Sexual reproduction is an obligate stage in the complex life cycle of Plasmodium parasites, the causative agents of malaria. While cyclic asexual replication of the parasite in the vertebrate host is associated with all clinical symptoms of malaria, the transmission of the disease to a new host relies on the sexual reproduction of the parasite in the mosquito. Transmission and reproductive success depend on the ability of the parasite to produce fertile male and female gametes at an optimal ratio. The molecular mechanisms of sex determination and development, therefore, hold the key to new transmission-blocking interventions and to a broader understanding of how life cycle decisions in an important group of parasites can be regulated. Recent breakthroughs have identified a master regulator of sexual commitment, but how one transcription factor can give rise to the completely different gene expression programs of male and female gametocytes remains elusive. Genetic screens and transcriptomic analyses in a rodent model have now led to the identification of a small panel of genes which I propose here will unlock the question of how sex ratio is determined. By applying a combination of state-of-the-art biochemical, cell biological and genetic techniques, I aim to characterize the function of three strongly supported, male-determining candidate genes. The obtained results will provide insights into how sex, and thus transmission, of malaria parasites is regulated. By elucidating the fascinating biology of sex determination in an ancient eukaryote that lacks sex chromosomes, the proposed work can reveal potentially novel pathways involved in the origin of eukaryotic sex.

Uncontrolled loss of neurons is a hallmark of neurodegenerative diseases (NDs) such as Alzheimer’s disease and amyotrophic lateral sclerosis (ALS). In NDs, an abnormal assembly of proteins and mRNAs known as a biomolecular condensate (BC) is believed to contribute to neurotoxicity and ensuing neuronal death. Despite high mortality and poor quality of patients’ lives, as well as the enormous socio-economic burden of patient care, the exact molecular and cellular mechanisms underlying ND pathogenesis remain largely unknown. This roadblock in ND studies primarily originates from mutual dependency between “molecular assembly” of general ND proteins and “functionality” of individual ND proteins. Molecular assembly is a dynamic process that can take place locally, and changes actively in its physical property by transitioning among soluble phase, liquid-like droplets, hydrogels and insoluble aggregates. To our knowledge, there is currently no technique to disassemble ND-related BCs to distinguish these physical and biochemical characteristics, especially in a physiologically relevant context. By integrating expertise in neurophysiology, chemical biology, and soft-matter biophysics, we propose to develop a conceptually unique methodology termed “dePOLYMER”. Here, light illumination or chemical administration actuates a genetically-encoded molecular probe designed to polymerize actin to generate constrictive force against an intended object such as BCs in living cells. When force density exceeds the surface tension of target BCs, dePOLYMER is expected to trigger their dispersion. We will specifically target stress granules as a model for non-pathogenic BCs, as well as pathogenic ALS-related BCs. Using a model for ALS, we will next aim to demonstrate dispersion of BCs consisting of ALS proteins in a manner specific for constituent proteins and cell types. In summary, the goal of our study is to offer a novel technique to efficiently disperse BCs in a rapidly inducible manner. Implementation of dePOLYMER in ALS model systems may enable future identification of the molecular and cellular foundation of neurotoxicity, thus a potentially new treatment strategy for NDs. Due to the inherently modular design of dePOLYMER probes, the technique should be generalizable to virtually all BCs whose molecular components are known, let alone other ND-related BCs.

Dense commensal microbial communities are found within the gut that protect us against pathogens. Yet, a much-discussed gap in our understanding is how these communities organise within the intestine, and how this organisation links to health outcomes. One particularly dense area of colonisation is the gut epithelial surface and associated mucus, as the region with the most permanent and intimate association with the host. My key hypothesis is that microbes at the mucus interface are particularly important for protection against pathogens that must overcome this barrier to access the epithelium in order to cause disease. I will test this in three aims: 1) I will develop new imaging methods to map the spatial organisation of microbes at the gut mucus interface facing challenge from the important pathogen Salmonella enterica serovar Typhimurium, with unprecedented throughput and detail. I will pioneer new methods for label-free pathogen and commensal identification in the gut what will allow to overcome the limited throughput in imaging-based microbiome research. 2) Based on the new imaging data, I will use custom image analysis to identify those commensal species that associate preferentially with the epithelial surface and with the pathogen. 3) Finally, I will test whether the spatial ecology of gut bacteria is predictive for colonisation resistance by assembling defined communities with different spatial organisations in gnotobiotic mice. Overall, my project promises for the first time to show how the spatial ecology of the microbiota is critical for the balance between health and disease.

