Epigenetics Podcast

Genome-Wide Investigation of Epigenetic Marks and Nucleosome Positioning (Keji Zhao)

In this episode of the Epigenetics Podcast, we caught up with Dr. Keji Zhao from the National Heart, Lung, and Blood Institute at the National Institutes of Health in Bethesda, MD, to talk about his work on the genome-wide investigation of epigenetic marks and nucleosome positioning.
Dr. Keji Zhao pioneered in the development of cutting-edge techniques in the field of epigenetics. Current methods at that time relied on DNA microarrays, however, Dr. Zhao wanted a more comprehensive and unbiased approach that would avoid the shortfalls of these array-based methods. Hence, he set out to develop new sequencing-based methods like ChIP-Seq and MNase-Seq with accompanying computational methods to analyze the huge amount of sequencing data that would be generated.
Using the above-mentioned techniques, Dr. Zhao was able to show that histone deacetylases (HDACs) and histone acetyltransferases (HATs) were found at inactive and active genes, respectively, as previously thought. Surprisingly, he was also able to show that HDACs were also located at active genes. Furthermore, both, HATs and HDACs can be found at low levels at silenced genes.
In this episode we discuss the story behind how Dr. Keji Zhao was one of the pioneers of the chromatin immunoprecipitation technology, how he discovered the genomic locations of HATs and HDACs, and in the end he shares some tips and tricks on how to get the best results in ChIP-Seq assays.
 
References
Artem Barski, Suresh Cuddapah, … Keji Zhao (2007) High-resolution profiling of histone methylations in the human genome (Cell) DOI: 10.1016/j.cell.2007.05.009
Dustin E. Schones, Kairong Cui, … Keji Zhao (2008) Dynamic regulation of nucleosome positioning in the human genome (Cell) DOI: 10.1016/j.cell.2008.02.022
Zhibin Wang, Chongzhi Zang, … Keji Zhao (2009) Genome-wide mapping of HATs and HDACs reveals distinct functions in active and inactive genes (Cell) DOI: 10.1016/j.cell.2009.06.049
Wenfei Jin, Qingsong Tang, … Keji Zhao (2015) Genome-wide detection of DNase I hypersensitive sites in single cells and FFPE tissue samples (Nature) DOI: 10.1038/nature15740
Binbin Lai, Weiwu Gao, … Keji Zhao (2018) Principles of nucleosome organization revealed by single-cell micrococcal nuclease sequencing (Nature) DOI: 10.1038/s41586-018-0567-3
Related Episodes
In Vivo Nucleosome Structure and Dynamics (Srinivas Ramachandran)
Development of Site-Specific ChIP Technologies (Hodaka Fujii)
Multiple Challenges in ChIP (Adam Blattler)
 
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The Role of lncRNAs in Tumor Growth and Treatment (Sarah Diermeier)

In this episode of the Epigenetics Podcast, we caught up with Dr. Sarah Diermeier from the University of Otago in New Zealand to talk about her work on the role of long non-coding RNAs in tumor growth and treatment.
Although only 1-2% of the human genome is transcribed into mRNAs that code for proteins, 75% of the genome is transcribed into non-coding RNAs. The function of these non-coding RNAs lie in the regulation of cellular processes and hence, offer the possibility of therapeutic intervention. Dr. Diermeier and her laboratory focus on a subset of these non-coding RNAs: the long non-coding RNAs (lncRNAs) that have been shown to play a role in breast and colorectal cancers.
This interview discusses how the Diermeier lab uses state-of-the-art techniques to both answer fundamental questions about biological mechanisms and also for translational research approaches. We also touch upon Dr. Diermeier becoming mother during her first years being a PI and the challenges and opportunities faced while raising a child and running a lab, and how the University of Otago and the State of New Zealand support young mothers in science.
This episode also tells the stories behind how Dr. Sarah Diermeier ended up in New Zealand, how her childhood influenced her career path, the role of lncRNAs in cancer, and how she deals with being a young PI and a mother at the same time.
 
References
R. Gualdi, P. Bossard, … K. S. Zaret (1996) Hepatic specification of the gut endoderm in vitro: cell signaling and transcriptional control (Genes & Development) DOI: 10.1101/gad.10.13.1670
L. A. Cirillo, C. E. McPherson, … K. S. Zaret (1998) Binding of the winged-helix transcription factor HNF3 to a linker histone site on the nucleosome (The EMBO journal) DOI: 10.1093/emboj/17.1.244
Lisa Ann Cirillo, Frank Robert Lin, … Kenneth S. Zaret (2002) Opening of compacted chromatin by early developmental transcription factors HNF3 (FoxA) and GATA-4 (Molecular Cell) DOI: 10.1016/s1097-2765(02)00459-8 
Related Episodes
Chromatin Structure and Dynamics at Ribosomal RNA Genes (Tom Moss)
The Role of Small RNAs in Transgenerational Inheritance in C. elegans (Oded Rechavi)
Influence of Dynamic RNA Methylation on Gene Expression (Chuan He)
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Unraveling Mechanisms of Chromosome Formation (Job Dekker)

