Jonathan Weissman, an HHMI Investigator based at the Whitehead Institute, and Jay Shendure, an HHMI Investigator at the University of Washington, worked independently on the problem, and each arrived at a solution built on the same audacious idea: instead of trying to watch cells divide, teach the cells to record their own divisions in DNA. The two teams developed distinct but conceptually related recording technologies, applied them to mouse embryos, and read out the accumulated records by sequencing individual cells. The result is a pair of complementary maps that reveal both what each cell became and where it came from, a combination that has never before been available for a mammal at this scale.

The historical benchmark for this kind of work dates to 1983, when researchers completed the lineage of the roundworm Caenorhabditis elegans, charting every single cell division from fertilized egg to adult. That feat was possible only because the roundworm embryo is transparent and develops outside the body, allowing scientists to sit at a microscope and watch each division as it happened. A mouse embryo, by contrast, grows inside its mother, hidden from direct observation, and expands from one cell to hundreds of millions of cells in just a few weeks. No microscope could follow that process, and no conventional measurement could capture it. As Weissman puts it, the new work is proof of principle that what was done with the roundworm in 1983 can now be done for mammals like mice and, by extension, like humans.

Weissman’s team solved the problem with a tool called PEtracer, unveiled in 2025, which relies on a genome-editing method known as prime editing. Prime editing can install precise, small changes into DNA without cutting both strands of the double helix, making it an ideal instrument for writing permanent marks into a genome. PEtracer deploys this capability at more than a hundred sites in the genome. Each time a cell divides, the recording machinery adds new marks, and those marks are inherited by every daughter cell, which then accumulate additional marks of their own. Over the course of development, the genome of each cell becomes a layered archive of its ancestry, with earlier marks shared by all descendants and later marks distinguishing individual branches of the family tree.

Reading the archive is where the power of the approach becomes clear. Because the marks are captured by sequencing individual cells, a single experiment yields two kinds of information at once. The shared mutations reveal the lineage, showing which cells are sisters, cousins, or distant relatives, while the natural gene expression profile of each cell reveals its identity and function. In the new research, Weissman’s team engineered stem cells carrying the PEtracer recording apparatus and injected them into a mouse embryo. As the embryo developed in utero, the heritable marks were incorporated into nearly every cell the embryo produced. By analyzing each cell at the end of development, the researchers assembled massive family trees that connected the final cell types of the mouse back to their common progenitors.

Shendure’s team took a parallel route with a technology called DNA Typewriter, which his group introduced in 2022. DNA Typewriter also uses prime editing, but it records each editing event on a dedicated string of DNA that functions like a ticker tape, logging divisions in sequence as the embryo grows. In the new study, the team injected the components of DNA Typewriter into a fertilized mouse egg, allowing the recording to begin at the very first division of life. As the cells multiplied, the tape accumulated a chronological record of the embryo’s cellular expansion. Reading that tape back allowed the researchers to reconstruct the developmental history of the animal from zygote to late organogenesis, the stage at which the major organs have taken shape.

The two technologies share a common motivation, one that Shendure articulated in explaining why recording is superior to existing approaches. Most biological measurements, he notes, depend either on live imaging, which is limited because most animal tissues are not transparent, or on genomics, which is destructive and captures only a single moment in time. Recording techniques change the equation entirely. By writing history into DNA as it happens, they enable measurements over time in settings that cannot be directly visualized, including the interior of a growing mammalian embryo. The cell divides, each daughter receives a mark, and those marks are inherited and extended through subsequent generations, so that by looking at the marks in the DNA at the end, the relationships among millions of cells can be reconstructed after the fact.

The scientific payoff of these maps is expected to be broad. Understanding how cells differentiate to build tissues is one of the central questions of developmental biology, and the new lineage trees provide a direct view of which progenitors give rise to which mature cell types. The maps also offer a way to study disease at its origins, revealing where and when a developing embryo is most vulnerable to environmental or genetic stressors. In cancer biology, the same recording tools can be turned on tumors to investigate how cancers initiate, grow, spread through the body, and develop resistance to therapies, questions that likewise unfold at moments and in places that researchers cannot observe directly. If the information can be recorded in DNA, Weissman explains, then the underlying processes can be inferred and reconstructed in detail even after they have occurred.

