Embryonic opioid exposure impairs inhibitory transmission of striatum in day-old chicks.

Studies of humans, mammalian animals, and chicks reveal that embryonic opioid exposure (EOE) changes the response to pharmacological rewards in postnatal individuals, which may be an outcome of permanent alterations to neural systems. However, the mechanism behind this alteration remains unclear. GABA transmitter has a trophic effect on early GABAergic neuronal development, and EOE decreases GABA concentration in developing brains. Here, we determined whether the development of inhibitory transmission was affected by EOE and whether altered GABA release was the underlying mechanism. We revealed that morphine administration in the early but not the late embryonic period decreased inhibitory transmission in the striatum of chicks. Meanwhile, day-old chicks with early embryonic morphine exposure showed increased psychomotor activity after acute morphine injection compared with saline-exposed chicks. Furthermore, GABA injection in the chick embryo following morphine administration mitigated damage to GABA transmission and recovered the behavioral response to acute morphine injection in chicks. Collectively, our findings suggest that abnormal GABA release in the early embryonic period induced by opioid exposure is attributable to functional and structural developments of the GABA synapse, and that the dysfunction of striatal GABA transmission may be linked to enhanced psychomotor response during initial drug exposure in postnatal life.

Three-Dimensional Architecture Reduced Graphene Oxide-LiFePO4 Composite: Preparation and Excellent Microwave Absorption Performance.

The present work reports preparation of 3D composites of reduced graphene oxide (RGO) with coral-like LiFePO4 particles in two steps, which involves the fabrication of LiFePO4 particles by the solvothermal method and the subsequent preparation of RGO/coral-like LiFePO4 composites by the etching method. The microwave absorption properties of LiFePO4 particles, coral-like LiFePO4 particles, and the RGO/coral-like LiFePO4 composites were studied. Our results show that the as-prepared RGO/coral-like LiFePO4 composites exhibit significantly improved microwave absorption properties compared with the pure LiFePO4 particles and coral-like LiFePO4 particles. The RGO/coral-like LiFePO4 composite (S-60) possesses optimized reflection loss (RL) performance with an RL value of -61.4 dB and a broad effective absorption bandwidth of 4 GHz (from 11.36 to 14.88 GHz and 16.32 to 16.8 GHz) at the matching thickness of only 2.4 mm. This demonstrates that the RGO/coral-like LiFePO4 composites can be superior candidates for lightweight and high-efficiency microwave absorbers.

WASH inhibits autophagy through suppression of Beclin 1 ubiquitination.

Autophagy degrades cytoplasmic proteins and organelles to recycle cellular components that are required for cell survival and tissue homeostasis. However, it is not clear how autophagy is regulated in mammalian cells. WASH (Wiskott-Aldrich syndrome protein (WASP) and SCAR homologue) plays an essential role in endosomal sorting through facilitating tubule fission via Arp2/3 activation. Here, we demonstrate a novel function of WASH in modulation of autophagy. We show that WASH deficiency causes early embryonic lethality and extensive autophagy of mouse embryos. WASH inhibits vacuolar protein sorting (Vps)34 kinase activity and autophagy induction. We identified that WASH is a new interactor of Beclin 1. Beclin 1 is ubiquitinated at lysine 437 through lysine 63 linkage in cells undergoing autophagy. Ambra1 is an E3 ligase for lysine 63-linked ubiquitination of Beclin 1 that is required for starvation-induced autophagy. The lysine 437 ubiquitination of Beclin 1 enhances the association with Vps34 to promote Vps34 activity. WASH can suppress Beclin 1 ubiquitination to inactivate Vps34 activity leading to suppression of autophagy.

Amorphous Phosphorus/Nitrogen-Doped Graphene Paper for Ultrastable Sodium-Ion Batteries.

As the most promising anode material for sodium-ion batteries (SIBs), elemental phosphorus (P) has recently gained a lot of interest due to its extraordinary theoretical capacity of 2596 mAh/g. The main drawback of a P anode is its low conductivity and rapid structural degradation caused by the enormous volume expansion (>490%) during cycling. Here, we redesigned the anode structure by using an innovative methodology to fabricate flexible paper made of nitrogen-doped graphene and amorphous phosphorus that effectively tackles this problem. The restructured anode exhibits an ultrastable cyclic performance and excellent rate capability (809 mAh/g at 1500 mA/g). The excellent structural integrity of the novel anode was further visualized during cycling by using in situ experiments inside a high-resolution transmission electron microscope (HRTEM), and the associated sodiation/desodiation mechanism was also thoroughly investigated. Finally, density functional theory (DFT) calculations confirmed that the N-doped graphene not only contributes to an increase in capacity for sodium storage but also is beneficial in regards to improved rate performance of the anode.

