3613 results for "*geneti*"

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• Natural Genetic Variation in the Human Genome

  In this study, we used existing whole genome sequencing data from the TOPMed Amish and Jackson Heart Study, as well as the GTEx study, to identify mobile element insertions in the genomes of these individuals.  A total of 1112 TOPMed Amish, 3331 TOPMed Jackson Heart Study, and 698 GTEx individuals were examined.  We used the Mobile Element Locator Tool (MELT) developed previously by our lab, along with a Cloud-based version of MELT (CloudMELT), to discover non-reference mobile element insertions (MEIs) in these genomes.  We discovered Alu, L1, SVA, and HERV-K MEIs and produced genotypes in individual genomes.  Build hg19 bams were used for the TOPMed samples, and build GRCh37 bams were used for the GTEx samples in this study.

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• Multimodal Profiling of 500,000 Memory T Cells from a Tuberculosis Cohort Identifies Cell State Associations with Demographics, Environment, and Disease

  We conducted CITE-seq to measure whole transcriptome gene expression and surface expression of 31 proteins. We assayed >500K memory T cells from 259 donors from a tuberculosis progression cohort (128 cases: former progressors and 131 controls: non-progresssors/latent infection) >4 years post-infection after returning to immune steady state. We defined 31 memory T cell states influenced by age, sex, genetic ancestry, and season. After correcting for these covariates, we found that one cell state (C-12), resembling the T helper cells Th17s, were depleted in cases compared to controls. When sorted ex vivo, this state responds to polyclonal or Mycobacterium tuberculosis (Mtb) peptide antigen stimulation with interleukin-17 (IL-17) or interferon gamma (IFNg).

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• Type 1 Diabetes Genetics Consortium (T1DGC): Multi-Ethnic ImmunoChip Study

  Type 1 diabetes (T1D) is characterized by an autoimmune attack that destroys the insulin-producing pancreatic beta cells and is driven by diverse genetic and environmental factors. Between 8-100 chromosome regions are known to contain variants that alter T1D risk, substantially fewer than many other common diseases. Less is known about the contribution of T1D risk alleles in non-European populations, despite recent increases in T1D diagnoses in multiple non-European ancestry groups. To address these gaps in T1D genetics, we doubled the sample size from the previous largest T1D association study, genotyped ancestrally diverse T1D cases, controls, and affected families with the Illumina ImmunoChip array, and imputed additional variants using a large haplotype reference panel. After quality filtering, a total of 61,427 participants and 140,333 genotyped ImmunoChip variants were included in analysis, providing dense coverage in 188 autosomal regions ("ImmunoChip regions") and sparse genotyping in other regions of the genome. Each participant was assigned to one of five ancestry groups using k-means clustering of ImmunoChip genotype principal components: European (EUR, N = 47,319), African Admixed (AFR, N = 4,290), Finnish (FIN, N = 6,991), East Asian (EAS, N = 588) and Other Admixed (AMR, N = 2,239). In total, 16,159 T1D cases, 25,386 controls (unrelated) and 6,143 trio families (i.e., an affected child and both parents) were genotyped and included in association analyses. Imputation with the National Heart, Lung, and Blood Institute (NHLBI) Trans-Omics for Precision Medicine (TOPMed) multi-ethnic reference panel was used to improve discovery power and fine-mapping resolution. After imputation, the number of variants in ImmunoChip regions with imputation R-squared > 0.8 and MAF > 0.005 in each ancestry group was 322,084 (AFR), 166,274 (EUR), 163,612 (FIN), 137,730 (EAS) and 188,550 (AMR). Imputed genotypes were compared in the same participants who have whole genome sequencing data, resulting in high concordance. Unrelated cases and controls (N = 41,545) were analyzed initially, assuming an additive inheritance model. T1D trio families (N = 6,143 trios, some trio families were multiplex and analyzed as multiple trios) were analyzed separately, with meta-analysis of case-control and trio results used for discovery of regions associated with T1D (p < 5×10-8). Summary-level data at each SNP (genotype and imputed) for type 1 diabetes (outcome) are provided in dbGaP.

