Biology subjects

Li, S.

Publications and source records attributed to Li, S..

At least 703 records · Page 39Linked to original sources

bioRxiv2023

T2T-YAO: a Telomere-to-telomere Assembled Diploid Reference Genome for Han Chinese

Since its initial release in 2001, the human reference genome has been continuously improved in both continuity and accuracy, and the recently-released telomere-to-telomere version--T2T-CHM13--reaches its top quality after 20 years of effort. However, T2T-CHM13 does not represent an authentic diploid human genome, but rather one derived from a simplified, nearly homozygous genome of a hydatidiform mole cell line. To address this limitation and provide an alternative pertinent to the Chinese population, the largest ethnic group in the world, we have assembled a complete diploid human genome of a male Han Chinese, T2T-YAO, which includes telomere-to-telomere assemblies for all the 22+X+M and 22+Y chromosomes in his two haploids inherited separately from his parents. Both haplotypes contain no artificial sequences or model nucleotides and possess a high quality comparable to CHM13, with fewer than one error per [~]14 Mb. Derived from the individual who lives in the aboriginal region of Han Chinese, T2T-YAO shows clear ancestry and potential genetic continuity from the ancient ancestors of the Han population. Each haplotype of T2T-YAO possesses [~]340 Mb exclusive sequences and [~]3100 unique genes as compared to CHM13, and their genome sequences show greater genetic distance to CHM13 than to each other in terms of nucleotide polymorphism and structural variations. The construction of T2T-YAO would serve as a high-quality diploid reference that enables precise delineation of genomic variations in a haplotype-sensitive manner, which could advance our understandings in human evolution, hereditability of diseases and phenotypes, especially within the context of the unique variations of the Chinese population.

genetics↗

bioRxiv2023

Deep mutational scanning of whole SARS-CoV-2 spike in an inverted infection system

In order to investigate SARS-CoV-2 mutations and their impact on immune evasion and infectivity, we developed a Deep Mutational Scanning (DMS) platform utilizing an inverted infection assay to measure spike expression, ACE2 affinity, and viral infectivity in human cells. Surprisingly, our analysis reveals that spike protein expression, rather than ACE2 affinity, is the primary factor affecting viral infectivity and correlated with SARS-CoV-2 evolution. Notably, within the N-terminal domain (NTD), spike expression and infectivity-enhancing mutations are concentrated in flexible loops. We also observed that Omicron variants BA.1 and BA.2 exhibit immune evasion through receptor binding domain (RBD) mutations, although these mutations reduce structural stability. Interestingly, the NTD has evolved to increase stability, compensating for the RBD instability and resulting in heightened overall infectivity. Our findings, available in SpikeScanDB, emphasize the importance of spike expression levels and compensatory mutations in both the NTD and RBD domains for shaping Omicron variant infectivity.

microbiology↗

bioRxiv2023

AI2BMD: efficient characterization of protein dynamics with ab initio accuracy

Biomolecular dynamics simulation is a fundamental technology for life sciences research, and its usefulness depends on its accuracy and efficiency. Classical molecular dynamics simulation is fast but lacks chemical accuracy. Quantum chemistry methods like density functional theory (DFT) can reach chemical accuracy but cannot scale to support large biomolecules. We introduce an AI-based ab initio biomolecular dynamics system (AI2BMD) that can efficiently simulate large biomolecules with ab initio accuracy. AI2BMD uses a protein fragmentation scheme and machine learning force field to achieve generalizable ab initio accuracy for energy and force calculations for various proteins comprising over 10,000 atoms. Compared to DFT, it reduces computational time by several orders of magnitude. With several hundred nanoseconds of dynamics simulations, AI2BMD demonstrated its capability of efficiently exploring the conformational space of peptides and proteins, deriving accurate 3J-couplings that match NMR experiments, and showing protein folding and unfolding tendencies. Furthermore, AI2BMD enables precise free energy calculations for protein folding, and the estimated melting temperatures are well aligned with experiments. AI2BMD could potentially complement wet-lab experiments, detect the dynamic processes of bioactivities, and enable biomedical research that is currently impossible to conduct.