Beyond the immediate biological insights, the data sets generated by the two teams are destined to play a role in computational biology. The researchers plan to use the lineage and cell fate information to train artificial intelligence models of embryogenesis, with the long-term goal of building a virtual embryo, a predictive computational model capable of forecasting developmental outcomes. Such a model would allow scientists to simulate how perturbations, from genetic mutations to environmental insults, might alter the trajectory of development, opening a new frontier in which mammalian embryogenesis can be studied computationally as well as experimentally.

There is also a humbling lesson embedded in the achievement, one that Weissman draws directly from the history of the roundworm map. When the C. elegans lineage was completed in the 1980s, it led to biological discoveries that no one could have anticipated at the time, precisely because understanding a process and its underlying molecular mechanisms generates questions no one had yet thought to ask. Weissman describes the coming wave of insights from the mouse lineage maps as a source of unknown unknowns, unexpected findings that will emerge simply from having the map in hand. Forty years after a transparent worm gave biology its first complete cellular family tree, two independent teams have brought that same power to a mammal, and the full consequences for understanding development, disease, and the origins of complex tissues are only beginning to come into view.

Subject of Research: Cell lineage tracing in mammalian embryonic development using DNA recording technologies

Article Title: Mapping how a single cell becomes an entire mouse

Article References: Mapping how a single cell becomes an entire mouse. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: cell lineage, mouse development, prime editing, PEtracer, DNA Typewriter, embryogenesis, single-cell sequencing, HHMI, Jonathan Weissman, Jay Shendure, developmental biology, virtual embryo

The team, led by Dania Camila Pulido-Barrera and Susan E. Mango at the Biozentrum of the University of Basel, used a technique called chromatin tracing, a DNA fluorescence in situ hybridization method that labels consecutive 100-kilobase segments along a chromosome and reconstructs their three-dimensional positions in single nuclei. Where population-averaged assays such as Hi-C blend thousands of cells into one consensus map, chromatin tracing preserves the individuality of each chromosome, allowing the researchers to sort thousands of traces into structural clusters. When they averaged their data, the result looked just like published Hi-C maps of the worm genome: smooth, featureless, and devoid of clear domain boundaries. But when they clustered the single-molecule traces, sharp, well-insulated domains popped into view.

Unsupervised clustering of more than five thousand chromosome traces from early embryos revealed seven distinct conformational groups. Three of them harbored roughly one-megabase domains with crisp boundaries and insulation scores nearly fourfold higher than the population average. The two strongest of these clusters accounted for about twenty percent of all traces and never appeared together in the same chromosome; instead, they alternated in an either-or fashion or merged into larger structures. This structural heterogeneity, the authors argue, is precisely why population-level assays have failed to detect such domains in C. elegans, a species long thought to lack canonical TADs because it has no CTCF protein, the insulator factor that anchors most TAD boundaries in vertebrates.

The researchers then asked which molecular machines build these domains. Their prime suspect was condensin I, a ring-shaped complex of the structural maintenance of chromosomes family that had previously been shown to fold the worm’s X chromosome into megabase-scale TADs during dosage compensation. Using a strong loss-of-function allele of dpy-28, which encodes a condensin I subunit, they traced chromosomes in condensin-depleted embryos. The effect was dramatic and selective. One of the two prominent wild-type domains, located at 19.7 to 20.9 megabases on chromosome V, vanished entirely in the mutant, while the neighboring domain at 18.2 to 19.6 megabases persisted, albeit slightly loosened. The condensin-dependent structure, with its sharp boundaries and TAD-like behavior, was christened a TADL, for TAD-like domain.

