ABSTRACTObjectiveTo assess whether women with a genetic predisposition to medical conditions known to increase preeclampsia risk have an increased risk of preeclampsia in pregnancy.DesignCase-control study.Setting and populationPreeclampsia cases (n=498) and controls (n=1864) of European ancestry from 5 US sites genotyped on a cardiovascular gene-centric array.MethodsSignificant single nucleotide polymorphisms (SNPs) from 21 traits in 7 disease categories (cardiovascular, inflammatory/autoimmune, insulin resistance, liver, obesity, renal, thrombophilia) with published genome-wide association studies (GWAS) were used to create a genetic instrument for each trait. Multivariable logistic regression was used to test the association of each continuous, scaled genetic instrument with preeclampsia. Odds of preeclampsia were compared across quartiles of the genetic instrument and evaluated for significance using a test for trend.Main Outcome Measurespreeclampsia.ResultsAn increasing burden of risk alleles for elevated diastolic blood pressure (DBP) and increased body mass index (BMI) were associated with an increased risk of preeclampsia (DBP: overall OR 1.11 (1.01-1.21), p=0.025; BMI: OR 1.10 (1.00-1.20), p=0.042), while risk alleles associated with elevated alkaline phosphatase (ALP) were protective (OR 0.89 (0.82-0.97), p=0.008), driven primarily by pleiotropic effects of variants in theFADSgene region. The effect of DBP genetic loci was even greater in early-onset (<34 weeks) preeclampsia cases (OR 1.30 (1.08-1.56), p=0.005). For all other traits, the genetic instrument was not robustly associated with preeclampsia risk.ConclusionsThese results suggest that the underlying genetic architecture of preeclampsia is shared with other disorders, specifically hypertension and obesity.TWEETABLE ABSTRACTGenetic predisposition to increased diastolic blood pressure and obesity increases the risk of preeclampsia.

The PERIOD2 (PER2) gene is a core molecular component of the circadian clock and plays an important role in the generation and maintenance of daily rhythms. Rs35333999, a missense variant of PER2 common in European populations, has been shown to associate with later chronotype. Chronotype relates to the timing of biological and behavioral activities, including when we sleep, eat, and exercise, and later chronotype is associated with longer intrinsic circadian period (cycle length), a fundamental property of the circadian system. Thus, we tested whether this PER2 variant was associated with circadian period and found significant associations with longer intrinsic circadian period as measured under forced desynchrony protocols, the ‘gold standard’ for intrinsic circadian period assessment. Minor allele (T) carriers exhibited significantly longer circadian periods when determinations were based on either core body temperature or plasma melatonin measurements, as compared to non-carriers (by 12 and 11 min, respectively; accounting for ~7% of inter-individual variance). These findings provide a possible underlying biological mechanism for inter-individual differences in chronotype, and support the central role of PER2 in the human circadian timing system.

22 Background: Tumor genomic instability is positively correlated with immunotherapy response. It confers different tumor phenotypes, including high TMB (TMB-H) and high MSI (MSI-H). Recently the US Food and Drug Administration approved MSI-H phenotype as a biomarker for immunotherapy, highlighting its importance, but also bringing up the question of how TMB as another promising biomarker is going to add value in the field. Here, we characterized TMB and MSI profiles to better understand the potential TMB contribution and identify genomic markers for it. Methods: 734 solid tumor were collected, with 462 CRC, and 272 GA samples. Large panel Next-Generation Sequencing assay with the ability to determine TMB and MSI, was performed on each sample. Based on the TMB and MSI status, patients were grouped into four categories: THMH (TMB-H and MSI-H), THMS (TMB-H and MSI-Stable), TLMH (TMB-Low and MSI-H), and TLMS (TMB-Low and MSI-Stable). To identify genes that are related to the interplay of TMB and MSI, Random Forest and Lasso Regression models were applied to identify genes most predictive of the four categories. Results: TMB and MSI are highly correlated in our cohort of CRC and GA tumors. However, 5.8% CRC and 12.9% GA samples are under THMS (Table 1). In these samples, alternate DNA repair pathways are potentially dysregulated, including the nucleotide excision pathway (ATRX, APC), DNA double strand break repair (FANCF, SETD2), and the previously described proofreading pathway (POLD1). We hypothesize that these patients may also derive clinical benefit from immunotherapy. Conclusions: Immunotherapy benefits could be extended to more patients by jointly measuring MSI and TMB. The corresponding marker genes could also be extended beyond the commonly known POLE/POLD1 genes. Orthogonal validation by Whole Exome Sequencing data of the in silico mined marker genes is currently underway. [Table: see text]

