Monitoring microseismicity of the Hengill Geothermal Field in Iceland

Induced seismicity is one of the main factors that reduces societal acceptance of deep geothermal energy exploitation activities, and felt earthquakes are the main reason for closure of geothermal projects. Implementing innovative tools for real-time monitoring and forecasting of induced seismicity was one of the aims of the recently completed COSEISMIQ project. Within this project, a temporary seismic network was deployed in the Hengill geothermal region in Iceland, the location of the nation’s two largest geothermal power plants. In this paper, we release raw continuous seismic waveforms and seismicity catalogues collected and prepared during this project. This dataset is particularly valuable since a very dense network was deployed in a seismically active region where thousand of earthquakes occur every year. For this reason, the collected dataset can be used across a broad range of research topics in seismology ranging from the development and testing of new data analysis methods to induced seismicity and seismotectonics studies.

Measurement(s)	Seismic waveforms (seismograms) • Seismicity (Origin time, location and magnitude of earthquakes)
Technology Type(s)	Seismic stations (velocity sensors) • SeisComP data acquisition and processing system

Bleeding Disorders in Women and Girls: State of the Science and CDC Collaborative Programs

Women and girls with bleeding disorders experience abnormal and excessive bleeding that can negatively impact their overall health and quality of life. In this report, we provide an overview of the biology, types, clinical care, and state of the science related to bleeding disorders in girls and women and describe Centers for Disease Control and Prevention (CDC) activities related to (1) surveillance of bleeding disorders in women; (2) scientific review, research, and collaboration to inform health care gaps in identifying and caring for women with bleeding disorders; and (3) development of health promotion and education programs to bring awareness about bleeding disorders to both women and girls in the population at large and various health care providers who care for women. Findings generated from surveillance and research activities inform the development of new public health programs aimed at improving diagnostic and health care services and empowering women with bleeding disorders with the knowledge they need to navigate a complex health care system with the need for specialty care services. Additional work is needed to improve provider awareness and understanding of the unique needs of women and girls with bleeding disorders to achieve appropriate care and treatment and ensure optimal outcomes and quality of life.

Dynamic earthquake triggering response tracks evolving unrest at Sierra Negra volcano, Galápagos Islands

The propensity for dynamic earthquake triggering is thought to depend on the local stress state and amplitude of the stress perturbation. However, the nature of this dependency has not been confirmed within a single crustal volume. Here, we show that at Sierra Negra volcano, Galápagos Islands, the intensity of dynamically triggered earthquakes increased as inflation of a magma reservoir elevated the stress state. The perturbation of short-term seismicity within teleseismic surface waves also increased with peak dynamic strain. Following rapid coeruptive subsidence and reduction in stress and background seismicity rates, equivalent dynamic strains no longer triggered detectable seismicity. These findings offer direct constraints on the primary controls on dynamic triggering and suggest that the response to dynamic stresses may help constrain the evolution of volcanic unrest.

Women and girls with haemophilia receiving care at specialized haemophilia treatment centres in the United States

INTRODUCTION

Females may have haemophilia with the same factor VIII (FVIII) or factor IX (FIX) levels as affected males. Characterization of females with haemophilia would be useful for health care planning to meet their unique needs. Federally-funded haemophilia treatment centres (HTCs) in the United States contribute data on all individuals with bleeding disorders receiving care to the Population Profile (HTC PP) component of the Community Counts Public Health Surveillance of Bleeding Disorders project.

AIMS

To estimate the number of females with haemophilia receiving care at HTCs in the United States and compare their characteristics with those of males with haemophilia.

METHODS

HTC PP data collected on people receiving care at an HTC from January 2012 through September 2020 with haemophilia A and B were evaluated by sex for demographic and clinical characteristics.

RESULTS

A factor level < 40% was reported for 23,196 males (97.8%) and 1667 females (47.6%) attending HTCs; 51 (.48%) severe, 79 (1.4%) moderate, and 1537 (17.9%) mild haemophilia patients were female. Females were older, more often White, and less often non-Hispanic than males. Females were less likely to have history of HIV or HCV infection, even among those with severe disease, but twice as likely to have infection status unknown. Females with mild haemophilia were more often uninsured than males.

CONCLUSIONS

Females with severe or moderate haemophilia are uncommon, even in specialized care centres; however, almost one in five patients with mild haemophilia was female, indicating needs for specialized care based on factor level and history for affected females.

How deep ocean-land coupling controls the generation of secondary microseism Love waves

Wind driven ocean wave-wave interactions produce continuous Earth vibrations at the seafloor called secondary microseisms. While the origin of associated Rayleigh waves is well understood, there is currently no quantified explanation for the existence of Love waves in the most energetic region of the microseism spectrum (3-10 s). Here, using terrestrial seismic arrays and 3D synthetic acoustic-elastic simulations combined with ocean wave hindcast data, we demonstrate that, observed from land, our general understanding of Rayleigh and Love wave microseism sources is significantly impacted by 3D propagation path effects. We show that while Rayleigh to Love wave conversions occur along the microseism path, Love waves predominantly originate from steep subsurface geological interfaces and bathymetry, directly below the ocean source that couples to the solid Earth. We conclude that, in contrast to Rayleigh waves, microseism Love waves observed on land do not directly relate to the ocean wave climate but are significantly modulated by continental margin morphologies, with a first order effect from sedimentary basins. Hence, they yield rich spatio-temporal information about ocean-land coupling in deep water.

