Fluctuations in host cell growth pose a critical challenge for maintaining reliable function in synthetic gene circuits. Growth-mediated dilution causes a global reduction in circuit component concentrations, which can significantly destabilize circuit behavior. However, effective strategies to counteract this problem remain lacking. Here, we present a phase-separation-based strategy to directly mitigate dilution effects. By fusing transcription factors (TFs) to intrinsically disordered regions (IDRs), we drive the formation of transcriptional condensates that concentrate TFs at their target promoters. These condensates buffer against prolonged rapid dilution of TF concentration and preserve bistable memory in self-activation circuits across variable growth conditions. We further show that this approach improves production efficiency in a cinnamic acid biosynthesis pathway. Together, our results establish liquid-liquid phase separation as an emerging design principle for constructing resilient synthetic circuits that maintain robust performance under dynamic growth conditions.

CRISPR screens have become standard gene discovery platforms in various contexts, including cancer. Yet commonly available CRISPR-Cas9 tools are increasingly recognized as unfit for in vivo investigations in immunocompetent contexts, due to broad immunogenicity of bacterial nucleases and reporters. Here, we show how conventional CRISPR screens in tumor grafts are systematically jeopardized by immunoediting in syngeneic and humanized immunocompetent hosts, resulting in iatrogenic clonal dropouts and ultimately compromising target identification. To resolve this, we present StealTHY, an immunogen-free CRISPR platform compatible with virtually all immunocompetent designs, enabling preservation of clonal architecture and exposing previously concealed cancer vulnerabilities. Among these, we identify the AMH-AMHR2 axis as a formerly unappreciated metastasis target. Thus, with StealTHY, we provide a new resource to expand the applicability of CRISPR screens to immunocompetent models, including humanized tumor grafts, revealing metastasis regulators of therapeutic relevance.

Gibbons (family Hylobatidae), small apes closely related to humans and great apes, remain understudied despite their threatened status. Here, we present extensive genomic resources, including chromosome-level reference genomes, whole-genome resequencing of 18 extant species, and mitochondrial genomes from 3 ancient samples. Using whole-genome alignments, we resolve the debated phylogeny of the four genera as (Hylobates, (Nomascus, (Symphalangus, Hoolock))). Phylogenetic analyses based on the ancient mitogenomes place the extinct Junzi imperialis within Nomascus, refuting its status as a distinct genus. Conservation genomics and ecological niche modeling analyses suggest historical dynamics in gibbon population size and habitat suitability, which are consistent with the potential impacts of past climate change. Through comparative genomics and transgenic mouse experiments, we identify a 205-bp deletion in the Sonic Hedgehog (SHH) gene associated with gibbons' elongated limbs. These findings advance understanding of gibbon evolution, biology, and conservation.

Biomarkers accurately informing prognostic assessment and therapeutic strategy are critical for improving patient outcome in oncology. Here, we apply a whole-genome, tumor-informed circulating tumor DNA (ctDNA) detection approach to address this challenge, leveraging 1,800 variants across 2,994 plasma samples from 431 patients with non-small cell lung cancer (NSCLC) from the TRACERx study. We show that ultrasensitive ctDNA detection below 80 parts per million both pre- and postoperatively is highly prognostic, and combinatorial analysis of the pre- and postoperative ctDNA status identifies an intermediate risk group, improving disease stratification. ctDNA kinetics demonstrate clinical utility during adjuvant therapy, where patients that "clear" ctDNA during adjuvant therapy experience improved outcomes. Moreover, characterization of patterns in postoperative ctDNA kinetics reveals insights into the timing, risk, and anatomical pattern of relapses. By incorporating longitudinal ultrasensitive ctDNA detection, we propose a refined schema for guiding the stratification and treatment recommendations in early stage NSCLC.