Pcid2 inactivates developmental genes in human and mouse embryonic stem cells to sustain their pluripotency by modulation of EID1 stability.

Self-renewal and differentiation are the hallmarks of embryonic stem cells (ESCs). However, it is largely unknown about how the pluripotency is regulated. Here we demonstrate that Pcid2 is required for the maintenance of self-renewal both in mouse and human ESCs. Pcid2 plays a critical role in suppression of ESC differentiation. Pcid2 deficiency causes early embryonic lethality before the blastocyst stage. Pcid2 associates with EID1 and is present in the CBP/p300-EID1 complex in the ESCs. We show that MDM2 is an E3 ligase for K48-linked EID1 ubiquitination for its degradation. For the maintenance of self-renewal, Pcid2 binds to EID1 to impede the association with MDM2. Then EID1 is not degraded to sustain its stability to block the HAT activity of CBP/p300, leading to suppression of the developmental gene expression. Collectively, Pcid2 is present in the CBP/p300-EID1 complex to control the switch balance of mouse and human ESCs through modulation of EID1 degradation.

Enhanced Photocatalytic Degradation of Rhodamine B Dye by Iron-Doped Europium Oxide Nanoparticles.

As a wide-bandgap rare-earth oxide, Eu2O3 was often utilized as an auxiliary material of other photocatalysts because its photocatalytic performance was limited by the luminescence characteristics of Eu3+ and low light utilization. In this study, we improved the photocatalytic degradation performance of the Eu2O3 nanoparticles by doping with Fe cations. The Eu2O3 nanoparticles with different Fe-doping concentrations (1, 3, and 5%, noted as EF1.0, EF3.0, and EF5.0, respectively) were synthesized via chemical precipitation and calcination methods. It was found that doping could reduce Eu2O3's bandgap, which probably originated from the introduction of oxygen vacancies with lower energy levels than the conduction band of Eu2O3. Compared with the undoped Eu2O3 nanoparticles with a removal efficiency of 22% for degrading rhodamine B dye within 60 min, the photocatalytic degradation efficiencies of EF1.0, EF3.0, and EF5.0 were demonstrated to be improved to 42, 48, and 33%, respectively, and EF3.0's performance was the best. The enhanced photocatalytic performance of the doped samples was related to the oxygen vacancies acting as capture centers for electrons, such that the photogenerated electron-hole pairs were efficiently separated and the redox reactions on the surface of the nanoparticles were enhanced accordingly. Additionally, the enhanced light absorption and broadened spectral band further improved EF3.0's degradation efficiency.

ALKBH5 deficiency attenuates oxygen-glucose deprivation-induced injury in mouse brain microvascular endothelial cells in an m6A dependent manner.

Structural and functional alterations in brain microvascular endothelial cells (BMECs) caused by oxygen-glucose deprivation (OGD) are involved in the pathogenesis of various brain disorders. AlkB homolog 5 (ALKBH5) is a primary m6A demethylase that regulates various cell processes, but its distinct roles in BMEC function remain to be clarified. In the present study, in mouse middle cerebral artery occlusion (MCAO) model, knockout of ALKBH5 reduced neurological deficits, infarct volumes and tissue apoptosis caused by ischemia/reperfusion injury. Evans blue leakage and decreased expression of the tight junction protein ZO-1 and Occludin were also attenuated by ALKBH5 knockout. During the exploration of the underlying mechanisms of the role of ALKBH5 in BMECs, we found that the expression of ALKBH5 was induced at both the mRNA and protein levels by hypoxia; however, its protein stability was impaired by OGD treatment. Knockdown of ALKBH5 expression increased total m6A levels and alleviated OGD-induced BMEC injury. At the same time, the selective ALKBH5 inhibitor Cpd 20m also exhibited a protective effect on cell injury. In contrast, overexpression of ALKBH5 increased the sensitivity of BMECs to OGD. Interestingly, the m6A sequencing data revealed that knockdown of ALKBH5altered the expression of many genes via m6A upregulation. The gene expression alterations were verified by real-time PCR. Taken together, our results suggest that ALKBH5, as well as its target genes, plays important roles in the regulation of brain microvascular endothelial cell function through its RNA demethylase activity.

