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2.
Front Immunol ; 15: 1342625, 2024.
Article in English | MEDLINE | ID: mdl-38449858

ABSTRACT

Introduction: Despite aggressive standard-of-care therapy, including surgery, radiation, and chemotherapy, glioblastoma recurrence is almost inevitable and uniformly lethal. Activation of glioma-intrinsic Wnt/ß-catenin signaling is associated with a poor prognosis and the proliferation of glioma stem-like cells, leading to malignant transformation and tumor progression. Impressive results in a subset of cancers have been obtained using immunotherapies including anti-CTLA4, anti-PD-1, and anti-PD-L1 or chimeric antigen receptor (CAR) T cell therapies. However, the heterogeneity of tumors, low mutational burden, single antigen targeting, and associated antigen escape contribute to non-responsiveness and potential tumor recurrence despite these therapeutic efforts. In the current study, we determined the effects of the small molecule, highly specific Wnt/CBP (CREB Binding Protein)/ß-catenin antagonist ICG-001, on glioma tumor cells and the tumor microenvironment (TME)-including its effect on immune cell infiltration, blood vessel decompression, and metabolic changes. Methods: Using multiple glioma patient-derived xenografts cell lines and murine tumors (GL261, K-Luc), we demonstrated in vitro cytostatic effects and a switch from proliferation to differentiation after treatment with ICG-001. Results: In these glioma cell lines, we further demonstrated that ICG-001 downregulated the CBP/ß-catenin target gene Survivin/BIRC5-a hallmark of Wnt/CBP/ß-catenin inhibition. We found that in a syngeneic mouse model of glioma (K-luc), ICG-001 treatment enhanced tumor infiltration by CD3+ and CD8+ cells with increased expression of the vascular endothelial marker CD31 (PECAM-1). We also observed differential gene expression and induced immune cell infiltration in tumors pretreated with ICG-001 and then treated with CAR T cells as compared with single treatment groups or when ICG-001 treatment was administered after CAR T cell therapy. Discussion: We conclude that specific Wnt/CBP/ß-catenin antagonism results in pleotropic changes in the glioma TME, including glioma stem cell differentiation, modulation of the stroma, and immune cell activation and recruitment, thereby suggesting a possible role for enhancing immunotherapy in glioma patients.


Subject(s)
Glioma , beta Catenin , Humans , Animals , Mice , Wnt Signaling Pathway , Neoplasm Recurrence, Local , Immunotherapy , Glioma/therapy , Tumor Microenvironment
3.
Nat Genet ; 56(4): 595-604, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38548990

ABSTRACT

Common genetic variants confer substantial risk for chronic lung diseases, including pulmonary fibrosis. Defining the genetic control of gene expression in a cell-type-specific and context-dependent manner is critical for understanding the mechanisms through which genetic variation influences complex traits and disease pathobiology. To this end, we performed single-cell RNA sequencing of lung tissue from 66 individuals with pulmonary fibrosis and 48 unaffected donors. Using a pseudobulk approach, we mapped expression quantitative trait loci (eQTLs) across 38 cell types, observing both shared and cell-type-specific regulatory effects. Furthermore, we identified disease interaction eQTLs and demonstrated that this class of associations is more likely to be cell-type-specific and linked to cellular dysregulation in pulmonary fibrosis. Finally, we connected lung disease risk variants to their regulatory targets in disease-relevant cell types. These results indicate that cellular context determines the impact of genetic variation on gene expression and implicates context-specific eQTLs as key regulators of lung homeostasis and disease.


Subject(s)
Pulmonary Fibrosis , Quantitative Trait Loci , Humans , Quantitative Trait Loci/genetics , Pulmonary Fibrosis/genetics , Gene Expression Regulation/genetics , Lung , Multifactorial Inheritance , Genome-Wide Association Study/methods , Polymorphism, Single Nucleotide
5.
Nat Med ; 30(4): 1001-1012, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38454126