In this episode of the Epigenetics Podcast, we caught up with Job Dekker from the University of Massachusetts Medical School to talk about his work on unraveling mechanisms of chromosome formation.
In 2002, during graduate school, Job Dekker was the first author on the paper describing the chromosome conformation capture (3C) method, which revolutionized the field of nuclear architecture. In the 3C protocol, chromatin is crosslinked using formaldehyde and then digested using a restriction enzyme. After ligating the digested blunt ends of crosslinked DNA fragments together they can be analyzed using qPCR. In the next couple of years 3C was further developed and methods like 4C, 5C, and Hi-C were published. This led to the generation of genome-wide contact maps which helped understand the 3-D organization of the nucleus.
Job Dekker’s research group is also part of the 4D Nucleome initiative, which is dedicated to understanding the structure of the human genome. More recent work of the lab includes analyzing interactions between and along sister chromatids with a method called SisterC and expanding their research to organisms like dinoflagellates to learn more about the basic organization principles of the genome.
In this episode, we discuss the story behind the idea of the chromosome conformation capture method, how close Job Dekker was to giving up on it, how the 3C methods evolved, the importance of data visualization, and we touch on parts of his current work on dinoflagellates.
 
References
Job Dekker, Karsten Rippe, … Nancy Kleckner (2002) Capturing Chromosome Conformation (Science) DOI: 10.1126/science.1067799
Josée Dostie, Todd A. Richmond, … Job Dekker (2006) Chromosome Conformation Capture Carbon Copy (5C): A massively parallel solution for mapping interactions between genomic elements (Genome Research) DOI: 10.1101/gr.5571506
Erez Lieberman-Aiden, Nynke L. van Berkum, … Job Dekker (2009) Comprehensive Mapping of Long-Range Interactions Reveals Folding Principles of the Human Genome (Science) DOI: 10.1126/science.1181369
Amartya Sanyal, Bryan R. Lajoie, … Job Dekker (2012) The long-range interaction landscape of gene promoters (Nature) DOI: 10.1038/nature11279
Marlies E. Oomen, Adam K. Hedger, … Job Dekker (2020) Detecting chromatin interactions between and along sister chromatids with SisterC (Nature Methods) DOI: 10.1038/s41592-020-0930-9 • Job Dekker, Andrew S. Belmont, … 4D Nucleome Network (2017) The 4D nucleome project (Nature) DOI: 10.1038/nature23884 • The 4D Nucleome Project
Related Episodes
Hi-C and Three-Dimensional Genome Sequencing (Erez Lieberman Aiden)
Identification of Functional Elements in the Genome (Bing Ren)
Biophysical Modeling of 3-D Genome Organization (Leonid Mirny)
Epigenetics and X-Inactivation (Edith Heard)
Dosage Compensation in Drosophila (Asifa Akhtar)
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Transcription and Polycomb in Inheritance and Disease (Danny Reinberg)

In this episode of the Epigenetics Podcast, we caught up with Dr. Danny Reinberg from the New York University School of Medicine to talk about his work on transcription and polycomb in inheritance and disease.
Dr. Danny Reinberg is a pioneer in the characterization of transcription factors for human RNA polymerase II. In his groundbreaking work in the 1990s, he purified the essential transcription factors and reconstituted the polymerase in vitro on both naked DNA and chromatin.  Dr. Reinberg next started focusing on the polycomb repressive complex 2 (PRC2), which is the only known methyltransferase for lysine 27 on histone H3. He biochemically characterized the PRC2 subunits EZH1 and EZH2. More recently, Dr. Reinberg has been investigating the role of PRC2 in neurons. 
This interview discusses the story behind how Dr. Danny Reinberg started his research career by identifying the essential RNA polymerase transcription factors, how he discovered and characterized the polycomb repressive complex 2 (PRC2), and what his research holds for the future.
 