The surviving domain received a different name: elCID, short for elegans condensin-independent domain. Further experiments showed that elCIDs are also indifferent to histone H3K9 methylation, the classic chemical mark of heterochromatin. Embryos lacking virtually all H3K9 methylation, due to mutations in the met-2 and set-25 methyltransferase genes, still formed both TADL and elCID domains. H3K9 methylation did matter, however, for compaction: mutant chromosomes were significantly larger and less densely packed, with radius-of-gyration measurements matching those of condensin mutants. In other words, the epigenetic mark controls how tightly the genome is squeezed, but not where its domain walls stand. Cohesin, the other major SMC complex, proved irrelevant at this scale, organizing chromatin only in loops of twenty to forty kilobases that are averaged away at the tracing resolution.

Extending their analysis upstream, the team discovered a second elCID spanning 17.0 to 17.9 megabases, a region containing the 5S ribosomal RNA genes and the spliced leader repeat locus, hence its name, the 5SL elCID. This domain kept its sharp boundary even when condensin or H3K9me3 was abolished. Curiously, although the 5S locus is central to ribosome biogenesis, it showed no spatial association with the nucleolus; the median distance between the two exceeded 1.3 micrometers, with 98.6 percent of measurements above 300 nanometers. RNA polymerase III foci marking the 5S genes instead occupied transcriptionally permissive microenvironments, with H3K9me3 depleted inside the foci and enriched in the surrounding chromatin, suggesting the domain packages its precious cargo in a protected but not heterochromatin-embedded pocket.

The boundaries of the two domain types bore entirely different molecular fingerprints. The TADL boundary at 19.7 megabases was marked by peaks of all five condensin I subunits, a high-occupancy transcription factor site, and a break in the repressive H3K9me3 and H3K27me3 marks. The elCID boundaries, by contrast, coincided with active H3K36me3 marks, depletion of repressive marks, and robust maternal messenger RNA, with only weak zygotic transcription. This last observation points to a surprising conclusion: the boundaries of condensin-independent domains may be inherited from the mother’s transcriptional activity, consistent with the maternal inheritance of H3K36me3. Repeat elements, including long terminal repeats and satellite sequences, were also enriched at all three boundaries, and a zinc finger factor called ZTF-6 showed modest enrichment near the 19.0-megabase boundary.

Developmental timing added another layer of distinction. The TADL domain was already detectable in roughly thirty percent of embryos before zygotic genome activation, when no transcription occurs in the region, indicating that it assembles without any help from gene expression. The 5SL elCID appeared at the minor wave of zygotic activation, while the second elCID emerged only at the nine-to-forty-cell stage, coinciding with the onset of robust zygotic transcription, hinting that this domain class may depend on transcriptional activity. Power-law analysis of spatial scaling showed that wild-type chromosomes progressively compacted over development, with the scaling exponent falling from 0.19 to 0.13, whereas H3K9me mutants remained decompacted throughout and condensin mutants showed a unique defect in local folding at the 100-kilobase scale.

Perhaps the most conceptually striking result came from statistical polymer modeling. Even a free polymer with only nearest-neighbor interactions produced apparent boundaries and insulation in simulated traces, showing that generic molecular jitter can masquerade as domain structure. But such simple models failed to reproduce the measured boundary probabilities and the excess variability seen in real embryos. Only when structured, locus-specific interactions were included did the simulations match the data. Notably, condensin loss reduced this structured variability while H3K9me loss did not, identifying condensin I as a major source of organized chromatin fluctuation. The modeling also revealed that closely spaced domains cooperatively reinforce one another’s boundaries, explaining why the condensin-independent elCID loses some boundary strength when its condensin-dependent TADL neighbor is dismantled.

The study forces a reinterpretation of earlier claims that C. elegans lacks TADs. That absence, the authors conclude, reflects conformational variability rather than a genuine lack of domains: structures present in only a minority of chromosomes dissolve into the average. The finding resonates with live-imaging work in mammalian cells showing that TADs occupy only a small fraction of chromosome conformations at any moment. Whether the same diversity of heterochromatin domains extends to euchromatic regions and other chromosomes remains to be tested, and the 100-kilobase probe spacing resolves only megabase-scale architecture, leaving finer features unexplored. Still, the message is clear: to understand how genomes fold, scientists must stop averaging and start watching chromosomes one molecule at a time.