In a rapidly changing world, a key focus in evolutionary biology is to better understand and predict how populations will respond to alterations in their environment. Sexual selection is a pervasive force that can alter how populations respond to natural selection. But, how sexual selection and the broader environment interact to influence adaptation is not well understood. I will determine the influence of male-male competition on adaptation of an herbivorous insect to a novel host plant using the leaf-footed bug Acanthocephala femorata. Male leaf-footed bugs compete for territories on host plants, using enlarged hind femurs to grapple and push other males off the plant. Host plants differ in their architecture, which affects which weapons and fighting styles are most effective and are selected for, altering sexual selection on male weapon morphology. Male success at colonising a novel host plant is therefore influenced by both sexually selected traits (fighting behaviour and weapon shape) and the environment (the plant’s architecture). I will manipulate sexual selection directly by changing the sex ratio and indirectly with different host plants to test how sexual selection influences the ability of leaf-footed bugs to adapt to a novel host plant. I predict that the role of sexual selection in facilitating adaptation to a novel host plant depends on the architecture of the host plant. These results will be important for understanding how host range evolution can occur in species that experience sexual selection, especially when the environment indirectly impacts sexual selection.

Some coral reefs recover from climate change-driven disturbances relatively quickly, while others stay barren because coral populations fail to replenish themselves though larval recruitment. Here, we propose to study neuro-molecular mechanisms of settlement decision-making in coral larvae, to identify intrinsic processes that might be responsible for success or failure of coral reef recovery. Our first aim is to identify and map all types of neurons (connectome) in a coral larva at different stages of competency and commitment to settlement. It will be accomplished by performing single-cell RNA-sequencing to identify neuronal types and mapping their molecular markers onto the neural network using serial section electron microscopy, in situ hybridization and immunohistochemistry. Our second aim is to validate the role of neuron-specific candidate genes by perturbing their function (using CRISPR/Cas9 knock-downs and antibody blocking) and assessing the effect on larval settlement behavior, gene expression, and neuronal morphology. We will use Acropora millepora, which is a representative of the largest and the most ecologically important genus of reef-building corals.

One of the ultimate goals in neuroscience is to understand neural correlates of perception, sensation and behaviors. For the past several decades, a number of studies have successfully imaged neuronal activities in behaving animals and further showed the behavioral causality of specific neural circuits by using various optogenetic techniques. More recently, additional significant efforts have made in order to minimize the size of optical system, such that real-time imaging can be done even in freely moving animals. However, high-resolution imaging of deep brain structure in behaving animals still remains challenging. This limitation has hampered our understanding of neural mechanisms in subcortical areas at the resolution of individual cells or synapses. Here I propose to develop a new design of miniaturized microscope by implementing my expertise with optical coherence detection into two-photon (2P) microscopy. This system will allow us to image deep brain areas with synapse resolution in freely behaving animals. Furthermore, both aberration correction and holographic excitation will be implemented with wavefront shaping, which will enables simultaneous imaging and holographic optogenetic control of neural circuits. Using this newly developed microscope, I would like to define neural activities in Nucleus Accumbens (NAc) (4 mm deep from the surface) that are associated with goal-directed behaviors. I will further test direct behavioral causality by selectively activating behaviorally-relevant neuronal populations. In summary, the proposed study will provide new optical approaches that will uncover various neural mechanisms underlying animal’s behaviors or cognition.

Brain metastases (BrM) represent the most common and aggressive neurological complication of systemic cancers, typically arising from melanoma, lung and breast cancers. With most patients living just over one year following BrM diagnosis, it is essential to understand the multistage process of dissemination of cancer cells from the primary tumor to the CNS and the importance of the tumor microenvironment (TME) in which BrM develop, to uncover novel therapeutic targets. The brain TME comprises a diverse spectrum of resident and peripheral immune cells, glial, vascular, and cancer cells. As the CNS was previously believed to be devoid of a lymphatic system, the trafficking of these cells into the CNS was thought to occur only via blood vessels. However, we hypothesize that the recently identified CNS lymphatic system may represent a potential route for both cancer and immune cells to reach the CNS through the lymphatic vessels within the dura mater. For this reason, I aim to evaluate how the lymphatic network evolves during BrM establishment, to determine to what extent cancer cells and peripheral immune cells are being transported through the lymphatics into the CNS, and to identify which molecular cues are responsible for the recruitment of these cells to the dura mater. To address these goals, transcriptomic and histological analyses of the dural microenvironment, in vivo imaging of the dura mater, and manipulation of the lymphatic system will be performed at different stages of BrM development. This experimental strategy will allow me to determine the potential impact of the lymphatic system in BrM establishment, an intriguing link that has not yet been explored.

