Blockade of a novel MAP4K4-LATS2-SASH1-YAP1 cascade inhibits tumorigenesis and metastasis in luminal breast cancer.

Novel components in the noncanonical Hippo pathway that mediate the growth, metastasis, and drug resistance of breast cancer (BC) cells need to be identified. Here, we showed that expression of SAM and SH3 domain-containing protein 1 (SASH1) is negatively correlated with expression of mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) in a subpopulation of patients with luminal-subtype BC. Downregulated SASH1 and upregulated MAP4K4 synergistically regulated the proliferation, migration, and invasion of luminal-subtype BC cells. The expression of LATS2, SASH1, and YAP1 and the phosphorylation of YAP1 were negatively regulated by MAP4K4, and LATS2 then phosphorylated SASH1 to form a novel MAP4K4-LATS2-SASH1-YAP1 cascade. Dephosphorylation of Yes1 associated transcriptional regulator (YAP1), YAP1/TAZ nuclear translocation, and downstream transcriptional regulation of YAP1 were promoted by the combined effects of ectopic MAP4K4 expression and SASH1 silencing. Targeted inhibition of MAP4K4 blocked proliferation, cell migration, and ER signaling both in vitro and in vivo. Our findings reveal a novel MAP4K4-LATS2-SASH1-YAP1 phosphorylation cascade, a noncanonical Hippo pathway that mediates ER signaling, tumorigenesis, and metastasis in breast cancer. Targeted intervention with this noncanonical Hippo pathway may constitute a novel alternative therapeutic approach for endocrine-resistant BC.

Voltage imaging and optogenetics reveal behaviour-dependent changes in hippocampal dynamics.

A technology that simultaneously records membrane potential from multiple neurons in behaving animals will have a transformative effect on neuroscience research1,2. Genetically encoded voltage indicators are a promising tool for these purposes; however, these have so far been limited to single-cell recordings with a marginal signal-to-noise ratio in vivo3-5. Here we developed improved near-infrared voltage indicators, high-speed microscopes and targeted gene expression schemes that enabled simultaneous in vivo recordings of supra- and subthreshold voltage dynamics in multiple neurons in the hippocampus of behaving mice. The reporters revealed subcellular details of back-propagating action potentials and correlations in subthreshold voltage between multiple cells. In combination with stimulation using optogenetics, the reporters revealed changes in neuronal excitability that were dependent on the behavioural state, reflecting the interplay of excitatory and inhibitory synaptic inputs. These tools open the possibility for detailed explorations of network dynamics in the context of behaviour. Fig. 1 PHOTOACTIVATED QUASAR3 (PAQUASAR3) REPORTS NEURONAL ACTIVITY IN VIVO.: a, Schematic of the paQuasAr3 construct. b, Photoactivation by blue light enhanced voltage signals excited by red light in cultured neurons that expressed paQuasAr3 (representative example of n = 4 cells). c, Model of the photocycle of paQuasAr3. d, Confocal images of sparsely expressed paQuasAr3 in brain slices. Scale bars, 50 µm. Representative images, experiments were repeated in n = 3 mice. e, Simultaneous fluorescence and patch-clamp recordings from a neuron expressing paQuasAr3 in acute brain slice. Top, magnification of boxed regions. Schematic shows brain slice, patch pipette and microscope objective. f, Simultaneous fluorescence and patch-clamp recordings of inhibitory post synaptic potentials in an L2-3 neuron induced by electrical stimulation of L5-6 in acute slice. g, Normalized change in fluorescence (ΔF/F) and SNR of optically recorded post-synaptic potentials (PSPs) as a function of the amplitude of the post-synaptic potentials. The voltage sensitivity was ΔF/F = 40 ± 1.7% per 100 mV. The SNR was 0.93 ± 0.07 per 1 mV in a 1-kHz bandwidth (n = 42 post-synaptic potentials from 5 cells, data are mean ± s.d.). Schematic shows brain slice, patch pipette, field stimulation electrodes and microscope objective. h, Optical measurements of paQuasAr3 fluorescence in the CA1 region of the hippocampus (top) and glomerular layer of the olfactory bulb (bottom) of anaesthetized mice (representative traces from n = 7 CA1 cells and n = 13 olfactory bulb cells, n = 3 mice). Schematics show microscope objective and the imaged brain region. i, STA fluorescence from 88 spikes in a CA1 oriens neuron. j, Frames from the STA video showing the delay in the back-propagating action potential in the dendrites relative to the soma. k, Sub-Nyquist fitting of the action potential delay and width shows electrical compartmentalization in the dendrites. Experiments in k-m were repeated in n = 2 cells from n = 2 mice.

