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In this episode of the Epigenetics Podcast, we talked with Nadav Ahituv from University of California, San Francisco about his work on mutations of gene regulatory elements in human disease.
Using massively parallel experiments, his lab revolutionized functional genomics by studying the impact of transcription factor binding sites on gene expression. His groundbreaking technology deciphered the regulatory language of gene expression by exploring transcription factor combinations, spacing, and orientation. By delving into the influence of DNA shape and gene topology, Nadav Ahituv's research provides a comprehensive understanding of gene regulation at the molecular level, shedding light on the complexity of genetic interactions.
The conversation delves into specific cases involving enhancers, gene sequencing, and 3D genomic structure, highlighting the impact of critical elements such as CTCF sites on gene expression. Discussions of haploid insufficiency and its implications for human health, using CRISPR technology to enhance gene expression, offer new possibilities for treating genetic diseases. Explorations of leptin-responsive regulatory elements in the hypothalamus and liver-associated transcription factors provide insights into metabolic regulation and gene expression networks in different tissues.
The episode also explores the epigenomic landscape, the evolution of methods from bulk approaches to single-cell analyses, and the role of AI and machine learning in deciphering complex genetic patterns. The conversation transitions to a unique study of bat embryonic development, dietary differences, and their implications for understanding wing development and metabolism in different bat species.
 
References

Ahituv, N., Zhu, Y., Visel, A., Holt, A., Afzal, V., Pennacchio, L. A., & Rubin, E. M. (2007). Deletion of ultraconserved elements yields viable mice. PLoS biology, 5(9), e234. https://doi.org/10.1371/journal.pbio.0050234


Matharu, N., Rattanasopha, S., Tamura, S., Maliskova, L., Wang, Y., Bernard, A., Hardin, A., Eckalbar, W. L., Vaisse, C., & Ahituv, N. (2019). CRISPR-mediated activation of a promoter or enhancer rescues obesity caused by haploinsufficiency. Science (New York, N.Y.), 363(6424), eaau0629. https://doi.org/10.1126/science.aau0629


Ushiki, A., Zhang, Y., Xiong, C., Zhao, J., Georgakopoulos-Soares, I., Kane, L., Jamieson, K., Bamshad, M. J., Nickerson, D. A., University of Washington Center for Mendelian Genomics, Shen, Y., Lettice, L. A., Silveira-Lucas, E. L., Petit, F., & Ahituv, N. (2021). Deletion of CTCF sites in the SHH locus alters enhancer-promoter interactions and leads to acheiropodia. Nature communications, 12(1), 2282. https://doi.org/10.1038/s41467-021-22470-z


Georgakopoulos-Soares, I., Deng, C., Agarwal, V., Chan, C. S. Y., Zhao, J., Inoue, F., & Ahituv, N. (2023). Transcription factor binding site orientation and order are major drivers of gene regulatory activity. Nature communications, 14(1), 2333. https://doi.org/10.1038/s41467-023-37960-5


Gordon, W. E., Baek, S., Nguyen, H. P., Kuo, Y. M., Bradley, R., Fong, S. L., Kim, N., Galazyuk, A., Lee, I., Ingala, M. R., Simmons, N. B., Schountz, T., Cooper, L. N., Georgakopoulos-Soares, I., Hemberg, M., & Ahituv, N. (2024). Integrative single-cell characterization of a frugivorous and an insectivorous bat kidney and pancreas. Nature communications, 15(1), 12. https://doi.org/10.1038/s41467-023-44186-y

 
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Ultraconserved Enhancers and Enhancer Redundancy (Diane Dickel)


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In this episode of the Epigenetics Podcast, we talked with Ana Cvejic from the Biotech Research & Innovation Centre at the University of Copenhagen about her work on using sc-multiomics to characterise human developmental hematopoiesis.
The conversation starts by delving into Ana's research on hematopoiesis, starting with her work on identifying novel genes controlling blood traits in zebrafish models. She explains her transition to single-cell methodologies and the application of single-cell RNA sequencing to study hematopoietic cells in zebrafish, focusing on thrombocyte lineage commitment and gene expression.
The discussion progresses to her groundbreaking study on human fetal hematopoiesis, where she combined single-cell RNA-seq with single-cell ATAC-seq to understand chromatin accessibility and gene expression dynamics. Ana then shares insights into the identification of new cell surface markers and the priming of hematopoietic stem cells, particularly in conditions like Down syndrome.
Furthermore, she then elaborates on the construction of a phylogenetic tree of blood development using whole-genome sequencing of single-cell-derived hematopoietic colonies from healthy human fetuses. She explains the motivation behind this study, highlighting the insights gained regarding stem cell quantities, developmental timelines, and mutations in blood development.
References