Genetic causes of haemophilia in women and girls

Women and girls reported as "haemophilic females" may have complex genetic causes for their haemophilia phenotype. In addition, women and girls may have excessive bleeding requiring treatment simply because they are heterozygous for haemophilia alleles. While severe and moderate haemophilia are rare in females, 16% of patients with mild haemophilia A and almost one-quarter of those with mild haemophilia B seen in U.S. haemophilia treatment centres are women and girls. A phenotypic female with a low level of factor VIII or factor IX may be classified into one of the following categories of causality: homozygosity (two identical haemophilia alleles), compound heterozygosity (two different haemophilia alleles), hemizygosity (one haemophilia allele and no normal allele), heterozygosity (one haemophilia allele and one normal allele), genetic causes other than haemophilia and non-genetic causes. Studies required for classification may include coagulation parameters, F8 or F9 sequencing, F8 inversion testing, multiplex ligation-dependent probe amplification, karyotyping and X chromosome inactivation studies performed on the patient and parents. Women and girls who are homozygous, compound heterozygous or hemizygous clearly have haemophilia, as they do not have a normal allele. Heterozygous women and girls with factor levels below the haemostatic range also meet the definitions used for haemophilia treatment.

Trends in Sickle Cell Disease-Related Mortality in the United States, 1979 to 2017

STUDY OBJECTIVE

We provide an updated assessment of trends in sickle cell disease (SCD)-related mortality, a significant source of mortality in the United States among black persons, using 1979 to 2017 US mortality data.

METHODS

SCD-related deaths were identified with International Classification of Diseases codes. Because SCD-related death is rare in other races, the analysis focused on black decedents. Age-specific and average annual SCD-related death rates were calculated. Causes of death codes were categorized into 20 groups relevant to SCD outcomes. SCD-related deaths were compared with non-SCD-related deaths after matching on race, sex, age group, and year of death.

RESULTS

There were 25,665 SCD-related deaths reported among blacks in the United States from 1979 through 2017. During that period, the annual SCD-related death rate declined in children and increased in adults, and the median age at death increased from 28 to 43 years. Acute causes of death, such as infection and cerebrovascular complications, were more common in younger age groups. Chronic complications were more common in adults. SCD-related deaths were more likely to be related to acute cardiac, pulmonary, and cerebrovascular complications; acute infections; and chronic cardiac and pulmonary complications and renal disorders; and less likely to be related to drug overdose and chronic infections than non-SCD-related deaths.

CONCLUSION

These data indicate SCD-related deaths are now more likely to be related to chronic complications of the disease than to acute complications. More research regarding prevention and treatment of chronic complications of SCD is necessary because persons with SCD are living longer.

Evaluation of CDC's Hemophilia Surveillance Program - Universal Data Collection (1998-2011) and Community Counts (2011-2019), United States

Problem/Condition

Hemophilia is an X-linked genetic disorder that primarily affects males and results in deficiencies in blood-clotting proteins. Hemophilia A is a deficiency in factor VIII, and hemophilia B is a deficiency in factor IX. Approximately one in 5,000 males are born with hemophilia, and hemophilia A is about four times as common as hemophilia B. Both disorders are characterized by spontaneous internal bleeding and excessive bleeding after injuries or surgery. Hemophilia can lead to repeated bleeding into the joints and associated chronic joint disease, neurologic damage, damage to other organ systems, and death. Although no precise national U.S. prevalence estimates for hemophilia exist because of the difficulty identifying cases among persons who receive care from various types of health care providers, two previous state-based studies estimated hemophilia prevalence at 13.4 and 19.4 per 100,000 males. In addition, these studies showed that 67% and 82% of persons with hemophilia received care in a federally funded hemophilia treatment center (HTC), and 86% and 94% of those with the most severe cases of hemophilia (i.e., those with the lowest levels of clotting factor activity in the circulating blood) received care in a federally funded HTC. As of January 2020, the United States had 144 HTCs.

Period Covered

1998–2019.

Description of the System

Surveillance for hemophilia, which is a complex, chronic condition, is challenging because of its low prevalence, the difficulty in ascertaining cases uniformly, and the challenges in routinely characterizing and tracking associated health complications. Over time, two systems involving many stakeholders have been used to conduct ongoing hemophilia surveillance. During 1998–2011, CDC and the HTCs collaborated to establish the Universal Data Collection (UDC) surveillance system. The purposes of the UDC surveillance system were to monitor human immunodeficiency virus (HIV) and bloodborne viral hepatitis in persons with hemophilia, thereby tracking blood safety, and to track the prevalence of and trends in complications associated with hemophilia. HTC staff collected clinical data and blood specimens from UDC participants and submitted them to CDC. CDC tested specimens for viral hepatitis and HIV. In 2011, the UDC surveillance system was replaced by a new hemophilia surveillance system called Community Counts. CDC and the HTCs established Community Counts to expand laboratory testing and the collection of clinical data to better identify and track emerging health issues in persons with hemophilia.