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• A Polygenic Score for Acute Vaso-Occlusive Pain in Pediatric Sickle Cell Disease

  Recurrent acute pain, or vaso-occlusive pain crisis (VOP), is the most common complication of sickle cell disease and correlates strongly with increased hospital visits and early mortality (PMID: 1710777). While the genetics of VOP in sickle cell patients has been studied (PMID: 29205277, 27883292, 25102390, 30079801, 22925497, 29531649, 29620434, 19468207, 20172753, 22576309, 30031848, 24136375, 27603703, 29559808), it is not fully understood.Using whole genome sequencing, we interrogated the α-thalassemia deletion -α3.7 and 133 candidate single-nucleotide polymorphisms (SNPs) across 66 genes for associations with VOP in 327 SCCRIP participants followed longitudinally over 6 years. Twenty-one SNPs in 9 loci were associated with VOP, including 3 (BCL11A, MYB, and the β-like globin gene cluster) that regulate erythrocyte fetal hemoglobin (HbF) levels and 6 (COMT, TBC1D1, KCNJ6, FAAH, NR3C1, and IL1A) that were associated previously with various pain syndromes. An unweighted PGS integrating all 21 SNPs was associated with the VOP event rate (estimate, 0.35; standard error, 0.04; P = 5.9 × 10−14) and VOP event occurrence (estimate, 0.42; standard error, 0.06; P = 4.1 × 10−13). These associations were stronger than those of any single locus. Our findings provide insights into the genetic modulation of VOP in children with SCD. More generally, we demonstrate the utility of WGS for investigating genetic contributions to the variable expression of SCD-associated morbidities.For publications, written, and/or oral presentations resulting from use of this data, please cite the following information: "The original data description for A Polygenic Score for Acute Vaso-Occlusive Pain in Pediatric Sickle Cell Disease can be found here: (Journal Citation Blood Adv. 2021 Jul 27;5(14):2839-2851) (PMID: 34283174)."

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• Germline Whole-Exome Sequencing of Lung Cancer in EAGLE

  EAGLE is a large population-based case-control study designed and conducted to investigate the genetic and environmental determinants of lung cancer and smoking persistence using an integrative approach that allows combined analysis of genetic, environmental, clinical, and behavioral data. Here, we applied whole exome sequencing (WES) to EAGLE study, in a group of 2,777 Italian subjects (including 1,461 lung cancer cases and 1,316 healthy controls). We derived gene-level burden tests to explore the cumulative effect of deleterious rare variants within protein-coding genes and the lung cancer risk. Additionally, at this site we include WES datasets of 1259 healthy controls from 1054 PLCO (The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial) subjects and 205 ACS (The American Cancer Society study) subjects.

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• Genetic Effects on Gene Expression and Splicing during Human Neurogenesis

  Interpretation of the function of non-coding risk loci for neuropsychiatric disorders and brain-relevant traits via gene expression and alternative splicing quantitative trait locus (e/sQTL) analyses is generally performed in bulk post-mortem adult tissue. However, genetic risk loci are enriched in regulatory elements active during neocortical differentiation, and regulatory effects of risk variants may be masked by heterogeneity in bulk tissue. Here, we map e/sQTLs, and allele-specific expression in cultured cells representing two major developmental stages, primary human neural progenitors (n=85) and their sorted neuronal progeny (n=74), identifying numerous loci not detected in either bulk developing cortical wall or adult cortex. Using colocalization and genetic imputation via transcriptome-wide association, we uncover cell-type specific regulatory mechanisms underlying risk for brain-relevant traits that are active during neocortical differentiation. Specifically, we identified a progenitor-specific eQTL for CENPW co-localized with common variant associations for cortical surface area and educational attainment.

