Identification of six novel susceptibility loci for dyslipidemia by longitudinal exome-wide association studies in Japanese

Background

The circulating concentrations of triglycerides, high density lipoprotein (HDL)-cholesterol, and low density lipoprotein (LDL)-cholesterol have a substantial genetic component. Although previous genome-wide association studies identified various genes and loci related to plasma lipid levels, those studies were conducted in a cross-sectional manner.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to hypertriglyceridemia, hypo-HDL-cholesterolemia, and hyper-LDL-cholesterolemia in Japanese. We have now performed longitudinal exome-wide association studies (EWASs) to identify novel loci for dyslipidemia by examining temporal changes in serum lipid profiles.

Methods

Longitudinal EWASs (mean follow-up period, 5 years) for hypertriglyceridemia (2056 case, 3966 controls), hypo-HDL-cholesterolemia (698 cases, 5324 controls), and hyper-LDL-cholesterolemia (2769 cases, 3251 controls) were performed with Illumina Human Exome arrays. The relation of genotypes of 24,691 single nucleotide polymorphisms (SNPs) that passed quality control to dyslipidemia-related traits was examined with the generalized estimating equation (GEE). To compensate for multiple comparisons of genotypes with each of the three conditions, we applied Bonferroni's correction for statistical significance of association. Replication studies with cross-sectional data were performed for hypertriglyceridemia (2685 cases, 4703 controls), hypo-HDL-cholesterolemia (1947 cases, 6146 controls), and hyper-LDL-cholesterolemia (1719 cases, 5833 controls).

Results

Longitudinal EWASs revealed that 30 SNPs were significantly (P<2.03 × 10–6 by GEE) associated with hypertriglyceridemia, 46 SNPs with hypo-HDL-cholesterolemia, and 25 SNPs with hyper-LDL-cholesterolemia. After examination of the relation of identified SNPs to serum lipid profiles, linkage disequilibrium, and results of the previous genome-wide association studies, we newly identified rs74416240 of TCHP, rs925368 of GIT2, rs7969300 of ATXN2, and rs12231744 of NAA25 as a susceptibility loci for hypo-HDL-cholesterolemia; and rs34902660 of SLC17A3 and rs1042127 of CDSN for hyper-LDL-cholesterolemia. These SNPs were not in linkage disequilibrium with those previously reported to be associated with dyslipidemia, indicating independent effects of the SNPs identified in the present study on serum concentrations of HDL-cholesterol or LDL-cholesterol in Japanese. According to allele frequency data from the 1000 Genomes project database, five of the six identified SNPs were monomorphic or rare variants in European populations. In the replication study, all six SNPs were associated with dyslipidemia-related phenotypes.

Conclusion

We have thus identified six novel loci that confer susceptibility to hypo-HDL-cholesterolemia or hyper-LDL-cholesterolemia. Determination of genotypes for these SNPs at these loci may prove informative for assessment of the genetic risk for dyslipidemia in Japanese.

Funding Acknowledgement

Type of funding source: None

Identification of two genes as novel susceptibility loci for type 2 diabetes mellitus in Japanese

Background

The heritability of Type 2 diabetes mellitus (T2DM) has been estimated to be 50% to 60%. Although genome-wide association studies identified >120 loci that confer susceptibility to T2DM, these studies were commonly conducted in a cross-sectional manner.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to T2DM in Japanese. We have now performed longitudinal exome-wide association studies (EWASs) to identify novel loci for T2DM by examining temporal changes in fasting plasma glucose (FPG) level, blood hemoglobin A1c (HbA1c) content, and the prevalence of T2DM.

Methods

Longitudinal EWASs (mean follow-up period, 5 years) were performed with Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip arrays and with 6,022 Japanese (755 subjects with T2DM, 5267 controls). The relation of genotypes of 24,579 SNPs that passed quality control to FPG level, blood HbA1c content, or the prevalence of T2DM was examined with the generalized estimating equation (GEE). To compensate for multiple comparisons of genotypes with each of the three parameters, we applied Bonferroni's correction for statistical significance of association.

Results

Longitudinal EWASs (GEE with adjustment for age, sex, body mass index, and smoking) revealed that rs6414624 of EVC (P<2.0×10–16 for T2DM, P=9.1×10–11 for FPG), rs78338345 of GGA3 (P<2.0×10–16 for T2DM, P=4.3×10–9 for FPG), rs10490775 of PTPRG (P<2.0×10–16 for T2DM, P=3.3×10–7 for FPG), and rs61739510 of GLT6D1 (P<2.0×10–16 for T2DM, P=5.8×10–7 for FPG) were significantly associated with the prevalence of T2DM and FPG levels; and rs11558471 in SLC30A8 with FPG level (P=1.8×10–8) and blood HbA1c content (P=1.2×10–7). After examination of the relation of identified SNPs to FPG level and blood HbA1c content, linkage disequilibrium of the SNPs, and results of the previous genome-wide association studies, we identified rs6414624 of EVC and rs78338345 of GGA3 as novel susceptibility loci for T2DM. In the identified SNPs (rs6414624 and rs7833834), FPG level, blood HbA1c content, and the prevalence of T2DM were significantly lower in homozygotes with the minor alleles than in homozygotes with the major alleles or heterozygotes. These results suggest that the minor alleles of rs6414624 and rs78338345 are protective against T2DM in Japanese. According to allele frequency data from the 1000 Genomes Project database, the minor G allele of rs78338345 of GGA3 is specifically distributed in East Asia. This suggests that the minor allele frequency may have increased in East Asian populations after the split of East Asian and non-East Asian populations.