An ultra-small organic dye nanocluster for enhancing NIR-II imaging-guided surgery outcomes.

PURPOSE: The accuracy of surgery for patients with solid tumors can be greatly improved through fluorescence-guided surgery (FGS). However, existing FGS technologies have limitations due to their low penetration depth and sensitivity/selectivity, which are particularly prevalent in the relatively short imaging window (< 900 nm). A solution to these issues is near-infrared-II (NIR-II) FGS, which benefits from low autofluorescence and scattering under the long imaging window (> 900 nm). However, the inherent self-assembly of organic dyes has led to high accumulation in main organs, resulting in significant background signals and potential long-term toxicity. METHODS: We rationalize the donor structure of donor-acceptor-donor-based dyes to control the self-assembly process to form an ultra-small dye nanocluster, thus facilitating renal excretion and minimizing background signals. RESULTS: Our dye nanocluster can not only show clear vessel imaging, tumor and tumor sentinel lymph nodes definition, but also achieve high-performance NIR-II imaging-guided surgery of tumor-positive sentinel lymph nodes. CONCLUSION: In summary, our study demonstrates that the dye nanocluster-based NIR-II FGS has substantially improved outcomes for radical lymphadenectomy.

Migration from Lysosome to Nucleus: Monitoring Lysosomal Alkalization-Related Biological Processes with an Aminofluorene-Based Probe.

Aberrant lysosomal alkalization is associated with various biological processes, such as oxidative stress, cell apoptosis, ferroptosis, etc. Herein, we developed a novel aminofluorene-based fluorescence probe named FAN to monitor the lysosomal alkalization-related biological processes by its migration from lysosome to nucleus. FAN possessed NIR emission, large Stokes shift, high pH stability, and high photostability, making it suitable for real-time and long-term bioimaging. As a lysosomotropic molecule, FAN can accumulate in lysosomes first and then migrate to the nucleus by right of its binding capability to DNA after lysosomal alkalization. In this manner, FAN was successfully used to monitor these physiological processes which triggered lysosomal alkalization in living cells, including oxidative stress, cell apoptosis, and ferroptosis. More importantly, at higher concentrations, FAN could also serve as a stable nucleus dye for the fluorescence imaging of the nucleus in living cells and tissues. This novel multifunctional fluorescence probe shows great promise for application in lysosomal alkalization-related visual research and nucleus imaging.

Retyping and molecular pathology diagnosis of dyschromatosis universalis hereditaria.

Dyschromatosis universalis hereditaria (DUH) is characterized by diffuse symmetrically distributed hypopigmented macules mixed with hyperpigmentation. DUH is divided into three types by Online Mendelian inheritance in man (OMIM) that is, DUH1 (OMIM 127500), DUH2 (OMIM 612715) and DUH3 (OMIM 615402) according to the different linkage regions. Although each condition possesses corresponding phenotypic characteristics and the prognosis for each is somewhat different, these disorders are highly overlapped and difficult to differentiate in the clinical setting. Our latest study reveals a novel DUH subtype that presents a mild phenotype of pigmentation anomalies and is named PER3rs772027021 SNP related DUH or DUH4 by us, which make the DUH subtype can be further retyped. Heterozygous distribution or mosaic-like distribution of melanin is a newly discovered pathological features that is uniquely demonstrated in the affected layers of DUH1 and DUH4 patients. In this review, DUH is further divided into four subtypes according the causative genes and their mutational sites, and the mutation regions described in the previous reports. To make an accurate diagnosis, we suggest that Sanger sequencing or the target region sequencing (TRS) to the candidate causative genes related melanogenesis may be the most effective and convenient method of clinical diagnosis or/and prenatal diagnosis for DUH and DUH-like patients. More importantly, heterozygous distribution or mosaic-like distribution of melanin can be utilized for differential diagnosis of DUH. We also investigate the underlying molecular mechanism to form mosaic-like melanin in the affected layers of hyper- and/or hypo-pigmented macules from DUH1 and DUH4 patients. This review provides a molecular and pathological delineation of four types of DUH and aims to establish a concise diagnostic strategy to allow clinical dermatologists to make an accurate diagnosis.

Generalization Analysis of Pairwise Learning for Ranking With Deep Neural Networks.