Bielczyk-Maczyńska, E., Serbanovic-Canic, J., Ferreira, L., Soranzo, N., Stemple, D. L., Ouwehand, W. H., & Cvejic, A. (2014). A loss of function screen of identified genome-wide association study Loci reveals new genes controlling hematopoiesis. PLoS genetics, 10(7), e1004450. https://doi.org/10.1371/journal.pgen.1004450


Athanasiadis, E. I., Botthof, J. G., Andres, H., Ferreira, L., Lio, P., & Cvejic, A. (2017). Single-cell RNA-sequencing uncovers transcriptional states and fate decisions in haematopoiesis. Nature communications, 8(1), 2045. https://doi.org/10.1038/s41467-017-02305-6


Ranzoni, A. M., Tangherloni, A., Berest, I., Riva, S. G., Myers, B., Strzelecka, P. M., Xu, J., Panada, E., Mohorianu, I., Zaugg, J. B., & Cvejic, A. (2021). Integrative Single-Cell RNA-Seq and ATAC-Seq Analysis of Human Developmental Hematopoiesis. Cell stem cell, 28(3), 472–487.e7. https://doi.org/10.1016/j.stem.2020.11.015

 
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Single Cell Epigenomics in Neuronal Development (Tim Petros)


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In this episode of the Epigenetics Podcast, we talked with Sven Heinz from the University of California in San Diego about his work on the impact of sequence variation on transcription factor binding affinities and genetic diversity.
Sven Heinz talks about a landmark study published in Nature that examined the impact of sequence variation on transcription factor binding affinities and downstream effects on gene expression. Modifying genetic sequences to understand the influence of different motifs provided valuable insights into how genetic variation shapes cellular responses and gene expression patterns, underscoring the importance of genetic diversity.
Methodological approaches using inducible systems to observe changes in transcription factor binding patterns highlight the critical role of motif variation and redundancy in transcription factor families. These studies provide essential insights into the complex network of transcriptional regulation and chromatin dynamics, revealing the nuanced mechanisms that control gene expression and chromatin organization. In addition, he is investigating how small nucleotide changes can significantly affect transcription factor binding in macrophages from different mouse strains, shedding light on the intricate effects of genetic variation on transcription factor binding.
Sven's career path from project scientist to assistant professor at UC San Diego and the Salk Institute reflects a journey marked by serendipitous opportunities and a collaborative, innovative research environment. The podcast delves into the effects of influenza virus infection on chromosomal territories, gene transcription, and chromatin structure, unraveling the sophisticated interplay between viral infection and host cell transcriptional regulation.
 
References

Heinz, S., Benner, C., Spann, N., Bertolino, E., Lin, Y. C., Laslo, P., Cheng, J. X., Murre, C., Singh, H., & Glass, C. K. (2010). Simple combinations of lineage-determining transcription factors prime cis-regulatory elements required for macrophage and B cell identities. Molecular cell, 38(4), 576–589. https://doi.org/10.1016/j.molcel.2010.05.004


Heinz, S., Romanoski, C. E., Benner, C., Allison, K. A., Kaikkonen, M. U., Orozco, L. D., & Glass, C. K. (2013). Effect of natural genetic variation on enhancer selection and function. Nature, 503(7477), 487–492. https://doi.org/10.1038/nature12615


Texari, L., Spann, N. J., Troutman, T. D., Sakai, M., Seidman, J. S., & Heinz, S. (2021). An optimized protocol for rapid, sensitive and robust on-bead ChIP-seq from primary cells. STAR protocols, 2(1), 100358. https://doi.org/10.1016/j.xpro.2021.100358

