bioRxiv @biorxivpreprint@qoto.org

Background: The pathological process of Alzheimer's disease (AD) typically takes up decades from onset to clinical symptoms. Early brain changes in AD include MRI-measurable features such as aItered functional connectivity (FC) and white matter degeneration. The ability of these features to discriminate between subjects without a diagnosis, or their prognostic value, is however not established. Methods: The main trigger mechanism of AD is still debated, although impaired brain glucose metabolism is taking an increasingly central role. Here we used a rat model of sporadic AD, based on impaired brain glucose metabolism induced by an intracerebroventricular injection of streptozotocin (STZ). We characterized alterations in FC and white matter microstructure longitudinally using functional and diffusion MRI. Those MRI-derived measures were used to classify STZ from control rats using machine learning, and the importance of each individual measure was quantified using explainable artificial intelligence methods. Results: Overall, combining all the FC and white matter metrics in an ensemble way was the best strategy to discriminate STZ rats, with a consistent accuracy over 0.85. However, the best accuracy early on was achieved using white matter microstructure features, and later on using FC. This suggests that consistent damage in white matter in the STZ group might precede FC. For cross-timepoint prediction, microstructure features also had the highest performance while, in contrast, that of FC was reduced by its dynamic pattern which shifted from early hyperconnectivity to late hypoconnectivity. Conclusions: Our study highlights the MRI-derived measures that best discriminate STZ vs control rats early in the course of the disease, with potential translation to humans. ### Competing Interest Statement The authors have declared no competing interest.

Embryos develop in a surrounding that guides key aspects of their development. For example, the anteroposterior (AP) body axis is always aligned with the geometric long axis of the surrounding eggshell in fruit flies and worms. The mechanisms that ensure convergence of the AP axis with the long axis of the eggshell remain unresolved. We investigate axis convergence in early C. elegans development, where the nascent AP axis, when misaligned, actively re-aligns to converge with the long axis of the egg. Here, we identify two physical mechanisms that underlie axis convergence. First, bulk cytoplasmic flows, driven by actomyosin cortical flows, can directly reposition the AP axis. Second, active forces generated within the pseudocleavage furrow, a transient actomyosin structure similar to a contractile ring, can drive a mechanical re-orientation such that it becomes positioned perpendicular to the long axis of the egg. This in turn ensures AP axis convergence. Numerical simulations, together with experiments that either abolish the pseudocleavage furrow or change the shape of the egg, demonstrate that the pseudocleavage furrow-dependent mechanism is the key driver of axis convergence. We conclude that active force generation within the actomyosin cortical layer drives axis convergence in the early nematode. ### Competing Interest Statement The authors have declared no competing interest.

During embryonic development, oriented cell divisions are important for patterned tissue growth and cell fate specification. Cell division orientation is controlled in part by asymmetrically localized polarity proteins, which establish functional domains of the cell membrane and interact with microtubule regulators to position the mitotic spindle. For example, in the 8-cell mouse embryo, apical polarity proteins form caps on the outside, contact-free surface of the embryo that position the mitotic spindle to execute asymmetric cell division. A similar radial or "inside-outside" polarity is established at an early stage in many other animal embryos, but in most cases it remains unclear how inside-outside polarity is established and how it influences downstream cell behaviors. Here, we explore inside-outside polarity in C. elegans somatic blastomeres using spatiotemporally controlled protein degradation and live embryo imaging. We show that PAR polarity proteins, which form apical caps at the center of the contact free membrane, localize dynamically during the cell cycle and contribute to spindle orientation and proper cell positioning. Surprisingly, apical PAR-3 can form polarity caps independently of actomyosin flows and the small GTPase CDC-42, and can regulate spindle orientation in cooperation with the key polarity kinase aPKC. Together, our results reveal a role for apical polarity caps in regulating spindle orientation in symmetrically dividing cells and provide novel insights into how these structures are formed. ### Competing Interest Statement The authors have declared no competing interest.