Conclusion

We have newly identified EVC and GGA3 as susceptibility loci for T2DM in Japanese. Determination of genotypes for these SNPs at these loci may prove informative for assessment of the genetic risk for T2DM in Japanese.

Funding Acknowledgement

Type of funding source: None

P1542Identification of 13 novel susceptibility loci for early-onset myocardial infarction, hypertension, or chronic kidney disease in Japanese

Background

Early-onset cardiovascular and renal diseases have a strong genetic component.

Purpose

To identify genetic variants that confer susceptibility to early-onset myocardial infarction (MI), hypertension, or chronic kidney disease (CKD) in Japanese. We have performed exome-wide association studies (EWASs) in subjects with early-onset forms of these diseases.

Methods

A total of 8093 individuals aged ≤65 years was enrolled in the study. The EWASs for MI, hypertension, and CKD were conducted with 6926 subjects (1152 cases, 5774 controls), 8080 subjects (3444 cases, 4636 controls), and 2556 subjects (1051 cases, 1505 controls), respectively. Genotyping of single nucleotide polymorphisms (SNPs) was performed with Illumina Human Exome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of allele frequencies for 31,245, 31,276, or 31,514 SNPs that passed quality control to MI, hypertension, and CKD, respectively, was examined with Fisher's exact test. Bonferroni's correction for statistical significance of association was applied to compensate for multiple comparisons of genotypes with MI, hypertension, or CKD.

Results

The EWASs of allele frequencies revealed that 25, 11, and 11 SNPs were significantly associated with MI (P<1.60 × 10–6), hypertension (P<1.60 × 10–6), or CKD (P<1.59 × 10–6), respectively. Multivariable logistic regression analysis with adjustment for covariates showed that all 25, 11, and 11 SNPs were significantly related to MI (P<0.0005), hypertension (P<0.0011), or CKD (P<0.0011), respectively. After examination of results from previous genome-wide association studies and linkage disequilibrium of the identified SNPs, we newly identified 11 loci (TMOD4, COL6A3, ADGRL3-CXCL8-MARCH1, OR52E4, TCHP-GIT2, CCDC63, 12q24.1, OAS3, PLCB2-VPS33B, GOSR2, ZNF77), six loci (MOB3C-TMOD4, COL6A3, COL6A5, CXCL8-MARCH1, NFKBIL1-6p21.3-NCR3, PLCB2-VPS33B), and seven loci (MOB3C-TMOD4, COL6A3, COL6A5, ADGRL3-CXCL8-MARCH1, MUC17, PLCB2-VPS33B, ZNF77) that were significantly associated with MI, hypertension, or CKD, respectively. Furthermore, six genes (TMOD4, COL6A3, CXCL8, MARCH1, PLCB2, VPS33B) were significantly associated with MI, hypertension, and CKD; two genes (ADGRL3, ZNF77) with MI and CKD; and two genes (COL6A5, MOB3C) with hypertension and CKD. Network analysis showed that the 13, 10, or 11 genes associated with MI, hypertension, or CKD, respectively, in the present study had direct or indirect interactions with the corresponding sets of 50 genes previously shown to be associated with MI, hypertension, or CKD.

Conclusion

We newly identified 13 loci (MOB3C-TMOD4, COL6A3, ADGRL3-CXCL8-MARCH1, OR52E4, TCHP-GIT2, CCDC63, 12q24.1, OAS3, PLCB2-VPS33B, ZNF77, COL6A5, NFKBIL1-NCR3, MUC17) that confer susceptibility to early-onset MI, hypertension, or CKD. Determination of genotypes for the SNPs at these loci may prove informative for assessment of the genetic risk for MI, hypertension, or CKD in Japanese.

P3718Identification of nine genes as novel susceptibility loci for early-onset ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage

Background

Given that substantial genetic components have been shown in ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH), a heritability may be higher in early-onset than late-onset individuals with these conditions. Although genome-wide association studies have identified various genes and loci significantly associated with ischemic stroke, ICH, or intracranial aneurysm mainly in European ancestry populations, genetic variants that contribute to susceptibility to these disorders in Japanese individuals remain to be identified definitively.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to ischemic stroke, ICH, or SAH in Japanese. We have now performed exome-wide association studies (EWASs) in early-onset subjects with these conditions and corresponding controls.

Methods

A total of 6649 individuals aged ≤65 years were examined. For the EWAS of ischemic or hemorrhagic stroke, 6224 individuals (450 subjects with ischemic stroke, 5774 controls) or 6179 individuals (261 subjects with ICH, 176 subjects with SAH, 5742 controls), respectively, were examined. EWASs were performed with the use of Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip. To compensate for multiple comparisons of allele frequencies with ischemic stroke, ICH, or SAH, we applied a false discovery rate (FDR) of <0.05 for statistical significance of association.