 
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In this episode of the Epigenetics Podcast, we talked with Sarah Marzi from the UK Dementia Research Institute at Imperial College London about her work on epigenetic changes in Alzheimer's Disease, and comparing CUT&Tag to ENCODE ChIP-Seq using limited cell samples.
The interview discusses Sarah Marzi's work on ChIP-Seq experiments and their significance in understanding Alzheimer's disease from an epigenetic perspective. The discussion touches on the widespread dysregulation and changes in acetylation, particularly in genes associated with Alzheimer's risk, providing insights into potential links between epigenetic insults and disease onset.
Moving on to the technical aspects of the study, the interview examines the strategic use of CUT&Tag. It explores the challenges and optimizations involved in accurately profiling limited cell samples. The dialogue also compares CUT&Tag to ENCODE ChIP-Seq, highlighting the complexities of peak calling and data interpretation across different methodologies.
 
References

Kumsta, R., Marzi, S., Viana, J. et al. Severe psychosocial deprivation in early childhood is associated with increased DNA methylation across a region spanning the transcription start site of CYP2E1. Transl Psychiatry 6, e830 (2016). https://doi.org/10.1038/tp.2016.95


Marzi, S. J., Schilder, B. M., Nott, A., Frigerio, C. S., Willaime‐Morawek, S., Bucholc, M., Hanger, D. P., James, C., Lewis, P. A., Lourida, I., Noble, W., Rodriguez‐Algarra, F., Sharif, J., Tsalenchuk, M., Winchester, L. M., Yaman, Ü., Yao, Z., The Deep Dementia Phenotyping (DEMON) Network, Ranson, J. M., & Llewellyn, D. J. (2023). Artificial intelligence for neurodegenerative experimental models. Alzheimer’s & Dementia, 19(12), 5970–5987. https://doi.org/10.1002/alz.13479


Marzi, S. J., Leung, S. K., Ribarska, T., Hannon, E., Smith, A. R., Pishva, E., Poschmann, J., Moore, K., Troakes, C., Al-Sarraj, S., Beck, S., Newman, S., Lunnon, K., Schalkwyk, L. C., & Mill, J. (2018). A histone acetylome-wide association study of Alzheimer’s disease identifies disease-associated H3K27ac differences in the entorhinal cortex. Nature Neuroscience, 21(11), 1618–1627. https://doi.org/10.1038/s41593-018-0253-7


Hu, D., Abbasova, L., Schilder, B. M., Nott, A., Skene, N. G., & Marzi, S. J. (2022). CUT&Tag recovers up to half of ENCODE ChIP-seq peaks in modifications of H3K27 [Preprint]. Genomics. https://doi.org/10.1101/2022.03.30.486382

 
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In this episode of the Epigenetics Podcast, we talked with Mark Parthun from Ohio State University about his work on the role of Hat1p in chromatin assembly.
Mark Parthun shares insights into his pivotal paper in 2004 that explored the link between type B histone acetyltransferases and chromatin assembly, setting the stage for his current research interests in epigenetics. He highlights the role of HAT1 in acetylating lysines on newly synthesized histones, its involvement in double-strand break repair, and the search for phenotypes associated with HAT1 mutations.
The discussion expands to a collaborative research project between two scientists uncovering the roles of HAT1 and NASP as chaperones in chromatin assembly. Transitioning from yeast to mouse models, the team investigated the effects of HAT1 knockout on mouse phenotypes, particularly in lung development and craniofacial morphogenesis. They also explored the impact of histone acetylation on chromatin dynamics and its influence on lifespan, aging processes, and longevity.
 