Pairwise learning is widely employed in ranking, similarity and metric learning, area under the ROC curve (AUC) maximization, and many other learning tasks involving sample pairs. Pairwise learning with deep neural networks was considered for ranking, but enough theoretical understanding about this topic is lacking. In this letter, we apply symmetric deep neural networks to pairwise learning for ranking with a hinge loss ϕh and carry out generalization analysis for this algorithm. A key step in our analysis is to characterize a function that minimizes the risk. This motivates us to first find the minimizer of ϕh-risk and then design our two-part deep neural networks with shared weights, which induces the antisymmetric property of the networks. We present convergence rates of the approximation error in terms of function smoothness and a noise condition and give an excess generalization error bound by means of properties of the hypothesis space generated by deep neural networks. Our analysis is based on tools from U-statistics and approximation theory.

Significant Enhancement of the Upconversion Emission in Highly Er3+ -Doped Nanoparticles at Cryogenic Temperatures.

Relatively low efficiency is the bottleneck for the application of lanthanide-doped upconversion nanoparticles (UCNPs). The high-level doping strategy realized in recent years has not improved the efficiency as much as expected. It is argued that cross relaxation (CR) is not detrimental to upconversion. Here we combine theoretical simulation and spectroscopy to elucidate the role of CR in upconversion process of Er3+ highly doped (HD) UCNPs. It is found that if CR is purposively suppressed, upconversion efficiency can be significantly improved. Specifically, we demonstrate experimentally that inhibition of CR by introducing cryogenic environment (40 K) enhances upconversion emission by more than two orders of magnitude. This work not only elucidates the nature of CR and its non-negligible adverse effects, but also provides a new perspective for improving upconversion efficiency. The result can be directly applied to cryogenic imaging and wide range temperature sensing.

Cross Relaxation Channel Tailored Temperature Response in Er3+ -rich Upconversion Nanophosphor.

Recently high doping of lanthanide ions (till 100 %) is realized unprecedentedly in nanostructured upconversion (UC) phosphors. However, oddly enough, this significant breakthrough did not result in a corresponding UC enhancement at ambient temperature, which hinders the otherwise very interesting applications of these materials in various fields. In this work, taking the Er3+ -rich UC nanosystem as an example, we confirm unambiguously that the phonon-assisted cross relaxation (CR) is the culprit. More importantly, combining the theoretical modeling and experiments, the precise roles of different CR channels on UC energy loss are quantitatively revealed. As a result, lowering the temperature can exponentially enhance the relevant UC luminescence by more than two orders of magnitude. Our comprehension will play an important role in promoting the UC performance and further application of high doping rare earth materials. As a proof of concept, an Er3+ -rich core/multi-shell nanophosphor is exploited which demonstrates the great potential of our finding in the field of ultra-sensitive temperature sensing.

Imipramine impedes glioma progression by inhibiting YAP as a Hippo pathway independent manner and synergizes with temozolomide.

Patients with malignant glioma often suffered from depression, which leads to an increased risk of detrimental outcomes. Imipramine, an FDA-approved tricyclic antidepressant, has been commonly used to relieve depressive symptoms in the clinic. Recently, imipramine has been reported to participate in the suppression of tumour progression in several human cancers, including prostate cancer, colon cancer and lymphomas. However, the effect of imipramine on malignant glioma is largely unclear. Here, we show that imipramine significantly retarded proliferation of immortalized and primary glioma cells. Mechanistically, imipramine suppressed tumour proliferation by inhibiting yes-associated protein (YAP), a recognized oncogene in glioma, independent of Hippo pathway. In addition to inhibiting YAP transcription, imipramine also promoted the subcellular translocation of YAP from nucleus into cytoplasm. Consistently, imipramine administration significantly reduced orthotopic tumour progression and prolonged survival of tumour-bearing mice. Moreover, exogenous overexpression of YAP partially restored the inhibitory effect of imipramine on glioma progression. Most importantly, compared with imipramine or temozolomide (TMZ) monotherapy, combination therapy with imipramine and TMZ exhibited enhanced inhibitory effect on glioma growth both in vitro and in vivo, suggesting the synergism of both agents. In conclusion, we found that tricyclic antidepressant imipramine impedes glioma progression by inhibiting YAP. In addition, combination therapy with imipramine and TMZ may potentially serve as promising anti-glioma regimens, thus predicting a broad prospect of clinical application.