Cells respond to physical force-induced signals by converting the mechanical stimulus into a biochemical response. This process, termed mechanotransduction, is an integral part of cellular physiology and has a profound impact on many biological processes including cell development and differentiation. The project goal is to provide a better understanding of the molecular mechanisms of the initiating 'mechanosensing' and its connection to variations in gene expression by studying the dynamic features of this mechanism at a single molecule level. Force transmission is a highly dynamic process and its investigation requires single molecule techniques with high temporal resolution. Therefore, the immediate aim will be to take advantage of and improve a unique ultra-fast optical trap, recently developed by the supervisor's group at the University of Florence that will allow the investigation of protein-protein interactions in vitro. In particular, the researcher will study the interactions between actin and putative mechanosensitive proteins, under various conditions of mechanical load. In a parallel research line, the researcher will develop an experimental setup and a methodology to apply mechanical stimuli on living cells and monitor the changes in gene expression profiles, with sensitivity down to the single molecule. The aim will be to correlate external mechanical stimuli on specific membrane receptors to intracellular signaling pathways and gene expression profiles, thus creating a powerful tool to enhance our current understanding of the molecular mechanisms of mechanotransduction in vivo.

One of the great questions concerns fate vs. chance. Are events destined to occur, or are they the result of specific antecedent conditions, any of which, were they different, would have led to a different outcome? Anolis lizards are recognized as among the best groups to investigate this question, and detailed study of their evolution has suggested a strong role for determinism. These studies, however, have focused on the phenotype; the extent to which genome evolution is deterministic or historically contingent is an open question. Until recently, detailed investigation of genome evolution has been limited to model organisms, for which little data are available on their ecology and behavior in natural settings, precluding study of the factors that have shaped their evolution. Now, advances in genomics and gene editing methods allow evolution to be studied in non-model organisms, permitting holistic studies from the genome to selective pressures in nature. Anolis lizards are the ideal group to combine genomic and organismal studies at multiple levels to address the extent to which evolutionary diversification is deterministic or contingent. This project will proceed as follows: Genomics: We will test for evolutionary determinism by investigating whether convergently evolved phenotypes are the result of the same or different genetic changes. Functional Tests of Candidate Loci: We will take advantage of recent advances in gene editing to directly test the role of these genetic changes in producing convergent phenotypes. To do so, we will use CRISPR-cas9 gene editing to modify genes in the lizard Anolis sagrei. We will examine genetically modified offspring to test the hypothesis that sequence variants produce the putative phenotypes. Behavior and Physiology: We will identify genes and the underlying sequence changes associated with the evolution of these traits, introduce these specific sequence variants into brown anoles, and then test whether the introduced sequence alterations produce the hypothesized behavioral and physiological phenotypes. Natural Selection: Once we have identified genetic changes underlying putatively adaptive phenotypes, we will design field experiments to test the hypothesis that natural selection favors those genotypes/phenotypes under particular environmental circumstances.

Sleep is a reversible state of quiescence during which an animal loses awareness of the external world. Although sleep is important for many brain functions, the mechanisms that underpin sleep and its functions are still poorly understood. The fruit fly, Drosophila melanogaster, has become a popular model for sleep research, because of the ability to probe the molecules and circuits involved in sleep. In this study, we will investigate the neural mechanisms by which the brain suppresses perception during sleep, with a focus on the well-characterized Drosophila olfactory system. Firstly, we will establish a system in which we can image neural activity of olfactory circuits during sleep. Secondly, we will investigate how sleep alters odor representations. Thirdly, we will examine the neural mechanisms underlying this sleep-dependent olfactory processing. Finally, we will examine the functional impact of sleep on olfactory behaviour. Overall, this study aims to reveal fundamental principles of sleep functions in sensory perception.