Results

This report is the first comprehensive summary of CDC’s hemophilia surveillance program, which comprises both UDC and Community Counts. Data generated from these surveillance systems have been used in the development of public health and clinical guidelines and practices to improve the safety of U.S. blood products and either prevent hemophilia-related complications or identify complications early. Several factors have played a role in the effectiveness of the UDC and Community Counts systems, including 1) a stable data collection design that was developed and is continually reviewed in close partnership with HTC regional leaders and providers to ensure surveillance activities are focused on maximizing the scientific and clinical impact; 2) flexibility to respond to emerging health priorities through periodic updates to data collection elements and special studies; 3) high data quality for many clinical indicators and state-of-the-art laboratory testing methods for hemophilia treatment product inhibitors (developed and refined in part based on CDC research); 4) timely data and specimen collection and submission, laboratory specimen testing, analysis, and reporting; and 5) the largest and most representative sample of persons with hemophilia in the United States and one of the largest and most comprehensive data collection systems on hemophilia worldwide.

Interpretation

CDC has successfully developed, implemented, and maintained a surveillance system for hemophilia. The program can serve as an example of how to conduct surveillance for a complex chronic disease by involving stakeholders, improving and building new infrastructure, expanding data collection (e.g., new diagnostic assays), providing testing guidance, establishing a registry with specimen collection, and integrating laboratory findings in clinical practice for the individual patient.

Public Health Action

Hemophilia is associated with substantial lifelong morbidity, excess premature deaths, and extensive health care needs throughout life. Through monitoring data from Community Counts, CDC will continue to characterize the benefits and adverse events associated with existing or new hemophilia treatment products, thereby contributing to maximizing the health and longevity of persons with hemophilia.

Seismic ground vibrations give advanced early-warning of subglacial floods

Glacier runoff and melt from volcanic and geothermal activity accumulates in glacier dammed lakes in glaciated areas around the world. These lakes eventually drain, creating hazardous subglacial floods that are usually only confirmed after they exit the glacier and reach local river systems, which can be many tens of kilometres from the flood source. Once in the river systems, they travel rapidly to populated areas. Such delayed detection represents a potentially lethal shortcoming in early-warning. Here we demonstrate how to advance early-warning potential through the analysis of four such floods in a glaciated region of Iceland. By comparing exceptional multidisciplinary hydrological, GPS and seismic ground vibration (tremor) data, we show that array analysis of seismic tremor can be used for early location and tracking of the subglacial flood front. Furthermore the timing and size of the impending flood can be estimated, prior to it entering the river system. Advanced warnings of between 20 to 34 hours are achieved for large (peak discharge of more than 3000 m³/s, accumulation time of ~ 5.25 years) to small floods (peak discharges from 210 to 380 m³/s, accumulation times of ~ 1.3 years) respectively.

Parvovirus B19 infection in sickle cell disease: An analysis from the Centers for Disease Control haemoglobinopathy blood surveillance project

OBJECTIVE

In the multicentre Haemoglobinopathy Blood Surveillance Project, to evaluate the seroprevalence of parvovirus B19 and DNA viral load in sickle cell disease (SCD).

BACKGROUND

Although the epidemiology of parvovirus B19 seropositivity in SCD has been well documented, there are few studies that have assessed possible persistent parvovirus DNAemia and associated risk factors including blood transfusion.

METHODS

A qualitative analysis of parvovirus B19 serology using ELISA and quantitative parvovirus B19 DNA by RT-PCR was performed in patients with SCD.

RESULTS

Of 322 patients, 113 (35%) were parvovirus IgG positive and 119 (37%) were IgM positive at enrolment. The prevalence of IgG positivity increased with age. 71/322 (22%) were parvovirus DNA positive at enrolment with a mean viral load of 15 227 ± 55 227 SD. (range 72-329 238 IU/mL). Patients who were positive for parvovirus B19 DNA received a significantly higher red blood cell transfusion volume in the prior year compared to patients who were negative (mean RBC volume = 8310 mL vs 5435 mL, respectively; P = .0073). Seventy-seven patients had follow-up testing approximately 1 year after enrolment and 11/28 (39%) patients had persistently positive IgM.

CONCLUSION

Further studies are needed to better understand the natural history of parvovirus B19 infection in SCD especially in relation to RBC transfusion as a risk factor, as well as disease outcome and severity.

Exome sequencing of family trios from the National Birth Defects Prevention Study: Tapping into a rich resource of genetic and environmental data

BACKGROUND

The National Birth Defects Prevention Study (NBDPS) is a multisite, population-based, case-control study of genetic and nongenetic risk factors for major structural birth defects. Eligible women had a pregnancy affected by a birth defect or a liveborn child without a birth defect between 1997 and 2011. They were invited to complete a telephone interview to collect pregnancy exposure data and were mailed buccal cell collection kits to collect specimens from themselves, their child (if living), and their child's father. Over 23,000 families representing more than 30 major structural birth defects provided DNA specimens.

METHODS

To evaluate their utility for exome sequencing (ES), specimens from 20 children with colonic atresia were studied. Evaluations were conducted on specimens collected using cytobrushes stored and transported in open versus closed packaging, on native genomic DNA (gDNA) versus whole genome amplified (WGA) products and on a library preparation protocol adapted to low amounts of DNA.

RESULTS

The DNA extracted from brushes in open packaging yielded higher quality sequence data than DNA from brushes in closed packaging. Quality metrics of sequenced gDNA were consistently higher than metrics from corresponding WGA products and were consistently high when using a low input protocol.