Auxin-inducible degron (AID) technology is powerful for chemogenetic control of proteolysis. However, generation of human cell lines to deplete endogenous proteins with AID remains challenging. Typically, homozygous degron-tagging efficiency is low and overexpression of an auxin receptor requires additional engineering steps. Here, we establish a one-step genome editing procedure with high-efficiency homozygous tagging and auxin receptor expression. We demonstrate its application in 5 human cell lines, including embryonic stem (ES) cells. The method allowed isolation of AID single-cell clones in 10 days for 11 target proteins with >80% average homozygous degron-tagging efficiency in A431 cells, and >50% efficiency for 5 targets in H9 ES cells. The tagged endogenous proteins were inducibly degraded in all cell lines, including ES cells and ES-cell derived neurons, with robust expected functional readouts. This method facilitates the application of AID for studying endogenous protein functions in human cells, especially in stem cells. ### Competing Interest Statement The authors have declared no competing interest.

Genetic code expansion via stop codon suppression is a powerful strategy to engineer proteins. Suppressor tRNAs are aminoacylated with noncanonical amino acids (ncAAs) by dedicated aminoacyl-tRNA synthetases (aaRS) and direct ncAA incorporation site-specifically during translation. These pairs of tRNA/aaRS must be orthogonal to the host's tRNAs, aaRS and natural amino acids. Pyrrolysyl-tRNA (PylT)/PylRS pairs from methanogenic archaea, as well as engineered tRNA/aaRS pairs derived from bacteria, are used for genetic code expansion in mammalian cells. Amber suppression is routinely achieved by transient introduction of the components leading to short-term and heterogeneous expression. Here, we demonstrate that stable integration of tRNA/aaRS genes allows for efficient, genetically encoded ncAA incorporation in diverse mammalian cell lines. We extend a general plasmid design and PiggyBac (PB) integration strategy developed for the Methanosarcina mazei PylT/PylRS pair to genomic integration of two tRNA/aaRS pairs of bacterial origin. We further explore suppression of ochre and opal stop codons and parallel incorporation of two distinct ncAAs, both accessible for click chemistry, by dual suppression in stable cell lines. Clonal selection allows for isolation of cells with high dual suppression efficiency and dual site-specific fluorescent labeling of a cell surface receptor using bioorthogonal click chemistries on live mammalian cells. ### Competing Interest Statement The authors have declared no competing interest.

Lack of non-muscle β-actin gene (Actb) leads to early embryonic lethality in mice, however mice with β- to γ-actin replacement develop normally and show no detectable phenotypes at young age. Here we investigated the effect of this replacement in the retina. During aging, these mice have accelerated degeneration of retinal structure and function, including elongated microvilli and defective mitochondria of retinal pigment epithelium (RPE), abnormally bulging photoreceptor outer segments (OS) accompanied by reduced transducin concentration and light sensitivity, and accumulation of autofluorescent microglia cells in the subretinal space between RPE and OS. These defects are accompanied by changes in the F-actin binding of several key actin interacting partners, including ezrin, myosin, talin, and vinculin known to play central roles in modulating actin cytoskeleton and cell adhesion and mediating the phagocytosis of OS. Our data show that β-actin protein is essential for maintaining normal retinal structure and function. ### Competing Interest Statement The authors have declared no competing interest.

Large scale networks of phase synchronization are considered to regulate the communication between brain regions fundamental to cognitive function, but the mapping to their structural substrates, i.e., the structure to function relationship, remains poorly understood. Biophysical Network Models (BNMs) have demonstrated the influences of local oscillatory activity and inter regional anatomical connections in generating alpha band (8 to 12 Hz) networks of phase synchronization observed with Electroencephalography (EEG) and Magnetoencephalography (MEG). Yet, the influence of inter regional conduction delays remains unknown. In this study, we compared a BNM with standard 'distance dependent delays', which assumes constant conduction velocity, to BNMs with delays specified by two alternative methods accounting for spatially varying conduction velocities, 'isochronous delays' and 'mixed delays'. We followed the Approximate Bayesian Computation (ABC) workflow, i) specifying neurophysiologically informed prior distributions of BNM parameters, ii) verifying the suitability of the prior distributions with Prior Predictive Checks, iii) fitting each of the three BNMs to alpha band MEG resting state data (N = 75) with Bayesian Optimisation for Likelihood Free Inference (BOLFI), and iv) choosing between the fitted BNMs with ABC model comparison on a separate MEG dataset (N = 30). Prior Predictive Checks revealed the range of dynamics generated by each of the BNMs to encompass those seen in the MEG data, suggesting the suitability of the prior distributions. Fitting the models to MEG data yielded reliable posterior distributions of the parameters of each of the BNMs. Finally, model comparison revealed the BNM with 'distance dependent delays', as the most probable to describe the generation of alpha band networks of phase synchronization seen in MEG. These findings suggest distance dependent delays contribute significantly to the neocortical architecture of human alpha band networks of phase synchronization. Hence, our study illuminates the role of inter regional delays in generating the large scale networks of phase synchronization that might subserve the communication between regions vital to cognition. ### Competing Interest Statement The authors have declared no competing interest.