Design of a KNN-BZT Ceramic with High Energy Storage Properties and Transmittance under Low Electric Fields.

With the advancement of science and technology, single-function ceramics have been difficult to meet the rapid development of electronic components. It is of great significance to find and develop multifunctional ceramics with excellent performance and environmental friendliness (such as good energy storage and transparency). Especially, the realization of its excellent performance under low electric fields has more reference and practical value. In this study, by Bi(Zn0.5Ti0.5)O3 (BZT) modification in (K0.5Na0.5)NbO3 (KNN), reducing grain size, and increasing band gap energy, the purpose of improving energy storage performance and transparency has been achieved under low electric field. The results show that the submicron average grain size decreased to 0.9 µm and the band gap energy (E g) increased to 2.97 eV for 0.90KNN-0.10BZT ceramics. The transparency is up to 69.27% in the near-infrared region (1344 nm) and the energy storage density is 2.16 J/cm3 under 170 kV/cm. Moreover, the 0.90KNN-0.10BZT ceramic exhibits a power density (P D) of 17.50 MW/cm3 and the stored energy can be discharged in 1.60 µs at 140 kV/cm. This revealed a potential application of KNN-BZT ceramic as an energy storage and transparent capacitor in the electronics industry.

Locus coeruleus input-modulated reactivation of dentate gyrus opioid-withdrawal engrams promotes extinction.

Extinction training during the reconsolidation window following memory recall is an effective behavioral pattern for promoting the extinction of pathological memory. However, promoted extinction by recall-extinction procedure has not been universally replicated in different studies. One potential reason for this may relate to whether initially acquired memory is successfully activated. Thus, the methods for inducing the memory into an active or plastic condition may contribute to promoting its extinction. The aim of this study is to find and demonstrate a manipulatable neural circuit that engages in the memory recall process and where its activation improves the extinction process through recall-extinction procedure. Here, naloxone-precipitated conditioned place aversion (CPA) in morphine-dependent mice was mainly used as a pathological memory model. We found that the locus coeruleus (LC)-dentate gyrus (DG) circuit was necessary for CPA memory recall and that artificial activation of LC inputs to the DG just prior to initiating a recall-extinction procedure significantly promoted extinction learning. We also found that activating this circuit caused an increase in the ensemble size of DG engram cells activated during the extinction, which was confirmed by a cFos targeted strategy to label cells combined with immunohistochemical and in vivo calcium imaging techniques. Collectively, our data uncover that the recall experience is important for updating the memory during the reconsolidation window; they also suggest a promising neural circuit or target based on the recall-extinction procedure for weakening pathological aversion memory, such as opioid withdrawal memory and fear memory.

Zeolite fly ash-enhanced coagulation treatment of oil recovery wastewater from polymer flooding.

Herein, an enhanced coagulation model is proposed in which zeolite is used as a crystal nucleus to promote flocs. The zeolite is prepared from fly ash by microwave-assisted hydrothermal synthesis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area and pore size analysis (BET) characterization confirmed the successful synthesis of ZFA, and improved the surface properties. Thus, the adsorption capacity of ZFA as crystal nucleus was improved, which enabled it to achieve better results in the process of enhanced coagulation. Compared with those of conventional coagulation, the oil content and SS removal rate of ZFA-enhanced coagulation increased by 85% and 44%, respectively. Compared with that of CFA-enhanced coagulation, the oil removal efficiency increased by 4%, and the SS removal efficiency increased by 9%. The optimal conditions of ZFA-enhanced coagulation were as follows: ZFA dosage of 100 mg/L, pH value of 5-8, ZFA particle size range of 60-75 µm, temperature of 40-50 ℃, and precipitation time of 30 min.

The role of hippocampus in memory reactivation: an implication for a therapeutic target against opioid use disorder.

Purpose of the review: The abuse of opioids induces many terrible problems in human health and social stability. For opioid-dependent individuals, withdrawal memory can be reactivated by context, which is then associated with extremely unpleasant physical and emotional feelings during opioid withdrawal. The reactivation of withdrawal memory is considered one of the most important reasons for opioid relapse, and it also allows for memory modulation based on the reconsolidation phenomenon. However, studies exploring withdrawal memory modulation during the reconsolidation window are lacking. By summarizing the previous findings about the reactivation of negative emotional memories, we are going to suggest potential neural regions and systems for modulating opioid withdrawal memory. Recent findings: Here, we first present the role of memory reactivation in its modification, discuss how the hippocampus participates in memory reactivation, and discuss the importance of noradrenergic signaling in the hippocampus for memory reactivation. Then, we review the engagement of other limbic regions receiving noradrenergic signaling in memory reactivation. We suggest that noradrenergic signaling targeting hippocampus neurons might play a potential role in strengthening the disruptive effect of withdrawal memory extinction by facilitating the degree of memory reactivation. Summary: This review will contribute to a better understanding of the mechanisms underlying reactivation-dependent memory malleability and will provide new therapeutic avenues for treating opioid use disorders.