Subject of Research: Single-molecule chromatin tracing of heterochromatin domain architecture in C. elegans embryos

Article Title: Single-molecule chromatin tracing reveals a diversity of megabase heterochromatin domains

Article References: Pulido-Barrera, D. C., You, J. E., Angonezi, A. L., Kuznetsov, A., Xu, F., Verheijen, T., Saw, A. N., Kos, P., Giorgetti, L., Molina, N., Brückner, D., & Mango, S. E. (2026). Single-molecule chromatin tracing reveals a diversity of megabase heterochromatin domains. Nature Structural & Molecular Biology. https://doi.org/10.1038/s41594-026-01895-4

Image Credits: AI Generated

DOI: 10.1038/s41594-026-01895-4

Keywords: chromatin tracing, heterochromatin, TADs, condensin I, C. elegans, H3K9 methylation, elCID, genome organization, 3D genomics, embryogenesis, loop extrusion, single-molecule imaging

The core obstacle is a trade-off that has haunted the field of synthetic apomixis since its inception. Apomixis is the natural ability of some plants, mostly wild relatives of crops, to produce seeds asexually: the embryo inside the seed is a genetic clone of the mother plant, no meiosis and no fertilization required. If engineers could install this trait into hybrid crops, each seed would carry the exact hybrid genotype, locking in the vigour of the original cross. Researchers have made real progress by hijacking the plant’s own developmental machinery. By mutating three genes involved in meiosis, they can replace the reductive cell division with a mitosis-like division, producing gametes that retain the full parental genome, a process called clonal gametogenesis or mitosis instead of meiosis, known as MiMe. By expressing the BABY BOOM transcription factor in egg cells, they can coax those unreduced egg cells into embryos without sperm delivery, generating clonal seeds.

The problem is that these two interventions fight each other. Inducing fertilization-independent embryogenesis in the egg cell is inefficient, and the resulting seeds are often fewer, smaller or less viable than normal. The egg cell is not naturally poised to launch an embryo; it is a terminally differentiated cell waiting for a sperm signal. Forcing a master embryonic regulator such as BABY BOOM to act there produces only a fraction of clonal seeds, and the plants that do form frequently show reduced fertility, undermining the very yield advantage that apomixis is supposed to preserve. This is the apomixis trade-off: the more aggressively you push asexual embryo initiation, the more you compromise the reproductive machinery that makes the seed viable in the first place. Breaking that trade-off has been the central engineering challenge of the field.

The new study, highlighted in the commentary, takes a different route by shifting the trigger from the maternal side to the paternal side. Instead of reprogramming the egg cell, the researchers identified HUAXU, a transcription factor that is normally expressed specifically in sperm cells. In ordinary sexual reproduction, the sperm delivers its paternal genome to the egg and, crucially, contributes signals that help activate the zygotic programme. HUAXU appears to be part of that paternal activation machinery: when deployed appropriately, it can trigger embryogenesis independently of the normal fertilization event. By coupling this sperm-derived embryogenesis cue with clonal gametogenesis, the team achieved near-complete clonal seed production in hybrid rice, meaning almost every seed carried the intact hybrid genome without genetic segregation.

The mechanistic insight matters as much as the agronomic result. Paternal activation of embryogenesis has long been recognized as a critical step in flowering plants, where the sperm cell does far more than deliver DNA. It contributes cues that reconfigure the egg cell from a quiescent state into an actively dividing zygote. The identification of HUAXU as a sperm-specific transcription factor capable of initiating this programme independently gives researchers a handle on a process that was previously accessible only through maternal reprogramming. It suggests that the egg cell may be more receptive to paternal signals than to forced maternal expression of embryonic regulators, which would explain why earlier strategies that placed BABY BOOM or similar factors under egg cell promoters produced low efficiencies and fertility costs.

