# Oliver Hahn

> I build AI-accelerated, closed-loop discovery systems for brain aging. At Calico my lab couples CRISPR screens, imaging and robotics with foundation models and agents. One finding: young immune cells put into an old brain age fast.

Role: Principal Investigator for Brain Aging, Calico Life Sciences.
BSc: Molecular Biotechnology, Technical University of Munich, 2009-2012.
MSc: Molecular Biosciences and Systems Biology, Heidelberg University, 2012-2014.
PhD: with Linda Partridge, Max Planck Institute for Biology of Ageing, Cologne, 2018.
Postdoc: with Tony Wyss-Coray, Stanford, 2018-2023.
Institutions: Technical University of Munich, Heidelberg University, Max Planck Institute for Biology of Ageing, Stanford University.

## CV (cv/)

I build AI-accelerated, closed-loop discovery systems for brain aging.
Citations (Google Scholar): citations 7,965, h-index 23, i10-index 30.

### Built

- Sentinel (2026): Agent that predicts antigen targets for unknown T cell receptors and designs validation experiments. 2nd of 70 teams and People's Choice, Bio x AI Hackathon at Y Combinator. Links: Code: https://github.com/Vanthys/tcr-agent.
- ANSWERBACK (2026): Fixed-budget agent querying archived experiments to find which secreted factors change cells. re:AGENT hackathon.
- In vivo immune cell replacement platform (2025): Swaps the aging brain's immune cells for young, gene-editable ones to find what drives aging. Links: Preprint: https://www.biorxiv.org/content/10.1101/2025.09.02.673859v1; Code: https://github.com/calico/Heterochronic_myeloidCellTransplantation; Alzforum: https://www.alzforum.org/news/research-news/regional-cues-and-natural-killer-cells-steer-microglial-aging.
- Aging mouse brain atlas (2023): RNA atlas of 15 mouse brain regions across 7 ages, with a public browser. Links: Cell paper: https://www.cell.com/cell/fulltext/S0092-8674(23)00805-X; Browser: https://twc-stanford.shinyapps.io/spatiotemporal_brain_map/; Code: https://github.com/olihahn/SpatioTemporal_Analysis.
- Ember (2026): Android cigar journal whose home screen is a painted terrace you can lean into. Links: Code: https://github.com/olihahn/ember-app.

### Skills

- AI and computation: Protein and genomic foundation models (ESM-2, Evo-2, Boltz-2, RFdiffusion, Borzoi), Agentic coding (Claude Code, Codex, Antigravity), Modal GPUs, Single-cell multi-omics, Causal network inference, ML for imaging, Python, R
- Lab platforms: In vivo CRISPR screens, Perturb-seq, Lab automation, High-content imaging, Two-photon imaging in living brains, Immune cell replacement

### Experience

- 2023 to present: Principal Investigator, Brain Aging, Calico Life Sciences. Leads brain aging research, building computational, in vitro and in vivo discovery platforms.
  - Perturb-seq screens of hundreds of gene targets, in vitro and in the aging brain.
  - Cell Painting screens of 2,500+ compounds, run with automation and AI.
  - Trusted tester for frontier lab AI tools and models.
- 2018 to 2023: Postdoctoral Scholar, Stanford University, Wyss-Coray lab. Built the aging mouse brain atlas and multiomic methods that measure aging across tissues.
- 2020 to 2023: Lead, American Heart Association / Allen Brain Health RNA-seq core, Stanford University. Ran bulk and single-cell RNA-seq projects for a consortium of ten Stanford labs.
- 2015 to 2018: PhD, Genetics and Bioinformatics, Max Planck Institute for Biology of Ageing and University of Cologne, Partridge lab. Diet, DNA methylation and aging in mice.
- 2012 to 2014: MSc, Molecular Biosciences and Systems Biology, Heidelberg University.
- 2009 to 2012: BSc, Molecular Biotechnology, Technical University of Munich.