References

Parthun, M. R., Widom, J., & Gottschling, D. E. (1996). The Major Cytoplasmic Histone Acetyltransferase in Yeast: Links to Chromatin Replication and Histone Metabolism. Cell, 87(1), 85–94. https://doi.org/10.1016/S0092-8674(00)81325-2


Kelly, T. J., Qin, S., Gottschling, D. E., & Parthun, M. R. (2000). Type B histone acetyltransferase Hat1p participates in telomeric silencing. Molecular and cellular biology, 20(19), 7051–7058. https://doi.org/10.1128/MCB.20.19.7051-7058.2000


Ai, X., & Parthun, M. R. (2004). The nuclear Hat1p/Hat2p complex: a molecular link between type B histone acetyltransferases and chromatin assembly. Molecular cell, 14(2), 195–205. https://doi.org/10.1016/s1097-2765(04)00184-4


Nagarajan, P., Ge, Z., Sirbu, B., Doughty, C., Agudelo Garcia, P. A., Schlederer, M., Annunziato, A. T., Cortez, D., Kenner, L., & Parthun, M. R. (2013). Histone acetyl transferase 1 is essential for mammalian development, genome stability, and the processing of newly synthesized histones H3 and H4. PLoS genetics, 9(6), e1003518. https://doi.org/10.1371/journal.pgen.1003518


Agudelo Garcia, P. A., Hoover, M. E., Zhang, P., Nagarajan, P., Freitas, M. A., & Parthun, M. R. (2017). Identification of multiple roles for histone acetyltransferase 1 in replication-coupled chromatin assembly. Nucleic Acids Research, 45(16), 9319–9335. https://doi.org/10.1093/nar/gkx545


Popova, L. V., Nagarajan, P., Lovejoy, C. M., Sunkel, B. D., Gardner, M. L., Wang, M., Freitas, M. A., Stanton, B. Z., & Parthun, M. R. (2021). Epigenetic regulation of nuclear lamina-associated heterochromatin by HAT1 and the acetylation of newly synthesized histones. Nucleic Acids Research, 49(21), 12136–12151. https://doi.org/10.1093/nar/gkab1044

 
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In this episode of the Epigenetics Podcast, we talked with Upasna Sharma from UC Santa Cruz about her work on a number of interesting projects on H2A.Z and telomeres, the impact of paternal diet on offspring metabolism, and the role of small RNAs in sperm.
In this interview Upasna Sharma discusses her work on the study of the paternal diet's impact on offspring metabolism. She reveals the discovery of small non-coding RNAs, particularly tRNA fragments, in mature mammalian sperm that may carry epigenetic information to the next generation. She explains the specific alterations in tRNA fragment levels in response to a low-protein diet and the connections found between tRNA fragments and metabolic status.
Dr. Sharma further explains the degradation and stabilization of tRNA fragments in cells and the processes involved in their regulation. She shares their observation of tRNA fragment abundance in epididymal sperm, despite the sperm being transcriptionally silent at that time. This leads to a discussion on the role of the epididymis in the reprogramming of small RNA profiles and the transportation of tRNA fragments through extracellular vesicles.
The conversation then shifts towards the potential mechanism of how environmental information could be transmitted to sperm and the observed changes in small RNAs in response to a low-protein diet. Dr. Sharma discusses the manipulation of small RNAs in embryos and mouse embryonic stem cells, revealing their role in regulating specific sets of genes during early development. However, the exact mechanisms that link these early changes to metabolic phenotypes are still being explored.
References

Sharma, U., Conine, C. C., Shea, J. M., Boskovic, A., Derr, A. G., Bing, X. Y., Belleannee, C., Kucukural, A., Serra, R. W., Sun, F., Song, L., Carone, B. R., Ricci, E. P., Li, X. Z., Fauquier, L., Moore, M. J., Sullivan, R., Mello, C. C., Garber, M., & Rando, O. J. (2016). Biogenesis and function of tRNA fragments during sperm maturation and fertilization in mammals. Science (New York, N.Y.), 351(6271), 391–396. https://doi.org/10.1126/science.aad6780


Sharma, U., Sun, F., Conine, C. C., Reichholf, B., Kukreja, S., Herzog, V. A., Ameres, S. L., & Rando, O. J. (2018). Small RNAs Are Trafficked from the Epididymis to Developing Mammalian Sperm. Developmental cell, 46(4), 481–494.e6. https://doi.org/10.1016/j.devcel.2018.06.023


Rinaldi, V. D., Donnard, E., Gellatly, K., Rasmussen, M., Kucukural, A., Yukselen, O., Garber, M., Sharma, U., & Rando, O. J. (2020). An atlas of cell types in the mouse epididymis and vas deferens. eLife, 9, e55474. https://doi.org/10.7554/eLife.55474

 
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