CONCLUSIONS

This proof-of-principle study established conditions under which ES can be applied to NBDPS specimens. Successful sequencing of exomes from well-characterized NBDPS families indicated that this unique collection can be used to investigate the roles of genetic variation and gene-environment interaction effects in birth defect etiologies, providing a valuable resource for birth defect researchers.

VKORC1-1639A allele influences warfarin maintenance dosage among Blacks receiving warfarin anticoagulation: a retrospective cohort study

AIM

The study objectives were to investigate the association between selected CYP2C9 and VKORC1 single nucleotide polymorphisms with serious bleeding or thrombotic risk, and to estimate mean daily maintenance dose of warfarin and international normalized ratio measurements among Blacks receiving warfarin anticoagulation.

METHODS

We conducted a retrospective cohort study among 230 Black adults receiving warfarin for a minimum of three consecutive months with a confirmed date of first dosage.

RESULTS

A lower mean daily maintenance dosage of warfarin was required to maintain an international normalized ratio measurement within the therapeutic range among Blacks with the VKORC1-1639G>A variant alleles ([G/A vs G/G, p = 0.02], [A/A vs G/A, p = 0.008] and [A/A vs G/G, p = 0.001]).

CONCLUSION

Data indicated that VKORC1-1639A variant allele influenced warfarin daily maintenance dosage among our small, likely admixed Black patient population.

Micrometre-scale deformation observations reveal fundamental controls on geological rifting

Many of the world’s largest volcanic eruptions are associated with geological rifting where major fractures open at the Earth’s surface, yet fundamental controls on the near-surface response to the rifting process are lacking. New high resolution observations gleaned from seismometer data during the 2014 Bárðarbunga basaltic dyke intrusion in Iceland allow us unprecedented access to the associated graben formation process on both sub-second and micrometre scales. We find that what appears as quasi steady-state near-surface rifting on lower resolution GPS observation comprises discrete staccato-like deformation steps as the upper crust unzips through repetitive low magnitude (M_W < 0) failures on fracture patches estimated between 300 m² and 1200 m² in size. Stress drops for these events are one to two orders of magnitude smaller than expected for tectonic earthquakes, demonstrating that the uppermost crust in the rift zone is exceptionally weak.

Evaluation of von Willebrand factor phenotypes and genotypes in Hemophilia A patients with and without identified F8 mutations

BACKGROUND

Hemophilia A (HA) is an X-linked bleeding disorder caused by a deficiency in factor VIII (FVIII). von Willebrand disease (VWD) is characterized by a quantitative or qualitative defect in von Willebrand factor (VWF). Patients with VWD with severely low VWF or VWD Type 2N (VWD2N), a VWD subtype distinguished by defective VWF binding to FVIII, may have reduced FVIII levels secondary to their VWD. These patients superficially resemble patients with HA and pose a potential for misdiagnosis.

OBJECTIVES

To investigate the unexplained cause of bleeding in HA patients without known FVIII mutations by assessing plasma VWF antigen (VWF:Ag), FVIII binding capacities and VWF genotypes.

PATIENTS/METHODS

Thirty-seven of 1027 patients with HA studied as part of the Hemophilia Inhibitor Research Study lacked identifiable F8 mutations. These patients (cases) and 73 patients with identified F8 mutations (controls) were evaluated for VWF:Ag, a patient's VWF capacity to bind FVIII (VWF:FVIIIB) and VWF sequence.

RESULTS

Four cases had VWF:Ag < 3 IU dL(-1) and VWF mutations consistent with Type 3 VWD. Six cases and one control were heterozygous for mutations previously reported to cause Type 1 VWD (VWD1) (n = five cases and one control) or predicted to be deleterious by Polyphen2 and SIFT prediction tools (n = 1 case). One control had VWF:Ag < 30 IU dL(-1) and seven patients (four cases and three controls), including two cases who were heterozygous for a known VWD2N mutation, had reduced VWF:FVIIIB.

CONCLUSIONS

These data emphasize that some patients diagnosed with HA require VWF assessments in order to achieve a comprehensive diagnosis and an optimal treatment strategy.

Discordance between self-report and genetic confirmation of sickle cell disease status in African-American adults

BACKGROUND

Sickle cell disease (SCD) is an autosomal recessive genetic disorder, with persons heterozygous for the mutation said to have the sickle cell trait (SCT). Serious adverse effects are mainly limited to those with SCD, but the distinction between disease and trait is not always clear to the general population. We sought to determine the accuracy of self-reported SCD when compared to genetic confirmation.

METHODS

From stratified random samples of Southern Community Cohort Study participants, we sequenced the β- globin gene in 51 individuals reporting SCD and 75 individuals reporting no SCD.

RESULTS

The median age of the group selected was 53 years (range 40-69) with 29% male. Only 5.9% of the 51 individuals reporting SCD were confirmed by sequencing, with the remaining 62.7% having SCT, 5.9% having hemoglobin C trait, and 25.5% having neither SCD nor trait. Sequencing results of the 75 individuals reporting no SCD by contrast were 100% concordant with self-report.

CONCLUSIONS

Misreporting of SCD is common in an older adult population, with most persons reporting SCD in this study being carriers of the trait and a sizeable minority completely unaffected. The results from this pilot survey support the need for increased efforts to raise community awareness and knowledge of SCD.