e18597 Background: Rapid advances in NGS technology have enabled high throughput generation of data allowing for more comprehensive approaches to precision medicine and improved cancer patient care. However, efficient and timely variant interpretation and reporting to guide physicians’ therapeutic decisions remains an unmet need. Manual interpretation of variants is onerous, unreproducible, and non-scalable. At the same time, full automation of highly-nuanced clinical interpretation without human intervention is still at a nascent stage and has high error rates. Herein, we describe development of a semi-automated platform that augments accuracy and efficiency of clinical interpretation and reporting by over 20-fold. Methods: To facilitate accurate and efficient variant interpretation and clinical reporting we developed and validated GENEKEEPER (KEW, Inc.; Cambridge, MA), a cloud-based knowledgebase and reporting tool. The underlying database architecture seamlessly integrates patient sequence data with numerous resources including, the internal knowledgebase, trial registries, professional guidelines, and other public databases. The internal knowledgebase includes over 40,000 variants from > 3,000 patient tumor specimens, annotated by PHD/MD expert analysts to be consistent with the AMP guidelines. Results: In an analysis of 20 sequenced tumors, curated using our platform, we noted a 10-fold increase in efficiency and 2-fold increase in accuracy as compared to manual curation. We also observed a near 100% congruency of reported clinical trials and therapies between different curators. The flexible architecture enabled facile implementation of AMP guidelines to enhance standardization and accuracy of variant interpretation. Overall the platform demonstrated a 20-fold increase in efficacy in report generation. Conclusions: Semi-automated curation platforms promote precision and efficacy in analyzing and reporting clinically relevant variants to guide informed treatment decisions. GENEKEEPER significantly reduces the laboriousness of manual curation and will empower clinical laboratories to exponentially scale-up NGS operations.

Context:Vitamin D inadequacy is common in the adult population of the United States. Although the genetic determinants underlying vitamin D inadequacy have been studied in people of European ancestry, less is known about populations with Hispanic or African ancestry.Objective:The Trans-Ethnic Evaluation of Vitamin D (TRANSCEN-D) genomewide association study (GWAS) consortium was assembled to replicate genetic associations with 25-hydroxyvitamin D [25(OH)D] concentrations from the Study of Underlying Genetic Determinants of Vitamin D and Highly Related Traits (SUNLIGHT) meta-analyses of European ancestry and to identify genetic variants related to vitamin D concentrations in African and Hispanic ancestries.Design:Ancestry-specific (Hispanic and African) and transethnic (Hispanic, African, and European) meta-analyses were performed with Meta-Analysis Helper software (METAL).Patients or Other Participants:In total, 8541 African American and 3485 Hispanic American (from North America) participants from 12 cohorts and 16,124 European participants from SUNLIGHT were included in the study.Main Outcome Measures:Blood concentrations of 25(OH)D were measured for all participants.Results:Ancestry-specific analyses in African and Hispanic Americans replicated single nucleotide polymorphisms (SNPs) in GC (2 and 4 SNPs, respectively). An SNP (rs79666294) near the KIF4B gene was identified in the African American cohort. Transethnic evaluation replicated GC and DHCR7 region SNPs. Additionally, the transethnic analyses revealed SNPs rs719700 and rs1410656 near the ANO6/ARID2 and HTR2A genes, respectively.Conclusions:Ancestry-specific and transethnic GWASs of 25(OH)D confirmed findings in GC and DHCR7 for African and Hispanic American samples and revealed findings near KIF4B, ANO6/ARID2, and HTR2A. The biological mechanisms that link these regions with 25(OH)D metabolism warrant further investigation.

