👤 Tadashi Yamakawa

Late-onset Alzheimer's disease (LOAD) is the most common form of dementia in the elderly, yet no curative treatments are available. Although genome-wide association studies (GWASs) have identified numerous genetic risk factors, these factors often differ among ethnic groups, and the mechanisms driving LOAD onset remain poorly understood. Most GWASs of LOAD have been conducted in European populations; the expansion of future studies to non-European populations should uncover novel genetic factors underlying LOAD pathogenesis. To identify novel LOAD-susceptible genes, we conducted whole-genome sequencing data analysis on 1928 Japanese individuals including 325 patients with LOAD and 1603 cognitively normal elderly controls. A GWAS for common variants identified a statistically significant association signal in rs429358, within the apolipoprotein E gene (APOE), which defines the APOE Show less

We aimed to determine the similarities and differences in the roles of genic and regulatory copy number variations (CNVs) in bipolar disorder (BD), schizophrenia (SCZ), and autism spectrum disorder (ASD). Based on high-resolution CNV data from 8708 Japanese samples, we performed to our knowledge the largest cross-disorder analysis of genic and regulatory CNVs in BD, SCZ, and ASD. In genic CNVs, we found an increased burden of smaller (<100 kb) exonic deletions in BD, which contrasted with the highest burden of larger (>500 kb) exonic CNVs in SCZ/ASD. Pathogenic CNVs linked to neurodevelopmental disorders were significantly associated with the risk for each disorder, but BD and SCZ/ASD differed in terms of the effect size (smaller in BD) and subtype distribution of CNVs linked to neurodevelopmental disorders. We identified 3 synaptic genes (DLG2, PCDH15, and ASTN2) as risk factors for BD. Whereas gene set analysis showed that BD-associated pathways were restricted to chromatin biology, SCZ and ASD involved more extensive and similar pathways. Nevertheless, a correlation analysis of gene set results indicated weak but significant pathway similarities between BD and SCZ or ASD (r = 0.25-0.31). In SCZ and ASD, but not BD, CNVs were significantly enriched in enhancers and promoters in brain tissue. BD and SCZ/ASD differ in terms of CNV burden, characteristics of CNVs linked to neurodevelopmental disorders, and regulatory CNVs. On the other hand, they have shared molecular mechanisms, including chromatin biology. The BD risk genes identified here could provide insight into the pathogenesis of BD. Show less

Lipid management, especially with respect to triglyceride (TG) metabolism, in patients with diabetes is not sufficient with current therapeutic agents, and new approaches for improvement are needed. Members of the angiopoietin-like protein (ANGPTL) family, specifically ANGPTL3, 4, and 8, have been reported as factors that inhibit lipoprotein lipase (LPL) activity and affect TGs. The present study investigated the association between lipid and glucose metabolism markers and the mechanism by which these proteins affect lipid metabolism. A total of 84 patients hospitalized for diabetes treatment were evaluated. Lipid and glucose metabolism markers in blood samples collected before breakfast, on the day after hospitalization, were analyzed. ANGPTL8 showed a significant positive correlation with TG values. HDL-C values displayed a significant positive correlation with ANGPTL3 but a negative correlation with ANGPTL4 and ANGPTL8. The results did not indicate a significant correlation among ANGPTL3, 4, and 8 levels. Thus, it is possible that the distribution of these proteins differs among patients. When patients were divided into groups according to the levels of ANGPTL3 and ANGPTL8, those with high levels of both ANGPTL3 and ANGPTL8 also had high levels of TG and small dense LDL-C/LDL-C (%). Multiple regression analysis indicated that low LPL, high ApoC2, high ApoC3, high ApoE, and high ANGPTL8 levels were the determinants of fasting hypertriglyceridemia. By contrast, no clear association was observed between any of the ANGPTLs and glucose metabolism markers, but ANGPTL8 levels were positively correlated with the levels of HOMA2-IR and BMI. Patients with high levels of both ANGPTL3 and ANGPTL8 had the worst lipid profiles. Among ANGPTL3, 4, and 8, ANGPTL8 is more important as a factor determining plasma TG levels. We anticipate that the results of this research will facilitate potential treatments targeting ANGPTL8 in patients with diabetes. Show less

CENP-B binds to CENP-B boxes on centromeric satellite DNAs (known as alphoid DNA in humans). CENP-B maintains kinetochore function through interactions with CENP-A nucleosomes and CENP-C. CENP-B binding to transfected alphoid DNA can induce Show less