Arthroscopic reconstruction of coracoclavicular ligament by suspensory fixation for management of acute acromioclavicular joint dislocation and MRI follow-up study. / å ³èŠ‚é•œä¸‹å–™é”éŸ§å¸¦é‡å»ºæ‚¬åŠå¼å›ºå®šæ²»ç–—æ€¥æ€§è‚©é”å ³èŠ‚è„±ä½åŠMRI随访.

OBJECTIVES: To explore the safety and effectiveness of arthroscopic reconstruction of coracoclavicular ligament by suspensory fixation to manage the acute acromioclavicular joint dislocation. METHODS: From January 2016 to December 2017, 18 cases of acute acromioclavicular joint dislocation were carried out with arthroscopic reconstruction of coracoclavicular ligament by double Endobutton plate suspensory fixation. Anteroposterior view X-ray plain radiographs were obtained on the second day, 6 months and 12 months after the surgery, MRI was performed in 1 year after operation. Meanwhile, subjective and objective scoring were obtained by Vsual Analogue Scale (VAS), Rating Scale of the American Shoulder and Elbow Surgeons (ASES) and University of California at Los Angeles Shoulder Rating Scale (UCLA). RESULTS: All patients were followed up for 12 to 30 months (an average of 18 months). There was no patient with infection, neurovascular injury, loosening and breakage of internal fixation, re-dislocation of acromioclavicular joint, clavicular fracture, coracoid process fracture, etc. Postoperative X-ray showed that all acromioclavicular joints were completely relocated. The follow-up of MRI after 1 year showed no obvious dislocation of acromioclavicular joint and good recovery of acromioclavicular space. Postoperative shoulder joint function, VAS, ASES, UCLA and acromioclavicular distance were significantly improved compared with those before surgery, with statistically significant differences (all P<0.05). CONCLUSIONS: Arthroscopic reconstruction of coracoclavicular ligament by suspensory fixation to manage the acute acromioclavicular joint dislocation has the advantages of minimal invasive, rapid functional recovery and less complications and satisfactory early clinical results.

CRISPR/Cas9-Assisted Seamless Genome Editing in Lactobacillus plantarum and Its Application in N-Acetylglucosamine Production.

Lactobacillus plantarum is a potential starter and health-promoting probiotic bacterium. Effective, precise, and diverse genome editing of Lactobacillus plantarum without introducing exogenous genes or plasmids is of great importance. In this study, CRISPR/Cas9-assisted double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) recombineering was established in L. plantarum WCFS1 to seamlessly edit the genome, including gene knockouts, insertions, and point mutations. To optimize our editing method, phosphorothioate modification was used to improve the dsDNA insertion, and adenine-specific methyltransferase was used to improve the ssDNA recombination efficiency. These strategies were applied to engineer L. plantarum WCFS1 toward producing N-acetylglucosamine (GlcNAc). nagB was truncated to eliminate the reverse reaction of fructose-6-phosphate (F6P) to glucosamine 6-phosphate (GlcN-6P). Riboswitch replacement and point mutation in glmS1 were introduced to relieve feedback repression. The resulting strain produced 797.3 mg/liter GlcNAc without introducing exogenous genes or plasmids. This strategy may contribute to the available methods for precise and diverse genetic engineering in lactic acid bacteria and boost strain engineering for more applications.IMPORTANCE CRISPR/Cas9-assisted recombineering is restricted in lactic acid bacteria because of the lack of available antibiotics and vectors. In this study, a seamless genome editing method was carried out in Lactobacillus plantarum using CRISPR/Cas9-assisted double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) recombineering, and recombination efficiency was effectively improved by endogenous adenine-specific methyltransferase overexpression. L. plantarum WCFS1 produced 797.3 mg/liter N-acetylglucosamine (GlcNAc) through reinforcement of the GlcNAc pathway, without introducing exogenous genes or plasmids. This seamless editing strategy, combined with the potential exogenous GlcNAc-producing pathway, makes this strain an attractive candidate for industrial use in the future.

Temperature Stability of a Hybrid Polarization-Maintaining Photonic Crystal Fiber Resonator and Its Application in a Resonant Fiber Optic Gyro.

