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11/15 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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10/15 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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9/15 Interestingly, we recently noted that in non-mammals (e.g., turtle), sex hormone production can occur independently of the interstitial lineage, via supporting cells This raises a question: are SLCs related to steroidogenic supporting cells in non-mammals? www.biorxiv.org/content/10.6...

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8/15 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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7/15 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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6/15 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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4/15 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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3/15 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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Darío Lupiáñez @dariloops.bsky.social · 23/03/2026

🚨Preprint🚨 An unexpected source of sex hormones in mammalian gonads: Supporting-like cells (SLCs) 🐇 SLCs have latent steroidogenic potential and may be an ancestral lineage conserved beyond mammals Led by @ivan-barbera-aura.bsky.social & V Chung Bluetorial 1/15👇 www.biorxiv.org/content/10.6...

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🏝️ In Crete island, enjoying the iconic Vertebrate Sex Determination Synposium @biol-vsd.bsky.social Thanks to the organizers for the invitation and especially to @nitzan-gonen.bsky.social & Humphrey Yao for making this meeting a reality

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Darío Lupiáñez @dariloops.bsky.social · 06/03/2026

🚨 Job Alert - Please share! 🙏 Interested in 3D gene regulation in development & evolution? 🤓🧬 💥 Our lab at @cabd-upo-csic.bsky.social is expanding! We’re recruiting: ✅ PhD students ✅ Postdocs 💻🧪 Experimental or computational backgrounds welcome 👇 Details below

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20/n We show that Meis1 and Meis2 act redundantly during sexual development Through allele deletions in transgenic mice, we show these genes are essential to specify sexual identity in both females and males The more Meis alleles deleted, regardless of the combination, the stronger the phenotype

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20/n Finally, we reconstructed gene-regulatory networks associated to #sexdetermination These networks are highly dynamic and include key sex-determining factors, as well as novel regulators like Meis genes

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19/n Importantly, we demonstrate that METALoci predictions are tissue specific. The deletion of the Fgf9 gonadal regulatory region causes sex reversal but overcomes the perinatal lung lethality typically associated with complete Fgf9 inactivation.

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18/n Mutant gonads displayed two distinct phenotypes with different degrees of male-to-female sex reversal, same as in the full Fgf9 knockout. Immunofluorescence revealed the simultaneous presence of testicular (SOX9) as well as ovarian (FOXL2) and meiotic markers (SYCP3).

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17/n RNA-seq analysis of XY E13.5 gonads revealed a downregulation of Fgf9, as well as of other testicular genes. In contrast, the female program was activated with the initiation of meiosis and the upregulation of ovarian genes.

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16/n We identified a non-coding region located approximately 250 Kb downstream of Fgf9, whose deletion was predicted to be disruptive for its regulation. To validate it, we generated different transgenic mouse lines carrying deletions of the region.

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15/n We tested the potential of METALoci as predictive tool for regulatory activity We investigated the regulation of Fgf9, a pro-testicular morphogen whose regulation was unknown We computationally scanned the locus and estimated the effect of 50Kb deletions on Fgf9 metaloci

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14/n From a regulatory perspective, we observe fundamental differences between the female and male pathways. Male differentiation involves increased #enhancer activity and more activation/repression of sex-specific genes than female differentiation.

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13/n Focusing on genes that transition from low to highly active 3D environments during Sertoli cell differentiation, we performed enrichment analysis. This demonstrates that METALoci accurately captures the biology of the underlying process, just based on regulatory activity.

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12/n METALoci quantified and compares regulatory activity between samples/conditions I.e. Sox9 transitions from a 3D environment with low activity to a highly active. We quantified and compared the temporal and sex-specific regulatory activity for all 24,027 genes in the mouse

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11/n Using Hi-C and H3K27Ac data, METALoci reconstructs the 3D enhancer hubs (or metaloci) for each gene during sex determination I.e. The testis-specific upregulation of Sox9 is associated with formation of a metaloci (in red) including its two known enhancers, TESCO & Enh13

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10/n METALoci repurposed this type of analysis to quantify gene regulation, based on the fact that #enhancers and their target genes may cluster within the 3D nuclear space and display similar #epigenetic properties

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9/n In the next image, you can see a map of the median household income in Paris. Red color indicates areas with high income surrounded by other blocks with similar income. The blue area shows the same for the low income. In pink-ish areas, there’s not a clear correlation.

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7/n Here, we applied METALoci, an approach that integrates #3DGenome and #Epigenetics data into a unified framework maps, developed by @jrotwitguez.bsky.social & @mamartirenom.bsky.social from @cnag-eu.bsky.social @crg.eu

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5/n Our initial analyses revealed a high degree of conservation in TAD structures and moderate changes in A/B compartments. 3D chromatin structure seems to be mostly preformed before #sexdetermination occurs!

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4/n We explored the 3D regulatory landscape of mammalian #sexdetermination in vivo, combining FACS sorting and low-input Hi-C. Focusing on the cell lineage initiating this process: bipotential supporting cells that differentiate into granulosa (XX) or Sertoli (XY), in mice.

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Darío Lupiáñez @dariloops.bsky.social · 03/02/2026

3/n Mammalian #sexdetermination is directed by the gonad, which can differentiate into ovary or testis. This depends on the presence or absence of a Y chromosome and the SRY gene. Sex-determining signals induce a physical and behavioral transformation of the entire organism.

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3/ For example, fetal steroidogenesis, a major gonadal function: Mammals ➡️ interstitial lineage Non-mammals ➡️ supporting lineage Even when cell lineages seems “homologous”, their functions have been evolutionarily rewired ⚙️

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Darío Lupiáñez @dariloops.bsky.social · 19/09/2025

🎁Wrapping up 5 days of science at the National Course of Genetics 🧬 by @segenetica.bsky.social and Conexion Genoma @csic.es As organizers, @aruizherrera.bsky.social and I have really enjoyed the organization. Thanks to all participants and professors for the lively discussion!! See you in 2027 😉

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Darío Lupiáñez @dariloops.bsky.social · 18/09/2025

🎉 Adrian de Reus @cbm-csic-uam.bsky.social and Andrea Sempere @cbgpmadrid.bsky.social were the winners of our giveaway 🥳 📖 They received a copy of #SerCientífico, the latest book by @lluismontoliu.bsky.social 🙌 Thanks for the generous donation, Lluis!

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Darío Lupiáñez @dariloops.bsky.social · 18/09/2025

🕛 Noon talks by Ana Losada @cniostopcancer.bsky.social on genome organization by cohesin, and @anaconesa.bsky.social @i2sysbio.es on RNA isoform detection and genome annotation🧬

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Darío Lupiáñez @dariloops.bsky.social · 18/09/2025

4️⃣ Fourth day of the CNG 2025 by @segenetica.bsky.social and Conexion Genoma. ☀️Morning talks by @mamartirenom.bsky.social @cnag-eu.bsky.social on structural genomics, and @radaiglesiaslab.bsky.social @univcantabria.bsky.social on long-range gene regulation

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And some truffle eggs for dinner 😅

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And some truffle eggs for dinner 😅

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🔚 Ending with short presentation from our talented participants on their current projects

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🔅Noon session with @gonzalezlabbcn.bsky.social from IBB @csic.es on transposable elements, and @aruizherrera.bsky.social from UAB on 3D chromatin organization

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