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• Clinical and Genetic Analysis of Costa Rican Patients with Parkinson's Disease

  This study is a pilot study designed to describe the clinical and genetic landscape of Parkinson's disease in Costa Rica. While most genetic studies have been conducted on Europeans, few have examined Parkinson's disease in Costa Ricans. 118 patients and 97 controls were recruited at the Movement Disorders Unit of the Department of Neurology, Hospital San Juan de Dios, Caja Costarricense de Seguro Social, Costa Rica. Familial Parkinson's disease genes were sequenced using Next-Generation Sequencing. We also measured and obtained different sociodemographic and clinical information.

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• Genome-Wide Approach to Measure Variant-Based Heritability of Drug Outcome Phenotypes

  Current pharmacogenetic approaches often use a few large-effect alleles to predict drug outcomes. However, many drug outcome phenotypes are determined by complex pathways that may be influenced by common single-nucleotide variants (SNVs) across the genome. We ascertained how much variation in drug response is explained by common SNVs for pharmacokinetic (drug levels) and pharmacodynamic phenotypes (highest creatinine) for 4 drugs: vancomycin, gentamicin, cyclosporine and tacrolimus.

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• Mechanisms of Restoring T Cell Immunity after Cure of Chronic Viral Infection

  We analyzed hepatitis C virus (HCV)-specific T cells and non-specific memory T cell populations from 6 patients with chronic HCV infection receiving 12 weeks of direct-acting antiviral (DAA) therapy with aritaprevir/ritonavir/ombitasvir + dasabuvir + ribavirin. All patients were treated successfully. Peripheral blood mononuclear cells were obtained from blood draws right before treatment initiation (Pre-DAA) and 12 months after the end of treatment (Post-DAA). In each patient, HCV-specific cells were sorted using two different HCV multimers: One representing an epitope present in the circulating HCV genome and one epitope where the virus had escaped the T cell response and thus the corresponding T cells did not receive a TCR signal in vivo. Sorted specific T-cell populations and memory T cell subpopulations were analyzed by extracting RNA and performing RNA sequencing using the Smart-Seq2 protocol. A group of 8 patients with acute self-limited HCV infection (resolvers) were included as control representing natural control of infection. These patients were studied 24 weeks after their last detectable HCV viremia. Finally, we confirmed the data from chronically treated patients in a confirmatory cohort, consisting of 9 patients after successful antiviral treatment.

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• Center for Common Disease Genomics [CCDG] - Neuropsychiatric: SPARK Simons Foundation Powering Autism Research for Knowledge

  In this study, we address the enormous challenges common complex diseases pose for genomic analysis and the enormous opportunities surmounting them offers for advancing healthcare. The common genetic disorders proposed for study here are believed to have extreme locus heterogeneity, requiring the analysis of large numbers of samples to comprehensively identify the genomic variants underlying them. We propose that a combination of deep population studies and joint analysis of SNPs, indels, and structural variants, both in coding and noncoding regions, will provide the next level of understanding of common genetic disorders. Whole genome sequencing (WGS) will be critical to this next-generation approach to the genomics of complex disease. WGS will need to be accompanied by the technical ability to generate and handle very large data sets, a particular focus and strength of New York Genome Center (NYGC). WGS will also need to be accompanied by new statistical tools and algorithms, which will be developed by the strong core group committed to this proposal.An overarching goal of this proposal, one that capitalizes on the power of WGS, is to identify disease-associated variants at the individual nucleotide level. In many cases, pathogenic mutations fall in noncoding regions of the genome, which can only be fruitfully explored with WGS. A major effort was put into building new computational strategies to functionally annotate noncoding transcribed sequences, and to build new datasets to enable such strategies, opening new frontiers of understanding of disease-related regulatory variants.