Results

The relation of allele frequencies of 31,245 single nucleotide polymorphisms (SNPs) that passed quality control to ischemic stroke was examined with Fisher's exact test, and 31 SNPs were significantly (FDR <0.05) associated with ischemic stroke. The relation of allele frequencies of 31,253 or 30,970 SNPs to ICH or SAH, respectively, was examined with Fisher's exact test, and six or two SNPs were significantly (FDR <0.05) associated with ICH or SAH, respectively. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension and diabetes mellitus revealed that 12 SNPs were significantly [P <0.0004 (Bonferroni's correction, 0.05/124)] related to ischemic stroke. Similar analysis with adjustment for age, sex, and the prevalence of hypertension revealed that six or two SNPs were significantly [P <0.0016 (0.05/32)] related to ICH or SAH, respectively. After examination of linkage disequilibrium of identified SNPs and results of previous genome-wide association studies, we have newly identified HHIPL2, CTNNA3, LOC643770, UTP20, and TRIB3 as susceptibility loci for ischemic stroke, DNTTIP2 and FAM205A as susceptibility loci for ICH, and FAM160A1 and OR52E4 as such loci for SAH.

Conclusion

We have thus newly identified nine genes that confer susceptibility to early-onset ischemic stroke, ICH, or SAH. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for ischemic stroke, ICH, or SAH in Japanese.

P5724Identification of 12 novel loci that confer susceptibility to early-onset dyslipidemia in Japanese

Background

The circulating concentrations of triglycerides, high density lipoprotein (HDL)–cholesterol, and low density lipoprotein (LDL)–cholesterol have a substantial genetic component, and the heritability of early-onset dyslipidemia is expected to be higher than that of late-onset forms of this condition.

Purpose

To identify genetic variants that confer susceptibility to early-onset hypertriglyceridemia, hypo–HDL-cholesterolemia, and hyper–LDL-cholesterolemia in Japanese. We have now performed exome-wide association studies (EWASs) for early-onset forms of these conditions.

Methods

A total of 8073 individuals aged ≤65 years was enrolled in the study. The EWASs for hypertriglyceridemia (2664 cases, 5294 controls), hypo–HDL-cholesterolemia (974 cases, 7085 controls), and hyper–LDL-cholesterolemia (2911 cases, 5111 controls) were performed with Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip arrays. The relation of allele frequencies for 31,198, 31,133, or 31,175 single nucleotide polymorphisms (SNPs) that passed quality control to hypertriglyceridemia, hypo–HDL-cholesterolemia, or hyper–LDL-cholesterolemia, respectively, was examined with Fisher's exact test. To compensate for multiple comparisons of genotypes with each of the three conditions, we applied Bonferroni's correction for statistical significance of association.

Results

The EWASs of allele frequencies revealed that 25, 28, or 65 SNPs were significantly associated with hypertriglyceridemia (P<1.60 × 10–6), hypo–HDL-cholesterolemia (P<1.61 × 10–6), or hyper–LDL-cholesterolemia (P<1.60 × 10–6), respectively. Multivariable logistic regression analysis with adjustment for age and sex showed that all 25, 28, or 65 of these SNPs were significantly related to hypertriglyceridemia (P<0.0005), hypo–HDL-cholesterolemia (P<0.0004), or hyper–LDL-cholesterolemia (P<0.0002), respectively. After examination of the relation of the identified SNPs to serum concentrations of triglycerides, HDL-cholesterol, or LDL-cholesterol, linkage disequilibrium of the SNPs, and results of previous genome-wide association studies, we newly identified chromosomal region 19p12 as a susceptibility locus for hypertriglyceridemia, eight loci (MOB3C-TMOD4, LPGAT1, EHD3, COL6A3, ZNF860-CACNA1D, COL6A5, DCLRE1C, ZNF77) for hypo–HDL-cholesterolemia, and three loci (KIAA0319-FAM65B, UBD, LOC105375015) for hyper–LDL-cholesterolemia. Network analysis showed that the 10 or three genes associated with hypo-HDL-cholesterolemia or hyper-LDL-cholesterolemia, respectively, had direct or indirect interactions with the 50 genes previously shown to be associated with dyslipidemia.

Conclusion

We have thus identified 12 novel loci that confer susceptibility to early-onset dyslipidemia. Determination of genotypes for the SNPs at these loci may prove informative for assessment of the genetic risk for hypertriglyceridemia, hypo–HDL-cholesterolemia, or hyper–LDL-cholesterolemia in Japanese.

P4470Identification of four genes as novel susceptibility loci for early-onset type 2 diabetes mellitus, metabolic syndrome, or hyperuricemia in Japanese

Background

Given that early-onset type 2 diabetes mellitus (T2DM), metabolic syndrome, and hyperuricemia have been shown to have strong genetic components, statistical power of a genetic association study may be increased by focusing on early-onset subjects with these conditions. Although genome-wide association studies have identified various genes and loci significantly associated with T2DM, metabolic syndrome, and hyperuricemia, genetic variants that contribute to predisposition to these conditions in Japanese individuals remain to be identified definitively.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to early-onset T2DM, metabolic syndrome, or hyperuricemia in Japanese. We have now performed exome-wide association studies (EWASs) for early-onset subjects with T2DM, metabolic syndrome, or hyperuricemia and corresponding controls.

