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Results for “developmental biology”

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At least 451 records · Page 25Linked to original sources

bioRxiv2026

Virus-Like Particles: The Next Frontier in Livestock Gene Editing

Pigs and chickens are not only the most important livestock species for global food production but also serve as key model organisms in various research disciplines. The pig is widely used in translational research due to its anatomical and physiological similarity to humans, providing valuable insights into immunology, metabolism, and disease mechanisms. In contrast, the chicken has become an essential model for studies related to poultry health, animal welfare, and developmental biology. Its externally developing embryo offers exceptional accessibility for experimental manipulation. Recent advances in genome editing technologies, particularly CRISPR/Cas9, have further expanded the potential of these species for functional genomic studies, although the efficient delivery of such tools remains a major challenge. By using virus-like particles (VLPs), we have been able to overcome this limitation. Here, we evaluated VLPs as delivery vehicles for genome engineering tools in pigs and chickens, two key livestock species at the human-animal interface. VLP-mediated delivery enabled efficient Cre recombination and high CRISPR/Cas9 editing rates in porcine cells, organoids, and oocytes, particularly when multiplexed. In chickens, VLPs supported robust Cre recombination and Cas9-mediated editing in cell culture, tracheal organ cultures, and in ovo. Reporter VLPs and dCas9 VLPs further demonstrated the versatility of this platform across porcine and avian systems. Together, these findings establish VLPs as an efficient and time-saving strategy for gene editing in livestock, with relevance for animal health, agricultural productivity, and translational One Health research.

genetics↗

bioRxiv2026

A Unified Control of Cellular Differentiation: From Temporal Multistability to Spatial Pattern Formation in Gene Regulatory Networks

How genetically identical cells spontaneously break symmetry to assume divergent fates is a fundamental problem in developmental biology. While modern genomics has mapped the vast molecular repertoire involved in gene regulation, understanding the mechanism of cell state transitions that drive differentiation remains a formidable challenge. To address this, we use a reaction-kinetic framework to analyze recurring motifs of two and three competing master regulators. While typically such circuits are studied numerically, we show that assuming symmetry in nodes and interactions provides exact analytical description of the bifurcations governing cell fate transitions. We find that the possible cell fates across all considered topologies are dictated by a single dimensionless quantity, {beta}--the ratio of protein degradation to production rates. In the binary Toggle Switch (TS), decreasing {beta} destabilizes the symmetric (stem cell) state, giving rise to two asymmetric (differentiated) fates via a supercritical pitchfork bifurcation. In the three-component Toggle Triad (TT), low values of {beta} yield three asymmetric fates through subcritical pitchfork bifurcation, creating an intermediate range of {beta} where both symmetric and asymmetric fates are simultaneously stable. For the Self-Activating Toggle Switch (SATS), we identify a new parameter for the self-activation threshold ({theta}) and show that decreasing{theta} progressively stabilizes the uncommitted state, leading to a regime of tristability. Building on these temporal bifurcations, we next address the feasibility of spatial structure formation: can these multistable fates stably coexist within a spatial domain? Through a minimal model of cell-cell communication via free diffusion, we extend these motifs into reaction-diffusion systems, which reveals a direct role of network topology on spatial organization. We prove that any heterogeneous pattern in two-node circuits is inherently transient and unstable. In contrast, the three-node repressive network supports the stable spatial coexistence of differentiated phenotypes through pure diffusion, a phenomenon we analyze by studying heteroclinic interface solutions as building blocks. By reducing complex regulatory dynamics to tractable models with physically meaningful parameters, we establish a minimal framework which relates topology to cell fate. Finally, the effects of temporal multistability on pattern formation provide an excellent studying ground for morphogenesis, synthetic biology, and the overarching problem of spatiotemporal self-organization.

systems biology↗

bioRxiv2026

Differentiable Vertex Model: Exploring Gradient-Based Optimization for Tissue Morphogenesis

