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Mark Pownall

@mpownall.bsky.social

575 followers 165 following 9 posts

pownall-lab.org | Sandler Fellow at UCSF | chromatin, transcription, microscopy (ChromExM), development 🐟🧬🔬

Posts Replies Media

Mark Pownall @mpownall.bsky.social · 15/09/2026

❗Postdoc positions available! We have multiple fully funded openings in the lab - please reach out if you’re interested. I’ll be at CSHL Epigenetics and Chromatin this week, so come find me if you’d like to learn more about the lab or potential projects

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Mark Pownall @mpownall.bsky.social · 17/08/2026

Together, our results support a model where nuclear RNA is a major determinant of chromatin organization during development. Lots of open questions remain about mechanism, how this fits with Hi-C data, and how conserved it is across cell states. Feedback and discussion welcome! DM or email me

Schematic of RNA-driven chromatin compaction

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Mark Pownall @mpownall.bsky.social · 17/08/2026

This could be because transcription promotes chromatin organization or RNA itself plays a role. We decoupled these possibilities by inhibiting nuclear RNA degradation, increasing nuclear RNA without increasing global Pol II elongation. This enhanced chromatin compaction without increasing H3K27me3.

Images of nuclei showing nascent RNA and DNA with or without exosome knockdown

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Mark Pownall @mpownall.bsky.social · 17/08/2026

What drives this major reorganization of chromatin? Surprisingly, transcription inhibition prevents much of this emergent chromatin compaction, despite significantly increasing H3K27me3 and H3K9me3. Subtle differences in phenotype between inhibitors provide a clue More details in the paper!

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Mark Pownall @mpownall.bsky.social · 17/08/2026

We started with improving ChromExM experimentally and computationally to reduce experimental burden and increase throughput (check out the supplement!). This enabled us to capture striking changes in chromatin organization from 3-6 hours post fertilization as embryos begin gastrulation

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Mark Pownall @mpownall.bsky.social · 17/08/2026

First preprint from the lab 🚨 We asked when and how global chromatin organization emerges during early development 🐟

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