Corticotropin-releasing factor receptor 1 in infralimbic cortex modulates social stress-altered decision-making.

Chronic stress could lead to a bias in behavioral strategies toward habits. However, it remains unclear which neuronal system modulates stress-induced behavioral abnormality during decision making. The corticotropin-releasing factor (CRF) system in the medial prefrontal cortex (mPFC), which has been implicated in governing strategy choice, is involved in the response to stress. The present study aimed to clarify whether altered function in cortical CRF receptors is linked to abnormal behaviors after chronic stress. In results, mice subjected to a 10-day social defeat preferred to use a habitual strategy. The infralimbic cortex (IL), but not the prelimbic cortex (PL) or anterior cingulate cortex (ACC), showed higher cFos expression in stress-subjected mice than in control mice, which may be associated with habitual behavior choice. Furthermore, CRF receptor 1 (CRFR1) agonist and antagonist infusion in IL during behavioral training mimicked and rescued stress-caused behavioral change in the decision-making assessment, respectively. An electrophysiological approach showed that the frequencies of both spontaneous IPSC and spontaneous EPSC, but not their amplitude, increased after stress and were modulated by CRFR1 agents. Further recordings revealed that an increased ratio of excitation to inhibition (E/I ratio) of IL by stress was rescued under conditions with CRFR1 antagonist. Collectively, these data indicate that CRFR1 plays a critical role in stress-permitted or enhanced glutamatergic and GABAergic presynaptic transmission in direct or indirect ways, as well as the modulation for E/I ratio in the IL. Thus, CRFR1 in the mPFC may be a proper target for treating cases of chronic stress-altered behavior.

Protection of ischemic white matter and oligodendrocytes in mice by 3K3A-activated protein C.

Subcortical white matter (WM) stroke accounts for 25% of all strokes and is the second leading cause of dementia. Despite such clinical importance, we still do not have an effective treatment for ischemic WM stroke, and the mechanisms of WM postischemic neuroprotection remain elusive. 3K3A-activated protein C (APC) is a signaling-selective analogue of endogenous blood protease APC that is currently in development as a neuroprotectant for ischemic stroke patients. Here, we show that 3K3A-APC protects WM tracts and oligodendrocytes from ischemic injury in the corpus callosum in middle-aged mice by activating protease-activated receptor 1 (PAR1) and PAR3. We show that PAR1 and PAR3 were also required for 3K3A-APC's suppression of post-WM stroke microglia and astrocyte responses and overall improvement in neuropathologic and functional outcomes. Our data provide new insights into the neuroprotective APC pathway in the WM and illustrate 3K3A-APC's potential for treating WM stroke in humans, possibly including multiple WM strokes that result in vascular dementia.

MicroRNA-mediated gene regulation plays a minor role in the transcriptomic plasticity of cold-acclimated zebrafish brain tissue.

BACKGROUND: MicroRNAs (miRNAs) play important roles in regulating the expression of protein-coding genes by directing the degradation and/or repression of the translation of gene transcripts. Growing evidence shows that miRNAs are indispensable player in organismal development with its regulatory role in the growth and differentiation of cell lineages. However, the roles of miRNA-mediated regulation in environmental adaptation of organisms are largely unknown. To examine this potential regulatory capability, we characterized microRNAomes from the brain of zebrafish raised under normal (28 °C) and cold-acclimated (10 °C, 10 days) conditions using Solexa sequencing. We then examined the expression pattern of the protein-coding genes under these two conditions with Affymetrix Zebrafish Genome Array profiling. The potential roles of the microRNAome in the transcriptomic cold regulation in the zebrafish brain were investigated by various statistical analyses. RESULTS: Among the total 214 unique, mature zebrafish miRNAs deposited on the miRBase website (release 16), 175 were recovered in this study. In addition, we identified 399 novel, mature miRNAs using multiple miRNA prediction methods. We defined a set of 25 miRNAs differentially expressed under the cold and normal conditions and predicted the molecular functions and biological processes that they involve through Gene Ontology (GO) annotation of their target genes. On the other hand, microarray analysis showed that genes related to mRNA processing and response to stress were overrepresented among the up-regulated genes in cold-stress, but are not directly corresponding to any of the GO molecular functions and biological processes predicted from the differential miRNAs. Using several statistical models including a novel, network-based approach, we found that miRNAs identified in this study, either individually or together, and either directly or indirectly (i.e., mediated by transcription factors), only make minor contribution to the change in gene expression patterns under the low-temperature condition. CONCLUSIONS: Our results suggest that the cold-stress response of mRNA expression may be governed mainly through regulatory modes other than miRNA-mediated regulation. MiRNAs in animal brains might act more as developmental regulators than thermal adaptability regulators.