Methods

A total of 8102 individuals aged ≤65 years was enrolled in the study. The EWAS for T2DM was performed with 7407 subjects (1696 cases, 5711 controls), that for metabolic syndrome with 4215 subjects (2296 cases, 1919 controls), and that for hyperuricemia with 7919 subjects (1365 cases, 6554 controls). Single nucleotide polymorphisms (SNPs) were genotyped with Illumina Human Exome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of allele frequencies for 31,210, 31,521, or 31,142 SNPs that passed quality control to T2DM, metabolic syndrome, or hyperuricemia, respectively, was examined with Fisher's exact test. To compensate for multiple comparisons of genotypes with T2DM, metabolic syndrome, or hyperuricemia, we applied Bonferroni's correction for statistical significance of association.

Results

The EWAS of allele frequencies revealed that four, six, or nine SNPs were significantly associated with T2DM (P<1.60 × 10–6), metabolic syndrome (P<1.59 × 10–6), or hyperuricemia (P<1.61 × 10–6), respectively. Multivariable logistic regression analysis with adjustment for age and sex revealed that three, six, or nine SNPs were significantly related to T2DM (P<0.0031), metabolic syndrome (P<0.0021), or hyperuricemia (P<0.0014). After examination of the association of identified SNPs to T2DM-, metabolic syndrome-, or hyperuricemia-related traits, linkage disequilibrium of the SNPs, and results of previous genome-wide association studies, we have newly identified ZNF860 and OR4F6 as susceptibility loci for T2DM, OR52E4 and OR4F6 for metabolic syndrome, and HERPUD2 for hyperuricemia.

Conclusion

Given that OR4F6 was significantly associated with both T2DM and metabolic syndrome, we thus newly identified four genes (ZNF860, OR4F6, OR52E4, HERPUD2) that confer susceptibility to early-onset T2DM, metabolic syndrome, or hyperuricemia. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for T2DM, metabolic syndrome, or hyperuricemia in Japanese.

P708Identification of 26 novel loci that confer susceptibility to early-onset coronary artery disease in a Japanese population

Background

Early-onset coronary artery disease (CAD) has a strong genetic component. Although genome-wide association studies have identified various genes and loci significantly associated with CAD mainly in European ancestry populations, genetic variants that contribute to susceptibility to this condition in Japanese individuals remain to be identified definitively.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to early-onset CAD in Japanese. We have now performed exome-wide association studies (EWASs) in subjects with early-onset CAD and controls.

Methods

A total of 7256 individuals aged ≤65 years was enrolled in the study. The EWAS was conducted with 1482 subjects with CAD and 5774 controls. Genotyping of single nucleotide polymorphisms (SNPs) was performed with Illumina Human Exome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of allele frequencies for 31,465 SNPs that passed quality control to CAD was examined with Fisher's exact test. To compensate for multiple comparisons of allele frequencies with CAD, we applied a false discovery rate (FDR) of <0.05 for statistical significance of association.

Results

The relation of allele frequencies for 31,465 SNPs to CAD with the use of Fisher's exact test showed that 170 SNPs were significantly (FDR <0.05) associated with CAD. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension, diabetes mellitus, and dyslipidemia revealed that 162 SNPs were significantly (P<0.05) related to CAD. A stepwise forward selection procedure was performed to examine the effects of genotypes for the 162 SNPs on CAD. The 54 SNPs were significant (P<0.05) and independent [coefficient of determination (R2), 0.0008 to 0.0297] determinants of CAD. These SNPs together accounted for 15.5% of the cause of CAD. After examination of results from previous genome-wide association studies and linkage disequilibrium of the identified SNPs, we newly identified 21 genes (RNF2, YEATS2, USP45, ITGB8, TNS3, FAM170B-AS1, PRKG1, BTRC, MKI67, STIM1, OR52E4, KIAA1551, MON2, PLUT, LINC00354, TRPM1, ADAT1, KRT27, LIPE, GFY, EIF3L) and five chromosomal regions (2p13, 4q31.2, 5q12, 13q34, 20q13.2) that were significantly associated with CAD. Gene ontology analysis showed that various biological functions were predicted in the 18 genes identified in the present study. The network analysis revealed that the 18 genes had potential direct or indirect interactions with the 30 genes previously shown to be associated with CAD or with the 228 genes identified in previous genome-wide association studies of CAD.

Conclusion

We have newly identified 26 loci that confer susceptibility to CAD. Determination of genotypes for the SNPs at these loci may prove informative for assessment of the genetic risk for CAD in Japanese.