Prothrombin G20210A mutation is associated with young-onset stroke: the genetics of early-onset stroke study and meta-analysis

BACKGROUND AND PURPOSE

Although the prothrombin G20210A mutation has been implicated as a risk factor for venous thrombosis, its role in arterial ischemic stroke is unclear, particularly among young adults. To address this issue, we examined the association between prothrombin G20210A and ischemic stroke in a white case-control population and additionally performed a meta-analysis.

METHODS

From the population-based Genetics of Early Onset Stroke (GEOS) study, we identified 397 individuals of European ancestry aged 15 to 49 years with first-ever ischemic stroke and 426 matched controls. Logistic regression was used to calculate odds ratios (ORs) in the entire population and for subgroups stratified by sex, age, oral contraceptive use, migraine, and smoking status. A meta-analysis of 17 case-control studies (n=2305 cases <55 years) was also performed with and without GEOS data.

RESULTS

Within GEOS, the association of the prothrombin G20210A mutation with ischemic stroke did not achieve statistical significance (OR=2.5; 95% confidence interval [CI]=0.9-6.5; P=0.07). However, among adults aged 15 to 42 years (younger than median age), cases were significantly more likely than controls to have the mutation (OR=5.9; 95% CI=1.2-28.1; P=0.03), whereas adults aged 42 to 49 years were not (OR=1.4; 95% CI=0.4-5.1; P=0.94). In our meta-analysis, the mutation was associated with significantly increased stroke risk in adults ≤55 years (OR=1.4; 95% CI=1.1-1.9; P=0.02), with significance increasing with addition of the GEOS results (OR=1.5; 95% CI=1.1-2.0; P=0.005).

CONCLUSIONS

The prothrombin G20210A mutation is associated with ischemic stroke in young adults and may have an even stronger association among those with earlier onset strokes. Our finding of a stronger association in the younger young adult population requires replication.

Abstract T P289: Genetic Variation in the Sulfonylurea Receptor 1 (Sur1)-regulated NCCa-ATP Channel and Stroke Outcome: The Genetics of Early Onset Stroke Study

Background and Purpose: Recent evidence indicates that the sulfonylurea receptor 1 (Sur1)-regulated NCCa-ATP channel is transcriptionally upregulated de novo in cells of the neurovascular unit in response to cerebral ischemia and plays a key role in the development of cerebral edema. We hypothesized that polymorphisms in the genes coding for the proteins associated with this channel may play a role in outcome following ischemic stroke.

Methods: From a biracial population-based study we identified 856 cases of first-ever ischemic stroke in women and men ages 15 to 49 years. 44 SNPs were genotyped in ABCC8, 16 SNPs in TRMP4, and 6 SNPs in SP1. Cases with diabetes were excluded since glyburide is known to block the Sur-1 NCCa-ATP channel. Lacunar strokes were excluded since edema is not hypothesized to contribute to outcome in this stroke subtype. Following exclusions the final population included 235 African-American and 342 Caucasian cases. Utilizing the modified Rankin Score at hospital discharge (0 to 3 and 4/5 combined), ethnicity-stratified regression analyses were performed against genotype in an additive model, controlling for age and gender.

Results: Among Caucasians there were 6 significantly associated TRMP4 SNPs (all with MAF~0.32; p=0.02-0.05) that were in strong linkage disequilibrium (D’>0.80). Among African-Americans there were 3 significantly associated TRMP4 SNPs (p=0.02-0.04). Notably, 2 of these 3 SNPs were also among those identified the Caucasians, rs909010 and rs1175791 (both AA SNPs with MAF~0.45). In ABCC8 there was 1 significant SNP (rs2299640; MAF=0.30; p=0.01) among African-Americans and none among Caucasians. SP1 analyses demonstrated no associated SNPs in either ethnicity.

Conclusions: Genetic variation in TRMP4 may play a role in outcome following ischemic stroke. Confirmatory studies are needed.

Association between baseline fetal hemoglobin levels and incidence of severe vaso-occlusive pain episodes in children with sickle cell anemia

The ameliorating effect of high fetal hemoglobin (HbF) levels on the incidence of pain episodes in sickle cell anemia (SCA) is well-known; however, in children this relationship is less clearly established. We hypothesized that higher HbF levels in children with SCA are associated with fewer severe pain episodes. A meta-analysis of data from the Silent Infarct Transfusion Trial (n = 456) and the Cooperative Study of Sickle Cell Disease (n = 764), demonstrated that baseline HbF levels were associated with the incidence of severe pain, commonly defined across studies as an event requiring hospitalization (P-value = 0.02).