The genetic susceptibility to preeclampsia, a pregnancy-specific complication with significant maternal and fetal morbidity, has been poorly characterized. To identify maternal genes associated with preeclampsia risk, we assembled 498 cases and 1864 controls of European ancestry from preeclampsia case-control collections in 5 different US sites (with additional matched population controls), genotyped samples on a cardiovascular gene-centric array composed of variants from ≈2000 genes selected based on prior genetic studies of cardiovascular and metabolic diseases and performed case-control genetic association analysis on 27 429 variants passing quality control. In silico replication testing of 9 lead signals with P<10−4 was performed in independent European samples from the SOPHIA (Study of Pregnancy Hypertension in Iowa) and Inova cohorts (212 cases, 456 controls). Multiethnic assessment of lead signals was then performed in samples of black (26 cases, 136 controls), Hispanic (132 cases, 468 controls), and East Asian (9 cases, 80 controls) ancestry. Multiethnic meta-analysis (877 cases, 3004 controls) revealed a study-wide statistically significant association of the rs9478812 variant in the pleiotropic PLEKHG1 gene (odds ratio, 1.40 [1.23–1.60]; Pmeta=5.90×10−7). The rs9478812 effect was even stronger in the subset of European cases with known early-onset preeclampsia (236 cases diagnosed <37 weeks, 1864 controls; odds ratio, 1.59 [1.27–1.98]; P=4.01×10−5). PLEKHG1 variants have previously been implicated in genome-wide association studies of blood pressure, body weight, and neurological disorders. Although larger studies are required to further define maternal preeclampsia heritability, this study identifies a novel maternal risk locus for further investigation.

Obstructive sleep apnea (OSA) is a common heritable disorder displaying marked sexual dimorphism in disease prevalence and progression. Previous genetic association studies have identified a few genetic loci associated with OSA and related quantitative traits, but they have only focused on single ethnic groups, and a large proportion of the heritability remains unexplained. The apnea-hypopnea index (AHI) is a commonly used quantitative measure characterizing OSA severity. Because OSA differs by sex, and the pathophysiology of obstructive events differ in rapid eye movement (REM) and non-REM (NREM) sleep, we hypothesized that additional genetic association signals would be identified by analyzing the NREM/REM-specific AHI and by conducting sex-specific analyses in multiethnic samples. We performed genomewide association tests for up to 19,733 participants of African, Asian, European, and Hispanic/Latino American ancestry in 7 studies. We identified rs12936587 on chromosome 17 as a possible quantitative trait locus for NREM AHI in men (N = 6,737; P = 1.7310(-8)) but not in women (P = 0.77). The association with NREMAHI was replicated in a physiological research study (N = 67; P = 0.047). This locus overlapping the RAI1 gene and encompassing genes PEMT1, SREBF1, and RASD1 was previously reported to be associated with coronary artery disease, lipid metabolism, and implicated in Potocki-Lupski syndrome and Smith-Magenis syndrome, which are characterized by abnormal sleep phenotypes. We also identified gene-by-sex interactions in suggestive association regions, suggesting that genetic variants for AHI appear to vary by sex, consistent with the clinical observations of strong sexual dimorphism.

Despite major progress in defining the genetic basis of Mendelian disorders, the molecular etiology of many cases remains unknown. Patients with these undiagnosed disorders often have complex presentations and require treatment by multiple health care specialists. Here, we describe an integrated clinical diagnostic and research program using whole-exome and whole-genome sequencing (WES/WGS) for Mendelian disease gene discovery. This program employs specific case ascertainment parameters, a WES/WGS computational analysis pipeline that is optimized for Mendelian disease gene discovery with variant callers tuned to specific inheritance modes, an interdisciplinary crowdsourcing strategy for genomic sequence analysis, matchmaking for additional cases, and integration of the findings regarding gene causality with the clinical management plan. The interdisciplinary gene discovery team includes clinical, computational, and experimental biomedical specialists who interact to identify the genetic etiology of the disease, and when so warranted, to devise improved or novel treatments for affected patients. This program effectively integrates the clinical and research missions of an academic medical center and affords both diagnostic and therapeutic options for patients suffering from genetic disease. It may therefore be germane to other academic medical institutions engaged in implementing genomic medicine programs.