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• Center for Common Disease Genomics [CCDG] - Neuropsychiatric: Simons Searchlight

  In this study, we address the enormous challenges common complex diseases pose for genomic analysis and the enormous opportunities surmounting them offers for advancing healthcare. The common genetic disorders proposed for study here are believed to have extreme locus heterogeneity, requiring the analysis of large numbers of samples to comprehensively identify the genomic variants underlying them. We propose that a combination of deep population studies and joint analysis of SNPs, indels, and structural variants, both in coding and noncoding regions, will provide the next level of understanding of common genetic disorders. Whole genome sequencing (WGS) will be critical to this next-generation approach to the genomics of complex disease. WGS will need to be accompanied by the technical ability to generate and handle very large data sets, a particular focus and strength of New York Genome Center (NYGC). WGS will also need to be accompanied by new statistical tools and algorithms, which will be developed by the strong core group committed to this proposal.An overarching goal of this proposal, one that capitalizes on the power of WGS, is to identify disease-associated variants at the individual nucleotide level. In many cases, pathogenic mutations fall in noncoding regions of the genome, which can only be fruitfully explored with WGS. A major effort was put into building new computational strategies to functionally annotate noncoding transcribed sequences, and to build new datasets to enable such strategies, opening new frontiers of understanding of disease-related regulatory variants.

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• Neuropsychiatric Genetics of African Populations - Psychosis (NeuroGAP-Psychosis)

  The NeuroGAP-Psychosis study was conducted in South Africa, Kenya, Uganda and Ethiopia as a response to the lack of genetic diversity in large genomic studies of psychiatric disorders. The study aims to expand knowledge of the genetic and environmental risk factors for neuropsychiatric disorders in Africa through large-scale sample collection and analysis. The initial design is a case-control study in which cases are individuals with schizophrenia or bipolar disorder and controls are age, sex and ancestry matched with individuals from the same geographic location. Cases are patients who are recruited from clinical facilities, both inpatient and outpatient. Controls are people who present for treatment for general medical conditions at health facilities. Data on phenotype, mental disorders, history of physical health problems, substance use and history of past traumatic events was collected from all participants. Additionally, a sample of saliva is collected for DNA extraction. DNA samples were sent to the Broad Institute for genotyping using Illumina Infinium Global Screening Array.  

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• The MD Anderson Colorectal Cancer Case Control Study

  Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the US. Driven by common disease common variants hypothesis, genome-wide association studies only identified a number of common susceptibility loci that explained a small portion of CRC heritability. We conducted a case-control study using whole exome sequencing to identify rare genetic variants with intermediate effect size that predispose individuals to colorectal cancer.

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• Kids First: Genomics of Orofacial Clefts in the Philippines

  Orofacial clefts (OFCs) are the most common craniofacial structural birth defect in humans caused by incomplete formation of the upper lip and/or the palate. Over 4,000 children in the Philippines are born with an OFC every year, and the Filipino OFC birth prevalence rate of 1 in 500 live births is one of the highest in the world. Genome-wide association studies support a multifactorial etiology for OFCs, but common variants only account for up to ~25% of the heritable risk in any one population. Sequencing studies in diverse populations is essential to fully understand the genetic architecture of OFCs. The study goals of the Kids First project are to sequence a collection of case-parent trios from the Philippines, in order to identify de novo mutations and inherited rare variants, and understand the population differences in common variant signals in the Philippines versus other populations. Approximately 373 trios from the Philippines were selected for whole genome sequencing (WGS) as part of this Gabriella Miller Kids First project.

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• Homozygous Duplication Identified by Whole Genome Sequencing Causes LRBA Deficiency

  In more than one third of primary immunodeficiency (PID) patients, extensive genetic analysis including whole exome sequencing (WES) fails to identify the genetic defect. Whole genome sequencing (WGS) is able to detect variants missed by other genomics platforms, enabling the molecular diagnosis of otherwise unresolved cases. Here, we report two siblings, offspring of consanguineous parents, who experienced similar severe events encompassing early onset of colitis, lymphoproliferation and hypogammaglobulinemia, typical of lipopolysaccharide (LPS)-responsive and beige-like anchor protein (LRBA) or cytotoxic T-lymphocyte-associated protein 4 (CTLA4) deficiencies. WGS of these patients detected a 12.3 kb homozygous tandem duplication that was absent in control cohorts and is predicted to disrupt the reading frame of the LRBA gene.