Efficiency and fertility are not academic details; they determine whether synthetic apomixis can ever leave the laboratory. Earlier landmark work, published in Nature in 2018 by Khanday, Skinner, Yang, Mercier and Sundaresan, demonstrated that synthetic clonal seeds could be made in rice, but at rates far too low for practical breeding, and subsequent refinements published in Nature Biotechnology in 2019 improved the system without eliminating the penalty. The commentary authors, who include researchers affiliated with the Laboratory of Advanced Breeding Technologies at the Institute of Genetics and Developmental Biology in Beijing, frame the new result as a turning point precisely because it resolves the efficiency-fertility conflict: near-complete clonality combined with minimal yield penalty means the hybrid’s agronomic performance is essentially preserved through the seed generation. A scalable strategy for fixing heterosis requires exactly this combination.

The implications for global agriculture are substantial. Hybrid varieties underpin a large share of rice production in Asia, and hybrid seed production depends on manual or chemical emasculation, carefully timed planting of male-sterile and restorer lines, and enormous logistical expense. If clonal hybrid seed became routine, breeders could propagate elite hybrids indefinitely, smallholder farmers could save their own seed without losing vigour, and the genetic gains locked into each cross would no longer evaporate after a single generation. The commentary also points toward broader applicability: because the strategy relies on conserved reproductive processes, sperm-derived embryogenesis cues and clonal gametogenesis, the same logic could in principle be transferred to other cereals and broadleaf crops where hybrid breeding is central but hybrid seed is costly.

Caution remains warranted, as the commentary itself makes clear. The reported work is a mechanistic and proof-of-concept advance in rice; translating it into varieties grown across millions of hectares will require testing stability across environments, confirming that clonal fidelity holds over multiple generations, and navigating regulatory frameworks for genome-edited crops, which differ sharply between jurisdictions. The commentary’s corresponding author, Yazhong Wang, is listed as an inventor on a European patent application related to earlier work in this area, a reminder that intellectual property will shape how quickly these tools reach breeders. Still, the trajectory of the field is unmistakable: from the discovery that meiosis can be replaced by mitosis, through the first synthetic clonal seeds, to a system that now approaches the completeness and fitness that practical agriculture demands.

What makes the HUAXU result resonate beyond the rice paddy is what it reveals about the logic of plant reproduction itself. The egg cell, it turns out, may not need to be forcibly reprogrammed from scratch; it may simply need the right paternal instruction at the right moment. By finding that instruction and delivering it in an unreduced gamete, the researchers effectively persuaded the plant to treat an asexual embryo as if fertilization had occurred, without the genetic consequences of fertilization. Breaking the apomixis trade-off, as the commentary’s title puts it, is therefore both an engineering milestone and a biological insight, one that converts a long-standing theoretical promise into a strategy that is, for the first time, plausibly scalable for fixing hybrid vigour in one of the world’s most important staple crops.

Subject of Research: Synthetic apomixis and clonal seed production in hybrid rice via the sperm-specific transcription factor HUAXU

Article Title: Breaking the apomixis trade-off

Article References: Li, T., Wang, B., & Wang, Y. (2026). Breaking the apomixis trade-off. Nature Plants. https://doi.org/10.1038/s41477-026-02404-7

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02404-7

Keywords: apomixis, hybrid rice, HUAXU, clonal seeds, heterosis, sperm cell, embryogenesis, plant biotechnology, clonal gametogenesis, seed development, plant breeding, transcription factor

The research, led by Lu-Yan Chan, Ming-Kin Wong, and Yong-Hong Yan as co-first authors in the laboratory of Zhongying Zhao at Hong Kong Baptist University, with collaborators at the National Institute of Biological Sciences in Beijing and the University of Science and Technology of China, focuses on CYL-1, the worm counterpart of cyclin L1. Cyclins are best known as the rhythmic partners of cyclin-dependent kinases, the enzymes that drive cells through the phases of the cell cycle. Yet a growing body of work has revealed that many cyclins moonlight in other processes, and cyclin L had previously been implicated in pre-mRNA splicing through its interaction with CDK-11 in cultured cell lines. What remained murky was whether this splicing connection mattered in a living, developing animal—and what else the protein might be doing there.