Precise control of gene expression is required for virtually all cellular functions, ensuring correct maintenance of cell identity and genomic stability. Chromatin remodeling complexes regulate gene expression and reorganize chromatin architecture by sliding, ejecting or changing the composition of nucleosomes along DNA. The ATP-dependent multi-subunit BRG-/BRM-associated factor (BAF or mammalian SWI/SNF) remodeling complex is one of the most frequently disrupted macromolecular assemblies in human cancers, as well as in a range of autism and intellectual disability syndromes. While the molecular activities of BAF complexes and their role in driving disease mechanisms are intensively studied, the specific roles for post-translational modifications (PTMs) on individual BAF subunits in mediating overall BAF complex function has remained largely unexplored. Further, specific upstream signaling pathways that alter BAF remodeling activity via placement of subunit PTMs in both healthy and disease states have not been explored. To address these key questions, we aim to define the compendium of BAF subunit PTMs, assess their functional roles, and identify the corresponding PTM-mediating enzymes and pathways. These approaches will enable us to answer fundamental questions regarding whether and how BAF subunit PTMs control complex activity, targeting, and functions in mediating DNA accessibility lending new insights in to remodeler function in both healthy and disease states. Delineating the pathways which activate or repress BAF function may implicate novel strategies for therapeutic intervention in cancer and other diseases.

Advancing age is a major risk factor for many neurodegenerative diseases, but the underlying mechanisms are not understood. The Crowston laboratory has recently demonstrated age-related impairment of neuronal recovery and associated increased neuronal death in an established optic nerve injury model. The predominant age-related changes were localized to excitatory synapses that activate ganglion cells in the retina. Because cholesterol is known to be important for synaptogenesis and recent evidence linking mutations in cholesterol metabolism with numerous neurodegenerative diseases, we hypothesize that age-related changes in cholesterol metabolism could be responsible for the observed defect in neuronal recovery through loss of synaptic plasticity. To test this hypothesis, experiments would be divided into two stages, a discovery stage and a hypothesis-driven stage. The aim of the discovery stage is to compare central nervous system (CNS) cholesterol metabolism in young versus aged animals, either with or without injury. If the hypothesis is correct, aged animals would be expected to have altered CNS cholesterol metabolism more susceptible to injury challenge. The hypothesis-driven stage is to then test how manipulating CNS cholesterol metabolism impacts synaptogenesis and recovery of visual function. This project will be done in collaboration with the Silver lab which has expertise in lipid transport and metabolism. Results would further our understanding of cholesterol metabolism in the aging CNS and how it impacts neuronal recovery.

The majority of the human transcriptome encodes non-coding RNAs that are not translated into protein. Long ncRNAs (LncRNAs) are 200 nucleotides or longer, and are involved in many cellular processes, including embryogenesis and DNA damage repair. Xist is an evolutionarily conserved LncRNA that plays a key role in dosage compensation in eutherian females. It does so by recruiting protein complexes that deposit repressive marks on histones on one X chromosome (XC), thereby leading to heterochromatin formation. Recent computational and biophysical studies suggest that Xist, as well as other LncRNAs, adopt higher order tertiary structures similar to ribozymes and group-II introns. Nonetheless, no high-resolution 3-D structures of Xist and its associated protein complexes have been determined. Thus, the precise molecular mechanism of XC inactivation remains unclear. In this proposal, I aim to biochemically identify and reconstitute Xist ribonucleoprotein (RNP) complexes involved in spreading and silencing of the XC. I will then determine the 3-D structures of Xist-protein complexes using a combination of electron cryomicroscopy and X-ray crystallography. In combination with biochemical and biophysical assays, I will characterize the native proteome associated with Xist, as well as the contributions of Xist tertiary structure towards recruitment of protein machineries including the polycomb complexes. These studies aim to elucidate molecular mechanisms of how Xist carries out gene silencing of the XC.