Imprinted genes are subject to germline epigenetic modification resulting in parental-specific allelic silencing. Although genomic imprinting is thought to be important for maternal behaviour, this idea is based on serendipitous findings from a small number of imprinted genes. Here, we undertook an unbiased systems biology approach, taking advantage of the recent delineation of specific neuronal populations responsible for controlling parental care, to test whether imprinted genes significantly converge to regulate parenting behaviour. Using single-cell RNA sequencing datasets, we identified a specific enrichment of imprinted gene expression in a recognised 'parenting hub', the galanin-expressing neurons of the preoptic area. We tested the validity of linking enriched expression in these neurons to function by focusing on MAGE family member L2 (Magel2), an imprinted gene not previously linked to parenting behaviour. We confirmed expression of Magel2 in the preoptic area galanin expressing neurons. We then examined the parenting behaviour of Magel2+/- null mice. Magel2-null mothers, fathers and virgin females demonstrated deficits in pup retrieval, nest building and pup-directed motivation, identifying a central role for this gene in parenting. Finally, we show that Magel2-null mothers and fathers have a significant reduction in POA galanin expressing cells, which in turn contributes to a reduced c-Fos response in the POA upon exposure to pups. Our findings identify a novel imprinted gene that impacts parenting behaviour and, moreover, demonstrates the utility of using single-cell RNA sequencing data to predict gene function from expression and in doing so here, have identified a purposeful role for genomic imprinting in mediating parental behaviour. ### Competing Interest Statement The authors have declared no competing interest.

The ability to remember what happened where and when constitutes the basic fabric of our memories and who we are. Forming and recalling memories depends on detecting novelty, building associations to prior knowledge, and dynamically retrieving context-relevant information. Previous studies have scrutinized the neural machinery for individual components of recognition or associative memory under laboratory conditions, such as recalling elements from arbitrary lists of words or pictures. In this study, we implemented a well-known card-matching game that integrates multiple components of memory formation together in a naturalistic setting to investigate the dynamic neural processes underlying complex natural human memory. We recorded intracranial field potentials from 1,750 depth or subdural electrodes implanted in 20 patients with pharmacologically-intractable epilepsy while they were performing the task. We leveraged generalized linear models to simultaneously assess the relative contribution of neural responses to distinct task components. Neural activity in the gamma frequency band signaled novelty and graded degrees of familiarity, represented the strength and outcome of associative recall, and finally reflected visual feedback on a trial-by-trial basis. The large-scale data and models enable dissociating and at the same time dynamically tracing the different cognitive components during fast, complex, and natural human memory behaviors. ### Competing Interest Statement The authors have declared no competing interest.

In this study, we generated a Digital Twin for SARS-CoV-2 by integrating data and meta-data with multiple data types and processing strategies, including machine learning, natural language processing, protein structural modeling, and protein sequence language modeling. This approach enabled the computational design of broadly neutralizing antibodies against over 1300 different historical strains of SARS-COV-2 containing 64 mutations in the receptor binding domain (RBD) region. The AI-designed antibodies were experimentally validated in real-virus neutralization assays against multiple strains including the newer Omicron strains that were not included in the initial design base. Many of these antibodies demonstrate strong binding capability in ELISA assays against the RBD of multiple strains. These results could help shape future therapeutic design for existing strains, as well as predicting hidden patterns in viral evolution that can be learned by AI for developing future antiviral treatments. ### Competing Interest Statement The authors have declared no competing interest.