e13011 Background: Clinical NGS is often limited by tumor only profiling. Discrimination between somatic and likely germline mutations when calling from tumor patient samples is a critical step for clinical genotyping. Many algorithms have been developed for somatic single nucleotide variant (SNV) detection in matched tumor-normal whole genome and whole exome sequencing. Here, we demonstrate approaches of how a cost-effective large gene panel sequencing can be used to call somatic and germline SNVs for tumor only samples. Methods: Tumor, adjacent normal, and matched normal samples are collected from five patients. The somatic mutations were called with GATK Mutect2 in tumor only and adjacent normal. The germline mutations were called individually for all 15 samples with GATK Haplotype caller. To remove germline mutations from tumor only somatic calls, the filters ExAc pop freq, 1000G pop freq, COSMIC were applied on the tumor only somatic calls. PPV (Positive predictive value) for each filter was calculated by dividing the number of somatic mutations in the post-filtering mutation data by the total number of unfiltered mutations. TPR (True Positive Rate, representing sensitivity) was calculated by dividing the number of true somatic mutations in the tumor-only post-filter. Results: Compared with germline mutations called from matched normal, 70% germline mutations were called in RAWE somatic calls. A PPV of 0.71 and a TPR of 0.95 were optimally provided when the filter ExAc pop freq > 0.01 and COSMIC ( > 5 occurrence) applied. For germline mutations called in tumor samples, when compared with those in blood samples and in adjacent normal samples, PPV is 0.99 and TPR is 0.97. For somatic mutations called with tumor-adjacent normal pair mode in Mutect2, PPV is 0.5 and TPR is 0.99. Conclusions: Optimization of tools and parameters in NGS large panels could detect somatic and germline variants with high specificity, sensitivity and accuracy, without matched or adjacent normal. For the germline variants, when adjacent normal is available, it could replace matched normal with high accuracy.

e23077 Background: Tumor mutation burden (TMB) is an informative biomarker for predicting response to immunotherapy in a growing number of malignancies. The TMB clinical applicability is limited due to cost and bioinformatics requirements of sequencing and analyis of whole exome/gemone. Here, we demonstrate that a large next generation sequencing (NGS) panel can accurately identify hypermutation status. Methods: A novel algorithmic approach to derive the predicted total mutation load (PTML) described in J Roszik et al, BMC Med, 2016, was applied to our large NGS panel, CANCERPLEX. Statistical weights were calculated for each of the genes using publically available TCGA database. The algorithm was tested using CANCERPLEX data of stomach adenocarcinoma (199), colorectal cancer (59), and lung cancer (60) cohorts (n = 318). The correlation of PTML status with mismatch repair (MMR) status (n = 11) was also tested. The correlation of PTML status with clinical outcome was assessed using WES data following distinct immunotherapies (n = 16). The actual total mutation load (ATML) was compared to PTML by downsampling the WES data to our region of interest. Results: The mean values of PTML were evaluated for stomach adenocarcinoma (199), colorectal cancer (59), and lung cancer (60) cohorts. The PTML results for these 3 cancer types were statistically similar, and therefore the cohorts were combined into one dataset (n = 318). The hypermutation threshold was calculated from the PTML distribution of the three cancer types. This hypermutation threshold was in high concordance with our MMR validation set (n = 11), and also correlated (0.86) with an independent validation set of clinical outcome data from WES, which had undergone treatment with distinct immunotherapies (n = 16). This threshold predicts response to immunotherapy with 90% accuracy. Conclusions: NGS across a large gene panel captures sufficient information to predict tumor mutation burden with a single threshold for hypermutation status for stomach adenocarcinoma, colorectal, and lung cancers. This threshold highly correlates with MMR status and clinical outcome for immunotherapy response. Additional cancer types are currently being tested for inclusion in this study.

