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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

This would have not been possible without our amazing collaborators from Pailhoux, Nef, Mckey and Rudaz labs.

Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Altogether, our findings highlight the plasticity of sex determination systems and how analogous functions can arise in evolution from diverse cellular lineages. These and other interesting findings are in the preprint. Have a look and let us know what you think!!

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Our data suggest a model in which mammalian supporting-like cells may be homologous to steroidogenic cells in non-mammalian species, both sharing conserved fate regulators such as PAX2/8 and TBX1.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Through comparative analyses, we find these cell types are transcriptionally similar and occupy a comparable anatomical position within the gonad, suggesting deep evolutionary conservation.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Interestingly, we recently noted that in non-mammals (e.g., turtle), sex hormone production can occur independently of the interstitial lineage, via the supporting cells. This raises a question: are the SLCs related to steroidogenic supporting cells in non-mammals? www.biorxiv.org/content/10.6...

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Again, in toto organ imaging revealed colocalization of supporting-like cells (PAX8+) with either rete fate (SOX9+) or a steroidogenic fate (CYP17A1+) markers, highlighting their dual developmental potential.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Lineage reconstructions shows that SLCs can give rise to two distinct populations: • A structural rete lineage, as described in other mammals (KRT8+, SOX9+) • A steroidogenic lineage, selectively observed in some species, expressing CYP17A1, CYP11A1 and STAR

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

But in the rabbit, supporting-like cells are strikingly abundant in the developing ovary. See this beautiful in toto organ imaging (by @jenmckey.bsky.social ), confirming colocalization of SLCs (PAX8+) with steroidogenic markers (CYP17A1), thus linking identity and function in situ.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

But why is this relevant? SLCs were recently identified in mouse gonads and were thought to mainly contribute to rete structures, essential for gamete transport. SLCs have been elusive for decades, mainly because they represent a tiny fraction of the mouse gonad. www.science.org/doi/10.1126/...

science.org

Origin, specification and differentiation of a rare supporting-like lineage in the developing mouse gonad

Previously uncharacterized supporting-like cells are involved in testicular and ovarian development.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Unexpectedly, we find that the steroidogenic program is activated in supporting-like cells (SLCs) in both sexes. It is maintained in ovaries, but in testes it is progressively replaced by interstitial fetal Leydig cells (FLCs), the canonical steroidogenic lineage.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

To solve this mystery, we generated a single-cell transcriptomic atlas of the rabbit gonad, a species in which estrogens are produced before the interstitial lineage differentiates.

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Sex hormones regulate reproduction, physiology and behaviour. In mammals, their production is thought to depend on interstitial cells that become Leydig or theca cells. But some species produce sex hormones before these lineages differentiate. How? 🤔

static.klipy.com

Baothelop Bunny with Glasses

ALT: Baothelop Bunny with Glasses

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Iván Barberá Aura @ivan-barbera-aura.bsky.social · 29/05/2026

Preprint from @dariloops.bsky.social lab !!🚨🚨 An unexpected source of sex hormones in the mammalian gonad: Supporting-like cells (SLCs). SLCs have a latent steroidogenic potential and may represent an ancestral lineage conserved beyond mammals. www.biorxiv.org/content/10.6...

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