ABSTRACT

Chimeric antigen receptor T cell (CAR-T) therapy is an emerging strategy to improve treatment outcomes for recurrent high-grade glioma, a cancer that responds poorly to current therapies. Here we report a completed phase I trial evaluating IL-13Rα2-targeted CAR-T cells in 65 patients with recurrent high-grade glioma, the majority being recurrent glioblastoma (rGBM). Primary objectives were safety and feasibility, maximum tolerated dose/maximum feasible dose and a recommended phase 2 dose plan. Secondary objectives included overall survival, disease response, cytokine dynamics and tumor immune contexture biomarkers. This trial evolved to evaluate three routes of locoregional T cell administration (intratumoral (ICT), intraventricular (ICV) and dual ICT/ICV) and two manufacturing platforms, culminating in arm 5, which utilized dual ICT/ICV delivery and an optimized manufacturing process. Locoregional CAR-T cell administration was feasible and well tolerated, and as there were no dose-limiting toxicities across all arms, a maximum tolerated dose was not determined. Probable treatment-related grade 3+ toxicities were one grade 3 encephalopathy and one grade 3 ataxia. A clinical maximum feasible dose of 200 × 106 CAR-T cells per infusion cycle was achieved for arm 5; however, other arms either did not test or achieve this dose due to manufacturing feasibility. A recommended phase 2 dose will be refined in future studies based on data from this trial. Stable disease or better was achieved in 50% (29/58) of patients, with two partial responses, one complete response and a second complete response after additional CAR-T cycles off protocol. For rGBM, median overall survival for all patients was 7.7 months and for arm 5 was 10.2 months. Central nervous system increases in inflammatory cytokines, including IFNγ, CXCL9 and CXCL10, were associated with CAR-T cell administration and bioactivity. Pretreatment intratumoral CD3 T cell levels were positively associated with survival. These findings demonstrate that locoregional IL-13Rα2-targeted CAR-T therapy is safe with promising clinical activity in a subset of patients. ClinicalTrials.gov Identifier: NCT02208362 .


Subject(s)
Glioblastoma , Glioma , Receptors, Chimeric Antigen , Humans , Neoplasm Recurrence, Local , Glioma/therapy , T-Lymphocytes , Glioblastoma/therapy , Immunotherapy, Adoptive/adverse effects , Immunotherapy, Adoptive/methods
6.
Am J Bioeth ; : 1-14, 2023 Nov 27.
Article in English | MEDLINE | ID: mdl-38010648

ABSTRACT

Harms and risks to groups and third-parties can be significant in the context of research, particularly in data-centric studies involving genomic, artificial intelligence, and/or machine learning technologies. This article explores whether and how United States federal regulations should be adapted to better align with current ethical thinking and protect group interests. Three aspects of the Common Rule deserve attention and reconsideration with respect to group interests: institutional review board (IRB) assessment of the risks/benefits of research; disclosure requirements in the informed consent process; and criteria for waivers of informed consent. In accordance with respect for persons and communities, investigators and IRBs should systematically consider potential group harm when designing and reviewing protocols, respectively. Research participants should be informed about any potential group harm in the consent process. We call for additional public discussion, empirical research, and normative analysis on these issues to determine the right regulatory and policy path forward.

7.
Cureus ; 15(8): e44388, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37779815

ABSTRACT

INTRODUCTION: Autistic individuals, now representing one in 36 individuals in the U.S., experience disproportionate physical health challenges relative to non-autistic individuals. The Health Resources and Services Administration's (HRSA) Autism Intervention Research Network on Physical Health (AIR-P) is an interdisciplinary, multi-center Research Network that aims to increase the health, well-being, and quality of life of autistic individuals. The current paper builds on the initial AIR-P Research Agenda (proposed in Year 1) and provides an updated vision for the Network. METHODS: Updates to the Research Agenda were made via the administration of a Qualtrics survey, and disseminated widely to all AIR-P entities, including the Research Node Leaders, Steering Committee, Autistic Researcher Review Board, and collaborating academic and non-academic entities. Network members were tasked with evaluating the Year 1 Research Agenda and proposing additional priorities. RESULTS: Within each Research Node, all Year 1 priorities were endorsed as continued priorities for research on autism and physical health. Specific topics, including co-occurring conditions and self-determination, advocacy, and decision-making, were particularly endorsed. Opportunities for exploratory studies and intervention research were identified across Research Nodes. Qualitative responses providing feedback on additional research priorities were collected. CONCLUSION: The updated AIR-P Research Agenda represents an important step toward enacting large-scale health promotion efforts for autistic individuals across the lifespan. This updated agenda builds on efforts to catalyze autism research in historically underrepresented topic areas while adopting a neurodiversity-oriented approach to health promotion.