OBJECTIVE:Genetic factors underlying susceptibility to rheumatoid arthritis (RA) in Arab populations are largely unknown. This genome-wide association study (GWAS) was undertaken to explore the generalizability of previously reported RA loci to Arab subjects and to discover new Arab-specific genetic loci.METHODS:The Genetics of Rheumatoid Arthritis in Some Arab States Study was designed to examine the genetics and clinical features of RA patients from Jordan, the Kingdom of Saudi Arabia, Lebanon, Qatar, and the United Arab Emirates. In total, >7 million single-nucleotide polymorphisms (SNPs) were tested for association with RA overall and with seropositive or seronegative RA in 511 RA cases and 352 healthy controls. In addition, replication of 15 signals was attempted in 283 RA cases and 221 healthy controls. A genetic risk score of 68 known RA SNPs was also examined in this study population.RESULTS:Three loci (HLA region, intergenic 5q13, and 17p13 at SMTNL2/GGT6) reached genome-wide significance in the analyses of association with RA and with seropositive RA, and for all 3 loci, evidence of independent replication was demonstrated. Consistent with the findings in European and East Asian populations, the association of RA with HLA-DRB1 amino acid position 11 conferred the strongest effect (P = 4.8 × 10-16 ), and a weighted genetic risk score of previously associated RA loci was found to be associated with RA (P = 3.41 × 10-5 ) and with seropositive RA (P = 1.48 × 10-6 ) in this population. In addition, 2 novel associations specific to Arab populations were found at the 5q13 and 17p13 loci.CONCLUSION:This first RA GWAS in Arab populations confirms that established HLA-region and known RA risk alleles contribute strongly to the risk and severity of disease in some Arab groups, suggesting that the genetic architecture of RA is similar across ethnic groups. Moreover, this study identified 2 novel RA risk loci in Arabs, offering further population-specific insights into the pathophysiology of RA.

e13104 Background: Somatic mutation calling is critical for cancer genotyping. Although rapid development of mutation detection is witnessed with the maturity of NGS, the need for high sensitivity often results in compromised specificity and manual inspection. Here, we propose a methodology that leverages different variant callers to account for specificity without compromising sensitivity. Methods: We designed a cohort of training samples (n = 22), each with known set of SNVs/InDels that were discovered by KEW CANCERPLEX platform. We assessed the performance of four prevailing mutation callers that utilize different statistical approaches and therefore have different calls, using the training samples. We optimized the parameters of the four variant callers to detect all expected variants. We then examined the intersections of every combination of the four callers and identified the best one that eliminated the highest rate of false calls. A customized tool was developed for the intersection of component SNVs and InDels and the report differences among different callers. We also collected another set of validation samples (n = 28), each with true mutations that were both curated and orthogonally validated. We used this set to further test the efficacy of the refined calling strategy. Results: From the training samples, we chose the combination that provides highest sensitivity and specificity. This refined mutation calling strategy removed ~20% false SNV calls and ~50% false InDel calls in average for each sample. This result was further confirmed by the validation samples. Conclusions: The curated set of mutations from the genetic test platforms can provide valuable gold standard to test and tune mutation callers. The conclusions drawn from the curated variants are in line with the experimentally validated variants and showcase the validity of this practice, which we applied to demonstrate that the strategy of intersecting variants from optimized variant callers will generate mutation calls of higher specificity without compromising sensitivity. This methodology reduces the number of variants for curation and improves curation procedures and turn-around time.

The risk of type 2 diabetes (T2D) is increased by abnormalities in sleep quantity and quality, circadian alignment, and melatonin regulation. A common genetic variant in a receptor for the circadian-regulated hormone melatonin (MTNR1B) is associated with increased fasting blood glucose and risk of T2D, but whether sleep or circadian disruption mediates this risk is unknown. We aimed to test if MTNR1B diabetes risk variant rs10830963 associates with measures of sleep or circadian physiology in intensive in-laboratory protocols (n = 58–96) or cross-sectional studies with sleep quantity and quality and timing measures from self-report (n = 4,307–10,332), actigraphy (n = 1,513), or polysomnography (n = 3,021). In the in-laboratory studies, we found a significant association with a substantially longer duration of elevated melatonin levels (41 min) and delayed circadian phase of dim-light melatonin offset (1.37 h), partially mediated through delayed offset of melatonin synthesis. Furthermore, increased T2D risk in MTNR1B risk allele carriers was more pronounced in early risers versus late risers as determined by 7 days of actigraphy. Our results provide the surprising insight that the MTNR1B risk allele influences dynamics of melatonin secretion, generating a novel hypothesis that the MTNR1B risk allele may extend the duration of endogenous melatonin production later into the morning and that early waking may magnify the diabetes risk conferred by the risk allele.