P14.113 The role of maintenance high-dose methotrexate chemotherapy in elderly primary CNS lymphoma patients with complete response to induction immunochemotherapy

BACKGROUND

The addition of high-dose methotrexate (HD-MTX)-based chemotherapy to whole brain irradiation (WBRT) has improved the prognosis of primary central nervous system lymphoma (PCNSL). However, the high neurotoxicity rates observed, especially in the elderly, raised interest in chemotherapy-only treatments. Withholding radiotherapy substantially decreases the risk of neurotoxicity, however, disease control may be compromised. Therefore, developing a novel treatment for the elderly PCNSL patients (ePCNSL) is crucial. In the elderly who cannot tolerate WBRT as a consolidation, maintenance treatment may serve as a feasible approach after an initial response. We treated ePCNSL with induction immunochemotherapy with rituximab (RIT) and HD-MTX, maintenance chemotherapy with HD-MTX and deferred WBRT. Here, we retrospectively investigated the prognosis for ePCNSL that became CR after the induction chemotherapy.

MATERIAL AND METHODS

Newly diagnosed ePCNSL (median age: 74 years) received biweekly RIT/ HD-MTX (375 mg/m2/dose; 3.5g/m2/dose) for 6 cycles (induction) followed by monthly RIT/MTX for 2 cycles (consolidation) and then were treated differently according to the radiological response. With CR patients, HD-MTX was continued with every 3 months (maintenance) for 2 years. Patients who did not obtain consent for maintenance therapy were followed up.

RESULTS

Of the 42 ePCNSL (median age 74 years), 26 had CR after induction and consolidation, of which 18 cases were carried out maintenance (M +) and 8 cases were followed up (M-). The median age was 74 and 76, respectively. Median progression-free survival (mPFS) was 73 months in the M+ group and 24.6 months in the M- group. Median overall survival (mOS) is 92.5 months versus 27.6 months, respectively. Both mPFS (P= 0.025) and mOS (P =0.0003) were significantly prolonged by maintenance therapy. In addition, ePCNSL with tumors involvement of deep brain structure had a poor prognosis.

CONCLUSION

It was suggested that maintenance treatment with HD-MTX may improve the prognosis for ePCNSL that reached complete response after induction therapy.

Combined chemotherapy and radiation therapy for central nervous system germ cell tumors: preliminary results of a Phase II study of the Japanese Pediatric Brain Tumor Study Group

The authors conducted a multiinstitutional phase II study to establish a postsurgical combined chemotherapy and radiation therapy regimen for patients with primary germ cell tumors of the brain. After surgical debulking of the tumor and histological verification, patients were divided into three therapeutic groups: good prognosis, intermediate prognosis, and poor prognosis. Patients received two kinds of chemotherapy (three courses) prior to receiving radiation therapy: carboplatin-etoposide combination ([CARB-VP]: carboplatin 450 mg/m(2) on Day 1, etoposide 150 mg/m(2) on Days 1-3) or ifosphamide-cisplatin-etoposide combination ([ICE]: ifosphamide 900 mg/m(2), cisplatin 20 mg/m(2), and etoposide 60 mg/m(2) on Days 1-5). Patients in the good prognosis group (those with germinomas) were treated with CARB-VP followed by local radiation therapy (24 Gy). Patients in the intermediate prognosis group received CARB-VP followed by local radiation therapy (50 Gy); they received five additional chemotherapy treatments. Patients in the poor prognosis group received ICE followed by whole craniospinal radiation therapy; they also received five additional chemotherapy treatments. Eighty-two patients were evaluated. For the 56 patients with germinomas, a 93% rate of complete remission after treatment was achieved. The remission rate was 76% for 21 patients in the intermediate prognosis group, and no recurrence was detected during a median follow-up period of 2.6 years. In the group of five patients with poor prognosis, the disease in three patients progressed during chemotherapy or radiation therapy and they died within 6 months. There were no serious complications in the surviving patients. The authors found their treatment protocols to be currently effective for patients with germinomas and those with an intermediate prognosis.

Critical factors regulating site-specific brain metastasis of murine melanomas

The intracarotid injection of B16 melanoma cells syngeneic to C57BL/6 mice and K-1735 melanoma cells syngeneic to C3H/HeN mice results in site-specific brain metastasis in C57BL/6 x C3H/HeN F1 mice. The K-1735 cells produce lesions only in the brain parenchyma, whereas the B16 cells produce lesions only in the meninges and ventricles. To determine the mechanisms that regulate this site-specific brain metastasis, we transfected the melanoma cells with DNA from plasmids pSV2neo or pSV2hvgro, which confer resistance to the drugs neomycin and hygromycin, respectively. Hybrids between the B16 and K-1735 cells were obtained by fusion. Cells of the K-1735 x K-1735 hybrid produced lesions only in the brain parenchyma of C57BL/6 x C3H/HeN F1 mice, whereas all B16 x K-1735 hybrids produced lesions only in the meninges and the ventricles. Initial cell arrest in the meninges or the brain parenchyma, production of collagenolytic activity, motility, and expression of CD44 did not predict or correlate with site-specific brain metastasis. The response of the different melanomas and hybrid cells to transforming growth factor-beta (TGF-beta) correlated with growth in the brain parenchyma. B16 cells and B16 x K-1735 hybrids bound more TGF-beta than K-1735 cells. The in vitro growth of B16 cells and all B16 x K-1735 hybrid cells was significantly inhibited by TGF-beta1 and TGF-beta2, whereas the growth of K-1735 cells and K-1735 x K-1735 hybrids was enhanced. Since TGF-beta is abundant in brain tissue, the results suggest that the ability of melanoma cells to proliferate in the brain parenchyma determines the production of site-specific brain metastasis.