Vertex models are widely used within the field of developmental biology to study tissue morphogenesis. These models are well-suited for modeling deformation at the cellular level where movement is driven by local forces. However, understanding how these microscopic movements coordinate to yield macroscopic phenomena such as the shapes of entire tissues remains a challenge. Here we study a top-down approach using differentiable programming on a simplified vertex model of a laminar tissue, and investigate whether the attributes of individual cells can be tuned to make the mesh as a whole acquire a predefined shape. We let the mesh evolve according to simple rules defined by the input to each polygon, and evaluate the resulting shape against a target boundary. Additionally, we show how the high degeneracy of the output can be reduced by constraining the polygon distributions: first, by adding simple penalties on tissue-wide attributes; and second, by dividing the tissue into regions, within which we bias the attributes toward characteristic values. Our study shows how a simple vertex model can be combined with differentiable programming to model developing tissues, and provides insight into the way individual cells must coordinate to yield macroscopic phenomena such as pre-programmed shapes.

biophysics↗

bioRxiv2026

The direct conversion of human somatic cells into neural-like cells involves a transition through a transient intermediate state.

BackgroundDirect conversion of human somatic cells into functional neurons could offer a faster way to generate patient-specific neurons for use in regenerative medicine, disease modelling, and drug development. Although it has been reported that neuronal direct reprogramming bypasses the intermediate pluripotent state, no reports have included time-lapse experiments, potentially overlooking transient intermediate states. Recent studies have shown that the conversion of human mesenchymal stromal cells (hMSCs) into neuron-like cells involves a transition through a transient intermediate state. Therefore, further research is needed to fully understand the process by which human somatic cells can become neurons without cell division. In this study we investigates whether direct neuronal reprogramming of human bone marrow-derived MSC (hBM-MSCs), dental pulp-derived MSC (hDP-MSCs), and adult human dermal fibroblasts (HDFa), involves a transient intermediate state, and sought to further validate the neuronal identity of hMSC-derived induced neurons. MethodsIn this study, we conducted time-lapse experiments to observe the transformation of hBM-MSCs, hDP-MSCs and HDFa, into neurons using a small-molecule-based direct reprogramming protocol. Cellular and ultrastructural changes were further characterized by confocal and electron microscopy. ResultsDirect conversion of hBM-MSCs, hDP-MSCs and HDFa into neuron-like cells occurred rapidly and in absence of cell division. Time-lapse analyses revealed that reprogramming proceeds through a transient intermediate state characterized by distinct morphological changes and dynamic nuclear remodelling. Furthermore, we found that neuron-like cells derived from hBM-MSCs and hDP-MSCs exhibit neuronal polarization, expressed specific neuronal and synaptic markers, formed interconnected cellular networks, and exhibited functional plasticity, providing further evidence that hMSCs can become functional neurons. ConclusionsThis study provides clear evidence that the direct neuronal reprogramming process involves a transition through an intermediate, transient state. Our findings also provide further evidence that hMSCs can become functional neurons. In summary, our work provides new insights into the direct neuronal reprogramming process, which is essential for advancing both developmental biology and regenerative medicine.

neuroscience↗

bioRxiv2026

Minos transposon-mediated transgenesis in the sea urchin Paracentrotus lividus

In the multitude of suitable experimental systems used for functional studies in the field of developmental biology, the sea urchin plays a central role due to its amenability to various methods, including both transient and stable transgenesis. Among others, transposable elements represent powerful tools for generating stable transgenic specimens, and Minos transposon turned out to be an excellent genetic tool in marine organisms, despite its efficiency being host-dependent. This study provides new evidence for the activity of Minos transposable elements and their stable integration into the genome of the Mediterranean sea urchin Paracentrotus lividus. Using the Minos-based technology coupled with a fully-automated system used for the qPCR screening of the Minos transposon integration, we devised a new pipeline for performing transgenesis-based functional studies in P. lividus.