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• Exome Sequencing for Head and Neck Cancer Susceptibility

  This study seeks to find low frequency or rare genetic variants in genes carried by subjects from families with unexplained familial risk of head and neck cancer. Whole exome sequencing was used to identify genetic variation in head and neck cancer cases.

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• Kids First: Congenital Heart Defects and Laterality Birth Defects

  Laterality defects occur in approximately 1:10,000 newborns and are associated with a range of structural birth defects and abnormalities of organ positioning. Gut malrotation, biliary atresia, asplenia or polysplenia, complex cardiovascular malformations, and midline defects such as neural tube defects, vertebral anomalies and rib fusions are found in various combinations in patients with laterality defects. In addition, a subset of laterality defects caused by abnormalities of cilia position or function are associated with additional medical problems such as chronic sinusitis and bronchiectasis that require specific preventive care; however these patients frequently are undiagnosed until late in disease course. The goal of this project is to elucidate the genetic architecture of laterality disorders in order to inform medical management and risk stratification and to prevent complications. Laterality disorders are genetically heterogeneous and we and others have previously identified single nucleotide variants inherited in an X-linked or autosomal recessive manner as explanations for a minority of cases. In addition, we have demonstrated copy number variants (CNVs) as a mechanism of disease that requires additional investigation. We hypothesize that the majority of cases result from complex genetic inheritance. We propose to investigate this hypothesis using a multifaceted analysis approach in our extremely well phenotyped cohort of 538 probands with laterality disorders. Nested within this cohort are 105 trios who have not had previous sequencing, probands who have had exome sequencing and are excellent candidates for gene discovery via whole genome sequencing (WGS), and families with multiple affected family members for family-based analysis. All trios will be analyzed by transmission disequilibrium test (TDT) including rare variant TDT. De novo mutations will also be identified from trios for potential gene discovery. Using all probands, we will identify the prevalence of pathogenic CNVs. In addition, we will perform burden analyses to identify genes, gene interactions, and pathways important for susceptibility to laterality disorders. Finally, our rare families with multiple affected members will be studied using family based segregation analysis. This comprehensive genetic analysis in patients with laterality disorders is necessary to identify the appropriate clinical diagnostic testing for risk stratification, to elucidate underlying genetic architecture and facilitate novel gene discovery, and to provide essential knowledge about genes and pathways impacting the development of laterality disorders.

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• Kids First: Genomic Etiologies of CHARGE Syndrome, Related Conditions and Structural Anomalies

