RESUMO
A number of species have recently recovered from near-extinction. Although these species have avoided the immediate extinction threat, their long-term viability remains precarious due to the potential genetic consequences of population declines, which are poorly understood on a timescale beyond a few generations. Woolly mammoths (Mammuthus primigenius) became isolated on Wrangel Island around 10,000 years ago and persisted for over 200 generations before becoming extinct around 4,000 years ago. To study the evolutionary processes leading up to the mammoths' extinction, we analyzed 21 Siberian woolly mammoth genomes. Our results show that the population recovered quickly from a severe bottleneck and remained demographically stable during the ensuing six millennia. We find that mildly deleterious mutations gradually accumulated, whereas highly deleterious mutations were purged, suggesting ongoing inbreeding depression that lasted for hundreds of generations. The time-lag between demographic and genetic recovery has wide-ranging implications for conservation management of recently bottlenecked populations.
Assuntos
Extinção Biológica , Genoma , Mamutes , Mutação , Animais , Mamutes/genética , Genoma/genética , Sibéria , Filogenia , Evolução Molecular , Fatores de TempoRESUMO
Contrary to multicellular organisms that display segmentation during development, communities of unicellular organisms are believed to be devoid of such sophisticated patterning. Unexpectedly, we find that the gene expression underlying the nitrogen stress response of a developing Bacillus subtilis biofilm becomes organized into a ring-like pattern. Mathematical modeling and genetic probing of the underlying circuit indicate that this patterning is generated by a clock and wavefront mechanism, similar to that driving vertebrate somitogenesis. We experimentally validated this hypothesis by showing that predicted nutrient conditions can even lead to multiple concentric rings, resembling segments. We additionally confirmed that this patterning mechanism is driven by cell-autonomous oscillations. Importantly, we show that the clock and wavefront process also spatially patterns sporulation within the biofilm. Together, these findings reveal a biofilm segmentation clock that organizes cellular differentiation in space and time, thereby challenging the paradigm that such patterning mechanisms are exclusive to plant and animal development.
Assuntos
Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/genética , Biofilmes/crescimento & desenvolvimento , Padronização Corporal/genética , Bacillus subtilis/metabolismo , Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Cinética , Modelos Biológicos , Nitrogênio/metabolismo , Transdução de Sinais/genética , Somitos/crescimento & desenvolvimento , Esporos Bacterianos/crescimento & desenvolvimento , Estresse Fisiológico/genética , Fatores de TempoRESUMO
We present a whole-cell fully dynamical kinetic model (WCM) of JCVI-syn3A, a minimal cell with a reduced genome of 493 genes that has retained few regulatory proteins or small RNAs. Cryo-electron tomograms provide the cell geometry and ribosome distributions. Time-dependent behaviors of concentrations and reaction fluxes from stochastic-deterministic simulations over a cell cycle reveal how the cell balances demands of its metabolism, genetic information processes, and growth, and offer insight into the principles of life for this minimal cell. The energy economy of each process including active transport of amino acids, nucleosides, and ions is analyzed. WCM reveals how emergent imbalances lead to slowdowns in the rates of transcription and translation. Integration of experimental data is critical in building a kinetic model from which emerges a genome-wide distribution of mRNA half-lives, multiple DNA replication events that can be compared to qPCR results, and the experimentally observed doubling behavior.
Assuntos
Células/citologia , Simulação por Computador , Trifosfato de Adenosina/metabolismo , Ciclo Celular/genética , Proliferação de Células/genética , Células/metabolismo , Replicação do DNA/genética , Regulação da Expressão Gênica , Imageamento Tridimensional , Cinética , Lipídeos/química , Redes e Vias Metabólicas , Metaboloma , Anotação de Sequência Molecular , Nucleotídeos/metabolismo , Termodinâmica , Fatores de TempoRESUMO
Northern East Asia was inhabited by modern humans as early as 40 thousand years ago (ka), as demonstrated by the Tianyuan individual. Using genome-wide data obtained from 25 individuals dated to 33.6-3.4 ka from the Amur region, we show that Tianyuan-related ancestry was widespread in northern East Asia before the Last Glacial Maximum (LGM). At the close of the LGM stadial, the earliest northern East Asian appeared in the Amur region, and this population is basal to ancient northern East Asians. Human populations in the Amur region have maintained genetic continuity from 14 ka, and these early inhabitants represent the closest East Asian source known for Ancient Paleo-Siberians. We also observed that EDAR V370A was likely to have been elevated to high frequency after the LGM, suggesting the possible timing for its selection. This study provides a deep look into the population dynamics of northern East Asia.