OBJECTIVE:To determine whether European Americans with polycystic ovary syndrome (PCOS) exhibit genetic differences associated with PCOS status and phenotypic features. DESIGN:Case-control association study in European Americans. SETTING:Academic center. SUBJECT(S):Women with PCOS diagnosed with the use of the National Institutes of Health criteria (n = 532) and control women with regular menstrual cycles and no evidence of hyperandrogenism (n = 432). INTERVENTION(S):Blood was drawn for measurement of sex steroids, metabolic parameters, and genotyping. MAIN OUTCOME MEASURE(S):Associations among PCOS status, phenotype, and genetic background identified with the use of principal component analysis. RESULT(S):Principal component analysis identified five principal components (PCs). PC1 captured northwest-to-southeast European genetic variation and was associated with PCOS status. Acanthosis was associated with southern European ancestry, and larger waist:hip ratio was associated with northern European ancestry. PC2 was associated with east-to-west European genetic variation and cholesterol levels. CONCLUSION(S):These data provide evidence for genetic influence based on European ethnicity in women with PCOS. There is also evidence for a genetic component in the phenotypic features of PCOS within a mixed European population. The data point to the need to control for population stratification in genetic studies in women of mixed European ethnicity. They also emphasize the need for better studies of PCOS prevalence and phenotype as a function of genetic background.

Objective: To examine the association between genetic predisposition to elevated C-reactive protein (CRP)and risk for preeclampsia using validated genetic loci for C-reactive protein. Methods: Preeclampsia cases (n = 177) and normotensive controls (n = 116) were selected from live birth certificates to nulliparous Iowa women during the period August 2002–May 2005. Disease status was verified by the medical chart review. Genetic predisposition to CRP was estimated by a genetic risk score on the basis of established loci for CRP levels. Logistic regression analyses were used to evaluate the relationships between the genotype score and preeclampsia. Replication analyses were performed in an independent, US population of preeclampsia cases (n = 516) and controls (n = 1,097) of European ancestry. Results: The genetic risk score (GRS) related to higher levels of CRP demonstrated a significantly decreased risk of preeclampsia (OR 0.89, 95% CI 0.82–0.96). When the GRS was analyzed by quartile, an inverse linear trend was observed (p = 0.0006). The results were similar after adjustments for the body mass index (BMI), smoking, and leisure-time physical activity. In the independent replication population, the association with the CRP GRS was also marginally significant (OR 0.97, 95% CI 0.92, 1.02). Meta-analysis of the two studies was statistically significant (OR 0.95, 95% CI 0.90, 0.99). Conclusion: Our data suggest an inverse, counterintuitive association between the genetic predisposition to elevated levels of CRP and a decreased risk of preeclampsia. This suggests that the blood CRP level is a marker of preeclampsia, but it does not appear to be a factor on the causal pathway.

In recent years, genome-wide association studies have identified 58 independent risk loci for coronary artery disease (CAD) on the autosome. However, due to the sex-specific data structure of the X chromosome, it has been excluded from most of these analyses. While females have 2 copies of chromosome X, males have only one. Also, one of the female X chromosomes may be inactivated. Therefore, special test statistics and quality control procedures are required. Thus, little is known about the role of X-chromosomal variants in CAD. To fill this gap, we conducted a comprehensive X-chromosome-wide meta-analysis including more than 43,000 CAD cases and 58,000 controls from 35 international study cohorts. For quality control, sex-specific filters were used to adequately take the special structure of X-chromosomal data into account. For single study analyses, several logistic regression models were calculated allowing for inactivation of one female X-chromosome, adjusting for sex and investigating interactions between sex and genetic variants. Then, meta-analyses including all 35 studies were conducted using random effects models. None of the investigated models revealed genome-wide significant associations for any variant. Although we analyzed the largest-to-date sample, currently available methods were not able to detect any associations of X-chromosomal variants with CAD.