Genome-wide meta-analysis of systolic blood pressure in children with sickle cell disease

In pediatric sickle cell disease (SCD) patients, it has been reported that higher systolic blood pressure (SBP) is associated with increased risk of a silent cerebral infarction (SCI). SCI is a major cause of neurologic morbidity in children with SCD, and blood pressure is a potential modulator of clinical manifestations of SCD; however, the risk factors underlying these complications are not well characterized. The aim of this study was to identify genetic variants that influence SBP in an African American population in the setting of SCD, and explore the use of SBP as an endo-phenotype for SCI. We conducted a genome-wide meta-analysis for SBP using two SCD cohorts, as well as a candidate screen based on published SBP loci. A total of 1,617 patients were analyzed, and while no SNP reached genome-wide significance (P-value<5.0 x 10(-8)), a number of suggestive candidate loci were identified. The most significant SNP, rs7952106 (P-value=8.57 x 10(-7)), was in the DRD2 locus on chromosome 11. In a gene-based association analysis, MIR4301 (micro-RNA4301), which resides in an intron of DRD2, was the most significant gene (P-value=5.2 x 10(-5)). Examining 27 of the previously reported SBP associated SNPs, 4 SNPs were nominally significant. A genetic risk score was constructed to assess the aggregated genetic effect of the published SBP variants, demonstrating a significant association (P=0.05). In addition, we also assessed whether these variants are associated with SCI, validating the use of SBP as an endo-phenotype for SCI. Three SNPs were nominally associated, and only rs2357790 (5' CACNB2) was significant for both SBP and SCI. None of these SNPs retained significance after Bonferroni correction. Taken together, our results suggest the importance of DRD2 genetic variation in the modulation of SBP, and extend the aggregated importance of previously reported SNPs in the modulation of SBP in an African American cohort, more specifically in children with SCD.

Acute chest syndrome is associated with single nucleotide polymorphism-defined beta globin cluster haplotype in children with sickle cell anaemia

Genetic diversity at the human β-globin locus has been implicated as a modifier of sickle cell anaemia (SCA) severity. However, haplotypes defined by restriction fragment length polymorphism sites across the β-globin locus have not been consistently associated with clinical phenotypes. To define the genetic structure at the β-globin locus more thoroughly, we performed high-density single nucleotide polymorphism (SNP) mapping in 820 children who were homozygous for the sickle cell mutation (HbSS). Genotyping results revealed very high linkage disequilibrium across a large region spanning the locus control region and the HBB (β-globin gene) cluster. We identified three predominant haplotypes accounting for 96% of the β(S) -carrying chromosomes in this population that could be distinguished using a minimal set of common SNPs. Consistent with previous studies, fetal haemoglobin level was significantly associated with β(S) -haplotypes. After controlling for covariates, an association was detected between haplotype and rate of hospitalization for acute chest syndrome (ACS) (incidence rate ratio 0·51, 95% confidence interval 0·29-0·89) but not incidence rate of vaso-occlusive pain or presence of silent cerebral infarct (SCI). Our results suggest that these SNP-defined β(S) -haplotypes may be associated with ACS, but not pain or SCI in a study population of children with SCA.

Abstract WP210: Prothrombin G20210A Mutation and Ischemic Stroke Risk in European Ancestry: The Genetics of Early Onset Stroke Study and Meta-Analysis of 2304 Young-Onset Stroke Cases

Background: Although the prothrombin G20210A mutation has been implicated in increased risk for venous thrombosis, its role in arterial ischemic stroke is unclear, particularly among young adults. To address this issue, we examined the association between prothrombin G20210A and ischemic stroke in Caucasian participants of the Genetics of Early Onset Stroke (GEOS) Study (n=396 cases) and also performed a meta-analysis of 17 case-control studies (n=2304 cases) examining the effect of prothrombin G20210A on ischemic stroke risk in young adults (<55 years).

Methods: A population-based case-control study identified 396 cases of women and men 15 to 49 years of age of European ancestry with first-ever ischemic stroke and 426 matched controls. Logistic regression was used to calculate odds ratios for the entire population and for subgroups stratified by gender, oral contraceptive use, smoking status, and age category.

Results: In the GEOS study, the prothrombin G20210A mutation was associated with a large but non-significant increase in ischemic stroke risk (OR=2.4, 95% CI: 0.9-6.5, p=0.08). However, among adults aged 15-42 (younger than the median age), cases were significantly more likely to have the prothrombin mutation than controls (OR=5.9, 95% CI: 1.1-28.5, p=0.03), whereas adults ages 42-49 were not (OR 1.1, 95% CI 0.3-4.4, p=0.94). In the meta-analysis of prior studies, the prothrombin G20210A mutation was significantly associated with stroke risk (OR 1.4, 95% CI: 1.1-1.9, p=0.02) with these results increasing in precision with addition of the GEOS results (OR=1.5, 95% CI: 1.1-2.0, p=0.005).

Conclusion: The prothrombin mutation is associated with ischemic stroke in young adults. The GEOS data suggests that, within the young adult age range, the prothrombin G20210A mutation may have an even stronger association among those with the earliest onset strokes. The finding of a stronger association in the ‘younger’ young adult population requires replication in other studies.

Magnetic resonance angiography-defined intracranial vasculopathy is associated with silent cerebral infarcts and glucose-6-phosphate dehydrogenase mutation in children with sickle cell anaemia

Silent cerebral infarct (SCI) is the most commonly recognized cause of neurological injury in sickle cell anaemia (SCA). We tested the hypothesis that magnetic resonance angiography (MRA)-defined vasculopathy is associated with SCI. Furthermore, we examined genetic variations in glucose-6-phosphate dehydrogenase (G6PD) and HBA (α-globin) genes to determine their association with intracranial vasculopathy in children with SCA. Magnetic resonance imaging (MRI) of the brain and MRA of the cerebral vasculature were available in 516 paediatric patients with SCA, enrolled in the Silent Infarct Transfusion (SIT) Trial. All patients were screened for G6PD mutations and HBA deletions. SCI were present in 41·5% (214 of 516) of SIT Trial children. The frequency of intracranial vasculopathy with and without SCI was 15·9% and 6·3%, respectively (P < 0·001). Using a multivariable logistic regression model, only the presence of a SCI was associated with increased odds of vasculopathy (P = 0·0007, odds ratio (OR) 2·84; 95% Confidence Interval (CI) = 1·55-5·21). Among male children with SCA, G6PD status was associated with vasculopathy (P = 0·04, OR 2·78; 95% CI = 1·04-7·42), while no significant association was noted for HBA deletions. Intracranial vasculopathy was observed in a minority of children with SCA, and when present, was associated with G6PD status in males and SCI.