molecular biology↗

bioRxiv2026

Killiverse: an interactive multi-omics web resource for killifish

BackgroundKillifish have emerged as valuable vertebrate model systems for investigating several disciplines including aging, regeneration, and developmental biology. Multi-omics datasets are increasingly being generated for killifish. However, their reuse remains limited due to computational challenges, largely due to the lack of accessible resources creating a bottleneck in widespread adoption of the killifish model. To address this, we developed Killiverse, a web resource for quick and intuitive exploration of multi-modal omics data dedicated to the model organism. ResultsKilliverse is an interactive, no-code, web-based platform designed for exploration of killifish multi-omics data. The platform aggregates a growing list of datasets including bulk transcriptomes, single-cell and single-nucleus transcriptomes, proteomes, and lipidomes processed through standardized pipelines and genome assemblies. Killiverse supports customized visualization and enables cross-study and cross-species analysis. It provides ortholog mapping to several established model organisms. By combining low-code software development with modern cloud technologies, the platform delivers a scalable browser-accessible application for the community. ConclusionsKilliverse enables rapid hypothesis development through the identification of patterns across studies and species. The ortholog maps allow the findings to be placed in a broader biological context. The platform represents an innovation in genomics data visualization that will serve as a template for future tool development. Killiverse is freely accessible at https://killiverse.org/.

genomics↗

bioRxiv2026

Same-section spatial metabolo-transcriptomics using Stereo-meta-seq reveals DHA-driven kidney maturation

A central unresolved question in developmental biology is whether local metabolites merely accompany, or actively instruct, tissue maturation. Addressing this question requires direct spatial coupling of metabolic states with genome-wide transcriptional programs in situ at high spatial resolution, which existing approaches do not readily achieve. Here, we introduce Stereo-meta-seq, a workflow that integrates quantitative MALDI-MSI with Stereo-seq spatial transcriptomics within a single tissue section. A conductive adapter was designed to overcome the electrical incompatibility of non-conductive Stereo-seq chips with vacuum MALDI platforms, improving efficiency of MSI detection that preserves RNA integrity. MALDI laser-ablation marks are retained in downstream Stereo-seq data and serve as intrinsic fiducials for direct co-registration at 10 m or 20 m resolution, enabling fine grained spatial metabolite-transcript integration. Applying Stereo-meta-seq to human kidney development, we uncover selective enrichment of docosahexaenoic acid (DHA) in maturing proximal tubules. Functional studies in human kidney organoids demonstrate that DHA activates PPAR-and HNF4-driven transcriptional programs and promotes proximal tubule maturation in vitro and after transplantation in vivo. These findings identify lipid metabolism as an instructive regulator of human nephrogenesis and establish Stereo-meta-seq as a practical platform for dissecting metabolite-gene coupling and tissue heterogeneity in situ.

Cell Biology↗

bioRxiv2026

An open-access CT-based 3D anatomical dataset of extant sharks across all major lineages

0Sharks exhibit extraordinary morphological diversity across a wide range of ecological niches, yet large-scale, high-resolution digital datasets of their internal anatomy remain limited. Here we present an open-access 3D shark anatomical repository derived from published X-ray computed tomography (CT) data, featuring manually segmented and systematically annotated models of the chondrocranium, visceral arches, axial skeleton, musculature, and viscera in standard STL format. The dataset comprises 117 individuals, representing 72 species across 25 families and all nine extant shark orders, with 115 full-body reconstructions and two head-only models. This open-access dataset offers a comprehensive resource for comparative anatomy, biomechanical simulations, evolutionary developmental biology and biomimetics research of extant sharks.

evolutionary biology↗

bioRxiv2026

The impact of temperature-induced vertebral anomalies on C-start swimming performance in Astyanax mexicanus (Teleostei: Characidae)

This study investigates the impact temperature-induced vertebral anomalies have on the C-start escape response of Astyanax mexicanus, a model species in evolutionary developmental biology. Employing three temperature treatments to induce varying degrees of skeletal anomalies, we assessed their effects on key swimming performance metrics including, C-start time, curvature coefficient, head displacement distance, and displacement velocity. Through the use of linear mixed models and generalized linear mixed models, our results reveal that specific anomalies such as vertebral fusions and anomalous haemal and neural spines affected the curving ability of C-start escape responses. However, these did not negatively impact other performance parameters, with velocity, distance, and response time showing no significant impacts from any anomaly types, when assessed individually. This suggests a complex interplay between structural deformities and compensatory physiological mechanisms that maintain functional performance. Other variables measured had a stronger and significant impact on swimming performance, including standard length, vertebral number, and temperature treatment, which influenced escape speed, curving ability, and overall locomotor performance. Our findings challenge conventional perceptions about the debilitating impact of vertebral anomalies, indicating that many affected fish can still effectively perform escape maneuvers critical for survival.