Chromatin structure is a key determinant of gene expression in eukaryotes, but it has not been possible to define the structure of cis-regulatory elements at the scale of the proteins that bind them. Here, we generate multidimensional chromosome conformation capture (3C) maps at base-pair resolution using Micro Capture-C ultra (MCCu). This can resolve contacts between individual transcription factor motifs within cis-regulatory elements. Using degron systems, we show that removal of Mediator complex components alters fine-scale promoter structure and that nucleosome depletion plays a key role in transcription factor-driven enhancer-promoter contacts. We observe that chromatin is partitioned into nanoscale domains by nucleosome-depleted regions. This structural conformation is reproduced by chemically specific coarse-grained molecular dynamics simulations of the physicochemical properties of chromatin. Combining MCCu with molecular dynamics simulations and super-resolution microscopy allows us to propose a unified model in which the biophysical properties of chromatin orchestrate contacts between cis-regulatory elements.

Dietary needs are dynamic, with optimal ranges for nutrients varying over time and across physiological states. How optimal nutrient set points are established and why they are adjusted remains largely unknown. In our efforts to understand the physiology of recovery, we made the surprising observation that mice restrict protein intake at the expense of caloric supply. We identified three amino acids-glutamine (Q), lysine (K), and threonine (T)-within dietary protein, which are necessary and sufficient for protein aversion during recovery from catabolic states. The anorexigenic effects of QKT are driven by ammoniagenesis in the gut, sensed by enterochromaffin cells in a TRPA1-dependent fashion and transduced to brainstem neurons via serotonin signaling, inducing anorexia. We propose that this mechanism serves as a first-line defense against ammonia toxicity. In summary, we identified a set of adaptive food preferences during recovery ("recovery behavior"), with implications for understanding diseases of pathologic recovery and the development of therapeutic interventions deployed to enhance recovery.

During cancer development, mutations promote changes in gene expression that cause transformation. Leukemia associated with aberrant HOXA expression is driven by translocations of nucleoporin genes or KMT2A as well as mutations in NPM1. The mechanistic convergence of these disparate mutations remains elusive. Here, we demonstrate that mutant nucleophosmin 1 (NPM1c) forms nuclear condensates in human cell lines, mouse models, and primary patient samples. We show NPM1c phase separation is necessary and sufficient to recruit NUP98 and KMT2A to condensates. Through extensive mutagenesis and pharmacological destabilization of phase separation, we find that NPM1c condensates are necessary for regulating gene expression, promoting in vivo leukemic expansion, and maintaining the undifferentiated leukemic state. Finally, we show that nucleoporin and KMT2A fusion proteins form condensates that are biophysically indistinguishable from NPM1c condensates. Together, these data define a new condensate that we term the coordinating body (C-body) and establish C-bodies as a therapeutic vulnerability in leukemia.

The traditional process of antibody discovery is limited by inefficiency, high costs, and low success rates. Recent approaches employing artificial intelligence (AI) have been developed to optimize existing antibodies and generate antibody sequences in a target-agnostic manner. In this work, we present MAGE (monoclonal antibody generator), a sequence-based protein language model (PLM) fine-tuned for the task of generating paired human variable heavy- and light-chain antibody sequences against targets of interest. We show that MAGE can generate novel and diverse antibody sequences with experimentally validated binding specificity against SARS-CoV-2, an emerging avian influenza H5N1, and respiratory syncytial virus A (RSV-A). MAGE represents a first-in-class model capable of designing human antibodies against multiple targets with no starting template.

Vision first evolved in the water, where the spectral content of light informs about viewing distance. However, whether and how aquatic visual systems exploit this "fact of physics" remains unknown. Here, we show that zebrafish use "color" information to suppress responses to the visual background. For this, zebrafish divide their intact ancestral cone complement into two opposing systems: PR1/4 ("red/UV cones") versus PR2/3 ("green/blue cones"). Of these, the achromatic PR1 and PR4, which are retained in mammals, are necessary and sufficient for vision. By contrast, the color-opponent PR2 and PR3, which are lost in mammals, are neither necessary nor sufficient for vision. Instead, they form an "auxiliary" system that spectrally suppresses the "core" drive from PR1 and PR4. Our insights challenge the long-held notion that vertebrate cone diversity primarily serves color vision and further hint at terrestrialization, not nocturnalization, as the leading driver for visual circuit reorganization in mammals.