Assuntos
Dinâmica Populacional , DNA Antigo/análise , Ásia Oriental , Feminino , Variação Genética , Genética Populacional , Genoma Humano , Geografia , Humanos , Camada de Gelo , Funções Verossimilhança , Masculino , Modelos Genéticos , Filogenia , Análise de Componente Principal , Fatores de TempoRESUMO
Throughout development and aging, human cells accumulate mutations resulting in genomic mosaicism and genetic diversity at the cellular level. Mosaic mutations present in the gonads can affect both the individual and the offspring and subsequent generations. Here, we explore patterns and temporal stability of clonal mosaic mutations in male gonads by sequencing ejaculated sperm. Through 300× whole-genome sequencing of blood and sperm from healthy men, we find each ejaculate carries on average 33.3 ± 12.1 (mean ± SD) clonal mosaic variants, nearly all of which are detected in serial sampling, with the majority absent from sampled somal tissues. Their temporal stability and mutational signature suggest origins during embryonic development from a largely immutable stem cell niche. Clonal mosaicism likely contributes a transmissible, predicted pathogenic exonic variant for 1 in 15 men, representing a life-long threat of transmission for these individuals and a significant burden on human population health.
Assuntos
Crescimento e Desenvolvimento , Mosaicismo , Espermatozoides/metabolismo , Adolescente , Envelhecimento/sangue , Alelos , Células Clonais , Estudos de Coortes , Humanos , Masculino , Modelos Biológicos , Mutação/genética , Fatores de Risco , Fatores de Tempo , Adulto JovemRESUMO
Lateral intraparietal (LIP) neurons represent formation of perceptual decisions involving eye movements. In circuit models for these decisions, neural ensembles that encode actions compete to form decisions. Consequently, representation and readout of the decision variables (DVs) are implemented similarly for decisions with identical competing actions, irrespective of input and task context differences. Further, DVs are encoded as partially potentiated action plans through balance of activity of action-selective ensembles. Here, we test those core principles. We show that in a novel face-discrimination task, LIP firing rates decrease with supporting evidence, contrary to conventional motion-discrimination tasks. These opposite response patterns arise from similar mechanisms in which decisions form along curved population-response manifolds misaligned with action representations. These manifolds rotate in state space based on context, indicating distinct optimal readouts for different tasks. We show similar manifolds in lateral and medial prefrontal cortices, suggesting similar representational geometry across decision-making circuits.
Assuntos
Tomada de Decisões , Percepção de Movimento/fisiologia , Lobo Parietal/fisiologia , Animais , Comportamento Animal , Julgamento , Macaca mulatta , Masculino , Modelos Neurológicos , Neurônios/fisiologia , Estimulação Luminosa , Córtex Pré-Frontal/fisiologia , Psicofísica , Análise e Desempenho de Tarefas , Fatores de TempoRESUMO
Only five species of the once-diverse Rhinocerotidae remain, making the reconstruction of their evolutionary history a challenge to biologists since Darwin. We sequenced genomes from five rhinoceros species (three extinct and two living), which we compared to existing data from the remaining three living species and a range of outgroups. We identify an early divergence between extant African and Eurasian lineages, resolving a key debate regarding the phylogeny of extant rhinoceroses. This early Miocene (â¼16 million years ago [mya]) split post-dates the land bridge formation between the Afro-Arabian and Eurasian landmasses. Our analyses also show that while rhinoceros genomes in general exhibit low levels of genome-wide diversity, heterozygosity is lowest and inbreeding is highest in the modern species. These results suggest that while low genetic diversity is a long-term feature of the family, it has been particularly exacerbated recently, likely reflecting recent anthropogenic-driven population declines.