8.
Eur J Med Genet ; 66(9): 104810, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37478903

ABSTRACT

Equitable and just genetic research and clinical translation require an examination of the ethical questions pertaining to vulnerable and marginalized communities. Autism research and advocate communities have expressed concerns over current practices of genetics research, urging the field to shift towards paradigms and practices that ensure benefits and avoid harm to research participants and the wider autistic community. Building upon a framework of bioethical principles, we provide the background for the concerns and present recommendations for ethically sustainable and justice-oriented genetic and genomic autism research. With the primary goal of enhancing the health, well-being, and autonomy of autistic persons, we make recommendations to guide priority setting, responsible research conduct, and informed consent practices. Further, we discuss the ethical challenges particularly pertaining to research involving highly vulnerable individuals and groups, such as those with impaired cognitive or communication ability. Finally, we consider the clinical translation of autism genetics studies, including the use of genetic testing. These guidelines, developed by an interdisciplinary working group comprising autistic and non-autistic individuals, will aid in leveraging the potential of genetics research to enhance the quality of life of autistic individuals and are widely applicable across stigmatized traits and vulnerable communities.


Subject(s)
Autistic Disorder , Humans , Autistic Disorder/genetics , Quality of Life , Informed Consent , Genetic Testing , Genomics
10.
bioRxiv ; 2023 Jun 29.
Article in English | MEDLINE | ID: mdl-36993211

ABSTRACT

Common genetic variants confer substantial risk for chronic lung diseases, including pulmonary fibrosis (PF). Defining the genetic control of gene expression in a cell-type-specific and context-dependent manner is critical for understanding the mechanisms through which genetic variation influences complex traits and disease pathobiology. To this end, we performed single-cell RNA-sequencing of lung tissue from 67 PF and 49 unaffected donors. Employing a pseudo-bulk approach, we mapped expression quantitative trait loci (eQTL) across 38 cell types, observing both shared and cell type-specific regulatory effects. Further, we identified disease-interaction eQTL and demonstrated that this class of associations is more likely to be cell-type specific and linked to cellular dysregulation in PF. Finally, we connected PF risk variants to their regulatory targets in disease-relevant cell types. These results indicate that cellular context determines the impact of genetic variation on gene expression, and implicates context-specific eQTL as key regulators of lung homeostasis and disease.

11.
Am J Hum Genet ; 109(1): 50-65, 2022 01 06.
Article in English | MEDLINE | ID: mdl-34919805

ABSTRACT

Lack of diversity in human genomics limits our understanding of the genetic underpinnings of complex traits, hinders precision medicine, and contributes to health disparities. To map genetic effects on gene regulation in the underrepresented Indonesian population, we have integrated genotype, gene expression, and CpG methylation data from 115 participants across three island populations that capture the major sources of genomic diversity in the region. In a comparison with European datasets, we identify eQTLs shared between Indonesia and Europe as well as population-specific eQTLs that exhibit differences in allele frequencies and/or overall expression levels between populations. By combining local ancestry and archaic introgression inference with eQTLs and methylQTLs, we identify regulatory loci driven by modern Papuan ancestry as well as introgressed Denisovan and Neanderthal variation. GWAS colocalization connects QTLs detected here to hematological traits, and further comparison with European datasets reflects the poor overall transferability of GWAS statistics across diverse populations. Our findings illustrate how population-specific genetic architecture, local ancestry, and archaic introgression drive variation in gene regulation across genetically distinct and in admixed populations and highlight the need for performing association studies on non-European populations.