Transcriptomic and genomic evolution under constant cold in Antarctic notothenioid fish.

The antifreeze glycoprotein-fortified Antarctic notothenioid fishes comprise the predominant fish suborder in the isolated frigid Southern Ocean. Their ecological success undoubtedly entailed evolutionary acquisition of a full suite of cold-stable functions besides antifreeze protection. Prior studies of adaptive changes in these teleost fishes generally examined a single genotype or phenotype. We report here the genome-wide investigations of transcriptional and genomic changes associated with Antarctic notothenioid cold adaptation. We sequenced and characterized 33,560 ESTs from four tissues of the Antarctic notothenioid Dissostichus mawsoni and derived 3,114 nonredundant protein gene families and their expression profiles. Through comparative analyses of same-tissue transcriptome profiles of D. mawsoni and temperate/tropical teleost fishes, we identified 177 notothenioid protein families that were expressed many fold over the latter, indicating cold-related up-regulation. These up-regulated gene families operate in protein biosynthesis, protein folding and degradation, lipid metabolism, antioxidation, antiapoptosis, innate immunity, choriongenesis, and others, all of recognizable functional importance in mitigating stresses in freezing temperatures during notothenioid life histories. We further examined the genomic and evolutionary bases for this expressional up-regulation by comparative genomic hybridization of DNA from four pairs of Antarctic and basal non-Antarctic notothenioids to 10,700 D. mawsoni cDNA probes and discovered significant to astounding (3- to >300-fold, P < 0.05) Antarctic-specific duplications of 118 protein-coding genes, many of which correspond to the up-regulated gene families. Results of our integrative tripartite study strongly suggest that evolution under constant cold has resulted in dramatic genomic expansions of specific protein gene families, augmenting gene expression and gene functions contributing to physiological fitness of Antarctic notothenioids in freezing polar conditions.

Endothelial LRP1 protects against neurodegeneration by blocking cyclophilin A.

The low-density lipoprotein receptor-related protein 1 (LRP1) is an endocytic and cell signaling transmembrane protein. Endothelial LRP1 clears proteinaceous toxins at the blood-brain barrier (BBB), regulates angiogenesis, and is increasingly reduced in Alzheimer's disease associated with BBB breakdown and neurodegeneration. Whether loss of endothelial LRP1 plays a direct causative role in BBB breakdown and neurodegenerative changes remains elusive. Here, we show that LRP1 inactivation from the mouse endothelium results in progressive BBB breakdown, followed by neuron loss and cognitive deficits, which is reversible by endothelial-specific LRP1 gene therapy. LRP1 endothelial knockout led to a self-autonomous activation of the cyclophilin A-matrix metalloproteinase-9 pathway in the endothelium, causing loss of tight junctions underlying structural BBB impairment. Cyclophilin A inhibition in mice with endothelial-specific LRP1 knockout restored BBB integrity and reversed and prevented neuronal loss and behavioral deficits. Thus, endothelial LRP1 protects against neurodegeneration by inhibiting cyclophilin A, which has implications for the pathophysiology and treatment of neurodegeneration linked to vascular dysfunction.

[The impact of microRNAs on the evolution of metazoan complexity].

MicroRNAs (miRNAs) are a novel class of ~22 nt non-coding small RNAs. As crucial post-transcriptional regulators, miRNAs are involved in comprehensive biological processes such as developmental timing, cell proliferation and differentiation, oncogenesis and viral defenses. In addition to the roles in ontogenic physiology, researches on the area of miRNA phylogenetic conservation and diversity suggested that miRNAs play important roles in animal evolution through driving phenotypic variations in development. It has been postulated that miRNAs have enormous impacts on phenotypic variation and developmental complexity. Here we reviewed recent advances in the studies on the roles of miRNA in animal evolution, from aspects of the rate of miRNA evolution, the spatio-temporal expression pattern, the variation of target sites, and miRNA gene dynamics. We gave evidence to support the hypothesis that innovations in miRNA-mediated regulations drive the increase of metazoan complexity.

