Biology subjects

Gallardo, S.

Publications and source records attributed to Gallardo, S..

4 recordsLinked to original sources

bioRxiv2026

Smad1 and Smad5 differentially transduce BMP signaling during in vitro differentiation of mouse embryonic stem cells into dorsal interneurons

A central unresolved question in development biology is how systems of overwhelming complexity arise from relatively few families of growth factors. Compounding this issue, signaling pathways often show signal convergence, where many ligands interact with fewer receptors, which then signal through a single second messenger complex. Here we investigate this question in the context of bone morphogenetic protein (BMP) signaling and its role directing dorsal spinal cord development, focusing on two receptor-regulated (R) Smads, Smad1 and Smad5. Multiple models have been proposed for their mode of action from acting redundantly through combined signal strength, to having distinct activities that drive different fate outcomes. We sought to distinguish between these models by generating CRISPR-edited Smad1 and Smad5 null mouse embryonic stem cell (ESC) lines to dissect the cell fate of activities of individual R-Smads, with a resolution not possible in vivo. Using a directed differentiation protocol for dorsal interneurons (dI), together with bioinformatic analyses, we have defined the roles of the R-Smads at key decision points along the dI specification timeline. Together, these findings support a model in which Smad1 and Smad5 play largely distinct roles in dorsal spinal cord development. While both R-Smads can activate canonical BMP-responsive transcriptional targets, they asymmetrically contribute to cell fate specification. Smad1 plays a restricted role, while Smad5 has a dominant role, regulating dorsal progenitor transcriptional dynamics and reiteratively directing the dorsal-most dI fates.

developmental biology↗

bioRxiv2025

In vivo human embryonic spinal cord atlas validates stem cell-derived human dorsal interneurons and reveals ASD spinal signatures

Restoring somatosensory function after spinal cord injury (SCI) faces fundamental challenges: neuronal subtypes must match both axial position and circuit identity, yet the developmental patterning of human dorsal spinal interneurons (dIs) remains incompletely defined. Here, we integrate six single-cell transcriptomics datasets derived from human embryonic spinal cord tissue spanning gestational weeks 4-25 to generate a reference atlas of early human somatosensory circuit development. The atlas reveals molecular signatures underlying expansion and specialization of dI4 and dI5 interneuron populations associated with mechanosensory and nociceptive processing. Guided by this resource, we established a neuromesodermal progenitor-based differentiation approach that generates dorsal interneurons spanning anterior-posterior identities. Comparison of in vivo and in vitro dI4/dI5 subclasses identified conserved gene networks associated with sensory modalities and revealed enrichment of autism spectrum disorder-associated genes within mechanosensory interneuron populations. Together, these findings clarify how human dorsal spinal interneuron diversity is established.

neuroscience↗

bioRxiv2025

A single factor for safer cellular rejuvenation

Ageing is a key driver of the major diseases afflicting the modern world. Slowing or reversing the ageing process would therefore drive significant and broad benefits to human health. Previously, the Yamanaka factors (OCT4, SOX2, KLF4, with or without c-MYC: OSK(M)) have been shown to rejuvenate cells based on accurate predictors of age known as epigenetic clocks. Unfortunately, OSK(M) induces dangerous pluripotency pathways, making it unsuitable for therapeutic use. To overcome this therapeutic barrier, we screened for novel factors by optimising directly for age reversal rather than for pluripotency. We trained a transcriptomic ageing clock, unhindered by the low throughput of bulk DNA methylation assays, to enable a screen of unprecedented scale and granularity. Our platform identified SB000, the first single gene intervention to rejuvenate cells from multiple germ layers with efficacy rivalling the Yamanaka factors. Cells rejuvenated by SB000 retain their somatic identity, without evidence of pluripotency or loss of function. These results reveal that decoupling pluripotency from cell rejuvenation does not remove the ability to rejuvenate multiple cell types. This discovery paves the way for cell rejuvenation therapeutics that can be broadly applied across age-driven diseases. HighlightsO_LISB000 drives multi-omic rejuvenation in human fibroblasts, as evidenced by substantial reversal of numerous epigenetic clocks, lowered single-cell transcriptomic age, and decreased senescence-associated gene expression. C_LIO_LIIn contrast to OSK(M), SB000 treatment maintains transcriptomic and functional measures of fibroblast identity without the activation of pluripotency. C_LIO_LISB000 rejuvenation generalises to keratinocytes, cells from another germ layer, with potency matching or surpassing OSK(M). C_LI

cell biology↗

bioRxiv2024

Developmental programmes drive cellular plasticity, disease progression and therapy resistance in lung adenocarcinoma

BackgroundCellular plasticity, involving loss of lineage determination and emergence of hybrid cell states, plays a pivotal role in non-small cell lung cancer (NSCLC) disease progression and therapy resistance. However, the full spectrum of atypical states generated in human NSCLC and the pathways that regulate them are yet to be fully elucidated. Here we examine the role of developmental programmes, alveogenesis and branching morphogenesis (BM), in regulating phenotypic diversity in NSCLC. MethodsTranscriptomic analysis of epithelial cells isolated from murine lungs at different stages of organogenesis were used to derive gene signatures for developmental programmes. Bulk tissue transcriptomic datasets from human NSCLC and non-neoplastic control samples were used to identify whether developmental programmes were associated with molecular, morphological, and clinical parameters. Single-cell RNA-sequencing was used to identify malignant cell states in human NSCLC (n = 16,621 epithelial cells from 72 samples) and protein level validation of these states was carried out using multiplexed immunohistochemistry (n = 40). ResultsMutually antagonistic regulation of alveogenesis and BM was found to account for a significant proportion of transcriptomic variance in human NSCLC bulk tissue datasets. BM activation was associated with poor overall survival rates in five independent lung adenocarcinoma (LUAD) cohorts (p=2.04e-13); and was significantly prognostic for resistance to tyrosine kinase inhibitors (TKIs; p=0.003) and immune checkpoint blockade (ICBs; p=0.014), in pre-treatment biopsies. Single-cell RNA-sequencing analysis revealed that malignant LUAD cells with loss of alveolar lineage fidelity predominantly acquired inflamed or basal-like cellular states, which were variably persistent in samples from TKI and ICB recurrence. ConclusionsOur results show LUAD tumours undergo reversion from an alveogenic to branching morphogenic phenotype during disease progression, generating inflamed or basal-like cell states that are variably persistent following TKI or ICB treatments. These findings identify prognostic biomarkers for therapy response and underscore the role of different cell states in resistance to multiple treatment modalities.

cancer biology↗