occurrence of sudden death in proband and her mother suggested that HOCM with this novel mutation might be associated with a high risk of sudden death irrespective of the absence of charge alteration.