Whether human lineage mutations (HLM) have contributed to human evolution via post-transcriptional modification remained unknown. We applied deep learning models Seqweaver to predict how HLM impacts RNA-binding protein affinity (RBP). At the threshold of the top 1% of human common variation, only 0.27% of HLM had large impacts on RBP. These HLMs enriched in a set of conserved genes that are highly expressed in adult excitatory neurons and prenatal Purkinje neurons, and involved in synapse organization and the GTPase pathway. These genes also carried excess damaging coding mutations that caused neurodevelopmental disorders, ataxia, and Schizophrenia. Among these genes, NTRK2 and ITPR1 had the most aggregated evidence of functional importance, pointing to an essential role in cognition and bipedalism. We concluded that a very small number of human-specific mutations have contributed to human speciation via impacts on post-transcriptional modification of critical brain-related genes. ### Competing Interest Statement The authors have declared no competing interest.

The ongoing emergence of SARS-CoV-2 Omicron subvariants and their rapid worldwide spread pose a threat to public health. From November 2022 to February 2023, newly emerged Omicron subvariants, including BQ.1.1, BF.7, BA.5.2, XBB.1, XBB.1.5, and BN.1.9, became prevalent global strains (>5% global prevalence). These Omicron subvariants are resistant to several therapeutic antibodies. Thus, the antiviral activities of current drugs such as remdesivir, molnupiravir, and nirmatrelvir, which target highly conserved regions of SARS-CoV-2, against newly emerged Omicron subvariants need to be evaluated. We assessed the antiviral efficacy of the drugs using half maximal inhibitory concentration (IC50) against human isolated 23 Omicron subvariants and four former SARS-CoV-2 variants of concern (VOC) and compared them with the antiviral efficacy of these drugs against the SARS-CoV-2 reference strain (hCoV/Korea/KCDC03/2020). Maximal IC50 fold changes of remdesivir, molnupiravir, and nirmatrelvir were 1.9- (BA.2.75.2), 1.2- (B.1.627.2), and 1.4-fold (BA.2.3), respectively, compared to median IC50 values of the reference strain. Moreover, median IC50-fold changes of remdesivir, molnupiravir, and nirmatrelvir against the Omicron variants were 0.96, 0.4, and 0.62, similar to 1.02, 0.88, and 0.67, respectively, of median IC50-fold changes for previous VOC. Although K90R and P132H in Nsp 5, and P323L, A529V, G671S, V405F, and ins823D in Nsp 12 mutations were identified, these amino acid substitutions did not affect drug antiviral activity. Altogether, these results indicated that the current antivirals retain antiviral efficacy against newly emerged Omicron subvariants, and provide comprehensive information on the antiviral efficacy of these drugs. Keywords: SARS-CoV-2, Omicron subvariant, remdesivir, molnupiravir, nirmatrelvir, antiviral activity ### Competing Interest Statement The authors have declared no competing interest.

In the last couple of years, the rapid advances and decreasing costs of sequencing technologies have revolutionized transcriptomic research. Long-read sequencing (LRS) techniques are able to detect full-length RNA molecules in a single run without the need for additional assembly steps. LRS studies have revealed an unexpected transcriptomic complexity in a variety of organisms, including viruses. A number of transcripts with proven or putative regulatory role, mapping close to or overlapping the replication origins (Oris) and the nearby transcription activator genes, have been described in herpesviruses. In this study, we applied both newly generated and previously published LRS and short-read sequencing datasets to discover additional Ori-proximal transcripts in nine herpesviruses belonging to all of the three subfamilies (alpha, beta and gamma). We identified novel long non-coding RNAs (lncRNAs), as well as splice and length isoforms of mRNAs and lncRNAs. Furthermore, our analysis disclosed an intricate meshwork of transcriptional overlaps at the examined genomic regions. Our results suggest the existence of a super regulatory center, which controls both the replication and the global transcription through multilevel interactions between the molecular machineries. ### Competing Interest Statement The authors have declared no competing interest.

Spinal and bulbar muscular atrophy (SBMA) is an X-linked disorder that affects males who inherit the androgen receptor (AR) gene with an abnormal CAG triplet repeat expansion. The resulting protein contains an elongated polyglutamine (polyQ) tract and causes motor neuron degeneration in an androgen-dependent manner. The precise molecular sequelae of SBMA are unclear. To assist with its investigation and the identification of therapeutic options, we report here a new model of SBMA in Drosophila melanogaster. We generated transgenic flies that express the full-length, human AR with a wild-type or pathogenic polyQ repeat. Each transgene is inserted into the same safe harbor site on the third chromosome of the fly as a single copy and in the same orientation. Expression of pathogenic AR, but not of its wild-type variant, in neurons or muscles leads to consistent, progressive defects in longevity and motility that are concomitant with polyQ-expanded AR protein aggregation and reduced complexity in neuromuscular junctions. Additional assays show adult fly eye abnormalities associated with the pathogenic AR species. The detrimental effects of pathogenic AR are accentuated by feeding flies the androgen, dihydrotestosterone. This new, robust SBMA model can be a valuable tool towards future investigations of this incurable disease. ### Competing Interest Statement The authors have declared no competing interest.