Assuntos
Evolução Molecular , Genoma , Perissodáctilos/genética , Animais , Demografia , Fluxo Gênico , Variação Genética , Geografia , Heterozigoto , Homozigoto , Especificidade de Hospedeiro , Cadeias de Markov , Mutação/genética , Filogenia , Especificidade da Espécie , Fatores de TempoRESUMO
Neural circuit assembly features simultaneous targeting of numerous neuronal processes from constituent neuron types, yet the dynamics is poorly understood. Here, we use the Drosophila olfactory circuit to investigate dynamic cellular processes by which olfactory receptor neurons (ORNs) target axons precisely to specific glomeruli in the ipsi- and contralateral antennal lobes. Time-lapse imaging of individual axons from 30 ORN types revealed a rich diversity in extension speed, innervation timing, and ipsilateral branch locations and identified that ipsilateral targeting occurs via stabilization of transient interstitial branches. Fast imaging using adaptive optics-corrected lattice light-sheet microscopy showed that upon approaching target, many ORN types exhibiting "exploring branches" consisted of parallel microtubule-based terminal branches emanating from an F-actin-rich hub. Antennal nerve ablations uncovered essential roles for bilateral axons in contralateral target selection and for ORN axons to facilitate dendritic refinement of postsynaptic partner neurons. Altogether, these observations provide cellular bases for wiring specificity establishment.
Assuntos
Condutos Olfatórios/citologia , Condutos Olfatórios/diagnóstico por imagem , Imagem com Lapso de Tempo , Animais , Axônios/fisiologia , Células Cultivadas , Dendritos/fisiologia , Drosophila melanogaster/citologia , Drosophila melanogaster/fisiologia , Microtúbulos/metabolismo , Neurônios Receptores Olfatórios/fisiologia , Fatores de TempoRESUMO
The anterior insular cortex (aIC) plays a critical role in cognitive and motivational control of behavior, but the underlying neural mechanism remains elusive. Here, we show that aIC neurons expressing Fezf2 (aICFezf2), which are the pyramidal tract neurons, signal motivational vigor and invigorate need-seeking behavior through projections to the brainstem nucleus tractus solitarii (NTS). aICFezf2 neurons and their postsynaptic NTS neurons acquire anticipatory activity through learning, which encodes the perceived value and the vigor of actions to pursue homeostatic needs. Correspondingly, aIC â NTS circuit activity controls vigor, effort, and striatal dopamine release but only if the action is learned and the outcome is needed. Notably, aICFezf2 neurons do not represent taste or valence. Moreover, aIC â NTS activity neither drives reinforcement nor influences total consumption. These results pinpoint specific functions of aIC â NTS circuit for selectively controlling motivational vigor and suggest that motivation is subserved, in part, by aIC's top-down regulation of dopamine signaling.
Assuntos
Tronco Encefálico/fisiologia , Córtex Insular/fisiologia , Motivação , Vias Neurais/fisiologia , Animais , Comportamento Animal , Dopamina/metabolismo , Feminino , Aprendizagem , Masculino , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Núcleo Accumbens/metabolismo , Fatores de TempoRESUMO
Electrical stimulation is a promising tool for modulating brain networks. However, it is unclear how stimulation interacts with neural patterns underlying behavior. Specifically, how might external stimulation that is not sensitive to the state of ongoing neural dynamics reliably augment neural processing and improve function? Here, we tested how low-frequency epidural alternating current stimulation (ACS) in non-human primates recovering from stroke interacted with task-related activity in perilesional cortex and affected grasping. We found that ACS increased co-firing within task-related ensembles and improved dexterity. Using a neural network model, we found that simulated ACS drove ensemble co-firing and enhanced propagation of neural activity through parts of the network with impaired connectivity, suggesting a mechanism to link increased co-firing to enhanced dexterity. Together, our results demonstrate that ACS restores neural processing in impaired networks and improves dexterity following stroke. More broadly, these results demonstrate approaches to optimize stimulation to target neural dynamics.