California Very Preterm Birth Study: design and characteristics of the population- and biospecimen bank-based nested case-control study

Very preterm birth (VPTB) is a leading cause of infant mortality, morbidity and racial disparity in the US. The underlying causes of VPTB are multiple and poorly understood. The California Very Preterm Birth Study was conducted to discover maternal and infant genetic and environmental factors associated with VPTB. This paper describes the study design, population, data and specimen collection, laboratory methods and characteristics of the study population. Using a large, population-based cohort created through record linkage of livebirths delivered from 2000 to 2007 in five counties of southern California, and existing data and banked specimens from statewide prenatal and newborn screening, 1100 VPTB cases and 796 control mother-infant pairs were selected for study (385/200 White, 385/253 Hispanic and 330/343 Black cases/controls, respectively). Medical record abstraction of cases was conducted at over 50 hospitals to identify spontaneous VPTB, improve accuracy of gestational age, obtain relevant clinical data and exclude cases that did not meet eligibility criteria. VPTB was defined as birth at <32 weeks in Whites and Hispanics and <34 weeks in Blacks. Approximately 55% of all VPTBs were spontaneous and 45% had medical indications or other exclusions. Of the spontaneous VPTBs, approximately 41% were reported to have chorioamnionitis. While the current focus of the California Very Preterm Birth Study is to assess the role of candidate genetic markers on spontaneous VPTB, its design enables the pursuit of other research opportunities to identify social, clinical and biological determinants of different types of VPTB with the ultimate aim of reducing infant mortality, morbidity and racial disparities in these health outcomes in the US and elsewhere.

A genome-wide association study of total bilirubin and cholelithiasis risk in sickle cell anemia

Serum bilirubin levels have been associated with polymorphisms in the UGT1A1 promoter in normal populations and in patients with hemolytic anemias, including sickle cell anemia. When hemolysis occurs circulating heme increases, leading to elevated bilirubin levels and an increased incidence of cholelithiasis. We performed the first genome-wide association study (GWAS) of bilirubin levels and cholelithiasis risk in a discovery cohort of 1,117 sickle cell anemia patients. We found 15 single nucleotide polymorphisms (SNPs) associated with total bilirubin levels at the genome-wide significance level (p value <5 × 10(-8)). SNPs in UGT1A1, UGT1A3, UGT1A6, UGT1A8 and UGT1A10, different isoforms within the UGT1A locus, were identified (most significant rs887829, p = 9.08 × 10(-25)). All of these associations were validated in 4 independent sets of sickle cell anemia patients. We tested the association of the 15 SNPs with cholelithiasis in the discovery cohort and found a significant association (most significant p value 1.15 × 10(-4)). These results confirm that the UGT1A region is the major regulator of bilirubin metabolism in African Americans with sickle cell anemia, similar to what is observed in other ethnicities.

RNA helicase A is important for germline transcriptional control, proliferation, and meiosis in C. elegans

RNA helicase A (RHA) is a multifunctional protein with established roles in chromatin regulation. The protein is conserved in worms, Drosophila, and mammals, but its role in worms has not been previously studied. We found that a deletion mutant lacking rha-1 has a temperature-sensitive defect in germline transcriptional silencing, consistent with RHA-1 having a function in transcription regulation. Transcriptional desilencing in these rha-1(tm329) mutants was associated with a loss of lysine 9 methylation on histone H3 that is normally associated with silenced chromatin. Other histone modifications are also mis-localized in the germ cells in the mutants. These defects in histone modifications suggest that there is a general transcription regulation defect in the mutant worms that results in a temperature-sensitive sterile phenotype. At the restrictive temperature, the extent of germ cell mitoses is reduced, and the mutants are sterile due to defects in meiosis and gametogenesis. Our results suggest that RHA-1 is a conserved transcription regulation protein that controls germline proliferation and development in C. elegans.

Comment on "Diffusion of epicenters of earthquake aftershocks, Omori's law, and generalized continuous-time random walk models"

Modeling of earthquake sequences using an epidemic-type aftershock sequence model by Phys. Rev. E 66, 061104 (2002)] has led these authors to conclude that previous analyses of apparent earthquake diffusions were flawed. We show here that diffusion analyses based on spatiotemporal correlation measures for earthquake populations are an appropriate method for capturing the space-time coupling present in earthquake triggering processes.