Subject(s)
Gene Expression Regulation , Genetics, Population , Genome, Human , Quantitative Trait Loci , Computational Biology/methods , DNA Methylation , Databases, Genetic , Genome-Wide Association Study , Genomics/methods , High-Throughput Nucleotide Sequencing , Humans , Indonesia , Male , Models, Genetic , Molecular Sequence Annotation , Multifactorial Inheritance , Quantitative Trait, Heritable , Selection, Genetic , Whole Genome Sequencing
12.
PLoS One ; 16(6): e0252457, 2021.
Article in English | MEDLINE | ID: mdl-34111141

ABSTRACT

In diploid cells, the paternal and maternal alleles are, on average, equally expressed. There are exceptions from this: a small number of genes express the maternal or paternal allele copy exclusively. This phenomenon, known as genomic imprinting, is common among eutherian mammals and some plant species; however, genomic imprinting in species with haplodiploid sex determination is not well characterized. Previous work reported no parent-of-origin effects in the hybrids of closely related haplodiploid Nasonia vitripennis and Nasonia giraulti jewel wasps, suggesting a lack of epigenetic reprogramming during embryogenesis in these species. Here, we replicate the gene expression dataset and observations using different individuals and sequencing technology, as well as reproduce these findings using the previously published RNA sequence data following our data analysis strategy. The major difference from the previous dataset is that they used an introgression strain as one of the parents and we found several loci that resisted introgression in that strain. Our results from both datasets demonstrate a species-of-origin effect, rather than a parent-of-origin effect. We present a reproducible workflow that others may use for replicating the results. Overall, we reproduced the original report of no parent-of-origin effects in the haplodiploid Nasonia using the original data with our new processing and analysis pipeline and replicated these results with our newly generated data.


Subject(s)
Wasps/genetics , Alleles , Animals , Female , Genomic Imprinting/genetics , Genomic Imprinting/physiology , Male
13.
Nature ; 593(7858): 238-243, 2021 05.
Article in English | MEDLINE | ID: mdl-33828297

ABSTRACT

Genome-wide association studies (GWAS) have identified thousands of noncoding loci that are associated with human diseases and complex traits, each of which could reveal insights into the mechanisms of disease1. Many of the underlying causal variants may affect enhancers2,3, but we lack accurate maps of enhancers and their target genes to interpret such variants. We recently developed the activity-by-contact (ABC) model to predict which enhancers regulate which genes and validated the model using CRISPR perturbations in several cell types4. Here we apply this ABC model to create enhancer-gene maps in 131 human cell types and tissues, and use these maps to interpret the functions of GWAS variants. Across 72 diseases and complex traits, ABC links 5,036 GWAS signals to 2,249 unique genes, including a class of 577 genes that appear to influence multiple phenotypes through variants in enhancers that act in different cell types. In inflammatory bowel disease (IBD), causal variants are enriched in predicted enhancers by more than 20-fold in particular cell types such as dendritic cells, and ABC achieves higher precision than other regulatory methods at connecting noncoding variants to target genes. These variant-to-function maps reveal an enhancer that contains an IBD risk variant and that regulates the expression of PPIF to alter the membrane potential of mitochondria in macrophages. Our study reveals principles of genome regulation, identifies genes that affect IBD and provides a resource and generalizable strategy to connect risk variants of common diseases to their molecular and cellular functions.


Subject(s)
Enhancer Elements, Genetic/genetics , Genetic Predisposition to Disease , Genetic Variation/genetics , Genome, Human/genetics , Genome-Wide Association Study , Inflammatory Bowel Diseases/genetics , Cell Line , Chromosomes, Human, Pair 10/genetics , Cyclophilins/genetics , Dendritic Cells , Female , Humans , Macrophages/metabolism , Male , Mitochondria/metabolism , Organ Specificity/genetics , Phenotype
14.
J Comput Biol ; 28(3): 296-303, 2021 03.
Article in English | MEDLINE | ID: mdl-33074720

ABSTRACT

Germline genetic variation contributes to cancer etiology, but self-reported race is not always consistent with genetic ancestry, and samples may not have identifying ancestry information. In this study, we describe a flexible computational pipeline, PopInf, to visualize principal component analysis output and assign ancestry to samples with unknown genetic ancestry, given a reference population panel of known origins. PopInf is implemented as a reproducible workflow in Snakemake with a tutorial on GitHub. We provide a preprocessed reference population panel that can be quickly and efficiently implemented in cancer genetics studies. We ran PopInf on The Cancer Genome Atlas (TCGA) liver cancer data and identify discrepancies between reported race and inferred genetic ancestry. The PopInf pipeline facilitates visualization and identification of genetic ancestry across samples, so that this ancestry can be accounted for in studies of disease risk.