Assuntos
Potenciais de Ação/fisiologia , Acidente Vascular Cerebral/fisiopatologia , Animais , Comportamento Animal/fisiologia , Fenômenos Biomecânicos/fisiologia , Estimulação Elétrica , Haplorrinos , Córtex Motor/fisiopatologia , Redes Neurais de Computação , Neurônios/fisiologia , Análise e Desempenho de Tarefas , Fatores de TempoRESUMO
DNA has not been utilized to record temporal information, although DNA has been used to record biological information and to compute mathematical problems. Here, we found that indel generation by Cas9 and guide RNA can occur at steady rates, in contrast to typical dynamic biological reactions, and the accumulated indel frequency can be a function of time. By measuring indel frequencies, we developed a method for recording and measuring absolute time periods over hours to weeks in mammalian cells. These time-recordings were conducted in several cell types, with different promoters and delivery vectors for Cas9, and in both cultured cells and cells of living mice. As applications, we recorded the duration of chemical exposure and the lengths of elapsed time since the onset of biological events (e.g., heat exposure and inflammation). We propose that our systems could serve as synthetic "DNA clocks."
Assuntos
Proteína 9 Associada à CRISPR/metabolismo , Animais , Sequência de Bases , Microambiente Celular , Simulação por Computador , Células HEK293 , Meia-Vida , Humanos , Mutação INDEL/genética , Inflamação/patologia , Integrases/metabolismo , Masculino , Camundongos Nus , Regiões Promotoras Genéticas/genética , RNA Guia de Cinetoplastídeos/genética , Reprodutibilidade dos Testes , Fatores de TempoRESUMO
Long-term subcellular intravital imaging in mammals is vital to study diverse intercellular behaviors and organelle functions during native physiological processes. However, optical heterogeneity, tissue opacity, and phototoxicity pose great challenges. Here, we propose a computational imaging framework, termed digital adaptive optics scanning light-field mutual iterative tomography (DAOSLIMIT), featuring high-speed, high-resolution 3D imaging, tiled wavefront correction, and low phototoxicity with a compact system. By tomographic imaging of the entire volume simultaneously, we obtained volumetric imaging across 225 × 225 × 16 µm3, with a resolution of up to 220 nm laterally and 400 nm axially, at the millisecond scale, over hundreds of thousands of time points. To establish the capabilities, we investigated large-scale cell migration and neural activities in different species and observed various subcellular dynamics in mammals during neutrophil migration and tumor cell circulation.
Assuntos
Algoritmos , Imageamento Tridimensional , Óptica e Fotônica , Tomografia , Animais , Cálcio/metabolismo , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Movimento Celular , Drosophila , Células HeLa , Humanos , Larva/fisiologia , Fígado/diagnóstico por imagem , Masculino , Camundongos Endogâmicos C57BL , Neoplasias/patologia , Ratos Sprague-Dawley , Razão Sinal-Ruído , Frações Subcelulares/fisiologia , Fatores de Tempo , Peixe-ZebraRESUMO
Development of the human intestine is not well understood. Here, we link single-cell RNA sequencing and spatial transcriptomics to characterize intestinal morphogenesis through time. We identify 101 cell states including epithelial and mesenchymal progenitor populations and programs linked to key morphogenetic milestones. We describe principles of crypt-villus axis formation; neural, vascular, mesenchymal morphogenesis, and immune population of the developing gut. We identify the differentiation hierarchies of developing fibroblast and myofibroblast subtypes and describe diverse functions for these including as vascular niche cells. We pinpoint the origins of Peyer's patches and gut-associated lymphoid tissue (GALT) and describe location-specific immune programs. We use our resource to present an unbiased analysis of morphogen gradients that direct sequential waves of cellular differentiation and define cells and locations linked to rare developmental intestinal disorders. We compile a publicly available online resource, spatio-temporal analysis resource of fetal intestinal development (STAR-FINDer), to facilitate further work.