Neurostimulation of the hippocampal formation has shown promising results for modulating memory but the underlying mechanisms remain unclear. In particular, the effects on hippocampal theta-nested gamma oscillations and theta phase reset, which are both crucial for memory processes, are unknown. Moreover, these effects cannot be investigated using current computational models, which consider theta oscillations with a fixed amplitude and phase velocity. Here, we developed a novel computational model that includes the medial septum, represented as a set of abstract Kuramoto oscillators producing a dynamical theta rhythm with phase reset, and the hippocampal formation, composed of biophysically-realistic neurons and able to generate theta-nested gamma oscillations under theta drive. We showed that this system can exhibit bistability in a specific range of parameters and that a single stimulation pulse could switch the network behavior from non-oscillatory to a state producing theta-nested gamma oscillations. Next, we demonstrated that for a theta input too weak to generate theta-nested gamma oscillations, pulse train stimulation at the theta frequency could restore seemingly physiological oscillations. Importantly, the presence of phase reset influenced whether these two effects depended on the phase at which stimulation onset was delivered, which has practical implications for designing neurostimulation protocols that are triggered by the phase of ongoing theta oscillations. This novel model opens new avenues for studying the effects of neurostimulation on the hippocampal formation. Furthermore, our hybrid approach that combines different levels of abstraction could be extended in future work to other neural circuits that produce dynamical brain rhythms. ### Competing Interest Statement The authors have declared no competing interest.

Type-I interferon (IFN-I) subtypes signal through the same IFNalpha receptor (IFNAR), and initiate temporal STAT1/2 activation to orchestrate innate and adaptive immunity. It remains unknown how IFNAR discriminates between subtypes (e.g., IFNalpha and IFNbeta), and how STAT1/2 signaling is affected by time-varying inputs. Here, we utilize our microfluidic system and live-cell imaging to quantify STAT1/2 activation dynamics in a reporter fibroblast model. Population-averaged and single-cell analyses reveal distinct STAT1/2 responses to various IFNalpha and IFNbeta inputs. Upon continuous stimulation, cells show less sensitivity but more sustained responses to IFNalpha over IFNbeta. A short IFNalpha pulse induces nearly homogeneous STAT1/2 dynamics, in contrast to heterogeneous responses in IFNbeta-pulsed cells. Distinct STAT1/2 refractory states emerge upon exposure to repeated IFN-I pulses, while alternating pulse stimulation reveals that IFNbeta can revoke STAT1/2 refractoriness caused by IFNalpha, but not vice versa. These findings highlight the differences between IFNalpha and IFNbeta signaling and how they can elicit distinct temporal cellular behaviors during viral infection. ### Competing Interest Statement The authors have declared no competing interest.

A hallmark of Dengue virus (DENV) pathogenesis is the potential for antibody-dependent enhancement, which is associated with deadly DENV secondary infection, complicates the identification of correlates of protection, and negatively impacts the safety and efficacy of DENV vaccines. ADE is linked to antibodies targeting the fusion loop (FL) motif of the envelope protein, which is completely conserved in mosquito-borne flaviviruses and required for viral entry and fusion. In the current study, we utilized saturation mutagenesis and directed evolution to engineer a functional variant with a mutated FL (D2-FL) which is not neutralized by FL-targeting monoclonal antibodies. The FL mutations were combined with our previously evolved prM cleavage site to create a mature version of D2-FL (D2-FLM), which evades both prM- and FL-Abs but retains sensitivity to other type-specific and quaternary cross-reactive (CR) Abs. CR serum from heterotypic (DENV4) infected non-human primates (NHP) showed lower neutralization titers against D2-FL and D2-FLM than isogenic wildtype DENV2 while similar neutralization titers were observed in serum from homotypic (DENV2) infected NHP. We propose D2-FL and D2-FLM as valuable tools to delineate CR Ab subtypes in serum as well as an exciting platform for safer live attenuated DENV vaccines suitable for naïve individuals and children. ### Competing Interest Statement The authors have declared no competing interest.