bioinformatics↗

bioRxiv2023

The Role and Mechanism of TEAD4 in Preimplantation Embryonic Development in Mice and Cattle

Tead4, a critical transcription factor expressed during preimplantation development, is essential for the expression of trophectoderm-specific genes in mice. However, the functional mechanism of Tead4 in mouse preimplantation development and its conservation across mammals remain unclear. Here, we report that Tead4 is a crucial transcription factor necessary for blastocyst formation in mice. Disruption of Tead4 through base editing results in developmental arrest at the morula stage. Additionally, RNA-seq analysis reveals dysregulation of 670 genes in Tead4 knockout embryos. As anticipated, Tead4 knockout leads to a decrease in trophectoderm genes Cdx2 and Gata3. Intriguingly, we observed a reduction in Krt8, suggesting that Tead4 influences the integrity of the trophectoderm epithelium in mice. More importantly, we noted a dramatic decrease in nuclear Yap in outside cells for Tead4-deficient morula, indicating that Tead4 directly regulates Hippo signaling. In contrast, bovine embryos with TEAD4 depletion could still develop to blastocysts with normal expression of CDX2, GATA3, and SOX2, albeit with a decrease in total cell number and ICM cell number. In conclusion, we propose that Tead4 regulates mouse blastocyst formation via Krt8 and Yap, both of which are critical regulators of mouse preimplantation development.

developmental biology↗

bioRxiv2023

xTrimoPGLM: Unified 100B-Scale Pre-trained Transformer for Deciphering the Language of Protein

Protein language models have shown remarkable success in learning biological information from protein sequences. However, most existing models are limited by either autoencoding or autoregressive pre-training objectives, which makes them struggle to handle protein understanding and generation tasks concurrently. We propose a unified protein language model, xTrimoPGLM, to address these two types of tasks simultaneously through an innovative pre-training framework. Our key technical contribution is an exploration of the compatibility and the potential for joint optimization of the two types of objectives, which has led to a strategy for training xTrimoPGLM at an unprecedented scale of 100 billion parameters and 1 trillion training tokens. Our extensive experiments reveal that 1) xTrimoPGLM significantly outperforms other advanced baselines in 18 protein understanding benchmarks across four categories. The model also facilitates an atomic-resolution view of protein structures, leading to an advanced 3D structural prediction model that surpasses existing language model-based tools. 2) xTrimoPGLM not only can generate de novo protein sequences following the principles of natural ones, but also can perform programmable generation after supervised fine-tuning (SFT) on curated sequences. These results highlight the substantial capability and versatility of xTrimoPGLM in understanding and generating protein sequences, contributing to the evolving landscape of foundation models in protein science. Trained weight for the xTrimoPGLM model, and downstream datasets are available at https://huggingface.co/proteinglm.

synthetic biology↗

bioRxiv2023

T4SEpp: a pipeline integrated with protein language models effectively predicting bacterial type IV secreted effectors

Many pathogenic bacteria use type IV secretion systems(T4SSs) to deliver effectors (T4SEs) into the cytoplasm of eukaryotic cells, causeing diseases. The identification of effectors is a crucial step in understanding the mechanisms of bacterial pathogenicity, but this remains a major challenge. In this study, we used the full-length embedding features generated by six pre-trained protein language models to train classifiers predicting T4SEs, and compared their performance. An integrated model T4SEpp was assembled by a module searching full-length, signal sequence and effector domain homologs of known T4SEs, a machine learning module based on the hand-crafted features extracted from the signal sequences, and the third module containing three best-performing protein language pre-trained models. T4SEpp outperformed the other state-of-the-art (SOTA) software tools, achieving [~]0.95 sensitivity at a high specificity of [~]0.99, based on the assessment of an independent testing dataset. Additionally, we performed a comprehensive search among 8,761 bacterial species, leading to the discovery of 227 species belonging to 3 phyla and 117 genera that possess T4SSs. Furthermore, leveraging the power of T4SEpp, we successfully identified a grand total of 12,622 plausible T4SEs. Overall, T4SEpp provides a better solution to assist in the identification of bacterial T4SEs, and facilitates studies of bacterial pathogenicity. T4SEpp is freely accessible at https://bis.zju.edu.cn/T4SEpp.