References
H. Lu, L. Zawel, … D. Reinberg (1992) Human general transcription factor IIH phosphorylates the C-terminal domain of RNA polymerase II (Nature) DOI: 10.1038/358641a0
A. Merino, K. R. Madden, … D. Reinberg (1993) DNA topoisomerase I is involved in both repression and activation of transcription (Nature) DOI: 10.1038/365227a0
G. Orphanides, W. H. Wu, … D. Reinberg (1999) The chromatin-specific transcription elongation factor FACT comprises human SPT16 and SSRP1 proteins (Nature) DOI: 10.1038/22350
Andrei Kuzmichev, Kenichi Nishioka, … Danny Reinberg (2002) Histone methyltransferase activity associated with a human multiprotein complex containing the Enhancer of Zeste protein (Genes & Development) DOI: 10.1101/gad.1035902
Andrei Kuzmichev, Raphael Margueron, … Danny Reinberg (2005) Composition and histone substrates of polycomb repressive group complexes change during cellular differentiation (Proceedings of the National Academy of Sciences of the United States of America) DOI: 10.1073/pnas.0409875102
Ozgur Oksuz, Varun Narendra, … Danny Reinberg (2018) Capturing the Onset of PRC2-Mediated Repressive Domain Formation (Molecular Cell) DOI: 10.1016/j.molcel.2018.05.023
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The Epigenetics of COVID-19

In this episode of the Epigenetics Podcast, we caught up with Dr. Sandra Atlante and Dr. Carlo Gaetano from the Instituti Clinici Scientifici Maugeri in Pavia, Italy, to talk about the roles epigenetic mechanisms play in COVID-19.
In early 2020 a novel coronavirus, SARS-CoV-2, emerged in Wuhan, China. This coronavirus causes the coronavirus disease 2019 (COVID-19) and rapidly spread all over the globe. In a worldwide effort, scientists and doctors tried to find drugs and looked for vaccines to help contain the spreading of the virus. It seems that an overreaction of the immune system, the so called "cytokine storm," could be one of the major complications of this disease. This reaction is not directly linked to the viral infection but is an overreaction of the body's own immune system. Therefore, small molecules that regulate gene expression via chromatin modifying enzymes might help keep the immune system in check.
In this episode we discuss how Dr. Gaetano and Dr. Atlante set up studies to investigate the epigenetic response to a SARS-CoV-2 infection, which epigenetic factors play a role in disease progression, and what we can expect from mutations of the virus in the future.
 
References
Sandra Atlante, Alessia Mongelli, … Carlo Gaetano (2020) The epigenetic implication in coronavirus infection and therapy (Clinical Epigenetics) DOI: 10.1186/s13148-020-00946-x
 
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Epigenetic Reprogramming During Mammalian Development (Wolf Reik)

In this episode of the Epigenetics Podcast, we caught up with Dr. Wolf Reik, Director at the Babraham Institute in Cambridge, UK, to talk about his work on the role of epigenetic factors in cellular reprogramming.
In the beginning of his research career, Dr. Wolf Reik worked on cellular reprogramming during embryogenesis. Epigenetic marks like DNA methylation or post-translational modifications of histone tails are removed and reprogrammed during embryogenesis, which can limit the amount of epigenetic information that can be passed on to future generations. However, this process is sometimes defective, which can lead to transgenerational epigenetic inheritance.
More recently, the laboratory of Dr. Wolf Reik has done pioneering work in the emerging field of single-cell experimental methods. The Reik lab developed a single-cell reduced representation bisulfite sequencing (scRRBS) approach to investigate DNA methylation at single-cell resolution. They also developed an integrated multi-omics approach called single-cell nucleosome, methylation, and transcription sequencing (scNMT-Seq) to map chromatin accessibility, DNA methylation, and RNA expression at the same time during the onset of gastrulation in mouse embryos.
In this interview, we discuss the story behind how Dr. Wolf Reik almost discovered 5-hmC and how he later moved into developing single-cell methods like scRRBS and single-cell multi-omics approaches.
 
References
W. Reik, A. Collick, … M. A. Surani (1987) Genomic imprinting determines methylation of parental alleles in transgenic mice (Nature) DOI: 10.1038/328248a0
W. Dean, F. Santos, … W. Reik (2001) Conservation of methylation reprogramming in mammalian development: aberrant reprogramming in cloned embryos (Proceedings of the National Academy of Sciences of the United States of America) DOI: 10.1073/pnas.241522698
Miguel Constância, Myriam Hemberger, … Wolf Reik (2002) Placental-specific IGF-II is a major modulator of placental and fetal growth (Nature) DOI: 10.1038/nature00819
Adele Murrell, Sarah Heeson, Wolf Reik (2004) Interaction between differentially methylated regions partitions the imprinted genes Igf2 and H19 into parent-specific chromatin loops (Nature Genetics) DOI: 10.1038/ng1402
Irene Hernando-Herraez, Brendan Evano, … Wolf Reik (2019) Ageing affects DNA methylation drift and transcriptional cell-to-cell variability in mouse muscle stem cells (Nature Communications) DOI: 10.1038/s41467-019-12293-4
Tobias Messmer, Ferdinand von Meyenn, … Wolf Reik (2019) Transcriptional Heterogeneity in Naive and Primed Human Pluripotent Stem Cells at Single-Cell Resolution (Cell Reports) DOI: 10.1016/j.celrep.2018.12.099
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​In vivo Nucleosome Structure and Dynamics (Srinivas Ramachandran)

