Publications by authors named "Sameer Chavan"

Thyroid diseases are common and highly heritable. Under the Global Biobank Meta-analysis Initiative, we performed a meta-analysis of genome-wide association studies from 19 biobanks for five thyroid diseases: thyroid cancer, benign nodular goiter, Graves' disease, lymphocytic thyroiditis, and primary hypothyroidism. We analyzed genetic association data from ~2.

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Obesity is a major public health crisis associated with high mortality rates. Previous genome-wide association studies (GWAS) investigating body mass index (BMI) have largely relied on imputed data from European individuals. This study leveraged whole-genome sequencing (WGS) data from 88,873 participants from the Trans-Omics for Precision Medicine (TOPMed) Program, of which 51% were of non-European population groups.

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Background: Genetic control of gene expression in asthma-related tissues is not well-characterized, particularly for African-ancestry populations, limiting advancement in our understanding of the increased prevalence and severity of asthma in those populations.

Objective: To create novel transcriptome prediction models for asthma tissues (nasal epithelium and CD4+ T cells) and apply them in transcriptome-wide association study (TWAS) to discover candidate asthma genes.

Methods: We developed and validated gene expression prediction databases for unstimulated CD4+ T cells (CD4+T) and nasal epithelium using an elastic net framework.

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Article Synopsis
  • Asthma shows significant differences in prevalence and characteristics among various ancestral groups, yet the reasons for these disparities are not well understood.
  • The Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) is analyzing genetic information from individuals of African ancestry to identify specific genes related to asthma.
  • In their findings, they discovered 389 differentially expressed genes (DEGs), with key networks linked to immune response and wound healing, revealing three main areas of dysregulation important for understanding asthma within these populations.
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Precision medicine initiatives across the globe have led to a revolution of repositories linking large-scale genomic data with electronic health records, enabling genomic analyses across the entire phenome. Many of these initiatives focus solely on research insights, leading to limited direct benefit to patients. We describe the biobank at the Colorado Center for Personalized Medicine (CCPM Biobank) that was jointly developed by the University of Colorado Anschutz Medical Campus and UCHealth to serve as a unique, dual-purpose research and clinical resource accelerating personalized medicine.

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Context: Thyroid nodule ultrasound-based risk stratification schemas rely on the presence of high-risk sonographic features. However, some malignant thyroid nodules have benign appearance on thyroid ultrasound. New methods for thyroid nodule risk assessment are needed.

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Article Synopsis
  • Obesity poses a significant public health challenge and is linked to high mortality rates, with prior studies focusing mostly on European populations.
  • This research utilized whole-genome sequencing data from a diverse group of 88,873 individuals, finding 18 new signals associated with body mass index (BMI) and highlighting a novel SNP prevalent among people of African descent.
  • The study emphasizes the importance of diverse genetic data in identifying new obesity-related variants, moving us closer to personalized medical interventions for this crisis.
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Biobanks facilitate genome-wide association studies (GWASs), which have mapped genomic loci across a range of human diseases and traits. However, most biobanks are primarily composed of individuals of European ancestry. We introduce the Global Biobank Meta-analysis Initiative (GBMI)-a collaborative network of 23 biobanks from 4 continents representing more than 2.

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Most transcriptome-wide association studies (TWASs) so far focus on European ancestry and lack diversity. To overcome this limitation, we aggregated genome-wide association study (GWAS) summary statistics, whole-genome sequences and expression quantitative trait locus (eQTL) data from diverse ancestries. We developed a new approach, TESLA (multi-ancestry integrative study using an optimal linear combination of association statistics), to integrate an eQTL dataset with a multi-ancestry GWAS.

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  • This study looked at how body size and shape traits, like height and BMI, can be linked to genetics and health problems related to the heart and metabolism.! -
  • Scientists analyzed DNA from over 22,000 people to find genetic connections to these traits and discovered some specific genes that might affect height and BMI.! -
  • They found important results related to height but faced difficulties in identifying the effects of rare genetic variants, which are harder to study but still important for understanding genetics.!
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  • Tobacco and alcohol use contribute significantly to global mortality rates, with heritability playing a key role in these behaviors.
  • This study utilized genetic data from a diverse population of 3.4 million individuals, including 21% non-European ancestry, to identify genetic variants linked to tobacco and alcohol use.
  • Findings showed that while increased genetic diversity improved the identification of genomic loci, polygenic risk scores were less effective across different ancestries, underscoring the need for larger and more diverse genetic datasets for better predictive outcomes.
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  • Common genetic variants account for less variation in complex traits like tobacco use than previously thought, leading to discussions about "missing heritability."
  • A study of over 26,000 individuals of European descent and nearly 12,000 of African descent found that rare genetic variants contribute significantly to the heritability of smoking behaviors.
  • The research revealed that rare variants could explain up to 74% of the heritability estimates for smoking traits, which are much higher than those based on common variants alone.
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  • - Human genetic studies show that shorter leukocyte telomere length (LTL) is linked to a higher risk of coronary artery disease (CAD), while the relationship between LTL and various cancers is less clear.
  • - Clonal hematopoiesis of indeterminate potential (CHIP), which involves the growth of blood cells with certain mutations, increases the risk for both blood cancers and CAD, with telomerase reverse transcriptase being a key genetic factor in CHIP.
  • - Research from the TOPMed program and UK Biobank reveals that longer genetically predicted LTL increases the likelihood of developing CHIP, which then leads to a decrease in measured LTL, providing insights into how these factors might contribute to CAD prevention.
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  • A large-scale GWAS was conducted on leukocyte traits using data from 61,802 individuals of diverse backgrounds, focusing on over 109 million genetic variants.
  • The study identified 7 associations related to leukocyte counts, including a significant variant on chromosome X linked to lower eosinophil counts and variants prevalent in African Americans associated with monocyte and lymphocyte counts.
  • Findings suggest that the discovered eosinophil-lowering variant may reduce the risk of allergic diseases, indicating the importance of diverse samples in uncovering genetic associations often overlooked in studies focusing on European ancestry.
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Background: Total serum IgE (tIgE) is an important intermediate phenotype of allergic disease. Whole genome genetic association studies across ancestries may identify important determinants of IgE.