Subject(s)
Genetics, Population/methods , Genomics/methods , Genetic Variation/genetics , Genome-Wide Association Study/methods , Humans , Neoplasms/genetics , Principal Component Analysis/methods , Reproducibility of Results , Software
15.
PLoS Genet ; 16(5): e1008749, 2020 05.
Article in English | MEDLINE | ID: mdl-32453742

ABSTRACT

Indonesia is the world's fourth most populous country, host to striking levels of human diversity, regional patterns of admixture, and varying degrees of introgression from both Neanderthals and Denisovans. However, it has been largely excluded from the human genomics sequencing boom of the last decade. To serve as a benchmark dataset of molecular phenotypes across the region, we generated genome-wide CpG methylation and gene expression measurements in over 100 individuals from three locations that capture the major genomic and geographical axes of diversity across the Indonesian archipelago. Investigating between- and within-island differences, we find up to 10.55% of tested genes are differentially expressed between the islands of Sumba and New Guinea. Variation in gene expression is closely associated with DNA methylation, with expression levels of 9.80% of genes correlating with nearby promoter CpG methylation, and many of these genes being differentially expressed between islands. Genes identified in our differential expression and methylation analyses are enriched in pathways involved in immunity, highlighting Indonesia's tropical role as a source of infectious disease diversity and the strong selective pressures these diseases have exerted on humans. Finally, we identify robust within-island variation in DNA methylation and gene expression, likely driven by fine-scale environmental differences across sampling sites. Together, these results strongly suggest complex relationships between DNA methylation, transcription, archaic hominin introgression and immunity, all jointly shaped by the environment. This has implications for the application of genomic medicine, both in critically understudied Indonesia and globally, and will allow a better understanding of the interacting roles of genomic and environmental factors shaping molecular and complex phenotypes.


Subject(s)
DNA Methylation , Ethnicity/genetics , Gene-Environment Interaction , Transcriptome , CpG Islands , Environment , Epigenesis, Genetic/physiology , Ethnicity/statistics & numerical data , Gene Expression Profiling/statistics & numerical data , Genetics, Population , Genome-Wide Association Study/statistics & numerical data , Genomics/methods , Humans , Indonesia/epidemiology , Islands/epidemiology , Pacific Islands/epidemiology , Pedigree , Phenotype , Polymorphism, Single Nucleotide , RNA-Seq
16.
Front Immunol ; 10: 2799, 2019.
Article in English | MEDLINE | ID: mdl-31849976

ABSTRACT

A low percentage of actinic keratoses progress to develop into cutaneous squamous cell carcinoma. The immune mechanisms that successfully control or eliminate the majority of actinic keratoses and the mechanisms of immune escape by invasive squamous cell carcinoma are not well-understood. Here, we took a systematic approach to evaluate the neoantigens present in actinic keratosis and cutaneous squamous cell carcinoma specimens. We compared the number of mutations, the number of neoantigens predicted to bind MHC class I, and the number of neoantigens that are predicted to bind MHC class I and be recognized by a T cell receptor in actinic keratoses and cutaneous squamous cell carcinomas. We also considered the relative binding strengths to both MHC class I and the T cell receptor in a fitness cost model that allows for a comparison of the immune recognition potential of the neoantigens in actinic keratosis and cutaneous squamous cell carcinoma samples. The fitness cost was subsequently adjusted by the expression rates of the neoantigens to examine the role of neoantigen expression in tumor immune evasion. Our analyses indicate that, while the number of mutations and neoantigens are not significantly different between actinic keratoses and cutaneous squamous cell carcinomas, the predicted immune recognition of the neoantigen with the highest expression-adjusted fitness cost is lower for cutaneous squamous cell carcinomas compared with actinic keratoses. These findings suggest a role for the down-regulation of expression of highly immunogenic neoantigens in the immune escape of cutaneous squamous cell carcinomas. Furthermore, these findings highlight the importance of incorporating additional factors, such as the quality and expression of the neoantigens, rather than focusing solely on tumor mutational burden, in assessing immune recognition potential.