zoology↗

bioRxiv2026

From Diverse Prior Knowledge to Mechanistic Causal Network Using PSoup: A Case Study in Shoot Branching

Mechanistic models of plant regulatory networks typically require extensive parameterization, limiting their generalisation and scalability. Here we present a parameter-free, topology-driven model of shoot branching that predicts phenotypic outcomes from network structure alone. We constructed a signed, directed causal network by distilling regulatory relationships from the published literature spanning many laboratories, species, years, data types, and methodological frameworks. This extracted the essential logic of the system, consistent with developmental-biological reasoning and anchored in empirical evidence. Using PSoup, which automatically translates network topology into algebraic equations, the model propagates information across the network and predicts the qualitative direction of change relative to a defined baseline, mirroring the comparative framework of biological experiments. The pipeline, from network construction through automated equation generation to prediction, is transparent and reproducible. Trained against branching phenotype data with 78 diverse perturbations spanning genetic mutations and hormone treatments, the model achieved 86% accuracy in predicting branching direction. On an independent test set of 84 perturbations measuring bud release and gene expression at nodes not used during training, accuracy reached 75%. The approach highlighted deficiencies in our understanding of the topology of the network around SMXL 6/7/8 and ABA nodes. Other errors came mainly from modelling choices, such as the threshold for scoring a node as changed relative to baseline. Beyond shoot branching, this work demonstrates a general strategy for synthesizing biological knowledge into validated predictive networks, providing a foundation for both applied breeding and the advancement of fundamental biology.

plant biology↗

bioRxiv2026

TGF-β2-induced Snail-mediated EndMT signaling relies on both Smad-dependent and independent pathways

Endothelial-to-mesenchymal transition (EndMT) has become a central mechanism in developmental biology, fibrosis, vascular disease, and cancer. We previously reported on an integrated signaling model in which TGF-{beta}2 induces EndMT through coordinated activation of Smad-dependent and Smad-independent signaling pathways converging on Snail, while GSK-3{beta} regulates Snail activity. We performed a systematic figure-by-figure reproducibility analysis of the original publication. Independent studies published between 2011 and 2026 were identified and curated according to predefined inclusion criteria. Each original experimental conclusion was evaluated for independent confirmation. In parallel, selected biochemical experiments were independently reproduced using newly acquired reagents and contemporary Western blot methodologies. Independent publications consistently reproduced each major mechanistic conclusion of the original study, including activation of Smad, ERK, PI3K/AKT, and p38 MAPK signaling, regulation of Snail expression, EndMT-associated marker switching, and GSK-3{beta}-dependent control of Snail activity. Independent laboratory experiments reproduced the principal biochemical findings using contemporary reagents and experimental workflows. The combined literature analysis and independent laboratory replication demonstrate that the mechanistic framework in our previous study has remained reproducible across multiple laboratories, endothelial cell types, disease models, and fifteen years of investigation. This work illustrates a complementary framework for assessing reproducibility that integrates direct experimental replication with cumulative independent validation.

cell biology↗

bioRxiv2026

Ageas enables time-agnostic cell fate inference from single-cell and spatial multi-omics data

Understanding cell fate decisions is fundamental to developmental biology and disease research. However, experimental lineage tracing requires genetic manipulation, which is impractical in many systems, particularly in humans. Computational approaches often rely on time-resolved measurements, which single-cell and spatial omics studies rarely provide. Here, we present Ageas, a time-agnostic transfer learning framework for cell fate inference from single-cell and spatial multi-omics data. Ageas overcomes these limitations by learning fate memory from terminal cell populations and transferring this information to progenitor or intermediate cells, enabling fate bias inference from static molecular snapshots. To enable robust generalization across molecular modalities, Ageas employs a data-adaptive ensemble strategy with automated model selection. In benchmark datasets with lineage-traced single-cell transcriptomic and epigenomic profiles, as well as spatial transcriptomics, Ageas achieves strong performance compared to existing methods. Applying Ageas to a 3D human embryo reveals a spatially organized anterior-posterior gradient of epiblast fate priming, with anterior epiblast cells biased toward ectodermal fates and posterior cells toward primitive streak-derived lineages, accompanied by regionally graded fate-associated regulatory programs. Together, these results establish Ageas as a general framework for decoding cell fate decisions from static molecular snapshots.