### Talks

- 2026: Panel, AI for preclinical neuroscience, PsyMed Ventures Frontier Neuro (un)Conference, San Francisco
- 2026: Keystone Symposia, Immune Aging and Innate Immunity, Banff, Canada
- 2025: Society for Neuroscience, San Diego
- 2025: Keystone Symposia, Neuroinflammation, Whistler, Canada
- 2022: 10x Genomics User Symposium, San Francisco
- 2022: Gordon Research Conference, Systems Aging, Newry, Maine
- 2020: Keystone Symposia, Intra- and Intercellular Mechanisms of Aging, Vancouver, Canada
- 2018: Cell Symposium, Aging and Metabolism, Sitges, Spain
- 2018: Healthy Ageing: From Molecules to Organisms, Cambridge, UK
- 2017: Gordon Research Seminar, Biology of Aging, Les Diablerets, Switzerland

## Science

- [Heterochronic myeloid cell replacement reveals the local brain environment as key driver of microglia aging](https://www.biorxiv.org/content/10.1101/2025.09.02.673859v1): bioRxiv (preprint), 2025, senior author and lead contact. DOI 10.1101/2025.09.02.673859. Young replacement microglia, the brain's immune cells, aged fast in old brains. Old ones looked young in young brains. Data: https://tinyurl.com/Microglial-Aging-Explorer. Commentary: Alzforum, https://www.alzforum.org/news/research-news/regional-cues-and-natural-killer-cells-steer-microglial-aging. Commentary: Lifespan.io, https://lifespan.io/news/microglial-aging-is-determined-by-their-environment/.
- [A spatio-temporal brain miRNA expression atlas identifies sex-independent age-related microglial driven miR-155-5p increase](https://www.nature.com/articles/s41467-025-59860-6): Nature Communications, 2025, contributing author. DOI 10.1038/s41467-025-59860-6. A microRNA atlas of 15 mouse brain regions. miR-155-5p rises with age in both sexes, driven by microglia.
- [Myeloid cell replacement is neuroprotective in chronic experimental autoimmune encephalomyelitis](https://www.nature.com/articles/s41593-024-01609-3): Nature Neuroscience, 2024, contributing author. DOI 10.1038/s41593-024-01609-3. Replacing immune cells by transplant improved neurological deficits in a mouse model of multiple sclerosis.
- [Atlas of the aging mouse brain reveals white matter as vulnerable foci](https://www.cell.com/cell/fulltext/S0092-8674(23)00805-X): Cell, 2023, first author. DOI 10.1016/j.cell.2023.07.027. We profiled 15 mouse brain regions across 7 ages. Glial aging runs faster in white matter than cortex.
- [Characterizing expression changes in noncoding RNAs during aging and heterochronic parabiosis across mouse tissues](https://www.nature.com/articles/s41587-023-01751-6): Nature Biotechnology, 2023, contributing author. DOI 10.1038/s41587-023-01751-6. A noncoding RNA map of 16 organs. miR-29c-3p tracks aging and returns to young levels in liver with young blood.
- [Ageing-associated changes in transcriptional elongation influence longevity](https://www.nature.com/articles/s41586-023-05922-y): Nature, 2023, contributing author. DOI 10.1038/s41586-023-05922-y. RNA polymerase speeds up with age in five species. Dietary restriction reverses most of this, and slowing polymerase extends lifespan.
- [Platelet factors are induced by longevity factor klotho and enhance cognition in young and aging mice](https://www.nature.com/articles/s43587-023-00468-0): Nature Aging, 2023, contributing author. DOI 10.1038/s43587-023-00468-0. Klotho raises platelet factors in blood. One of them, PF4, improves cognition in young and old mice.
- [Young CSF restores oligodendrogenesis and memory in aged mice via Fgf17](https://www.nature.com/articles/s41586-022-04722-0): Nature, 2022, contributing author. DOI 10.1038/s41586-022-04722-0. Young cerebrospinal fluid improved memory in old mice. Fgf17 alone did too.
- [Exercise plasma boosts memory and dampens brain inflammation via clusterin](https://www.nature.com/articles/s41586-021-04183-x): Nature, 2021, contributing author. DOI 10.1038/s41586-021-04183-x. Plasma from running mice reduced brain inflammation in sedentary mice, through proteins including clusterin.
- [Dysregulation of brain and choroid plexus cell types in severe COVID-19](https://www.nature.com/articles/s41586-021-03710-0): Nature, 2021, contributing author. DOI 10.1038/s41586-021-03710-0. Brains from COVID-19 patients showed no molecular trace of virus but broad changes in barrier cells and microglia.
- [CoolMPS for robust sequencing of single-nuclear RNAs captured by droplet-based method](https://doi.org/10.1093/nar/gkaa1127): Nucleic Acids Research, 2020, first author. DOI 10.1093/nar/gkaa1127. CoolMPS sequencing reproduced standard Illumina results on single-nucleus RNA from young and old mouse hippocampus.
- [Ageing hallmarks exhibit organ-specific temporal signatures](https://www.nature.com/articles/s41586-020-2499-y): Nature, 2020, co-first author. DOI 10.1038/s41586-020-2499-y. Organs hit the same aging hallmarks on different schedules. Immune activation shows first in white fat.
- [Lipid-droplet-accumulating microglia represent a dysfunctional and proinflammatory state in the aging brain](https://www.nature.com/articles/s41593-019-0566-1): Nature Neuroscience, 2020, contributing author. DOI 10.1038/s41593-019-0566-1. Microglia fill with lipid droplets as brains age. These cells clear debris poorly and drive inflammation.
- [A single-cell transcriptomic atlas characterizes ageing tissues in the mouse](https://www.nature.com/articles/s41586-020-2496-1): Nature, 2020, consortium member. DOI 10.1038/s41586-020-2496-1. A single-cell atlas of aging across 23 mouse tissues and organs.
- [A nutritional memory effect counteracts the benefits of dietary restriction in old mice](https://www.nature.com/articles/s42255-019-0121-0): Nature Metabolism, 2019, first author. DOI 10.1038/s42255-019-0121-0. In 800 mice, stopping dietary restriction at 24 months raised mortality fast. Starting it late helped only weakly. Commentary: Nature Metabolism News & Views, https://www.nature.com/articles/s42255-019-0128-6.
- [Hepatic gene body hypermethylation is a shared epigenetic signature of murine longevity](https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1007766): PLOS Genetics, 2018, first author. DOI 10.1371/journal.pgen.1007766. Dietary restriction, rapamycin and dwarf genetics each add methylation inside gene bodies in mouse liver.
- [Dietary restriction protects from age-associated DNA methylation and induces epigenetic reprogramming of lipid metabolism](https://link.springer.com/article/10.1186/s13059-017-1187-1): Genome Biology, 2017, co-first author. DOI 10.1186/s13059-017-1187-1. Dietary restriction delayed age-related epigenetic changes in mouse liver and added methylation at lipid genes. Commentary: Genome Biology Research Highlight, https://link.springer.com/article/10.1186/s13059-017-1245-8.
- [The Sense of Smell Impacts Metabolic Health and Obesity](https://www.cell.com/cell-metabolism/fulltext/S1550-4131(17)30357-1): Cell Metabolism, 2017, contributing author. DOI 10.1016/j.cmet.2017.06.015. Mice that lost smell neurons resisted diet-induced obesity. Losing smell after obesity reduced fat mass.
- [Inferring causal molecular networks: empirical assessment through a community-based effort](https://www.nature.com/articles/nmeth.3773): Nature Methods, 2016, consortium member. DOI 10.1038/nmeth.3773. A community challenge scored over 2,000 networks for causal links in cancer cell signaling.