RATIONALE:Obstructive sleep apnea is a common disorder associated with increased risk for cardiovascular disease, diabetes, and premature mortality. Although there is strong clinical and epidemiologic evidence supporting the importance of genetic factors in influencing obstructive sleep apnea, its genetic basis is still largely unknown. Prior genetic studies focused on traits defined using the apnea-hypopnea index, which contains limited information on potentially important genetically determined physiologic factors, such as propensity for hypoxemia and respiratory arousability. OBJECTIVES:To define novel obstructive sleep apnea genetic risk loci for obstructive sleep apnea, we conducted genome-wide association studies of quantitative traits in Hispanic/Latino Americans from three cohorts. METHODS:Genome-wide data from as many as 12,558 participants in the Hispanic Community Health Study/Study of Latinos, Multi-Ethnic Study of Atherosclerosis, and Starr County Health Studies population-based cohorts were metaanalyzed for association with the apnea-hypopnea index, average oxygen saturation during sleep, and average respiratory event duration. MEASUREMENTS AND MAIN RESULTS:Two novel loci were identified at genome-level significance (rs11691765, GPR83, P = 1.90 × 10-8 for the apnea-hypopnea index, and rs35424364; C6ORF183/CCDC162P, P = 4.88 × 10-8 for respiratory event duration) and seven additional loci were identified with suggestive significance (P < 5 × 10-7). Secondary sex-stratified analyses also identified one significant and several suggestive associations. Multiple loci overlapped genes with biologic plausibility. CONCLUSIONS:These are the first genome-level significant findings reported for obstructive sleep apnea-related physiologic traits in any population. These findings identify novel associations in inflammatory, hypoxia signaling, and sleep pathways.

The sleep electroencephalogram (EEG) is highly heritable in humans and yet little is known about the genetic basis of inter-individual differences in sleep architecture. The aim of this study was to identify associations between candidate circadian gene variants and the polysomnogram, recorded under highly controlled laboratory conditions during a baseline, overnight, 8 h sleep opportunity. A candidate gene approach was employed to analyze single-nucleotide polymorphisms from five circadian-related genes in a two-phase analysis of 84 healthy young adults (28 F; 23.21 ± 2.97 years) of European ancestry. A common variant in Period2 (PER2) was associated with 20 min less slow-wave sleep (SWS) in carriers of the minor allele than in noncarriers, representing a 22% reduction in SWS duration. Moreover, spectral analysis in a subset of participants (n = 37) showed the same PER2 polymorphism was associated with reduced EEG power density in the low delta range (0.25-1.0 Hz) during non-REM sleep and lower slow-wave activity (0.75-4.5 Hz) in the early part of the sleep episode. These results indicate the involvement of PER2 in the homeostatic process of sleep. Additionally, a rare variant in Melatonin Receptor 1B was associated with longer REM sleep latency, with minor allele carriers exhibiting an average of 65 min (87%) longer latency from sleep onset to REM sleep, compared to noncarriers. These findings suggest that circadian-related genes can modulate sleep architecture and the sleep EEG, including specific parameters previously implicated in the homeostatic regulation of sleep.

Mutations in the colony stimulating factor 1 receptor (CSF1R) have recently been discovered as causal for hereditary diffuse leukoencephalopathy with axonal spheroids. We identified a novel, heterozygous missense mutation in CSF1R [c.1990G > A p.(E664K)] by exome sequencing in five members of a family with hereditary diffuse leukoencephalopathy with axonal spheroids. Three affected siblings had characteristic white matter abnormalities and presented with progressive neurological decline. In the fourth affected sibling, early progression halted after allogeneic haematopoietic stem cell transplantation from a related donor. Blood spot DNA from this subject displayed chimerism in CSF1R acquired after haematopoietic stem cell transplantation. Interestingly, both parents were unaffected but the mother's blood and saliva were mosaic for the CSF1R mutation. Our findings suggest that expression of wild-type CSF1R in some cells, whether achieved by mosaicism or chimerism, may confer benefit in hereditary diffuse leukoencephalopathy with axonal spheroids and suggest that haematopoietic stem cell transplantation might have a therapeutic role for this disorder.