To find out, the team first established where and when CYL-1 operates. Fluorescently tagged versions of the protein revealed that CYL-1 is expressed ubiquitously, residing in cell nuclei throughout the entire course of worm development. That broad, persistent nuclear presence hinted that the protein is not a niche player confined to one tissue or stage, but a general component of the gene-expression machinery whose loss should ripple across the organism. The next step was to identify who CYL-1 actually works with inside those nuclei.

Using co-immunoprecipitation followed by mass spectrometry—a technique in which a bait protein is pulled down from worm extracts along with everything physically bound to it, and the captured partners are then identified by their peptide fingerprints—the researchers mapped CYL-1’s interaction network in vivo. The results confirmed that CYL-1 forms complexes with two worm CDK-11 isoforms, CDK-11.1 and CDK-11.2, and also identified a highly conserved protein called EELO-1, named for its association with early transcriptional elongation, as a core interactor. Together with the splicing-associated factor SAP30BP highlighted in the study’s title, these proteins define a complex that sits at the junction of transcription and RNA processing.

Genetic analysis then revealed how essential this machinery is. When the researchers interfered with cyl-1, cdk-11.1, cdk-11.2, or eelo-1 using RNA interference, embryos failed to develop normally, and the two CDK-11 paralogs were shown to act redundantly: knocking down either alone was survivable to a degree, but compromising both sharply reduced embryonic viability. This redundancy is a classic signature of duplicated genes that share a critical function, and it means the worm tolerates losing one copy of the kinase only because the other can carry the load. The four proteins, in other words, are not optional accessories but load-bearing pillars of mRNA biogenesis during embryogenesis.

The mechanistic heart of the study lies in what those pillars actually do to RNA. Immunostaining assays, which use antibodies to visualize the location of specific molecular marks on proteins, showed that loss of CYL-1 disrupts events at the very start of the transcription cycle, affecting transcriptional initiation and the elongation of RNA polymerase along the gene body. RNA sequencing of embryos depleted of each complex member added a genome-wide view: beyond changes in overall transcript levels, the researchers documented widespread defects in pre-mRNA splicing, with alternative splicing patterns shifting substantially and differently depending on which of the four genes—cyl-1, cdk-11.1, cdk-11.2, or eelo-1—had been silenced. That last detail matters. If the four proteins were simply interchangeable parts of one machine, depleting any of them would produce the same splicing fingerprint. Instead, each leaves a distinct signature, suggesting partially specialized roles within a shared complex.

Perhaps the most striking finding came from asking a developmental question rather than a biochemical one. Using established cell fate markers—reporter constructs that fluoresce only when a cell has committed to a particular identity—the team demonstrated that CDK-11.1, CDK-11.2, and EELO-1 are involved in regulating cell fate specification during development. In an embryo, every cell carries the same genome; what distinguishes a muscle cell from a neuron is which subset of genes is transcribed and how those transcripts are processed. A complex that influences both transcriptional output and splicing is therefore ideally positioned to shape that decision, and the new data indicate that it does. The result reframes splicing factors not merely as editors of genetic text but as participants in the regulatory logic that assigns identities to embryonic cells.

Importantly, the study also uncovers an asymmetry within the complex. While CYL-1 is required for transcriptional initiation, elongation, and splicing, its partners CDK-11.1, CDK-11.2, and EELO-1 carry the additional responsibility of governing cell fate determination—a role that CYL-1 itself did not show in these assays. This differential division of labor between a cyclin and its interactors adds a nuanced twist to cyclin biology. It suggests that the familiar cyclin-CDK pairing can be modular: the kinase and its associated factors may perform functions beyond, and independent of, the cyclin that helps recruit or activate them. For an organism as experimentally tractable as C. elegans, whose transparent embryos allow researchers to watch every cell division in real time, such a system offers a powerful platform for dissecting how those roles are partitioned at the molecular level.

The evolutionary implications extend well beyond worms. CDK-11 and cyclin L are conserved across metazoans, including mammals, where CDK11 has been implicated in cell cycle control, apoptosis, and RNA processing, and where splicing deregulation is increasingly recognized as a driver of developmental disorders and cancer. EELO-1’s conservation means the worm findings likely illuminate a broadly shared architecture of gene expression. If a CDK-11-containing complex couples transcriptional elongation and splicing to cell fate decisions in nematodes, the same coupling may operate in vertebrate embryos, stem cells, and disease states where differentiation goes awry. The study does not test these possibilities directly, but it establishes the in vivo framework that such future work in other organisms can build upon.