bioinformatics↗

bioRxiv2026

Cell cycle control of chromatin creates a therapeutic window for epigenetic therapy in tumors

The relationship between cell cycle length and differentiation competence is well established in developmental biology, particularly in embryonic stem cells, where a short G1 phase maintains pluripotency and G1 lengthening permits lineage commitment. Whether this principle operates in cancer cells, where the cell cycle is deregulated and G1 is frequently shortened, and whether it can be pharmacologically exploited for therapy, has not been tested. Here we show that the duration of G1 is a causal determinant of chromatin state in cancer cells and that extending G1 creates a therapeutic window for epigenetic drugs. Using acute myeloid leukemia (AML) as a model, we demonstrate that low-dose palbociclib, at concentrations well below those required for cytostatic arrest, extends G1 without halting proliferation. This modest prolongation reshapes the histone modification landscape: repressive marks (H3K9me2/3, H4K20me2/3) increase while acetylation decreases, and chromatin accessibility rises broadly in the euchromatic compartment. Naturally slow-cycling AML lines share this epigenetic signature regardless of their oncogenic driver mutations, and pharmacologically extending G1 in fast-cycling cells recapitulates it, establishing G1 length as a causal regulator of the cancer epigenome rather than a passive correlate. To identify epigenetic vulnerabilities created by G1 extension, we performed complementary drug and CRISPR-Cas9 screens in G1-extended AML cells. Both approaches converged on LSD1 (KDM1A): slow-cycling AML cells are intrinsically sensitive to LSD1 inhibition, while fast-cycling cells become sensitive when G1 is prolonged. The combination of low-dose palbociclib and LSD1 inhibition triggers differentiation and significantly prolongs survival in AML xenograft models. p21 (CDKN1A) emerges as the central molecular determinant of this response. In slow-cycling AML cells, p21 is highly expressed and its knockdown abolishes LSD1 inhibitor sensitivity. Structure-function analysis using p21 mutants separates the two known activities of p21: the CDK-inhibitory function (which extends G1) is required for sensitization, whereas the PCNA-binding function is dispensable. Three pharmacological routes converge on the same endpoint, CDK inhibition, G1 extension, and a differentiation-competent chromatin state: direct CDK4/6 inhibition by palbociclib, p21 overexpression, and p21 induction through HDAC or EZH1/2 inhibitors. Palbociclib bypasses the requirement for p21 entirely, confirming that G1 length itself, not p21 as a protein, is the critical variable. Mechanistically, the combination of G1 extension and LSD1 inhibition produces a qualitatively distinct chromatin state rather than an additive one. ATAC-seq reveals thousands of combination-exclusive accessible regions, enriched for footprints of myeloid differentiation transcription factors including SPI1/PU.1, IRF1, and STAT1/2. A double-lock principle governs this remodeling: palbociclib drives the removal of repressive marks (H3K9me3 and H3K27me3), while LSD1 inhibition installs active marks at the newly accessible regions. The ncBAF chromatin remodeling complex, identified in our CRISPR screen and validated by knockout of its essential subunits BRD9 and SMARCD1, is specifically required for this response. Loss of ncBAF abolishes the combination-induced chromatin remodeling and differentiation program but does not affect the initial G1 extension or retinoic acid-induced differentiation, indicating that ncBAF specifically couples cell-cycle modulation to chromatin remodeling rather than acting as a general differentiation factor. The principle generalizes beyond AML. In melanoma, breast cancer, and small-cell lung cancer (SCLC), sensitivity to LSD1 inhibition tracks with p21 expression and cycling speed. Primary melanoma samples stratified by p21 recapitulate the same pattern: p21-high, slow-cycling cells are sensitive; p21-low, fast-cycling cells are resistant but can be sensitized by palbociclib cotreatment. Cisplatin-induced drug-tolerant persister (DTP) cells, which emerge as a slow-cycling, chemo-resistant population and upregulate both p21 and LSD1, become vulnerable to LSD1 inhibition and are eradicated by the combination. In melanoma patient-derived xenograft (PDX) models, p21-high tumors respond to LSD1 inhibitor monotherapy, while p21-low tumors are sensitized by palbociclib cotreatment, with p21 knockdown abolishing the response. Together, these findings establish cell-cycle duration as a tunable regulator of the cancer epigenome and demonstrate that pharmacological G1 extension converts cytostatic CDK4/6 inhibition into an epigenetic sensitization strategy. Both fast-proliferating and slow-cycling tumor compartments (including drug-resistant persisters) can be targeted by matching the epigenomic state to the appropriate combination of cell-cycle modulators and epigenetic drugs. p21 emerges as a candidate biomarker for patient stratification. More broadly, our work repositions the cell cycle from a passive conduit for proliferation signals to an active, druggable regulator of chromatin fate, with implications that extend from cancer therapy to stem cell biology and regenerative medicine.

