Tracing cell ancestries (i.e., lineages) is fundamental to understanding the principles of development in multicellular organisms and unraveling complex biological processes involving the differentiation of diverse cell types with distinct lineage hierarchies. In humans, direct experimental lineage tracing is not ethically feasible, so researchers must rely on naturally occurring mutations that arise as cells divide and age. Our group has shown that it is possible to reconstruct lineages in normal, noncancerous human cells using natural variations in both nuclear and mitochondrial DNA, drawing on diverse types of genomic data. We are particularly focused on studying cell ancestries ancestry during the earliest stages of human development, including germline lineage tracing across generations. Our work had shed light on how early pre-gastrulation lineages are transmitted and contribute to the ongoing evolution of the human genome. With advances in genomic technologies and analytical methods, the scientific community is approaching a major milestone: the construction of a comprehensive, high-resolution map of human embryonic and fetal cell lineages. We are committed to contributing to this transformative effort including contribution to the SMaHT project.
Single-cell genomics is a powerful approach for studying somatic mosaicism in both healthy tissues and cancer. The genome of an individual cell can be interrogated either through clonal expansion—culturing a single cell to generate a colony—or through in vitro whole-genome amplification (WGA) using polymerases. Although WGA has inherent limitations, it can be applied to any cell type regardless of proliferative potential, making it a broadly applicable strategy for single-cell genomics. Using these approaches, our work investigates somatic mosaicism and its dynamics across development, adulthood, aging, and disease. We have shown that mutations begin to accumulate in the developing human immediately after conception, arising at nearly each cell division and continuing throughout life—such that no two cells in a person are likely to have exactly the same genome.
Mutations that accumulate in DNA throughout an individual’s life give rise to a mosaic body, where each cell carries a unique set of genetic alterations — a phenomenon known as somatic mosaicism. Although somatic mosaicism is widespread, its study has been limited by challenges in detecting such variants, both at the single-cell level and in bulk tissue samples. Recently, our group has developed computational methods to accurately detect somatic mosaic mutations by leveraging deep whole-genome sequencing of human tissue samples. Using this approach, we discovered that in the human brain, certain cells undergo clonal expansion with age, outcompeting their peers and leading to an increased burden of detectable mosaic mutations — a phenomenon we refer to as brain hypermutability. We found that this overgrowth is associated with damaging mutations in cancer driver genes. Our ongoing work focuses on uncovering the origin of this phenomenon and identifying the specific cell type(s) responsible for the clonal expansion.
Copy number variation (CNV) in the genome is a complex phenomenon that remains a vital frontier in genetics. While somatic copy number alterations (CNA) are frequently associated with cancer progression and treatment response, they are also critical drivers in developmental disorders, aging, and various genetic diseases. Our laboratory focuses on the discovery and analysis of these variations to address a wide spectrum of clinical and scientific questions. We have developed and continually improve CNVpytor (CNVnator), widely adopted methods for CNV discovery from whole genome sequencing data. These tools rank among the best in the field and are highly optimized for cloud environments, enabling ultra-low-cost genotyping (as low as $0.03 per sample).
Advances in transcriptomic and epigenomic profiling techniques, including single-cell RNA-seq and ATAC-seq, provide powerful opportunities to study the consequences of genomic variants—both inherited and somatic—particularly in non-coding regions of the genome where their effects remain poorly understood. Our laboratory is focused on elucidating such effects, with an emphasis on variants that contribute to neurodevelopmental disorders such as autism spectrum disorder and Tourette syndrome (TS). Recently, leveraging single-nucleus transcriptomic and open chromatin datasets from the postmortem striatum of adult TS patients and matched controls, we analyzed gene expression and chromatin accessibility across defined cell types. These analyses revealed a reduction in GABAergic and cholinergic interneurons in TS brains. Additional findings suggest that interneuron loss leads to chronic hyperactivity of medium spiny neurons, resulting in metabolic stress, microglial activation, and disruption of basal ganglia homeostasis. Our ongoing work seeks to further define the regulatory landscape of TS using an expanded sample set.