What makes the work resonate beyond its immediate field is the picture it paints of gene expression as a single, physically continuous process rather than a relay of disconnected stages. The RNA polymerase that reads a gene, the factors that splice its transcript, and the regulatory network that decides a cell’s destiny are, in this emerging view, held together in one macromolecular assembly. A defect anywhere in that assembly—an underactive kinase, a missing cyclin, an absent elongation factor—can propagate outward from a biochemical glitch to a developmental outcome: an embryo that fails to survive, or a cell that adopts the wrong identity. By grounding that logic in the concrete genetics of a living animal, the Hong Kong-led team has turned a splicing complex into a lens on one of biology’s deepest questions—how a genome becomes an organism—and provided a molecular handle that researchers studying development, RNA biology, and disease will now be eager to pull.

Subject of Research: The role of a CYL-1/CDK-11/EELO-1 complex in pre-mRNA splicing and cell fate specification during C. elegans development

Article Title: A CDK-11/SAP30BP/CYL-1 complex links pre-mRNA splicing to developmental cell fate decisions

Article References: Chan, L.-Y., Wong, M.-K., Yan, Y.-H., Ho, V. W. S., Ma, Y., Xie, D., Ye, P., Zeng, J., Dong, M.-Q., Guang, S., & Zhao, Z. (2026). A CDK-11/SAP30BP/CYL-1 complex links pre-mRNA splicing to developmental cell fate decisions. BMC Biology. https://doi.org/10.1186/s12915-026-02734-0

Image Credits: AI Generated

DOI: 10.1186/s12915-026-02734-0

Keywords: CYL-1, CDK-11, EELO-1, pre-mRNA splicing, cell fate determination, C. elegans, embryogenesis, cyclin-dependent kinase, transcriptional elongation, developmental genetics, mRNA biogenesis, BMC Biology

Glycans are carbohydrate chains attached to proteins and lipids, and they are far more than metabolic fuel. In animals ranging from sea urchins to humans, they serve as molecular identity tags, mediating cell-to-cell recognition, fertilization, immune defense, and tissue organization. Lectins, a diverse family of sugar-binding proteins, read these tags and translate them into biological action. In marine organisms, glycans have been implicated in mucosal immunity of embryos, cellular interactions during development, fertilization success, egg development, and embryogenesis itself. Yet despite the ecological importance of corals, almost nothing was known about the glycan landscape of a developing coral embryo until now.

The research team, led by Kanokpron Loeslakwiboon and Hsing-Hui Li of National Sun Yat-Sen University and the National Museum of Marine Biology and Aquarium, together with colleagues including Sujune Tsai, Zhi-Hong Wen and Chiahsin Lin, chose Galaxea fascicularis as their study organism. This reef-building stony coral has recently emerged as a promising model system for coral symbiosis research, and its embryos are relatively accessible for laboratory work. Spawning colonies were induced in the lab, embryos were collected at defined developmental stages, and the researchers set out to profile the sugars present at each stage of the journey from fertilized egg to late-stage embryo.

The analytical centerpiece of the study was a lectin array, a technique that exploits the exquisite specificity of lectins for particular sugar structures. Each lectin on the array recognizes a characteristic glycan signature, and when fluorescently labeled samples bind to the array, the pattern of binding reveals which glycans are present and in what relative abundance. The team used a Cy3 dye detection method, allowing them to quantify binding signals and construct a comparative glycan profile for each developmental stage. This approach, long used in mammalian glycobiology, had rarely been applied to the early life stages of a reef coral.

The results delivered a clear headline finding: mannose was the most abundant glycan present in Galaxea fascicularis embryos at every stage examined. Mannose, a simple hexose sugar, is a cornerstone of many glycan structures in eukaryotic cells, and its dominance in coral embryos suggests it plays a central role in early development. The researchers propose that mannose may be significant for cell proliferation, because it can serve as an energy source to drive the demanding processes of embryonic development. Rapidly dividing embryos need both building materials and fuel, and an abundant, readily mobilized sugar could supply both.