A fiber ring resonator (FRR) constructed using a Panda polarization-maintaining fiber does not effectively solve the problem of temperature-related polarization fluctuation, which considerably limits the detection accuracy of the resonant fiber optic gyro. The polarization-maintaining photonic crystal fiber (PM-PCF) can improve the thermal stability of the FRR. In this study, a structure that can simultaneously detect the polarization fluctuation of two FRRs is designed. We analyzed and verified the polarization phase shift errors of these two types of fibers, which are caused by the thermally induced birefringence changes. Theoretical simulation and experimental results confirm that a PM-PCF can be used to optimize the FRR, which can effectively suppress the polarization fluctuation.

A novel P53/POMC/Gαs/SASH1 autoregulatory feedback loop activates mutated SASH1 to cause pathologic hyperpigmentation.

p53-Transcriptional-regulated proteins interact with a large number of other signal transduction pathways in the cell, and a number of positive and negative autoregulatory feedback loops act upon the p53 response. P53 directly controls the POMC/α-MSH productions induced by ultraviolet (UV) and is associated with UV-independent pathological pigmentation. When identifying the causative gene of dyschromatosis universalis hereditaria (DUH), we found three mutations encoding amino acid substitutions in the gene SAM and SH3 domain containing 1 (SASH1), and SASH1 was associated with guanine nucleotide-binding protein subunit-alpha isoforms short (Gαs). However, the pathological gene and pathological mechanism of DUH remain unknown for about 90 years. We demonstrate that SASH1 is physiologically induced by p53 upon UV stimulation and SASH and p53 is reciprocally induced at physiological and pathophysiological conditions. SASH1 is regulated by a novel p53/POMC/α-MSH/Gαs/SASH1 cascade to mediate melanogenesis. A novel p53/POMC/Gαs/SASH1 autoregulatory positive feedback loop is regulated by SASH1 mutations to induce pathological hyperpigmentation phenotype. Our study demonstrates that a novel p53/POMC/Gαs/SASH1 autoregulatory positive feedback loop is regulated by SASH1 mutations to induce pathological hyperpigmentation phenotype.

p53 regulates ERK1/2/CREB cascade via a novel SASH1/MAP2K2 crosstalk to induce hyperpigmentation.

We previously reported that three point mutations in SASH1 and mutated SASH1 promote melanocyte migration in dyschromatosis universalis hereditaria (DUH) and a novel p53/POMC/Gαs/SASH1 autoregulatory positive feedback loop is regulated by SASH1 mutations to induce pathological hyperpigmentation phenotype. However, the underlying mechanism of molecular regulation to cause this hyperpigmentation disorder still remains unclear. In this study, we aimed to investigate the molecular mechanism undergirding hyperpigmentation in the dyschromatosis disorder. Our results revealed that SASH1 binds with MAP2K2 and is induced by p53-POMC-MC1R signal cascade to enhance the phosphorylation level of ERK1/2 and CREB. Moreover, increase in phosphorylated ERK1/2 and CREB levels and melanogenesis-specific molecules is induced by mutated SASH1 alleles. Together, our results suggest that a novel SASH1/MAP2K2 crosstalk connects ERK1/2/CREB cascade with p53-POMC-MC1R cascade to cause hyperpigmentation phenotype of DUH.

Electrostatic Assembly Guided Synthesis of Highly Luminescent Carbon-Nanodots@BaSO4 Hybrid Phosphors with Improved Stability.

Carbon nanodots (CNDs)@BaSO4 hybrid phosphors are fabricated in an easy and low-cost process by sequentially assembling Ba2+ and SO42- ions onto the surface of carbon nanodots through electrostatic attraction. CNDs act as the nucleus to attract these reactive ions and provide the luminescent centers in the hybrid phosphors. This strategy is versatile for a variety of negatively charged CNDs with different emission colors. The advantage of the resultant hybrid phosphors is that their luminescence exhibits excellent thermal and photostability, as well as remarkable resistance to strong acid/alkali and common organic solvents. These merits allow for the fabrication of CNDs-based light-emitting diodes using the CNDs@BaSO4 hybrid phosphors as a color conversion layer.

Analysis of Online Composite Mirror Descent Algorithm.

We study the convergence of the online composite mirror descent algorithm, which involves a mirror map to reflect the geometry of the data and a convex objective function consisting of a loss and a regularizer possibly inducing sparsity. Our error analysis provides convergence rates in terms of properties of the strongly convex differentiable mirror map and the objective function. For a class of objective functions with Hölder continuous gradients, the convergence rates of the excess (regularized) risk under polynomially decaying step sizes have the order [Formula: see text] after [Formula: see text] iterates. Our results improve the existing error analysis for the online composite mirror descent algorithm by avoiding averaging and removing boundedness assumptions, and they sharpen the existing convergence rates of the last iterate for online gradient descent without any boundedness assumptions. Our methodology mainly depends on a novel error decomposition in terms of an excess Bregman distance, refined analysis of self-bounding properties of the objective function, and the resulting one-step progress bounds.