Simultaneous radiolabel, genetic tagging and proliferation assays to study the organ distribution and fate of metastatic cells

We compared the suitability of 3 techniques to study tumor cell survival in the lungs of mice and proliferation into metastases. Genetic tagging of tumor cells with the bacterial beta-galactosidase marker gene lacZ, radiolabeling of tumor cells with [I-125]IdUrd, and S-phase labeling of cells with bromodeoxyuridine (BrdUrd) were used simultaneously to track the fate of highly metastatic K-1735 X-21 melanoma cells injected into syngeneic C3H/HeN mice. The melanoma cells were transfected with a plasmid containing lacZ and neomycin resistance genes. After growth in selective medium, the cells were incubated in medium containing [I-125]IdUrd and then injected i.v. into mice. Lungs isolated at various times after i.v. injection were processed for staining with X-gal, radioactive monitoring, and immunohistochemical staining with a monoclonal antibody against BrdUrd. At early time points, the presence of lacZ-positive cells directly correlated with radioactivity associated with viable cells. However, the expression of the beta-galactosidase was only stable for 1 week, and by 3 weeks after injection, large metastases contained only a few lacZ-positive cells. The combination of lacZ tagging with BrdUrd proliferation assay accurately identified dividing tumor cells in micrometastases. The simultaneous use of these 3 techniques allowed us to conclude that quantitative analysis of tumor cell survival is best accomplished by radioactive labeling of cells, whereas the use of lacZ-tagged cells allowed for studies of localization. Analysis of tumor cell proliferation requires the use of both lacZ tagging and immunohistochemistry using anti-BrdUrd antibodies. Since the process of metastasis consists of a series of distinct steps, each technique presents its own advantages and limitations.

Cleft Lip in Oculodentodigital Dysplasia Suggests Novel Roles for Connexin43

Oculodentodigital Dysplasia (ODDD) is a rare syndrome involving anomalies in eye, tooth, and digit formation, caused by mutations in CX43/ GJA1. In addition to classic dental features, ODDD includes oral and craniofacial accessory symptoms such as characteristic facial appearance and cleft palate. However, there have been no reports of ODDD accompanied by cleft lip. Herein we report, for the first time, a male, sporadic, Asian proband presenting bilateral cleft lip. By direct sequence analysis, our proband was diagnosed as having ODDD with a heterozygous mutation, codon 142 G>A in GJA1 and CX43E48K. We excluded the possibility of pathogenic mutations in B3GALTL, BMP4, TFAP2A, PVRL1, IRF6, and MSX1. To address how CX43/ GJA1 is related to cleft lip, we performed immunohistochemistry using mouse and human mid-facial tissue. CX43 expression was detected in the nasal compartment and nasal and maxillary processes at murine developmental stage E12.5. Furthermore, CX43 expression was found in the epithelial tissue inside the human subepithelial cleft lip that completes epithelial fusion. Therefore, we suggest that CX43/ GJA1 is involved in lip formation. Our case report of ODDD with a bilateral cleft lip suggests that CX43/ GJA1 might be a novel candidate gene for syndromic cleft lip.

Association of a polymorphism of BTN2A1 with type 2 diabetes mellitus in Japanese individuals

AIMS

We previously showed that the C→T polymorphism (rs6929846) of BTN2A1 was significantly associated with myocardial infarction in Japanese individuals by a genome-wide association study. Given that diabetes mellitus is an important risk factor for myocardial infarction, the association of rs6929846 of BTN2A1 with myocardial infarction might be attributable, at least in part, to its effect on susceptibility to diabetes. The purpose of this study was to examine the relation of rs6929846 of BTN2A1 to Type 2 diabetes mellitus.

METHODS

A total of 8650 Japanese individuals from two independent subject panels were examined: Panel A comprised 1141 individuals with Type 2 diabetes and 3161 control subjects and panel B comprised 1664 individuals with Type 2 diabetes and 2684 control subjects.

RESULTS

The chi-square test revealed that rs6929846 of BTN2A1 was significantly related to the prevalence of Type 2 diabetes in subject panel A (P = 0.0002) and subject panel B (P=0.006). Multivariable logistic regression analysis with adjustment for age, sex, body mass index and smoking status revealed that rs6929846 was significantly associated with Type 2 diabetes (P = 0.0006; odds ratio 1.25) in all individuals, with the T allele representing a risk factor for this condition. Multiple regression analysis with adjustment for age, sex and body mass index revealed that rs6929846 was significantly (P=0.04) related to blood glycosylated haemoglobin content in control subjects.

CONCLUSIONS

BTN2A1 may be a susceptibility gene for Type 2 diabetes in Japanese individuals.