Contextual fear learning is heavily dependent on the hippocampus. Despite evidence that catecholamines contribute to contextual encoding and memory retrieval, the precise temporal dynamics of their release in the hippocampus during behavior is unknown. In addition, new animal models are required to probe the effects of altered catecholamine synthesis on release dynamics and contextual learning. Utilizing GRABNE and GRABDA sensors, in vivo fiber photometry, and two new mouse models of altered locus coeruleus norepinephrine (LC-NE) synthesis, we investigate norepinephrine (NE) and dopamine (DA) release dynamics in dorsal hippocampal CA1 during contextual fear conditioning. We report that aversive foot-shock increases both NE and DA release in dorsal CA1, while freezing behavior associated with recall of fear memory is accompanied by decreased release. Partial loss of LC-NE synthesis reveals that NE release dynamics are modulated by sex. Moreover, we find that recall of recent fear memory is sensitive to both partial and complete loss of LC-NE synthesis throughout prenatal and postnatal development, similar to prior observations of mice with global loss of NE synthesis beginning postnatally. In contrast, remote recall is compromised only by complete loss of LC-NE synthesis beginning prenatally. Overall, these findings provide novel insights into the role of NE in contextual fear and the precise temporal dynamics of both NE and DA during freezing behavior, and highlight a complex relationship between genotype, sex, and NE signaling. ### Competing Interest Statement The authors have declared no competing interest.

The revolution of ‘omics’ technologies highlighted that associated microorganisms (also called microbiota) are integrated into the metabolic functions of their hosts. Yet when performing any particular type of ‘omics’ experiment, be it metabolomics, transcriptomics, or (meta)genomics, it is extremely difficult to interpret the observed relationships between metabolites, transcripts, and microbial species. This is due to the massive amount of data generated for each ‘omics’ technology, but also the cognitive challenge of interconnecting these observations and contextualizing them in their biological (eco)system. For these reasons, there is a need for testing methods that can facilitate the translation of these ‘omics’ experimental observations into putative molecular processes or biological interactions. To accelerate the interpretation of ‘omics’ data from a description of microbial, transcript, or metabolite identities or abundances into a functional understanding of the interplay between the individual entities of the biological system, we designed a novel multi-omics strategy for the annotation and integration of metabolomics and metagenomics data. We generated metabolome and microbiome datasets by LC-MS/MS based metabolomics profiling and metagenomic sequencing, respectively. Comprehensive metabolite annotations were obtained by molecular networking and computational annotation of fragmentation spectra. Associations between microbes and GNPS molecular networks were predicted by machine learning and visualized as an extensively annotated, nested interaction network in Cytoscape. As a proof of concept, we applied this strategy to scalp swabs from a cohort of healthy volunteers with varying scalp sebum levels and were able to elucidate the antagonistic interaction between two well-characterized microbes, Staphylococcus epidermidis and Cutibacterium acnes . ### Competing Interest Statement PCD is an advisor to Cybele and co-founder and scientific advisor to Ometa and Enveda, with prior approval by UC San Diego.

Single-cell RNA sequencing (scRNA-seq) technologies have been driving the development of algorithms of clustering heterogeneous cells. We introduce a novel clustering algorithm scQA, which can effectively and efficiently recognize different cell types via qualitative and quantitative analysis. It iteratively extracts quasi-trend-preserved genes to conform a consensus by representing expression patterns with dropouts qualitatively and quantitatively, and, then automatically clusters cells using a new label propagation strategy without specifying the number of cell types in advance. Validated on 20 public scRNA-seq datasets, scQA consistently outperformed 9 salient tools in both accuracy and efficiency across 16 out of 20 datasets tested, and ranked top 2 or 3 across the other 4 datasets. Furthermore, we demonstrate scQA can extract informative genes in both perspectives of biology and data wise by performing consensus, allowing genes used for landmark construction multiple characteristics, which is essential for clustering cells accurately. Overall, scQA could be a useful tool for discovery of cell types that can be integrated into general scRNA-seq analyses. ### Competing Interest Statement The authors have declared no competing interest.