iiinova — where your digital self keeps evolving

Syd Sattler @sydsat.bsky.social · 30/06/2026

Thanks! The cell tracking was done using the software package Ultrack from @jookuma.bsky.social et al, 2025 in @loicaroyer.bsky.social lab!

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Syd Sattler @sydsat.bsky.social · 29/06/2026

15/ Huge thanks to my co-authors (Nicholas Lammers, Sebastian Hriscu, Clare Booth, and @coletrapnell.bsky.social)Thank you @ohnolog.bsky.social for taking me on as his first grad student — I’m so excited to share this work!

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Syd Sattler @sydsat.bsky.social · 29/06/2026

14/ Our takeaway: Annual killifish redeploy a conserved neutrophil program far earlier in development than other vertebrates. The cell type is conserved, but the developmental route has changed.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

13/ When we disrupted ALPM development with retinoic acid, the ALPM vascular progenitor domain (cyan) was strongly reduced or abolished, but spi1b+ myeloid cells (magenta) persisted on the yolk. This showed that primitive myelopoiesis is uncoupled from the ALPM in killifish.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

12/ Live imaging showed vascular cells (cyan) moving out from the ALPM to form yolk sac vasculature, while highly migratory myeloid cells moved across the yolk, as seen with the ubiquitous membrane marker (orange).

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Syd Sattler @sydsat.bsky.social · 29/06/2026

11/ Finally, we explored the ALPM, the classic site of primitive myeloid and vascular cells in zebrafish. In killifish, vascular progenitors (cyan) arise from the ALPM along a canonical trajectory, but unlike zebrafish, the killifish ALPM is not a major source of myeloid cells (magenta).

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Syd Sattler @sydsat.bsky.social · 29/06/2026

10/ We then added additional scRNAseq timepoints and Sebastian Hriscu, a talented CS undergrad, developed SKiRA — Single-cell Killifish RNA Atlas — an interactive app for exploring this new embryogenesis atlas.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

9/ We then asked whether these early neutrophils were functional. We found that they were motile, amoeboid, moved faster than neighboring deep cells, and responded to wound sites.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

8/ We show this peripheral domain is BMP-active and outside the Nodal organizer. Inhibiting Nodal with A-83-01 disrupted mesendoderm formation (cyan+magenta) but neutrophils (yellow) still emerged. Inhibiting BMP with LDN strongly reduced early neutrophils (yellow).

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Syd Sattler @sydsat.bsky.social · 29/06/2026

7/ Here is a mercator projection of the embryo as it finishes epiboly and the aggregate (blue) forms. Immune progenitors (black) give rise to lcp1+ immune cells (orange). Huge thanks to Nicholas Lammers who developed the cell tracking pipeline and produced this incredible movie.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

6/ Tracing neutrophils back in developmental time, we found they emerged sparsely and asynchronously, often as sister cell pairs, in a salt-and-pepper pattern at the aggregate periphery.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

5/ To watch this process live, we generated an endogenous eGFP-lcp1 reporter to mark neutrophils and a ubiquitous nuclear marker to provide spatial context for in toto light-sheet microscopy.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

4/ Spatially, these cells (yellow+magenta) appeared around the periphery of the forming aggregate and on the yolk surface, when cells are largely still dispersed and the mesendoderm (cyan) was still organizing.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

3/ Using scRNA-seq at the incipient aggregate stage, we identified a population of cells expressing the neutrophil gene program, including spi1b, lcp1, and mpx. We show this program is activated before germ layers are resolved.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

2/ Annual killifish have highly unusual early development: deep cells disperse across the yolk, lose cell-cell contacts, and later aggregate to form the embryo - a stage called the incipient aggregate.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

1/ In many vertebrates, primitive myeloid cells arise from BMP-patterned ventral mesoderm during segmentation. Annual killifish let us ask whether that tissue context is required — or whether the myeloid program can be deployed elsewhere.

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Syd Sattler @sydsat.bsky.social · 29/06/2026

What if an embryo made immune cells before it finished building the tissue they usually come from? In our new preprint, we show that annual killifish embryos specify neutrophils before germ layers are fully resolved. www.biorxiv.org/content/10.6... Huge thanks to my PI, @ohnolog.bsky.social ! 🧵

biorxiv.org

Early immune cell development precedes gastrulation in annual killifish

During embryogenesis, cell types arise in a predictable order because developmental regulators act sequentially. But how evolutionary changes in morphogenesis reshape the signaling environments that a...

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Syd Sattler @sydsat.bsky.social · 23/03/2025

Thank you @nwdbio.bsky.social for supporting my research and awarding my talk with the first place travel award to attend @socdevbio.bsky.social’s national SDB conference!!! See you all in Puerto Rico 🚀🧬 !!!

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