Association of a polymorphism of BTN2A1 with hypertension in Japanese individuals

BACKGROUND

We previously showed that the C→T polymorphism (rs6929846) in butyrophilin, subfamily 2, member A1 gene (BTN2A1) was associated with myocardial infarction in Japanese individuals. Given that hypertension is a major risk factor for myocardial infarction, the association of rs6929846 of BTN2A1 with myocardial infarction might be attributable, at least in part, to its effect on susceptibility to hypertension. We have thus examined the relation of rs6929846 of BTN2A1 to hypertension in Japanese individuals.

METHODS

A total of 8,567 Japanese individuals from two independent subject panels were examined: Subject panels A and B comprised 2,317 hypertensive individuals and 1,933 controls, and 2,911 hypertensive individuals and 1,406 controls, respectively. The genotype of rs6929846 was determined by a method that combines the PCR and sequence-specific oligonucleotide probes with suspension array technology.

RESULTS

Multivariable logistic regression analysis with adjustment for covariates revealed that rs6929846 of BTN2A1 was significantly associated with hypertension in subject panel A (P = 2.6 × 10(-6); odds ratio, 1.69) and in subject panel B (P = 0.0284; odds ratio, 1.24), with the T allele representing a risk factor for hypertension. The rs6929846 was associated with systolic blood pressure (BP) in subject panels A (P = 0.0063) and B (P = 0.0115) and with diastolic BP in subject panel B (P = 0.0323), with the T allele being related to high BP.

CONCLUSIONS

BTN2A1 may be a susceptibility gene for hypertension in Japanese individuals. Determination of genotype for this polymorphism may prove informative for assessment of the genetic risk for hypertension.

Cerebral aneurysms in the perforating artery manifesting intracerebral and subarachnoid haemorrhage--report of two cases

BACKGROUND

An arteriosclerotic aneurysm in the perforating artery has been focused on as a causative factor for hypertensive intracerebral haemorrhage. However, its pathogenesis remains unknown, and its existence is still a controversy.

CASE DESCRIPTION

A 62-year-old female and a 70-year-old male with a history of hypertension suffered from intracerebral haemorrhage accompanied by subarachnoid haemorrhage. Cerebral angiograms demonstrated an aneurysm arising from the perforating artery at the central location of the haematoma in both cases. The aneurysms were confirmed as the cause of bleeding during microsurgery, and were resected. Histological examination of the surgical specimens revealed that the walls of the aneurysms lacked internal elastic lamina and consisted only of the adventitia.

CONCLUSION

These findings demonstrate that the aneurysm in the perforating artery can be a causative factor for hypertensive intracerebral haemorrhage, and indicate that the loss of internal elastic lamina induced by hypertension may contribute to the formation of the aneurysm of the perforating artery.

Dendritic cells activate antitumor immunity for malignant intracranial germ cell tumor: a case report

We report a 22-year-old male patient with a history of intracranial malignant germ cell tumor (GCT) who had undergone tumor resection twice, followed by radiation and chemotherapy. The tumor had rapidly recurred along the entire ventricular wall with extensive invasion into the brain parenchyma. The serum level of human beta-chorionic gonadotropin (beta-hCG) was 232.3 ng/ml on admission. Although tissue samples of the recurrent tumor could not be obtained, the previous histological diagnosis of germinoma and elevated serum beta-hCG levels suggested recurrence of malignant GCT. The patient declined chemotherapy but accepted dendritic cell (DC)-based immunotherapy. DC inoculation five times resulted in rapid tumor shrinkage and a significant decrease in the serum level of beta-hCG. Here we discuss the effectiveness of immunotherapy using DCs for recurrent intracranial malignant GCTs.

Recurrence of Infantile Supratentorial Ependymoma after 23-Year Remission following Surgical Removal and Radiation Therapy

We report on a patient with ependymoma who had a recurrence after long-term remission. The patient developed frontoparietal ependymoma at the age of one year and ten months. The tumor was radically removed and postoperative radiation therapy was performed. A calcified area adjacent to the area of surgical removal remained unchanged until the patient was 18 years old. The patient was healthy except for mild hemiparesis until an MRI scan performed when he was 25 years old showed regrowth of the tumor. The patient underwent surgery with additional radiation therapy and was discharged. The 23-year interval until tumor recurrence in this case is far beyond the so-called risk period of “Collins’ law”. Immunohistochemical study with MIB-1 and anti-p53 antibody showed a high proliferative potential of the primary and recurrent tumors and possible p53 mutation in the primary tumor. This is the first report to describe the detailed clinical course and histological features of a recurrent infantile ependymoma that progressed after Collins’ risk period. It seems that follow-up of ependymoma patients after initial treatment should be performed regularly for a longer period in cases showing radiological evidence of a residual lesion.