bioinformatics↗

bioRxiv2023

Role of Articulatory Motor Networks in Perceptual Categorization of Speech Signals: A 7 T fMRI Study

BACKGROUNDThe association between brain regions involved in speech production and those that play a role in speech perception is not yet fully understood. We compared speech production related brain activity with activations resulting from perceptual categorization of syllables using high field 7 Tesla functional magnetic resonance imaging (fMRI) at 1-mm isotropic voxel resolution, enabling high localization accuracy compared to previous studies. METHODSBlood oxygenation level dependent (BOLD) signals were obtained in 20 normal hearing subjects using a simultaneous multi-slice (SMS) 7T echo-planar imaging (EPI) acquisition with whole-head coverage and 1 mm isotropic resolution. In a speech production localizer task, subjects were asked to produce a silent lip-round vowel /u/ in response to the visual cue "U" or purse their lips when they saw the cue "P". In a phoneme discrimination task, subjects were presented with pairs of syllables, which were equiprobably identical or different along an 8-step continuum between the prototypic /ba/ and /da/ sounds. After the presentation of each stimulus pair, the subjects were asked to indicate whether the two syllables they heard were identical or different by pressing one of two buttons. In a phoneme classification task, the subjects heard only one syllable and asked to indicate whether it was /ba/ or /da/. RESULTSUnivariate fMRI analyses using a parametric modulation approach suggested that left motor, premotor, and frontal cortex BOLD activations correlate with phoneme category variability in the /ba/-/da/ discrimination task. In contrast, the variability related to acoustic features of the phonemes were the highest in the right primary auditory cortex. Our multivariate pattern analysis (MVPA) suggested that left precentral/inferior frontal cortex areas, which were associated with speech production according to the localizer task, play a role also in perceptual categorization of the syllables. CONCLUSIONSThe results support the hypothesis that articulatory motor networks in the left hemisphere that are activated during speech production could also have a role in perceptual categorization of syllables. Importantly, high voxel-resolution combined with advanced coil technology allowed us to pinpoint the exact brain regions involved in both perception and production tasks.

neuroscience↗

bioRxiv2023

Pan-cancer characterization of ncRNA synergistic competition uncovers potential carcinogenic biomarkers

Non-coding RNAs (ncRNAs) act as important modulators of gene expression and they have been confirmed to play critical roles in the physiology and development of malignant tumors. Understanding the synergism of multiple ncRNAs in competing endogenous RNA (ceRNA) regulation can provide important insights into the mechanisms of malignant tumors caused by ncRNA regulation. In this work, we present a framework, SCOM, for identifying ncRNA synergistic competition. We systematically construct the landscape of ncRNA synergistic competition across 31 malignant tumors, and reveal that malignant tumors tend to share hub ncRNAs rather than the ncRNA interactions involved in the synergistic competition. In addition, the synergistic competition ncRNAs (i.e. ncRNAs involved in the synergistic competition) are likely to be involved in drug resistance, contribute to distinguishing molecular subtypes of malignant tumors, and participate in immune regulation. Furthermore, SCOM can help to infer ncRNA synergistic competition across malignant tumors and uncover potential diagnostic and prognostic biomarkers of malignant tumors. Altogether, the SCOM framework and the resulting web-based database SCOMdb (www.comblab.cn/SCOMdb/) serve as a useful resource for exploring ncRNA regulation and to accelerate the identification of carcinogenic biomarkers. Author summaryAbundant evidence reveals that ncRNAs are important modulators of gene expression, and it is important for us to understand the regulation of ncRNAs in malignant tumors. In this work, we hypothesize that ncRNAs acting as ceRNAs can crosstalk with each other in the form of synergistic competition. We name the hypothesis as the ncRNA synergistic competition hypothesis. To uncover potential carcinogenic biomarkers, we present a framework, SCOM, for identifying ncRNA synergistic competition in malignant tumors. From the perspective of synergistic competition, we have shown that the synergistic competition ncRNAs are likely to involve in drug resistance, contribute to distinguishing molecular subtypes of malignant tumors, and participate in immune regulation. In addition, the synergistic competition ncRNAs are potential diagnostic and prognostic biomarkers of malignant tumors. We believe that the proposed framework SCOM and the web-based database SCOMdb can contribute to the design of reliable diagnosis and treatment biomarkers for malignant tumors.