cancer biology↗

bioRxiv2026

A scalable in vitro cell competition model identifies preleukemic super competitor clones

Preleukemic and leukemic conditions are frequently characterized by the acquisition of recurrent genetic mutations in hematopoietic stem cells (HSCs). One of the most frequently mutated genes in both clonal hematopoiesis and myeloid malignancies is the ten-eleven translocation 2 (TET2) gene, which encodes an epigenetic enzyme with a critical role in the regulation of gene transcription. While substantial work has shown that TET2 loss-of-function mutations lead to a clonal advantage, the underpinning cellular mechanism remains unclear, especially with respect to the early interactions with other cells. To study these early cell interactions of mutant and non-mutant cells, we developed an in vitro clonal competition platform where single-cell derived cultures are split into subclonal fractions which can be simultaneously cross-competed against multiple different clones of an opposing genotype. We identify a novel preleukemic cell phenotype that parallels the developmental biology phenomenon of super-competition, whereby ~10% of TET2-mutant clones actively and selectively suppress wild type (WT) cell expansion and, in some cases, completely eliminate WT clones. Molecular profiling and functional assays point to RAC1-GEF signalling inhibition as a specific WT cell vulnerability that is promoted, and tolerated, by neighbouring TET2-mutated clones. In addition to pinpointing selective drivers of non-mutant cell suppression, this clonal competition platform offers a broadly applicable new approach to study cell competition dynamics at an unprecedented scale.

cancer biology↗

bioRxiv2026

Dissecting functional elements in giant genomes using the first generation of high quality salamander assemblies

Salamanders are an enduring and historically significant group that helped originate multiple scientific fields of study, including regeneration, cytogenetics, experimental embryology, cloning, evolutionary developmental biology and evolution of extreme genome size. We generated a high-quality, single haplotype assembly for the 32 Gb axolotl (Ambystoma mexicanum) genome using an F1 hybrid between axolotl and a divergent relative the tiger salamander (A. tigrinum). Using multi-genome alignments to other salamanders that meet VGP metrics, we leveraged strong conservation of karyotypic structure to identify >523,000 highly conserved non-coding elements within massively expanded intronic and intergenic regions, the vast majority of which are unique to the salamander lineage. Orthogonal measures of chromatin state and enhancer activity confirmed that many conserved elements correspond to cis-regulatory sequences and identified several thousand that are utilized during regeneration. The conserved elements identified here will enable robust functional genomic analyses of tissue regeneration and other traits that uniquely empower salamander models in biological research.

genomics↗

bioRxiv2017

A safer, urea-based in situ hybridization method improves detection of gene expression in diverse animal species

