Single-Molecule Adenine Methylated Oligonucleosome Sequencing Assay (SAMOSA) (Vijay Ramani)

In this episode of the Epigenetics Podcast, we talked with Vijay Ramani from the Gladstone Institute about his work on Single-Molecule Adenine Methylated Oligonucleosome Sequencing Assay (SAMOSA).

Our discussion starts with Vijay Ramani's impactful contributions to the field during his time in Jay Shendure's lab, where he worked on several innovative methods, including RNA proximity ligation. This project was conceived during his graduate studies, aiming to adapt techniques from DNA research to investigate RNA structures—a largely unexplored area at the time. We delved into the nuances of his experiences in graduate school, emphasizing how critical it was to have mentors who provided room for creativity and autonomy in experimental design.

Dr. Ramani then shares insights about his foray into developing more refined methodologies, such as in-situ DNA Hi-C, a revolutionary protocol tailored for three-dimensional genomic mapping. He explained the rationale behind his projects, comparing the outcomes with contemporaneous advancements in methods like Micro-C. The discussion highlighted the importance of understanding enzyme bias in chromatin studies and the need for meticulous experimental design to ensure the validity of biological interpretations.

We further explored exciting advancements in single-cell genomics, specifically Ramani's work on developing sci-Hi-C. This innovative technique leverages combinatorial indexing to allow high-resolution mapping of chromatin architecture at the single-cell level, a significant leap forward in understanding the complexities of gene regulation.

As we progress, Ramani detailed his transition from graduate student to independent investigator starting his own lab. He elaborated on the challenges and excitements associated with establishing his research focus in chromatin structure and function using advanced sequencing technologies. Employing various strategies, including the innovative SAMOSA assay, his research seeks to elucidate the mechanisms by which chromatin structure influences transcriptional regulation.

We also discussed the heterogeneity of chromatin and its implications for gene expression. Ramani provided a fascinating perspective on how variations in chromatin structure could affect gene activity, highlighting potential avenues for future research that aims to untangle the complex dynamics at play in both healthy and diseased states.

References

• Ramani, V., Cusanovich, D., Hause, R. et al. Mapping 3D genome architecture through in situ DNase Hi-C. Nat Protoc 11, 2104–2121 (2016). https://doi.org/10.1038/nprot.2016.126

• Nour J Abdulhay, Colin P McNally, Laura J Hsieh, Sivakanthan Kasinathan, Aidan Keith, Laurel S Estes, Mehran Karimzadeh, Jason G Underwood, Hani Goodarzi, Geeta J Narlikar, Vijay Ramani (2020) Massively multiplex single-molecule oligonucleosome footprinting eLife 9:e59404. https://doi.org/10.7554/eLife.59404

• Abdulhay, N.J., Hsieh, L.J., McNally, C.P. et al. Nucleosome density shapes kilobase-scale regulation by a mammalian chromatin remodeler. Nat Struct Mol Biol 30, 1571–1581 (2023). https://doi.org/10.1038/s41594-023-01093-6

• Nanda, A.S., Wu, K., Irkliyenko, I. et al. Direct transposition of native DNA for sensitive multimodal single-molecule sequencing. Nat Genet 56, 1300–1309 (2024). https://doi.org/10.1038/s41588-024-01748-0

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• Epigenetic Mechanisms in Genome Regulation and Developmental Programming (James Hackett)

• Chromatin Profiling: From ChIP to CUT&RUN, CUT&Tag and CUTAC (Steven Henikoff)

• Split-Pool Recognition of Interactions by Tag Extension (SPRITE) (Mitch Guttman)

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