bioinformatics↗

bioRxiv2023

HD mutation results in a dominant negative effect on HTT function

Huntingtons disease (HD) remains an incurable and fatal neurodegenerative disease long after CAG-expansion mutation in the huntingtin gene (HTT) was identified as the cause. The underlying pathological mechanism, whether HTT loss of function or gain of toxicity results from mutation, remains a matter of debate. In this study, we genetically modulated wild-type or mutant HTT expression levels in isogenic human embryonic stem cells to systematically investigate their contribution to HD-specific phenotypes. Using highly reproducible and quantifiable in vitro micropattern-based assays, we observed comparable phenotypes with HD mutation and HTT depletion. However, halving endogenous wild-type HTT levels did not strongly recapitulate the HD phenotypes, arguing against a classical loss of function mechanism. Remarkably, expression of CAG-expanded HTT in non-HD cells induced HD-like phenotypes akin to HTT depletion. By corollary, these results indicate a dominant negative effect of mutated HTT on its wild-type counterpart. Complementation with additional copies of wild-type HTT ameliorated the HD-associated phenotypes, strongly supporting a classical dominant negative mechanism. Understanding the molecular basis of this dominant negative effect will guide the development of efficient clinical strategies to counteract the deleterious impact of mutant HTT on the wild-type protein.

cell biology↗

bioRxiv2023

Intrarenal myeloid subsets associated with kidney injury are comparable in mice and patients with lupus nephritis

Resident macrophages and infiltrating monocytes in kidneys of patients with lupus nephritis are altered both in frequency and function relative to their counterparts in healthy kidneys. The extent to which mouse models might be useful in developing approaches to target these cells for treating lupus nephritis is poorly understood. Here, we studied four common lupus mouse models that share clinical, serologic, and histopathologic kidney changes with humans. Using single-cell profiling and multiplex spatial imaging to analyze the intrarenal myeloid compartment with the onset of clinical disease in these models, we identified monocyte and macrophage subsets that expand or contract in kidneys with clinical nephritis. A unique subset of classical monocytes expanded with the onset of disease and expressed genes such as CD9, Spp1, Ctsd, Cd63, Apoe, and Trem2 that were previously shown to be induced by tissue injury and play a role in inflammation, lipid metabolism and tissue repair in other organs. Resident macrophages transitioned from a pro-inflammatory to a similar injury-associated state with onset of disease. To test whether these findings in mouse models were also observed in humans, we re-analyzed monocytes and macrophages in a single-cell RNAseq dataset of kidney biopsies from 155 patients with lupus nephritis and 30 healthy donors, collected by the NIH AMP RA/SLE consortium. Human monocytes and macrophages showed conserved changes in gene expression programs associated with lupus nephritis disease indices, and localized to similar kidney microenvironments as in mice. By identifying myeloid subsets and disease-associated alterations in biological processes that are conserved across species, we provide a strong rationale for functional studies of these cells and pathways in mice to uncover mechanisms and find targets relevant to human lupus nephritis. One sentence summaryThis study characterizes intrarenal myeloid cells from four lupus mouse models and 155 patients with lupus nephritis using single-cell RNA-seq and imaging, and identifies novel infiltrating and resident myeloid subsets that are conserved between mouse and human lupus nephritis, thus providing a map and strong rationale for functional studies in mice with relevance to human disease.