In situ hybridization is a widely employed technique allowing spatial visualization of gene expression in fixed specimens. It has proven to be essential to our understanding of biological processes, including developmental regulation. In situ protocols are today routine in numerous laboratories, and although details might change, they all include a hybridization step, where specific antisense RNA or DNA probes anneal to the target nucleic acids strand. This step, in general, is carried out at high temperatures and in a denaturing solution, the hybridization buffer, commonly containing 50% (v/v) formamide. An important drawback is that hot formamide poses a significant health risk and so must be handled with great care.\n\nWe were prompted to test alternative hybridization solutions for in situ detection of gene expression in the medusa of the hydrozoan Clytia hemisphaerica, where traditional protocols caused extensive deterioration of the morphology and texture during hybridization, hindering observation and interpretation of results. Inspired by optimized protocols for Northern and Southern blot analysis, we substituted the 50% formamide with an equal volume of 8 M urea solution in the hybridization buffer. The new protocol yielded better morphologies and consistency of tissues, and also notably improved the resolution of the signal, allowing more precise localization of gene expression, as well as reduced staining at non-specific sites. Given the improved results using a less toxic hybridization solution, we tested the urea protocol on a number of other metazoans: two brachiopod species (Novocrania anomala and Terebratalia transversa) and the worm Priapulus caudatus, obtaining a similar reduction of aspecific probe binding. Overall, substitution of formamide by urea in in situ hybridization offers safer alternative protocols, potentially useful in research, medical and teaching contexts. We encourage other workers to test this approach on their study organisms, and hope that they will also obtain better sample preservation, more precise expression patterns and fewer problems due to aspecific staining, as we report here for Clytia medusae and Novocrania and Terebratalia developing larvae.

developmental biology↗

bioRxiv2019

Is evolution predictable? Quantitative genetics under complex genotype-phenotype maps

A fundamental aim of post-genomic 21st century biology is to understand the genotype-phenotype map (GPM) or how specific genetic variation relates to specific phenotypic variation (1). Quantitative genetics approximates such maps using linear models, and has developed methods to predict the response to selection in a population (2, 3). The other major field of research concerned with the GPM, developmental evolutionary biology or evo-devo (1, 4-6), has found the GPM to be highly nonlinear and complex (4, 7). Here we quantify how the predictions of quantitative genetics are affected by the complex, nonlinear maps found in developmental biology. We combine a realistic development-based GPM model and a population genetics model of recombination, mutation and natural selection. Each individual in the population consists of a genotype and a multi-trait phenotype that arises through the development model. We simulate evolution by applying natural selection on multiple traits per individual. In addition, we estimate the quantitative genetics parameters required to predict the response to selection. We found that the disagreements between predicted and observed responses to selection are common, roughly in a third of generations, and are highly dependent on the traits being selected. These disagreements are systematic and related to the nonlinear nature of the genotype-phenotype map. Our results are a step towards integrating the fields studying the GPM.

evolutionary biology↗

bioRxiv2022

Frem1 activity regulated by Sonic Hedgehog signaling in the cranial neural crest mesenchyme guides midfacial morphogenesis

The Frem/Fras family of extracellular matrix proteins has been linked to human face shape variation and malformation, but little is known about their regulation and biological roles in facial development. During midfacial morphogenesis in mice, we observed Frem1 expression in the embryonic growth centers that form the median upper lip, nose, and palate. Expansive spatial gradients of Frem1 expression in the cranial neural crest cell (cNCC) mesenchyme of these tissues suggested transcriptional regulation by a secreted morphogen. Accordingly, Frem1 expression paralleled that of the conserved Sonic Hedgehog (Shh) target gene Gli1 in the cNCC mesenchyme. Suggesting direct transcriptional regulation by Shh signaling, we found that Frem1 expression is induced by SHH ligand stimulation or downstream pathway activation in cNCCs and observed GLI transcription factor binding at the Frem1 transcriptional start site during midfacial morphogenesis. Shh pathway antagonism reduced Frem1 expression during pathogenesis of midfacial hypoplasia, and FREM1 was sufficient to induce cNCC proliferation in a concentration-dependent manner. These findings provide novel insight into the mechanism by which the Shh pathway drives midfacial morphogenesis and reveal a functional role for Frem1 in cNCC biology that establishes the developmental basis for FREM1-associated face shape variation and malformation.

developmental biology↗