  Developmental disorders with structural birth defects account for the majority of morbidity and mortality in children's hospitals, and the genetic bases of many clinical phenotypes remain unknown. Genetic testing for individuals with structural malformations has uncovered the basis of many such birth defects; however, many more cases remain unsolved, posing challenges for diagnosis, treatment, and prevention. Multiple anomaly conditions are particularly challenging to diagnose, since they often present with unique combinations of clinical features that vary widely between affected individuals, even in the same family. CHARGE Syndrome (Coloboma of the eye, Heart Defects, Atresia of the choanae, Retardation of growth and development, Genital abnormalities including pubertal delay and infertility, Ear abnormalities with deafness and vestibular disorders) is a multiple anomaly condition that affects a wide variety of organ systems. CHARGE Syndrome is caused in most cases by monoallelic pathogenic variants in CHD7, the gene encoding ATP-dependent helicase chromodomain DNA binding protein 7. Both de novo and inherited variants in CHD7 have been reported in CHARGE, and a growing number of families present with individuals who test positive for a pathogenic CHD7 variant yet exhibit only mild features. Similarly, individuals with CHARGE Syndrome often exhibit broad variability and reduced penetrance of clinical features, consistent with pleiotropic roles for CHD7 during development and/or additional genetic contributors or modifying alleles. Recent work has also implicated RERE, KMT2D, EP300, and PUF60 in having a role in CHARGE Syndrome.We hypothesize that (1) some cases of CHARGE are due to other genetic etiologies including oligogenicity, and (2) genetic modifiers contribute to the broad clinical variability and reduced penetrance of CHARGE features. To address these hypotheses, we have generated a cohort of 223 deeply clinically phenotyped individuals with CHARGE Syndrome and related disorders and structural anomalies who tested negative by chromosomal microarray, single gene sequencing, next generation panel sequencing, or exome sequencing. These individuals exhibit clinical CHARGE-like features including structural birth defects affecting craniofacial, ocular, neurosensory, brain, heart, mediastinal, renal, genitourinary, and skeletal organs. Our cohort includes these 223 individuals as well as affected and unaffected family members who consented to clinical and research genetic testing and donated blood samples for DNA and RNA isolation and sequencing. Building on this valuable cohort, we propose to use exome and genome sequencing to identify novel genetic etiologies of CHARGE and related developmental disorders for which alternative genetic tests have been inconclusive. Identification of novel pathogenic genetic variants and contributing modifier alleles within the coding and non-coding portion of the genome of these individuals will improve genetic diagnosis and provide important insights toward understanding the developmental mechanisms of structural birth defects.

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• Kids First: Genetic Basis of Fetal Alcohol Spectrum Disorders

  Fetal Alcohol Spectrum Disorder (FASD) is estimated to occur in at least 1-5% of all children in the USA and is a major public health issue. However, in addition to alcohol, other susceptibility factors, such as maternal or fetal genetic variation, must play a role as not all children prenatally exposed to alcohol are similarly affected. The proposed study will examine the role of genetic susceptibility for FASD. This work will help to inform more effective intervention efforts for this common congenital disorder.

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• Modeling Malignant Progression in Glioma

  Gliomas are the most common primary brain tumor in humans. Low-grade gliomas (WHO grade II) invariably progress to high-grade gliomas (WHO grade III or IV). Although malignant progression may take many years, the survival rate after transformation to a high-grade glioma is poor, often only 12-15 months. In this data set, we have identified low-grade gliomas that have progressed to high-grade gliomas or high-grade gliomas that have progressed from low-grade gliomas. Some cases are matched pairs (meaning we have both the original low-grade tumor and the subsequent high-grade tumor). The samples deposited have been analyzed with bulk-RNA sequencing. They are also de-identified but are clinically annotated. When available, genetic information including IDH mutation status, 1p/19q deletion and histological subtype are also included.

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• Characterizing Disease-Causing Variants Using Personal Genomes with Large Recurrent Deletions

  Individuals with recurrent genomic deletions are known to present variable clinical phenotypes, despite the apparent identical range of the genomic segments being affected in their genomes. We propose to study the phenotypic variability and the molecular polymorphism in individuals with the recurrent 17q12 deletions or the recurrent 1q21.1 deletions, with the objective to establish causal relationship between the genotypes and the incompletely penetrant clinical phenotypes. Genome sequencing and phenotypic data from individuals with the deletions and their relatives are included in this submission.

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• Whole Genome Sequencing of Bilateral Cleft Lip and Palate Families from Africa: CIDR

  The focus of this study is to identify and test both common and rare genetic variants that elevate risk for CL/P, and to identify genetic variants associated with specific orofacial cleft (OFC) phenotypes in the population that has accumulated the greatest genetic variation in the human race. We hypothesize that bilateral complete cleft lip and palate (BCLP), the most clinically severe form of OFC, is associated with a higher mutation load than less severe forms (cleft lip only and unilateral cleft lip and palate) and focusing on BCLP will facilitate the discovery of novel risk variants.