During the past decade, high-throughput next-generation technologies coupled with computational algorithms have enabled us to better understand the biology of cancer as well as the molecular underpinnings of its development and progression. Numerous functionally significant point mutations as well as structural alterations have been identified in several types and subtypes of cancers that illustrate the diverse landscape of the cancer genome. In our laboratory, we focus on the discovery and analysis of somatic point mutations and structural alterations, including deletions, duplications, and copy number changes, in colon cancer and glioma. We are especially interested in understanding the relationship between patterns of genetic alterations and modes of evolution of cancer, as well as molecular differences between cancer-free and cancer-adjacent polyps.
Tourette disorder is characterized by motor hyperactivity and tics that are believed to originate in basal ganglia. Postmortem immunocytochemical analyses previously revealed decreases in cholinergic, parvalbumin, and somatostatin interneurons (IN) within the caudate/putamen of individuals with TS. We obtained transcriptome and open chromatin datasets by snRNAseq and snATAC-seq, respectively, from caudate/putamen postmortem specimens of 6 adult TS and 6 matched normal control (NC). Differential gene expression and differential chromatin accessibility analyses were performed in identified cell types.The data reproduced the known cellular composition of the human striatum, including a majority of medium spiny neurons (MSN) and small populations of GABAergic and cholinergic IN. IN were decreased by ∼50% in TS brains, with no difference in other cell types. Differential gene expression analysis suggested that mitochondrial oxidative metabolism in MSN and synaptic adhesion and function in IN were both decreased in TS subjects, while there was activation of immune response in microglia. Gene expression changes correlated with changes in activity of cis-regulatory elements, suggesting a relationship of transcriptomic and regulatory abnormalities in MSN, OL and AST of TS brains. This initial analysis of the TS basal ganglia transcriptome at the single cell level confirms the loss and synaptic dysfunction of basal ganglia IN, consistent with in vivo basal ganglia hyperactivity. In parallel, oxidative metabolism was decreased in MSN and correlated with activation of microglia cells, attributable at least in part to dysregulated activity of putative enhancers, implicating altered epigenomic regulation in TS.
More: https://www.biologicalpsychiatryjournal.com/article/S0006-3223(25)00064-2/abstract
Little is known about the origin of germ cells in humans. We previously leveraged post-zygotic mutations to reconstruct zygote-rooted cell lineage ancestry trees in a phenotypically normal woman, termed NC0. Here, by sequencing the genome of her children and their father, we analyze the transmission of early pre-gastrulation lineages and corresponding mutations across human generations. We find that the germline in NC0 is polyclonal and is founded by at least two cells likely descending from the two blastomeres arising from the first zygotic cleavage. Analyzes of public data from several multi-children families and from 1934 familial quads confirm this finding in larger cohorts, revealing that known imbalances of up to 90:10 in early lineages allocation in somatic tissues are not reflected in mutation transmission to offspring, establishing a fundamental difference in lineage allocation between the soma and the germline. Analyzes of all the data consistently suggest that the germline has a balanced 50:50 lineage allocation from the first two blastomeres.
More: https://www.nature.com/articles/s41467-024-53485-x
Copy number variation (CNV) and alteration (CNA) analysis is a crucial component in many genomic studies and its applications span from basic research to clinic diagnostics and personalized medicine. CNVpytor is a tool featuring a read depth-based caller and combined read depth and B-allele frequency (BAF) based 2D caller to find CNVs and CNAs. The tool stores processed intermediate data and CNV/CNA calls in a compact HDF5 file—pytor file. Here, we describe a new track in igv.js that utilizes pytor and whole genome variant files as input for on-the-fly read depth and BAF visualization, CNV/CNA calling and analysis. Embedding into HTML pages and Jupiter Notebooks enables convenient remote data access and visualization simplifying interpretation and analysis of omics data.