All existing life on Earth is the result of natural selection acting upon earlier forms of life, shaping the lineages over time. In order for selective advantages to accumulate over successive generations, the offspring must retain some attributes of the parent. Thus at some point early in life’s origins, a sustainably propagating cell must have emerged, one that could divide and produce offspring with reasonable fidelity. While genetic information propagation is largely understood--nucleic acids or their precursors preserve information by sequence complementarity--it is less obvious how the other properties of primitive cells, such as their membrane composition, could have been preserved across many generations. This remains a key open question in the emergence of life on Earth. We propose to answer this question by taking a bottom-up approach, in which we attempt to build a synthetic cell that can accomplish the essential tasks of stable propagation--membrane growth, feeding, and division--using the simplest components possible. In order to succeed, we will address a number of questions fundamental to biology. For example, to create a synthetic cell that can grow its own membrane, we must discover the mechanisms governing phospholipid synthesis, which could be determined by the rates of molecular motion or chemical reactions, the availability of nutrients, or incompatibilities between the molecules involved. Similarly, to feed our synthetic cell to sustain its growth, we must elucidate the physical rules governing membrane permeability. Finally, to induce division, we must understand the fundamental physics governing membrane bending, curvature, and fusion. We will combine cutting-edge techniques and perspectives from across all three fields of science to succeed in this ambitious endeavor. Kuruma, a biologist, will synthesize membrane material from simple building blocks in vesicles. Wang, a chemist, will analyze the properties of membranes to understand lipid packing, linking together membrane permeability with membrane fusion. And, Rogers, a physicist, will explore the physics of membrane bending and devise new strategies to induce cell fission. By working together, we will paint a comprehensive picture of how stable cell propagation could have emerged, as well as solve one part of the puzzle of how life as we know it could have come to exist.

How organs control their growth to achieve the correct final size is an enduring mystery of biology. In wildtype Drosophila, for example, left and right wing areas rarely differ by more than 1%. We previously found that the hormone Dilp8 controls this developmental precision, as in absence of the hormone, the fluctuating asymmetry (FA) of bilateral organs is strongly increased. In this proposal, we hypothesize that the hormone Dilp8 and cell death cooperate to limit wing size variability. To test this idea and explore its consequences, we will integrate methods from developmental biology with quantitative data analysis and modeling from physics. In particular, we will show how changes in cell death in dilp8 mutants are quantitatively related to changes in final wing size. Our results will provide new insights into how organ size is controlled and refined in biological systems.

Brain-wide representations of ongoing behavior were recently observed in neuronal activity patterns measured form various organisms such as worms, flies, and mice. Surprisingly, also primary sensory areas, like the V1 visual cortex in mice, previously thought to exclusively represent sensory information are also strongly modulated by behavioral variables like running speed. While this phenomenon seems to be prevalent, its functions and underlying neuronal mechanisms are elusive. I hypothesize that motor commands are integral components of sensorimotor transformations. Like others have suggested for the V1 area, I propose that this sensorimotor integration allows behavior-dependent sensory gain control, and more speculatively also involves predictive coding, i.e. that perception is tuned to unexpected outcomes of the animal's explorative movements. To address these hypotheses, I will use the tractable model organism C. elegans which is amendable to the cutting-edge whole-brain calcium imaging technology. I will develop new whole-brain imaging assays in freely-moving worms. I will then use these assays to search for gain-control circuits where the sensitivity of sensory neurons is modulated by different behavioral states. I will also look for predictive-coding circuits involving error-coding neurons, sensitive to unexpected stimuli. To study the behavioral relevance of these mechanisms, e.g. during navigation, I will interfere with the neuronal activity of the relevant circuits via optogenetics and other transgenic inhibition tools. Therefore, by combining these different approaches I aim to uncover generalizable functions and mechanisms of brain-wide motor representations.

Naturalistic behaviors are refined and stabilized throughout an animal’s life. Their formation is dependent upon multiple internal and external cues, giving rise to both stereotypical intraspecific responses and individually-unique behavioral patterns. The striatum has been widely implicated in controlling voluntary action and encoding behavioral modules and sequences in adulthood. However, how striatal dynamics might support and structure the evolution of behavior throughout development remains surprisingly unexplored. Here, I propose to incorporate longitudinal, unsupervised behavioral phenotyping with high-throughput in-vivo neuronal recordings in freely-behaving mice in order to characterize the evolution of naturalistic behavioral modules and their neural correlates from weaning to adulthood. To explore the interplay between external cues, circuit dynamics and behavioral plasticity, I will confound environmental features during development and study how behavioral adaptation is reflected in the underlying single-cell and population striatal codes. Finally, I will utilize this large-scale dataset to investigate the emergence of behavioral variation and to identify the neural correlates of individuality.