Assuntos
Intestinos/citologia , Intestinos/crescimento & desenvolvimento , Análise de Célula Única , Células Endoteliais/citologia , Sistema Nervoso Entérico/citologia , Feto/embriologia , Fibroblastos/citologia , Humanos , Imunidade , Enteropatias/congênito , Enteropatias/patologia , Mucosa Intestinal/crescimento & desenvolvimento , Intestinos/irrigação sanguínea , Ligantes , Mesoderma/citologia , Neovascularização Fisiológica , Pericitos/citologia , Células-Tronco/citologia , Fatores de Tempo , Fatores de Transcrição/metabolismoRESUMO
The heartbeat is initiated by voltage-gated sodium channel NaV1.5, which opens rapidly and triggers the cardiac action potential; however, the structural basis for pore opening remains unknown. Here, we blocked fast inactivation with a mutation and captured the elusive open-state structure. The fast inactivation gate moves away from its receptor, allowing asymmetric opening of pore-lining S6 segments, which bend and rotate at their intracellular ends to dilate the activation gate to â¼10 Å diameter. Molecular dynamics analyses predict physiological rates of Na+ conductance. The open-state pore blocker propafenone binds in a high-affinity pose, and drug-access pathways are revealed through the open activation gate and fenestrations. Comparison with mutagenesis results provides a structural map of arrhythmia mutations that target the activation and fast inactivation gates. These results give atomic-level insights into molecular events that underlie generation of the action potential, open-state drug block, and fast inactivation of cardiac sodium channels, which initiate the heartbeat.
Assuntos
Canal de Sódio Disparado por Voltagem NAV1.5/química , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Animais , Arritmias Cardíacas/genética , Microscopia Crioeletrônica , Células HEK293 , Frequência Cardíaca/efeitos dos fármacos , Humanos , Ativação do Canal Iônico , Modelos Moleculares , Simulação de Dinâmica Molecular , Mutação/genética , Miocárdio , Canal de Sódio Disparado por Voltagem NAV1.5/isolamento & purificação , Canal de Sódio Disparado por Voltagem NAV1.5/ultraestrutura , Propafenona/farmacologia , Conformação Proteica , Ratos , Sódio/metabolismo , Fatores de Tempo , Água/químicaRESUMO
The Eastern Eurasian Steppe was home to historic empires of nomadic pastoralists, including the Xiongnu and the Mongols. However, little is known about the region's population history. Here, we reveal its dynamic genetic history by analyzing new genome-wide data for 214 ancient individuals spanning 6,000 years. We identify a pastoralist expansion into Mongolia ca. 3000 BCE, and by the Late Bronze Age, Mongolian populations were biogeographically structured into three distinct groups, all practicing dairy pastoralism regardless of ancestry. The Xiongnu emerged from the mixing of these populations and those from surrounding regions. By comparison, the Mongols exhibit much higher eastern Eurasian ancestry, resembling present-day Mongolic-speaking populations. Our results illuminate the complex interplay between genetic, sociopolitical, and cultural changes on the Eastern Steppe.
Assuntos
Genética Populacional , Pradaria , Arqueologia , Europa (Continente) , Feminino , Frequência do Gene/genética , Pool Gênico , Heterogeneidade Genética , Genoma Humano , Geografia , Haplótipos/genética , História Antiga , Humanos , Masculino , Mongólia , Análise de Componente Principal , Fatores de TempoRESUMO
All proteins interact with other cellular components to fulfill their function. While tremendous progress has been made in the identification of protein complexes, their assembly and dynamics remain difficult to characterize. Here, we present a high-throughput strategy to analyze the native assembly kinetics of protein complexes. We apply our approach to characterize the co-assembly for 320 pairs of nucleoporins (NUPs) constituting the ≈50 MDa nuclear pore complex (NPC) in yeast. Some NUPs co-assemble fast via rapid exchange whereas others require lengthy maturation steps. This reveals a hierarchical principle of NPC biogenesis where individual subcomplexes form on a minute timescale and then co-assemble from center to periphery in a â¼1 h-long maturation process. Intriguingly, the NUP Mlp1 stands out as joining very late and associating preferentially with aged NPCs. Our approach is readily applicable beyond the NPC, making it possible to analyze the intracellular dynamics of a variety of multiprotein assemblies.