Objective: We aimed to increase understanding of genetic variants affecting tIgE production across the ancestry and allergic disease spectrum by leveraging data from the National Heart, Lung and Blood Institute Trans-Omics for Precision Medicine program; the Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA); and the Atopic Dermatitis Research Network (N = 21,901).

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  • Researchers examined how well polygenic risk scores (PRSs) can predict the occurrence and severity of atopic dermatitis (AD) by using genetic information.
  • They utilized a dataset of 1,619 European American individuals and included data from related allergic conditions and specific genetic mutations (FLG LOF variants).
  • Results showed that incorporating a broader range of genetic data significantly improved the prediction accuracy for AD and its severity, suggesting PRSs could be a valuable tool in identifying individuals at higher risk for severe AD.
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  • - The study investigates how genetic ancestry influences asthma health disparities, focusing on Peruvian children to see if their ancestry affects asthma severity, total serum IgE levels, and lung function.
  • - Results show that indigenous ancestry (NAT) is linked to higher IgE levels and better lung function, while Iberian ancestry (IBS) is associated with lower IgE levels and poorer lung function in controls.
  • - A significant genetic region on chromosome 6 (HLA-DR/DQ) is linked to asthma and IgE levels, while a novel genetic locus on chromosome 19 related to lung function was found and validated in another group of Brazilian children with asthma.
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Background: Eczema herpeticum (EH) is a rare complication of atopic dermatitis (AD) caused by disseminated herpes simplex virus (HSV) infection. The role of rare and/or deleterious genetic variants in disease etiology is largely unknown. This study aimed to identify genes that harbor damaging genetic variants associated with HSV infection in AD with a history of recurrent eczema herpeticum (ADEH+).

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  • Asthma is a chronic inflammatory disease of the airways, and while studies have looked at its genetic roots, the role of HLA alleles has been underexplored until now.
  • This study focused on a large group of individuals of African ancestry to investigate associations between HLA alleles and asthma-related traits, using advanced computational techniques to analyze genetics.
  • Although no direct association with asthma susceptibility was found, the study identified a specific HLA allele linked to higher total serum IgE levels, highlighting the potential of advanced computational methods in understanding complex genetic associations.
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  • Scientists studied how DNA changes (called methylation) might be linked to a skin condition called atopic dermatitis (AD), especially when it gets worse with a virus (called eczema herpeticum).
  • They looked at blood samples from different groups: people with AD and eczema herpeticum, people with AD without it, and healthy people.
  • The researchers found specific DNA changes that were connected to how severe the skin condition was, especially related to a type of immune cell called eosinophils, suggesting a link between these changes and the body's immune response.
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We identified a strong association between peanut allergy and the locus in LEAP participants in the peanut avoidance group with 58.6% of carriers developing peanut allergy at 60 months as compared to 12.7% of non-carriers.

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  • Asthma affects people differently depending on their race, and there haven't been enough studies on people of African ancestry.
  • A new study looked at data from 7,009 people with asthma and 7,645 without, and found strong links to four previously known gene areas.
  • The study also discovered two new gene areas that might be especially important for asthma risk in people of African ancestry.
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In the version of this article initially published, the statement "there are no pan-genomes for any other animal or plant species" was incorrect. The statement has been corrected to "there are no reported pan-genomes for any other animal species, to our knowledge." We thank David Edwards for bringing this error to our attention.

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We used a deeply sequenced dataset of 910 individuals, all of African descent, to construct a set of DNA sequences that is present in these individuals but missing from the reference human genome. We aligned 1.19 trillion reads from the 910 individuals to the reference genome (GRCh38), collected all reads that failed to align, and assembled these reads into contiguous sequences (contigs).

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