Sensitivity analysis of heat dissipation factors in a hot oil pipeline based on orthogonal experiments.

The study of phase-change heat-transfer characteristics of crude oil has been one of the hot issues in the field of gathering and transportation. The process of phase-change heat transfer of crude oil involves many complicated problems such as natural convection treatment, latent heat treatment, phase-change interface determination and fluid characteristic change. A mathematical model based on the additional capacity heat method is proposed in this article, and the momentum equations of crude oil liquid phase are presented for Newtonian and non-Newtonian fluids. The aim of this study was to investigate the influence of different factors on the heat transfer performance during the shutdown process of an overhead pipe. Experiments were conducted to verify the model and the solution method; the experimental and model results showed good agreement with a maximum relative error of 4.57%. The temperature fields and solidification conditions of crude oil in pipelines under different shutdown conditions were determined, and the sensitivity of the main effect factors was determined through an orthogonal experiment. The results show that the order of influence was oil initial temperature >thickness of insulating layer >air temperature >thickness of wax layer. The results of the study have important guiding significance on the control of shutdown time and the determination of restarting schemes.

Effective Strategy to Achieve Excellent Energy Storage Properties in Lead-Free BaTiO3-Based Bulk Ceramics.

Although extensive studies have been done on lead-free dielectric ceramics to achieve excellent dielectric behaviors and good energy storage performance, the major problem of low energy density has not been solved so far. Here, we report on designing the crossover relaxor ferroelectrics (CRFE), a crossover region between the normal ferroelectrics and relaxor ferroelectrics, as a solution to overcome the low energy density. CRFE exhibits smaller free energy and lower defect density in the modified Landau theory, which helps to obtain ultrahigh energy density and efficiency. The (1-x)Ba0.65Sr0.35TiO3-xBi(Mg2/3Nb1/3)O3 ((1-x)BST-xBMN) (x = 0, 0.08, 0.1, 0.18, 0.2) ceramic was synthesized by a solid-state reaction method. The solid solutions exhibit dielectric frequency dispersion, which suggests typical relaxor characteristics with the increasing BMN content. The crossover ferroelectrics of 0.9BST-0.1BMN ceramic possesses a high energy storage efficiency (η) of 85.71%, a high energy storage density (W) of 3.90 J/cm3, and an ultrahigh recoverable energy storage density (Wrec) of 3.34 J/cm3 under a dielectric breakdown strength of 400 kV/cm and is superior to other lead-free BaTiO3 (BT)-based energy storage ceramics. It also exhibits strong thermal stability in the temperature range from 25 to 150 °C under an electric field of 300 kV/cm, with the fluctuations below 3% and with the energy storage density and energy efficiency at about 2.8 J/cm3 and 82.93%, respectively. The enhanced recoverable energy density and breakdown strength of BT-based materials with significantly high energy efficiency make it a promising candidate to meet the wide requirements for high power applications.

Characterization of microRNAs in cephalochordates reveals a correlation between microRNA repertoire homology and morphological similarity in chordate evolution.

Cephalochordates, urochordates, and vertebrates comprise the three extant groups of chordates. Although higher morphological and developmental similarity exists between cephalochordates and vertebrates, molecular phylogeny studies have instead suggested that the morphologically simplified urochordates are the closest relatives to vertebrates. MicroRNAs (miRNAs) are regarded as the major factors driving the increase of morphological complexity in early vertebrate evolution, and are extensively characterized in vertebrates and in a few species of urochordates. However, the comprehensive set of miRNAs in the basal chordates, namely the cephalochordates, remains undetermined. Through extensive sequencing of a small RNA library and genomic homology searches, we characterized 100 miRNAs from the cephalochordate amphioxus, Branchiostoma japonicum, and B. floridae. Analysis of the evolutionary history of the cephalochordate miRNAs showed that cephalochordates possess 54 miRNA families homologous to those of vertebrates, which is threefold higher than those shared between urochordates and vertebrates. The miRNA contents demonstrated a clear correlation between the extent of miRNA overlapping and morphological similarity among the three chordate groups, providing a strong evidence of miRNAs being the major genetic factors driving morphological complexity in early chordate evolution.