Analysis of the p300/CBP-Associated Factor (PCAF) gene in astrocytic tumors

The PCAF gene encodes the p300/CBP-Associated Factor (PCAF), a histone acetyltransferase, which regulates p53 by acetylation of Lys320 in the C-terminal portion of p53. While the p53 gene is one of the most frequently mutated tumor suppressor genes in human tumors, such mutations occur in only 30% of astrocytic tumors. Since PCAF can regulate p53 activity, abrogation of PCAF function by PCAF gene mutation could be an alternate mechanism to inactivate the p53 pathway in tumors lacking p53 mutations. To test this hypothesis, we determined the nucleotide sequence of the entire PCAF coding region in 37 astrocytic tumors (17 glioblastomas, 10 anaplastic astrocytomas, 7 low-grade astrocytomas, and 3 pilocytic astrocytomas). We detected two single-nucleotide alterations that represented non-deleterious polymorphisms (GAG > GAA Glu103Glu, AAT > AGT Asn386Ser) but no obvious functional mutations. Moreover, the frequency of the Asn386Ser allele that contained Ser386 in glioma patients was not statistically different from its frequency in individuals without disease, and no significant association was observed between the PCAF polymorphisms and the presence or absence of p53 mutations in the tumors. We conclude that the PCAF gene is not mutated during the development of the astrocytic tumors studied here.

Combined transhorizontal-supracerebellar approach for microvascular decompression of trigeminal neuralgia

A combined approach for microvascular decompression of trigeminal neuralgia is reported. Arachnoid dissection of the cerebellar horizontal fissure (transhorizontal approach) allowed easy identification of the root exit zone of the trigeminal nerve. The superior semilunar lobule was pulled back rostrally so that retraction of the acoustic nerve was minimal. After identification of the offending vessels, the supracerebellar artery was mobilized and dissected out through the supracerebellar route, which was also less invasive to the acoustic nerve than the standard approach. By combining these two approaches, the whole surface of the trigeminal nerve can be observed easily. Thus, the offending vessels can be readily identified, mobilized and moved away from the trigeminal nerve with minimal retraction of the acoustic nerve.

Langerhans cell histiocytosis limited to the pituitary-hypothalamic axis--two case reports

Langerhans cell histiocytosis rarely presents as a solitary lesion in the pituitary-hypothalamic region, and is indistinguishable from germinoma, which occurs much more frequently, especially in Japanese. A 14-year-old girl and a 9-year-old girl presented with polydipsia and polyuria as the initial symptoms. Magnetic resonance (MR) imaging demonstrated a round mass at the pituitary stalk appearing as isointense on T1-weighted imaging and hyperintense on T2-weighted imaging. Endocrinological examination revealed mild hypopituitarism with central diabetes insipidus. Both patients underwent open craniotomy. Histological examination revealed granulomatous tissue with eosinophil infiltration and frequent Langerhans histiocyte clustering, compatible with the diagnosis of Langerhans cell histiocytosis. Low-dose local irradiation of 20 Gy was administered. First patient was followed up for 8 years, and her hypopituitarism gradually improved to a minimal level with only amenorrhea as the residual symptom. Recent MR imaging showed no residual mass at the region. Second patient was followed up for 15 months, and her diabetes insipidus is stable. MR imaging performed 5 months after the treatment showed marked reduction of the mass. These cases reemphasize the importance of histological diagnosis for lesions with similar neuroimaging appearances. Biopsy and low-dose irradiation are an effective treatment for this rare and essentially benign lesion, as opposed to attempting total removal of the mass.

HRG4 (UNC119) mutation found in cone-rod dystrophy causes retinal degeneration in a transgenic model

PURPOSE

To investigate the function and pathogenicity of HRG4, a photoreceptor synaptic protein homologous to the Caenorhabditis elegans neuroprotein UNC119.

METHODS

HRG4 was screened for mutations in patients with various retinopathies, and a transgenic mouse model was constructed and analyzed based on a mutation found.

RESULTS

A heterozygous premature termination codon mutation was found in a 57-year-old woman with late-onset cone-rod dystrophy. In some transgenic mice carrying the identical mutation, age-dependent fundus lesions developed accompanied by electroretinographic changes consistent with defects in photoreceptor synaptic transmission (depressed b-wave, normal c-wave), and retinal degeneration occurred with marked synaptic and possible transsynaptic degeneration.

CONCLUSIONS

HRG4, the only synaptic protein known to be highly enriched in photoreceptor ribbon synapses, is now shown to be pathogenic when mutated.

Systemic hyalinosis of delayed onset

We report a 46-year-old Japanese male with systemic hyalinosis. The condition had not been present during youth but was clearly evident in the patient's forties. The present case is remarkable because of a delayed onset.

Radiation-induced aneurysm and moyamoya vessels presenting with subarachnoid haemorrhage

A rare case of a ruptured internal carotid artery (ICA) aneurysm, with ICA stenosis and moyamoya vessels, was diagnosed in a young female patient after radiotherapy for optic glioma. Retrospective analysis revealed that an extraordinarily high dose of radiation (110 Gy) had been delivered to the area around the ICA in two therapeutic sessions. Clipping and wrapping of the aneurysm were performed and the patient made a good recovery. A review of the literature suggested that rupture of radiation-induced aneurysms is a rare event, but may be fatal. Considerable care must therefore be taken when delivering high-dose radiation to cerebral arteries. We suggest that the incidence of radiation-induced moyamoya vessels is higher in younger patients.