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• The Spatio-Temporal Evolution of Multiple Myeloma from Baseline to Relapse-Refractory States

  In multiple myeloma, the spatio-temporal evolution patterns of cancer cells in the bone marrow remain largely unknown. Here, we applied spatial-longitudinal sequencing, including a total of 179 samples collected from 25 patients during a follow-up of up to 14 years. Our study highlights focal bone lesions (FL) as hotspots of tumor evolution and provides possible explanations for their negative prognostic impact. We show a close phylogenetic relationship between baseline FL and relapse clones. In patients with ≥3 FDG-PET-positive FL at diagnosis, relapse was driven by multiple distinct sub-clones, whereas in other patients, a single-cell expansion was typically seen (p<0.01). Applying imaging-guided sampling, we identified a novel evolutionary pattern with unique treatment-resistant sub-clones at distinct locations. We observed multiple selective clonal sweeps, resistant clones that can be hidden over years, and epigenetic modifier mutations as a new class of relapse aberrations. Here we show that imaging can enhance tumor evolution studies and response assessment. The sophisticated evolution mechanisms in myeloma and presence of single cells that can drive relapse even after 10 years of remission suggest that a prerequisite for curative therapies would be to overcome not only tumor heterogeneity but also dormancy.

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• Kids First: The Genomic Basis of Structural Birth Defects Associated with Chromosome 18 Copy Number Changes

  Chromosome abnormalities are a common cause of structural birth defects. Both childhood cancers and structural birth defects are critical and costly conditions associated with substantial morbidity and mortality. Elucidating the underlying genetic etiology of these diseases has the potential to profoundly improve preventative measures, diagnostics, and therapeutic interventions.However, because these genomic copy number changes involve multiple genes and because most of these conditions are individually rare, defining the specific causative genes behind specific phenotypes has been a challenge. We met that challenge by spending the last 28 years enrolling and evaluating anyone with a chromosome 18 abnormality. The cohort now includes over 700 individuals with a wide variety of chromosome 18 copy number changes (CNV), as well as their parents. Because the vast majority of these participants have individually unique CNVs, we have been able to perform extensive genotype-phenotype correlations resulting in 58 publications. Of the 263 genes on chromosome 18, 28 are linked to specific hemizygous phenotypes. However, most have low penetrance. Genomic sequence data could identify variants in the extant allele that are hypermorphic and compensate for hemizygosity, or are hypomorphic and exacerbate hemizygosity. Additionally, there are phenotypes within this cohort that are rare, or an extreme version of one of the more common phenotypes. Genomic sequence data could help discover new biallelic conditions by revealing functional sequence variants of the extant allele. In both of these cases, there could also be variants in other genes on other chromosomes that may be associated with the phenotype that confer susceptibility or resilience. Inclusion of this unique cohort in the Gabriella Miller Kids First Pediatric Research Program can advance the goals of the program in several ways. First, by adding known susceptibility loci to the existing Kids First cohorts for the structural birth defects that are also found in our cohort. Second, for those structural birth defects known to be polygenetic, this cohort has a single defined risk factor which can simplify the search for secondary factors. Third, these studies can also bring clarity to people with chromosome 18 conditions and help to make the genotype more accurately predict phenotype. This approach could be a model for understanding the many other rare chromosome abnormalities which collectively are a common cause of structural birth defects.

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• Genetic Study of Northern Kenya Pastoral Populations

  Human populations in Africa are the most genetically diverse in the world, having a rich history, and yet are severely understudied. The purpose of this study is to understand the population history of four ethnolinguistic groups in northern Kenya - the Turkana, Samburu, Rendille, and Borana. This study aims to measure the extent of variation among several genetic systems in these populations, with the goal to better understand the broader population history in northern Kenya and to add to the current knowledge of population genetics in Africa.

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