In interspecific hybrids between Drosophila melanogaster and Drosophila simulans, the D. simulans nucleoporin-encoding Nup96(sim) and Nup160(sim) can cause recessive lethality if the hybrid does not also inherit the D. simulans X chromosome. In addition, Nup160(sim) leads to recessive female sterility in the D. melanogaster genetic background. Here, we conducted carefully controlled crosses to better understandthe relationship between Nup96(sim) and Nup160(sim). Nup96(sim) did not lead to female sterility in the D. melanogaster genetic background, and double introgression of Nup96(sim) and Nup160(sim) did not generally lead to lethality when one was heterozygous and the other homozygous (hemizygous). It appears that introgression of additional autosomal D. simulans genes is necessary to cause lethality and that the effect of the introgression is dominant to D. melanogaster alleles. Interestingly, the genetic background affected dominance of Nup96(sim), and double introgression carrying homozygous Nup96(sim) and hemizygous Nup160(sim) resulted in lethality. Thus, Nup96(sim) and Nup160(sim) seem to be two components of the same incompatibility. Show less

Carbamoylphosphate synthetase I deficiency (CPS1D) is a urea-cycle disorder characterized by episodes of life-threatening hyperammonemia. Correct diagnosis is crucial for patient management, but is difficult to make from clinical presentation and conventional laboratory tests alone. Enzymatic or genetic diagnoses have also been hampered by difficult access to the appropriate organ and the large size of the gene (38 exons). In this study, in order to address this diagnostic dilemma, we performed the largest mutational and clinical analyses of this disorder to date in Japan. Mutations in CPS1 were identified in 16 of 18 patients with a clinical diagnosis of CPS1D. In total, 25 different mutations were identified, of which 19 were novel. Interestingly, in contrast to previous reports suggesting an extremely diverse mutational spectrum, 31.8% of the mutations identified in Japanese were common to more than one family. We also identified two common polymorphisms that might be useful for simple linkage analysis in prenatal diagnosis. The accumulated clinical data will also help to reveal the clinical presentation of this rare disorder in Japan. Show less

BPAG1 (bullous pemphigoid antigen 1) was originally identified as a 230-kDa hemidesmosomal protein and belongs to the plakin family, because it consists of a plakin domain, a coiled-coil rod domain and a COOH-terminal intermediate filament binding domain. To date, alternatively spliced products of BPAG1, BPAG1e, and BPAG1n are known. BPAG1e is expressed in epithelial tissues and localized to hemidesmosomes, on the other hand, BPAG1n is expressed in neural tissues and muscles and has an actin binding domain at the NH(2)-terminal of BPAG1e. BPAG1 is also known as a gene responsible for Dystonia musculorum (dt) neurodegeneration syndrome of the mouse. Another plakin family protein MACF (microtubule actin cross-linking factor) has also an actin binding domain and the plakin domain at the NH(2)-terminal. However, in contrast to its high homology with BPAG1 at the NH(2)-terminal, the COOH-terminal structure of MACF, including a microtubule binding domain, resembles dystrophin rather than plakins. Here, we investigated RNAs and proteins expressed from the BPAG1 locus and suggest novel alternative splicing variants, which include one consisting of the COOH-terminal domain structure homologous to MACF. The results indicate that BPAG1 has three kinds of cytoskeletal binding domains and seems to play an important role in linking the different types of cytoskeletons. Show less

The genetic progressive myoclonus epilepsies (PMEs) are clinically characterized by the triad of stimulus sensitive myoclonus (segmental lightning like muscular jerks), epilepsy (grand mal and absences) and progressive neurologic deterioration (dementia, ataxia, and various neurologic signs depending on the cause). Etiologically heterogenous, PMEs are rare and mostly autosomal recessive disorders, with the exception of autosomal dominant dentatorubral-pallidoluysian atrophy and mitochondrial encephalomyopathy with ragged red fibers (MERRF). In the last five years, specific mutations have been defined in Lafora disease (gene for laforin or dual specificity phosphatase in 6q24), Unverricht-Lundborg disease (cystatin B in 21q22.3), Jansky-Bielschowsky ceroid lipofuscinoses (CLN2 gene for tripeptidyl peptidase 1 in 11q15), Finnish variant of late infantile ceroid lipofuscinoses (CLN5 gene in 13q21-32 encodes 407 amino acids with two transmembrane helices of unknown function), juvenile ceroid lipofuscinoses or Batten disease (CLN3 gene in 16p encodes 438 amino acid protein of unknown function), a subtype of Batten disease and infantile ceroid lipofuscinoses of the Haltia-Santavuori type (both are caused by mutations in palmitoyl-protein thiosterase gene at 1p32), dentadorubropallidoluysian atrophy (CAG repeats in a gene in 12p13.31) and the mitochondrial syndrome MERRF (tRNA Lys mutation in mitochondrial DNA). In this review, we cover mainly these rapid advances. Show less