Assuntos
Substâncias Macromoleculares/metabolismo , Complexos Multiproteicos/metabolismo , Saccharomyces cerevisiae/metabolismo , Coloração e Rotulagem , Bioensaio , Cinética , Modelos Biológicos , Poro Nuclear/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Fatores de TempoRESUMO
Hippocampal activity represents many behaviorally important variables, including context, an animal's location within a given environmental context, time, and reward. Using longitudinal calcium imaging in mice, multiple large virtual environments, and differing reward contingencies, we derived a unified probabilistic model of CA1 representations centered on a single feature-the field propensity. Each cell's propensity governs how many place fields it has per unit space, predicts its reward-related activity, and is preserved across distinct environments and over months. Propensity is broadly distributed-with many low, and some very high, propensity cells-and thus strongly shapes hippocampal representations. This results in a range of spatial codes, from sparse to dense. Propensity varied â¼10-fold between adjacent cells in salt-and-pepper fashion, indicating substantial functional differences within a presumed cell type. Intracellular recordings linked propensity to cell excitability. The stability of each cell's propensity across conditions suggests this fundamental property has anatomical, transcriptional, and/or developmental origins.
Assuntos
Hipocampo/anatomia & histologia , Hipocampo/fisiologia , Animais , Comportamento Animal/fisiologia , Fenômenos Biofísicos , Cálcio/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Modelos Neurológicos , Células Piramidais/fisiologia , Recompensa , Análise e Desempenho de Tarefas , Fatores de TempoRESUMO
Every decision we make is accompanied by a sense of confidence about its likely outcome. This sense informs subsequent behavior, such as investing more-whether time, effort, or money-when reward is more certain. A neural representation of confidence should originate from a statistical computation and predict confidence-guided behavior. An additional requirement for confidence representations to support metacognition is abstraction: they should emerge irrespective of the source of information and inform multiple confidence-guided behaviors. It is unknown whether neural confidence signals meet these criteria. Here, we show that single orbitofrontal cortex neurons in rats encode statistical decision confidence irrespective of the sensory modality, olfactory or auditory, used to make a choice. The activity of these neurons also predicts two confidence-guided behaviors: trial-by-trial time investment and cross-trial choice strategy updating. Orbitofrontal cortex thus represents decision confidence consistent with a metacognitive process that is useful for mediating confidence-guided economic decisions.
Assuntos
Comportamento/fisiologia , Córtex Pré-Frontal/fisiologia , Animais , Comportamento de Escolha/fisiologia , Tomada de Decisões , Modelos Biológicos , Neurônios/fisiologia , Ratos Long-Evans , Sensação/fisiologia , Análise e Desempenho de Tarefas , Fatores de TempoRESUMO
RNA viruses are among the most prevalent pathogens and are a major burden on society. Although RNA viruses have been studied extensively, little is known about the processes that occur during the first several hours of infection because of a lack of sensitive assays. Here we develop a single-molecule imaging assay, virus infection real-time imaging (VIRIM), to study translation and replication of individual RNA viruses in live cells. VIRIM uncovered a striking heterogeneity in replication dynamics between cells and revealed extensive coordination between translation and replication of single viral RNAs. Furthermore, using VIRIM, we identify the replication step of the incoming viral RNA as a major bottleneck of successful infection and identify host genes that are responsible for inhibition of early virus replication. Single-molecule imaging of virus infection is a powerful tool to study virus replication and virus-host interactions that may be broadly applicable to RNA viruses.
Assuntos
Biossíntese de Proteínas , Vírus de RNA/fisiologia , Replicação Viral/fisiologia , Linhagem Celular Tumoral , Sobrevivência Celular , Células HEK293 , Interações Hospedeiro-Patógeno , Humanos , Interferons/metabolismo , Transporte de RNA , RNA Viral/genética , Reprodutibilidade dos Testes , Imagem Individual de Molécula , Fatores de TempoRESUMO
Rapid phasic activity of midbrain dopamine neurons is thought to signal reward prediction errors (RPEs), resembling temporal difference errors used in machine learning. However, recent studies describing slowly increasing dopamine signals have instead proposed that they represent state values and arise independent from somatic spiking activity. Here we developed experimental paradigms using virtual reality that disambiguate RPEs from values. We examined dopamine circuit activity at various stages, including somatic spiking, calcium signals at somata and axons, and striatal dopamine concentrations. Our results demonstrate that ramping dopamine signals are consistent with RPEs rather than value, and this ramping is observed at all stages examined. Ramping dopamine signals can be driven by a dynamic stimulus that indicates a gradual approach to a reward. We provide a unified computational understanding of rapid phasic and slowly ramping dopamine signals: dopamine neurons perform a derivative-like computation over values on a moment-by-moment basis.