Subject(s)
Antigens, Neoplasm/immunology , Biomarkers, Tumor , Carcinoma, Squamous Cell/etiology , Disease Susceptibility , Keratosis, Actinic/etiology , Skin Neoplasms/etiology , Algorithms , Disease Susceptibility/immunology , Epitope Mapping , Epitopes/immunology , HLA Antigens/genetics , HLA Antigens/immunology , Histocompatibility Testing , Humans , Lymphocytes, Tumor-Infiltrating/immunology , Lymphocytes, Tumor-Infiltrating/metabolism , Lymphocytes, Tumor-Infiltrating/pathology , Models, Biological , Mutation , Exome Sequencing
17.
BMC Cancer ; 19(1): 951, 2019 Oct 15.
Article in English | MEDLINE | ID: mdl-31615477

ABSTRACT

BACKGROUND: Sex-differences in cancer occurrence and mortality are evident across tumor types; men exhibit higher rates of incidence and often poorer responses to treatment. Targeted approaches to the treatment of tumors that account for these sex-differences require the characterization and understanding of the fundamental biological mechanisms that differentiate them. Hepatocellular Carcinoma (HCC) is the second leading cause of cancer death worldwide, with the incidence rapidly rising. HCC exhibits a male-bias in occurrence and mortality, but previous studies have failed to explore the sex-specific dysregulation of gene expression in HCC. METHODS: Here, we characterize the sex-shared and sex-specific regulatory changes in HCC tumors in the TCGA LIHC cohort using combined and sex-stratified differential expression and eQTL analyses. RESULTS: By using a sex-specific differential expression analysis of tumor and tumor-adjacent samples, we uncovered etiologically relevant genes and pathways differentiating male and female HCC. While both sexes exhibited activation of pathways related to apoptosis and cell cycle, males and females differed in the activation of several signaling pathways, with females showing PPAR pathway enrichment while males showed PI3K, PI3K/AKT, FGFR, EGFR, NGF, GF1R, Rap1, DAP12, and IL-2 signaling pathway enrichment. Using eQTL analyses, we discovered germline variants with differential effects on tumor gene expression between the sexes. 24.3% of the discovered eQTLs exhibit differential effects between the sexes, illustrating the substantial role of sex in modifying the effects of eQTLs in HCC. The genes that showed sex-specific dysregulation in tumors and those that harbored a sex-specific eQTL converge in clinically relevant pathways, suggesting that the molecular etiologies of male and female HCC are partially driven by differential genetic effects on gene expression. CONCLUSIONS: Sex-stratified analyses detect sex-specific molecular etiologies of HCC. Overall, our results provide new insight into the role of inherited genetic regulation of transcription in modulating sex-differences in HCC etiology and provide a framework for future studies on sex-biased cancers.


Subject(s)
Carcinoma, Hepatocellular/epidemiology , Carcinoma, Hepatocellular/genetics , Liver Neoplasms/epidemiology , Liver Neoplasms/genetics , Aged , Biomarkers, Tumor/genetics , Cohort Studies , Female , Gene Expression Regulation, Neoplastic/genetics , Gene Frequency/genetics , Genes, Neoplasm/genetics , Genotype , Humans , Incidence , Male , Middle Aged , Sex Factors , Signal Transduction/genetics , Transcriptome/genetics
18.
Nat Commun ; 10(1): 145, 2019 01 11.
Article in English | MEDLINE | ID: mdl-30635564

ABSTRACT

Sex determination is a fundamentally important and highly diversified biological process, yet the mechanisms behind the origin of this diversity are mostly unknown. Here we suggest that the evolution of sex determination systems can be driven by a chromosomal inversion. We show that an XY system evolved recently in particular nine-spined stickleback (Pungitius pungitius) populations, which arose from ancient hybridization between two divergent lineages. Our phylogenetic and genetic mapping analyses indicate that the XY system is formed in a large inversion that is associated with hybrid sterility between the divergent lineages. We suggest that a new male-determining gene evolved in the inversion in response to selection against impaired male fertility in a hybridized population. Given that inversions are often associated with hybrid incompatibility in animals and plants, they might frequently contribute to the diversification of sex determination systems.