## Projects

- [Ember](https://github.com/olihahn/ember-app): A cigar journal for Android. Its home screen is a painted terrace you can lean into.
- [Sentinel](https://github.com/Vanthys/tcr-agent): Agent proposing antigen targets for unknown T cell receptors. Second of 70 teams and People's Choice, Bio x AI Hackathon.
- [Brain aging atlas browser](https://twc-stanford.shinyapps.io/spatiotemporal_brain_map/): Explore gene expression across 15 mouse brain regions and 7 ages. Code and data are public.

## Writing

- [What changes in normal human brain aging](writing/human-brain-aging/): 284 human brains echo our mouse atlas: microglia and other glia change most with age, especially in white matter.
- [Biology has to be able to answer back](writing/biology-answer-back/): AI in biology needs causal tests in living systems. We read them, write changes into them, and reason over results.
- [What my Paperpile library says about me](writing/paperpile-library/): I pointed Claude Code at my 2,052 saved papers. It found my forgotten PhD project on cardiolipin.
- [First unlock from vibe science: public datasets](writing/public-datasets/): AI agents make public data usable fast. I combined 107,219 perturbations from 5 Perturb-seq sources into one collection.
- [Computational biology is the quiet AI win](writing/computational-biology/): Computational biology is where AI is doing the most for science right now, more than hypothesis generators or lab robots.
- [DNA methylation dynamics in murine ageing and longevity (PhD thesis abstract, University of Cologne)](https://kups.ub.uni-koeln.de/8577/): My PhD on how DNA methylation changes with aging, dietary restriction and longevity in mice.

## Data

- [papers.json](papers.json): every paper with title, venue, year, DOI, link and summary.

## Links

- [X](https://x.com/Oliver__Hahn)
- [LinkedIn](https://www.linkedin.com/in/oliver-hahn-ph-d-2363b3141/)
- [Google Scholar](https://scholar.google.com/citations?user=vpa2PmUAAAAJ)
- [GitHub](https://github.com/olihahn)