New NIH funded research from our group now out. We are interested in development and evolution of cell types and adult phenotypes. In this paper, postdoc Dylan Huang and collaborators asked how a pigmentary ornament of bright white cells develops on the fin of zebrafish. www.pnas.org/doi/10.1073/... - ThreadSky

dparichy.bsky.social • 4 days ago

New NIH funded research from our group now out. We are interested in development and evolution of cell types and adult phenotypes. In this paper, postdoc Dylan Huang and collaborators asked how a pigmentary ornament of bright white cells develops on the fin of zebrafish. https://www.pnas.org/doi/10.1073/pnas.2424180122

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dparichy.bsky.social•4 days ago

We showed previously that white cells—melanoleucophores—differentiate from melanophores. Here we show how this occurs, with massive changes in transcriptome, turnover of pigmentary organelles, loss of melanin and gain of white guanine crystals.

dparichy.bsky.social•4 days ago

Here’s a kickass FIB-SEM movie of a transitional cell, showing organelles in various states of degradation or development (this took a week of instrument time).

dparichy.bsky.social•4 days ago

We hypothesized that positional information specifies where transdifferentiation should happen. scRNA-seq, mutants and transgenes showed that one such cue is Agouti-related Asip1, which acts in concert with another Agouti peptide, Asip2b,

dparichy.bsky.social•4 days ago

But even knocking out both Agouti genes didn’t eliminate all the white cells so we looked further and identified an additional role for BMPs, which pattern the fin more generally. Here BMPs signal through non-canonical receptors including Rgmb.

dparichy.bsky.social•4 days ago

So how do BMP (and Agouti) drive fate conversion? Transcription factors Foxd3 (well known) and Runx3 (not well known in pigment biology) are downstream of BMP and necessary and sufficient to effect melanin loss and purine gain.

dparichy.bsky.social•4 days ago

Putting it all together, we think this is what’s going on.

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