Hypoxia plays a central role in the pathogenesis of myocardial infarctions by causing immediate cellular damage within the short time scale of minutes to hours. Pathways that govern the acute response of heart tissue to hypoxia are poorly characterized. Currently, the procedure for stopping imminent tissue damage due to heart attack is percutaneous coronary intervention. Thus, systematically elucidating pathways involved in acute hypoxic response will lead to novel pharmacologic interventions aimed at protecting against the adverse cellular effects of hypoxia. One major challenge for the systematic study is that hypoxia response involves diverse processes, affecting cellular changes to metabolic, epigenetic, and transcriptional states, and hypoxia response is dynamic and can affect spatial organization within the cell. An appealing approach to overcome this challenge is phenotypic profiling, which offers a scalable, microscopy-based approach to convert complex cellular response to perturbations into high-dimensional vectors, referred to as phenotypic “profiles”. Here, I propose to apply phenotypic profiling to conduct a systematic study of the sensing and regulatory network governing acute cellular response to severe hypoxia in cardiomyocyte cells. My specific aims are to: (1) Establish a scalable platform for phenotypically profiling acute cellular response to severe hypoxia; and (2) Identify novel hypoxia sensors and regulatory pathways that govern acute cellular response to hypoxia using this platform.

It is a longstanding goal to decipher cell fate decisions during human development. Stem cell-based culture systems, combined with single-cell sequencing and CRISPR-Cas technologies, offer exciting possibilities to track human cell identities at unprecedented resolution and to engineer specific cell types with high precision. In this proposal, I will develop novel methods to record cell histories, trace lineages, and program human cell fates, with a focus on the human retina. In the first aim, I will develop a fate recording system in induced pluripotent stem cells (iPSCs) that unites evolvable barcodes with molecular memory recorders (Cas1/2) that capture expressed RNA into DNA. This will be used to simultaneously record real transcriptome and lineage histories along the path of cell fate acquisition. In the second aim, I will adopt the CRISPR-Cas12a(Cpf1) system that enables multiplexed gene activation to engineer cell fates based on predictions learned from single-cell transcriptome dissection of organ development. I will focus my project on human retina development where we have a well-characterized three-dimensional organoid culture system, and extensive data analyzing cell fates that emerge in these organoids. This focus will provide insights into the molecular mechanisms controlling human retinogenesis, and at the same time identify methods to engineer specific retinal cell types for therapeutic screening. The strategies and technologies developed in this project are applicable beyond the retina and will contribute to our understanding of general cell fate decisions in humans and guide cell type engineering with clinical potential.

Fertilization, the fusion of two highly specialized cells, the egg and sperm, marks the beginning of life of all sexually reproducing organisms. Despite its fundamental role, we still understand very little about how sperm-egg interaction is controlled. Research so far has mostly focused on identifying proteins that mediate gamete attachment and fusion while largely neglecting the fact that fertilization is an inherently dynamic process, during which the two gametes get together, interact and fuse. Although the sperm is in general viewed as the ‘active’, motile partner during gamete encounter and interaction, a key open question remains whether the egg does also play an ‘active’ role in the fertilization process, e.g. by generating forces that might actively engulf the sperm. To tackle this fundamental gap in our knowledge, we propose a two-pronged, cross-disciplinary approach to 1) characterize the mechanosensitive properties of the egg before, during and after fertilization by state-of-the-art biophysical techniques; and 2) pioneer the development of a bottom-up fertilization assay that we term ‘synthetic fertilization synapse’. As such, we envision to reconstitute sperm-egg interaction dynamics in a simplified in vitro system, in which we will replace the sperm by specific proteins in micro-structured lipid bilayers to study the impact of ligand mobility, number, and spatio-temporal organization on egg activity. In combination, we will use a controlled micro-confinement-based force actuator approach to perform global and local mechanical stimulation of the egg. Mechano-chemical responses of the egg will be measured by state-of-the-art high-resolution imaging and quantitative force measurement techniques. Zebrafish gametes will serve as main model systems, which will be complemented by experiments in mouse gametes. Tackling this highly challenging problem of the biophysical control of fertilization becomes only feasible by combining our different core expertise in an interdisciplinary approach. Our research will provide fundamental insights into the dynamics of sperm-egg interaction and its mechanosensitive regulation. These insights promise to transform our currently rudimentary knowledge of the mechanism of fertilization.