Microbial eukaryotes remain understudied despite their critical ecological importance, with the exception of a few established models. They are often small, difficult to culture, and resistant to standard labeling and imaging techniques. Here, we use ultrastructure expansion microscopy (U-ExM) to carry out high-resolution volumetric imaging of over 200 cultured planktonic eukaryotes across major lineages. By combining U-ExM with pan- and specific immuno-labeling, we reveal microtubule and centrin-containing elements and assign molecular identities to enigmatic cytoskeletal structures observed previously only by electron microscopy. This comprehensive resource provides a basis for understanding cytoskeletal diversity, phenotypic plasticity, and evolutionary dynamics. Moreover, our approach extends to mixed environmental samples, paving the way for environmental cell biology at ultrastructural resolution-a crucial step toward understanding and protecting ecosystems in the face of accelerating biodiversity loss.

The female Aedes aegypti mosquito's remarkable ability to hunt humans and transmit pathogens relies on her unique biology. Here, we present the Aedes aegypti Mosquito Cell Atlas, a comprehensive single-nucleus RNA sequencing dataset of more than 367,000 nuclei from 19 dissected tissues of adult female and male Aedes aegypti, providing cellular-level resolution of mosquito biology. We identify novel cell types and expand our understanding of sensory neuron organization of chemoreceptors across all sensory tissues. Our analysis uncovers male-specific cells and sexually dimorphic gene expression in the antenna and brain. In female mosquitoes, we find that glial cells, rather than neurons, undergo the most extensive transcriptional changes in the brain following blood feeding. Our findings provide insights into the cellular basis of mosquito behavior and sexual dimorphism. The Aedes aegypti Mosquito Cell Atlas resource enables systematic investigation of cell-type-specific expression across all mosquito tissues.

In this issue of Cell, Han et al. find that tumor cells metastasizing to the bone marrow hijack macrophages to seize iron from red blood cells. This metabolic plunder thereby fuels tumor progression while contributing to anemia.

Saturation genome editing meets functional phenotyping to turn sequencing ambiguity into actionable diagnoses.

Symbiosis is widespread in nature and plays a fundamental role in organism adaptation and evolution. In nutritional endosymbiosis, host cells accommodate intracellular bacteria and act as a "metabolic factory," requiring extensive metabolic exchanges between host and endosymbiont. To investigate the mechanisms supporting these exchanges, we used the association between the bacterium Sodalis pierantonius and the insect Sitophilus spp. that thrives on an exclusive cereal diet. Volume electron microscopy uncovered that endosymbionts generate complex membranous tubular networks (tubenets) that connect bacteria and drastically increase their exchange surface with the host cytosol. In situ high spatial resolution chemical analysis indicated that tubenets are enriched in carbohydrates, which are the main substrate used by bacteria to generate nutrients for the host. Multiple membranous structures favoring nutrient absorption are described in multicellular organisms. This work demonstrates that bacteria have convergently evolved a similar "biostrategy" that enhances nutrient acquisition by increasing membrane interface.

The second trimester of pregnancy is a pivotal stage in human immune system development. Utilizing single-cell RNA sequencing and T cell receptor sequencing, we profiled 2,868,420 immune cells from 321 samples across 23 organs, including adult tissues as comparators. We identify an extrathymic CD4+ T cell subset mediating TOX2+ precursor cells' transition to mature naive CD4+ T cells. Contrary to the prevailing paradigm of fetal immune quiescence, we uncover widespread memory/activated T cells and tissue-resident memory clones shared across organs, indicating systemic immune activity beyond localized barrier defense. Cell-cell communication and functional assays indicate two tolerance mechanisms that suppress fetal T cell activation: ARG1+ neutrophils and a PTGES3/PTGER4 signaling pathway. We also find that hematopoietic stem cells (HSCs) disperse across multiple organs and show that HSCs from non-canonical hematopoietic organs differentiate into diverse immune lineages. These findings provide insights into human immune system maturation and tolerance in fetuses and adults.