Meiotic pairing and imprinted X chromatin assembly in Caenorhabditis elegans

The genetic imprinting of individual loci or whole chromosomes, as in imprinted X-chromosome inactivation in mammals, is established and reset during gametogenesis; defects in this process in the parent can result in disease in the offspring. We describe a sperm-specific chromatin-based imprinting of the X chromosome in the nematode Caenorhabditis elegans that is restricted to histone H3 modifications. The epigenetic imprint is established during spermatogenesis and its stability in the offspring is affected by the presence of a pairing partner during meiosis in the parental germ line. We observed that DNA lacking a pairing partner during meiosis, the normal situation for the X chromosome in males, is targeted for methylation of histone H3 at Lys9 (H3-Lys9) and can be silenced. Targeting unpaired DNA for silencing during meiosis, a potential hallmark of genome defense, could therefore have a conserved role in imprinted X-chromosome inactivation and, ultimately, in sex chromosome evolution.

Fertilization in vitro increases non-disjunction during early cleavage divisions in a mouse model system

BACKGROUND

We have been studying an unusual mouse-the BALB/cWt (Wt) male-in which the Y chromosome is susceptible to high rates of mitotic non-disjunction, particularly at the first two cleavage divisions. As these are the same divisions that human embryos generated through assisted reproductive technology must complete in an artificial setting, analysis of the Wt Y chromosome allows us to examine the effect of fertilization and culture in vitro on mammalian chromosome segregation.

METHODS

We performed standard mouse IVF, cultured embryos in 5% CO2 in air or in a lowered oxygen atmosphere, and used fluorescence in-situ hybridization to examine the sex chromosome constitutions of 2-, 4-, 8- and 16-cell stage Wt Y-bearing embryos.

RESULTS

We observed a significant increase in mosaic sex chromosome aneuploidy at each embryonic stage in embryos cultured in 5% CO2 in air, but under lowered oxygen conditions mosaicism returned to control (in-vivo) levels.

CONCLUSIONS

Our results demonstrate that slight alterations in in-vitro conditions may have a considerable impact on the genetic quality of assisted reproductive technology-derived embryos and suggest that the genetic quality of embryos should be a fundamental concern in the development of new culture systems for clinical use.

Analysis of a malsegregating mouse Y chromosome: evidence that the earliest cleavage divisions of the mammalian embryo are non-disjunction-prone

Despite the clinical importance of human aneuploidy, we know little of the causes of mammalian non-disjunction. In part, this reflects the fact that, unlike lower organisms, segregation 'impaired' chromosomes are virtually non-existent in mammals. To address this issue, we have studied the mouse Y chromosome on the BALB/cWt ('Wt') inbred background, a system in which loss of the Y chromosome in gonadal tissue has been linked to hermaphroditism. Our results indicate that the Wt Y chromosome is stably transmitted during meiotic cell divisions, but non-disjoins at an extremely high frequency in mitosis. Surprisingly, the non-disjunction events are largely restricted to the earliest cleavage divisions, indicating that there is a temporal 'window' during which the Wt Y chromosome is susceptible to non-disjunction. The non-disjunction phenotype has both cis and trans components: the Wt Y chromosome malsegregates on a variety of genetic backgrounds, demonstrating an intrinsic defect; however, the incidence of non-disjunction is significantly influenced by strain background, indicating the existence of modifying loci and thus providing evidence for a genetic effect on mammalian non-disjunction. These studies suggest that the earliest cell divisions in mammals are non-disjunction-prone, an interpretation which provides an explanation for the high rate of chromosome mosaicism observed in studies of in vitro fertilization (IVF)-derived human preimplantation embryos. Further, our observations raise the possibility that the IVF setting adversely affects chromosome segregation and suggest that genetic quality be an important consideration in any attempt to improve or modify in vitro procedures for use on human eggs and embryos.

Alphoid variant-specific FISH probes can distinguish autosomal meiosis I from meiosis II non-disjunction in human sperm

Over the past few years, several groups have used fluorescence in situ hybridization (FISH) to study aneuploidy in human sperm. Several important observations have derived from these studies, including the demonstration of chromosome-specific variation in non-disjunction frequencies, and the possible association of aneuploidy with environmental agents and with increasing paternal age. However, an important technical limitation of these studies has been the inability to distinguish between autosomal non-disjunction occurring at meiosis I and meiosis II. In the present report, we describe a simple FISH-based approach designed to overcome this limitation. Using oligonucleotide probes capable of distinguishing subtle differences in the alpha satellite sequences of chromosome 17, we demonstrate that (in appropriate heterozygotes) it is possible to simultaneously identify disomic sperm and to determine the meiotic stage of origin of the additional chromosome. This novel approach has important implications for future FISH sperm studies, since the ability to distinguish between meiosis I and meiosis II non-disjunction will make it possible to determine whether putative etiological agents affect chromosome segregation at both, or only one, of the two meiotic stages.

Temporally Unstable Recurrence of Earthquakes Due to Breaks in Fractal Scaling

Observed sequences of large earthquakes are not consistent in either recurrence time or energy release; long-term prediction has been impossible even in areas, such as Parkfield, with well-defined recurrence intervals. The seismic gap hypothesis, which predicts characteristic earthquakes in areas of the circum-Pacific belt that have not produced recent great earthquakes, has also failed to predict the observed clustering of high-energy events. Models in which fractal scaling is broken at high magnitude predict that characteristic events and recurrence behavior will be unstable in time. The central predictions of these models are supported by recent observations at Landers and Big Bear in California.