Spinal cord injury effectively ameliorated by neuroprotective effects of rosmarinic acid.

OBJECTIVE: Pathophysiology of spinal cord injury (SCI) causes primary and secondary effects leading to loss of neuronal function. The aim of the present study was to investigate the role of rosmarinic acid (RA) in protection against SCI. METHODS: The experimental study was carried out in male wistar rats categorized into three groups. Group I - sham operated rats; Group II - SCI; Group III - SCI followed by RA treatment (10 mg/kg). The spinal tissues after treatment schedule were analyzed for oxidative stress status through determination of reactive oxygen species (ROS), lipid peroxidation, protein damage (carbonyl and sulfhydryl contents), and antioxidant enzyme activities. The expression of oxidative stress factors NF-κB and Nrf-2 was determined by Western blot analysis. Further pro-inflammatory cytokines (TNF-α, IL-6, MCP-1, and IL-1ß) were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: The results show that treatment with RA significantly enhances the antioxidant status and decrease the oxidative stress in wistar rats post-SCI. RA effectively ameliorated inflammatory mechanisms by downregulation of NF-κB and pro-inflammatory cytokines post-SCI. CONCLUSION: The study demonstrates for the first time on the role of RA in protecting the spinal cord from injury and demonstrates its neuroprotection in wistar rats.

Value of multi-b value DWI in the assessment of early cerebral changes in asymptomatic HIV-positive adolescents.

Background Magnetic resonance imaging (MRI) and functional MRI techniques have been widely used in the diagnosis of human immunodeficiency virus (HIV) infection related diseases. Purpose To explore whether magnetic resonance diffusion-weighted imaging (DWI) can track water molecular diffusion changes in the brain of asymptomatic HIV-positive adolescents. Material and Methods Multi-b value DWI was performed in 23 adolescents, including 15 HIV-positive participants and eight HIV-negative healthy participants. Mean apparent diffusion coefficient (ADC), slow apparent diffusion coefficient (ADCs) values, fast apparent diffusion coefficient (ADCf) values, distribution diffusion coefficient (DDC) values, and heterogeneity index (α) values were calculated within regions of interest (ROIs) in the frontal lobes, basal ganglia, and temporal lobe. Non-parametric tests were then performed. Results In the bilateral frontal lobes, the mean α values in HIV-positive participants were significantly increased compared with those in healthy participants (right side P = 0.001; left side P = 0.000). In the left frontal lobe, the mean DDC value in HIV-positive participants was significantly increased compared with that in healthy participants ( P = 0.008). In the bilateral frontal lobes, the mean ADCf values in HIV-positive participants were significantly lower than those in healthy participants (right side P = 0.011; left side P = 0.008). In the left basal ganglia, the mean α values in HIV-positive participants were significantly lower than that in healthy participants ( P = 0.013). Conclusion Multi-b value DWI could reflect the early characteristics of water molecule diffusion in HIV infections.

Online Pairwise Learning Algorithms.

Pairwise learning usually refers to a learning task that involves a loss function depending on pairs of examples, among which the most notable ones are bipartite ranking, metric learning, and AUC maximization. In this letter we study an online algorithm for pairwise learning with a least-square loss function in an unconstrained setting of a reproducing kernel Hilbert space (RKHS) that we refer to as the Online Pairwise lEaRning Algorithm (OPERA). In contrast to existing works (Kar, Sriperumbudur, Jain, & Karnick, 2013 ; Wang, Khardon, Pechyony, & Jones, 2012 ), which require that the iterates are restricted to a bounded domain or the loss function is strongly convex, OPERA is associated with a non-strongly convex objective function and learns the target function in an unconstrained RKHS. Specifically, we establish a general theorem that guarantees the almost sure convergence for the last iterate of OPERA without any assumptions on the underlying distribution. Explicit convergence rates are derived under the condition of polynomially decaying step sizes. We also establish an interesting property for a family of widely used kernels in the setting of pairwise learning and illustrate the convergence results using such kernels. Our methodology mainly depends on the characterization of RKHSs using its associated integral operators and probability inequalities for random variables with values in a Hilbert space.