Perhaps more intriguing than the abundance of mannose was the pattern of change over time. Across the early stages of development, the glycan profiles remained remarkably stable, with only minor shifts observed. This developmental conservatism suggests that the early embryo relies on a consistent molecular toolkit, one laid down in the egg and maintained through the initial rounds of cell division. The picture changed at later stages of embryogenesis. As embryos approached the point where they must produce well-formed structures, the researchers suggest, they may require more energy and may increase their intake of monosaccharides accordingly. In other words, the sugar economy of the embryo appears to shift as morphogenesis accelerates, moving from a stable maintenance phase toward a more energy-intensive construction phase.

The findings resonate with a broader body of work on the role of carbohydrates in animal development. Glycoprotein synthesis has long been recognized as essential to embryonic development across the animal kingdom, and studies in sea urchins have shown that carbohydrate interactions are involved in cellular adhesion during gastrulation and in the fertilization process itself. Cell surface carbohydrates and lectins are known to participate in early development in organisms from mice to marine invertebrates, and even the reassociation of dissociated animal cells depends on specific carbohydrate groups at the cell surface. What the new study adds is a temporal dimension: a stage-by-stage map of how these sugars wax and wane as a coral embryo matures.

The work also connects to the growing literature on glycans in coral biology more broadly. Previous studies have profiled the glycan composition of coral mucus, revealing that the carbohydrate makeup of the gel-forming mucus layer varies among species and even correlates with coral phylogeny. Others have characterized mannose-binding lectins from corals that can bind both pathogens and symbiotic algae, hinting at a dual role for sugar recognition in immunity and symbiosis establishment. Lectin-glycan interactions have been shown to mediate the recognition between coral hosts and their dinoflagellate symbionts, the photosynthetic partners that power reef ecosystems. By extending glycan analysis to the embryo, the Taiwanese team has filled a conspicuous gap in this picture, showing that sugar biology matters from the very first hours of a coral’s life.

Why does this matter beyond the laboratory? Coral reefs are under unprecedented pressure from warming waters, acidification, and pollution, and conservationists increasingly rely on assisted reproduction and coral culture techniques to restore damaged reefs. Understanding the biochemical requirements of embryos could improve hatchery protocols, larval rearing conditions, and cryopreservation methods. If mannose availability influences cell proliferation and energy supply during development, then culture media and rearing environments might be tuned to support embryos at the stages when their sugar demands change. The authors note that their findings may provide a benefit to coral culture and conservation efforts, and the study’s timing is significant given that Galaxea fascicularis is being positioned as a model organism for the field.

There are, of course, limits to what a first study can establish. The lectin array reveals which glycans are present and how their relative abundance changes, but it does not identify every glycan structure in molecular detail, nor does it pinpoint the genes and enzymes that regulate their synthesis. Future work combining glycomics with transcriptomics could link the observed sugar dynamics to the underlying developmental genetic program, much as earlier molecular studies have charted gene expression from fertilization to metamorphosis in reef-building corals. Still, the study marks a genuine first: a total glycan profile tracked across the embryonic development of a coral. As reefs worldwide struggle to regenerate, even the smallest molecular insights into how coral life begins may prove to be valuable currency for the scientists working to keep them alive.

Subject of Research: Glycan profile changes during embryonic development of the reef-building coral Galaxea fascicularis

Article Title: Glycan dynamics across embryonic development in the coral Galaxea fascicularis

Article References: Glycan dynamics across embryonic development in the coral Galaxea fascicularis. (n.d.). https://doi.org/10.1007/s00338-026-02955-3

Image Credits: AI Generated

DOI: 10.1007/s00338-026-02955-3

Keywords: glycans, coral, Galaxea fascicularis, embryogenesis, lectin array, mannose, glycobiology, coral reefs, marine biology, cell proliferation, coral conservation, Taiwan