In this episode of the Epigenetics Podcast, we caught up with Dr. Srinivas Ramachandran, Assistant Professor at the University of Colorado, Anschutz Medical Campus, to talk about his work on ​in vivo nucleosome structure and dynamics.
Dr. Srinivas Ramachandran studies the structure and dynamics of nucleosomes during cellular processes like transcription and DNA replication. During transcription, as the RNA polymerase transcribes along the DNA, it needs to pass nucleosomes. Dr. Ramachandran investigated the effect of nucleosomes on transcription and also studied how different histone variants affect this process. He found that the first nucleosome within a gene body is a barrier for the progression of RNA polymerase, and that presence of the histone variant H2A.Z in this first nucleosome lowers this barrier.
Furthermore, Dr. Ramachandran developed a method called mapping in vivo nascent chromatin using EdU and sequencing (MINCE-Seq), enabling the study of chromatin landscapes right after DNA replication. In MINCE-Seq, newly replicated DNA is labeled right after the replication fork has passed by with the nucleotide analog ethynyl deoxyuridine (EdU), which can then be coupled with biotin using click chemistry. After the purification of newly replicated DNA and MNase digestion, the chromatin landscape can be analyzed.
In this interview, we discuss the story behind how Dr. Ramachandran found his way into chromatin research, what it was like to start a wet lab postdoc with a bioinformatics background, and what he is working on now to unravel nucleosomal structure and dynamics in his own lab.
 
References
Christopher M. Weber, Srinivas Ramachandran, Steven Henikoff (2014) Nucleosomes are context-specific, H2A.Z-modulated barriers to RNA polymerase (Molecular Cell) DOI: 10.1016/j.molcel.2014.02.014
Srinivas Ramachandran, Steven Henikoff (2016) Transcriptional Regulators Compete with Nucleosomes Post-replication (Cell) DOI: 10.1016/j.cell.2016.02.062
Srinivas Ramachandran, Kami Ahmad, Steven Henikoff (2017) Transcription and Remodeling Produce Asymmetrically Unwrapped Nucleosomal Intermediates (Molecular Cell) DOI: 10.1016/j.molcel.2017.11.015
Satyanarayan Rao, Kami Ahmad, Srinivas Ramachandran (2020) Cooperative Binding of Transcription Factors is a Hallmark of Active Enhancers (bioRxiv) DOI: 10.1101/2020.08.17.253146
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Pioneer Transcription Factors and Their Influence on Chromatin Structure (Ken Zaret)

In this episode of the Epigenetics Podcast, we caught up with Dr. Ken Zaret, Professor in the Department of Cell and Developmental Biology at the Perelman School of Medicine, University of Pennsylvania, to talk about his work on pioneer transcription factors and their influence on chromatin structure.
Embryonic development is a complex process that needs to be tightly regulated. Multiple regulatory factors contribute to proper development, including a family of specialized regulatory proteins called "pioneer factors." Our guest Dr. Ken Zaret found that these pioneer factors are among the first proteins to bind to chromatin during development and that they can prime important regulatory genes for activation at a later developmental stage. Furthermore, he and his team showed that there might be a "pre-pattern" that exists in cells that determines their developmental fate.
Pioneer factors are not only important in embryonic development, they can also help restart transcription after mitosis. Dr. Zaret and his colleagues demonstrated that FoxA stays bound to chromosomes during mitosis, leading to a rapid reactivation of essential genes at the exit of mitosis.
In this interview, we discuss the story behind how Dr. Zaret discovered pioneer transcription factors like FoxA, how these factors are influenced by the chromatin environment, and how they function.
 
References
R. Gualdi, P. Bossard, … K. S. Zaret (1996) Hepatic specification of the gut endoderm in vitro: cell signaling and transcriptional control (Genes & Development) DOI: 10.1101/gad.10.13.1670
L. A. Cirillo, C. E. McPherson, … K. S. Zaret (1998) Binding of the winged-helix transcription factor HNF3 to a linker histone site on the nucleosome (The EMBO journal) DOI: 10.1093/emboj/17.1.244
Lisa Ann Cirillo, Frank Robert Lin, … Kenneth S. Zaret (2002) Opening of compacted chromatin by early developmental transcription factors HNF3 (FoxA) and GATA-4 (Molecular Cell) DOI: 10.1016/s1097-2765(02)00459-8
Kenneth S. Zaret (2020) Pioneer Transcription Factors Initiating Gene Network Changes (Annual Review of Genetics) DOI: 10.1146/annurev-genet-030220-015007
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