Subject(s)
Chromosome Inversion/genetics , Sex Chromosomes/genetics , Sex Determination Processes/genetics , Smegmamorpha/genetics , Animals , Biological Evolution , Chromosome Mapping , Evolution, Molecular , Female , Fertility/genetics , Male , Phylogeny , Quantitative Trait Loci/genetics , Smegmamorpha/physiology
19.
Mol Biol Evol ; 30(5): 1131-44, 2013 May.
Article in English | MEDLINE | ID: mdl-23436913

ABSTRACT

Recombination suppression leads to the structural and functional differentiation of sex chromosomes and is thus a crucial step in the process of sex chromosome evolution. Despite extensive theoretical work, the exact processes and mechanisms of recombination suppression and differentiation are not well understood. In threespine sticklebacks (Gasterosteus aculeatus), a different sex chromosome system has recently evolved by a fusion between the Y chromosome and an autosome in the Japan Sea lineage, which diverged from the ancestor of other lineages approximately 2 Ma. We investigated the evolutionary dynamics and differentiation processes of sex chromosomes based on comparative analyses of these divergent lineages using 63 microsatellite loci. Both chromosome-wide differentiation patterns and phylogenetic inferences with X and Y alleles indicated that the ancestral sex chromosomes were extensively differentiated before the divergence of these lineages. In contrast, genetic differentiation appeared to have proceeded only in a small region of the neo-sex chromosomes. The recombination maps constructed for the Japan Sea lineage indicated that recombination has been suppressed or reduced over a large region spanning the ancestral and neo-sex chromosomes. Chromosomal regions exhibiting genetic differentiation and suppressed or reduced recombination were detected continuously and sequentially in the neo-sex chromosomes, suggesting that differentiation has gradually spread from the fusion point following the extension of recombination suppression. Our study illustrates an ongoing process of sex chromosome differentiation, providing empirical support for the theoretical model postulating that recombination suppression and differentiation proceed in a gradual manner in the very early stage of sex chromosome evolution.


Subject(s)
Sex Chromosomes/genetics , Smegmamorpha/genetics , X Chromosome/genetics , Y Chromosome/genetics , Animals , Evolution, Molecular , Female , Heterozygote , Male , Phylogeny , Recombination, Genetic/genetics , Smegmamorpha/classification
20.
BMC Genomics ; 12: 474, 2011 Sep 29.
Article in English | MEDLINE | ID: mdl-21958112

ABSTRACT

BACKGROUND: Studies of closely related species with different sex chromosome systems can provide insights into the processes of sex chromosome differentiation and evolution. To investigate the potential utility of molecular markers in studying sex chromosome differentiation at early stages of their divergence, we examined the levels and patterns of genetic differentiation between sex chromosomes in nine-spined (Pungitius pungitius) and three-spined sticklebacks (Gasterosteus aculeatus) using microsatellite markers. RESULTS: A set of novel microsatellite markers spanning the entire length of the sex chromosomes were developed for nine-spined sticklebacks using the sequenced genomes of other fish species. Sex-specific patterns of genetic variability and male-specific alleles were identified at most of these loci, indicating a high degree of differentiation between the X and Y chromosomes in nine-spined sticklebacks. In three-spined sticklebacks, male-specific alleles were detected at some loci confined to two chromosomal regions. In addition, male-specific null alleles were identified at several other loci, implying the absence of Y chromosomal alleles at these loci. Overall, male-specific alleles and null alleles were found over a region spanning 81% of the sex chromosomes in three-spined sticklebacks. CONCLUSIONS: High levels but distinct patterns of sex chromosome differentiation were uncovered in the stickleback species that diverged 13 million years ago. Our results suggest that the Y chromosome is highly degenerate in three-spined sticklebacks, but not in nine-spined sticklebacks. In general, the results demonstrate that microsatellites can be useful in identifying the degree and patterns of sex chromosome differentiation in species at initial stages of sex chromosome evolution.


Subject(s)
Sex Chromosomes , Smegmamorpha/genetics , Alleles , Animals , Evolution, Molecular , Female , Genetic Loci , Genetic Variation , Heterozygote , Male , Microsatellite Repeats
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