More: https://academic.oup.com/bioinformatics/article/40/8/btae453/7715874
Regulation of gene expression through enhancers is one of the major processes shaping the structure and function of the human brain during development. High-throughput assays have predicted thousands of enhancers involved in neurodevelopment, and confirming their activity through orthogonal functional assays is crucial. Here, we utilized Massively Parallel Reporter Assays (MPRAs) in stem cells and forebrain organoids to evaluate the activity of ~ 7000 gene-linked enhancers previously identified in human fetal tissues and brain organoids. We used a Gaussian mixture model to evaluate the contribution of background noise in the measured activity signal to confirm the activity of ~ 35% of the tested enhancers, with most showing temporal-specific activity, suggesting their evolving role in neurodevelopment. The temporal specificity was further supported by the correlation of activity with gene expression. Our findings provide a valuable gene regulatory resource to the scientific community.
More: https://www.nature.com/articles/s41598-024-54302-7
ALUMNI:
| 10. | An AP endonuclease 1-DNA polymerase beta complex: theoretical prediction of interacting surfaces. , Uzun A, Strauss PR, Ilyin VA PLoS Comput Biol 2008; 4(4):e1000066 ![]()
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| 1. | Efficiency Profile Method To Study The Hit Efficiency Of Drift Chambers. , Bel'kov A, Lanyov A, Spiridonov A, Walter M, Hulsbergen W Particles and Nuclei, Letters 2002; 5 (114); :40-52 |
Immediatly available
Somatic Mosaicism • Human Development • Aging • Cancer • Cell Lineage
We are is seeking a computational postdoctoral fellow to study somatic mutations and their roles in human development, aging, and disease.
Our lab combines large-scale human genome sequencing with computational and statistical method development to investigate fundamental questions in human biology. We use naturally occurring somatic mutations as markers of cell ancestry, reconstruct developmental cell lineages, study how mutations accumulate and expand during aging, and investigate their contributions to neurological disease and cancer.
The successful candidate will have substantial freedom to shape a project around their interests. Potential directions include:
The lab participates in major collaborative efforts studying somatic variation across human tissues, providing opportunities to work with exceptionally rich genomic datasets and with investigators across computational genomics, human genetics, neuroscience, developmental biology, and medicine.
Our work spans both computational-method development and biological discovery. Recent studies from the lab and our collaborations have addressed human embryonic cell lineage, somatic mutation across tissues, brain mosaicism and neuropsychiatric disease, cancer evolution, and computational methods for detecting genomic variation.
Postdoctoral fellows are encouraged to develop independent scientific directions, lead projects and publications, collaborate broadly, and build a research program that supports their next career step.
We welcome applicants with a Ph.D. or equivalent training in computational biology, bioinformatics, genomics, human genetics, statistics, computer science, or a related quantitative field.
Strong candidates will have:
Prior expertise in somatic mosaicism is not required. Experience in human genetics, statistical genomics, cancer genomics, single-cell genomics, structural variation, algorithm development, or machine learning is particularly welcome.
More information about our research and publications is available at abyzovlab.org.
Please send a CV, including your publication record and contact information for three references, to abyzov.alexej@mayo.edu.
In your email, briefly describe the scientific questions that interest you and how your background could contribute to or expand the research directions of the lab.
Please include “Postdoc application – [Your Name]” in the subject line.
application accepted year-round
Applications are invited for an internship at the Mayo Clinic. Anticipated projects will be related to the analysis of whole genome sequencing data, with the aims of studying germline and somatic variants (SNPs, CNVs, etc.). The analysis will involve applications of commonly used, and in-house developed, software tools, and making biological hypothesis from statistical data analysis. Intern applicants with strong programming skills will have opportunities to participate in developing new tools and improving our existing software.
To apply, please email your CV, including a list of publications to abyzov dot alexej at mayo dot edu. Please include the phrase “Internship application” and your full name in the subject of the email.