immunology↗

bioRxiv2023

Systematic single-cell analysis reveals dynamic control of transposable element activity orchestrating the endothelial-to-hematopoietic transition

BackgroundThe endothelial-to-hematopoietic transition (EHT) process during definitive hematopoiesis in vertebrate is highly conserved. Stage-specific expression of transposable elements (TEs) has been detected during zebrafish EHT and may promote hematopoietic stem cell formation by activating inflammatory signaling. However, little is known about how TEs contribute to the EHT process in human and mouse. ResultsWe reconstructed the single-cell EHT trajectories of human and mouse, and resolved the dynamic expression patterns of TEs during EHT. Most TEs presented a transient co-upregulation pattern along the conserved EHT trajectories. Enhanced TE activation was tightly associated with the temporal relaxation of epigenetic silencing systems. TE products can be sensed by multiple pattern recognition receptors, triggering inflammatory signaling to facilitate the emergence of hematopoietic stem cells. Furthermore, we observed that hypoxia-related signals were enriched in cells with higher TE expression. Additionally, we constructed the hematopoietic cis-regulatory network of accessible TEs and identified potential enhancers derived by TEs, which may boost the expression of specific EHT marker genes. ConclusionsOur study provides a systematic vision on how TEs are dynamically controlled to promote the hematopoietic fate decision through transcriptional and cis-regulatory networks, and pre-train the immunity of nascent hematopoietic stem cells.

bioinformatics↗

bioRxiv2023

Cross-species single-cell annotation with orthologous marker gene groups

Single-cell RNA sequencing (scRNA-seq) technology has been widely used in characterizing various cell types from in plant growth and development1-6. Applications of this technology in Arabidopsis have benefited from the extensive knowledge of cell-type identity markers7,8. Contrastingly, accurate labeling of cell types in other plant species remains a challenge due to the scarcity of known marker genes9. Various approaches have been explored to address this issue; however, studies have found many closest orthologs of cell-type identity marker genes in Arabidopsis do not exhibit the same cell-type identity across diverse plant species10,11. To address this challenge, we have developed a novel computational strategy called Orthologous Marker Gene Groups (OMGs). We demonstrated that using OMGs as a unit to determine cell type identity enables assignment of cell types by comparing 15 distantly related species. Our analysis revealed 14 dominant clusters with substantial conservation in shared cell-type markers across monocots and dicots.

bioinformatics↗

bioRxiv2023

Ketamine rescues anhedonia by cell-type and input specific adaptations in the Nucleus Accumbens

Ketamines role in providing a rapid and sustained antidepressant response, particularly for patients unresponsive to conventional treatments, is increasingly recognized. A core symptom of depression, anhedonia, or the loss of enjoyment or interest in previously pleasurable activities, is known to be significantly alleviated by ketamine. While several hypotheses have been proposed regarding the mechanisms by which ketamine alleviates anhedonia, the specific circuits and synaptic changes responsible for its sustained therapeutic effects are not yet understood. Here, we show that the nucleus accumbens (NAc), a major hub of the reward circuitry, is essential for ketamines effect in rescuing anhedonia in mice subjected to chronic stress, a critical risk factor in the genesis of depression in humans. Specifically, a single exposure to ketamine rescues stress-induced decreased strength of excitatory synapses on NAc D1 dopamine receptor-expressing medium spiny neurons (D1-MSNs). By using a novel cell-specific pharmacology method, we demonstrate that this cell-type specific neuroadaptation is necessary for the sustained therapeutic effects of ketamine. To test for causal sufficiency, we artificially mimicked ketamine-induced increase in excitatory strength on D1-MSNs and found that this recapitulates the behavioral amelioration induced by ketamine. Finally, to determine the presynaptic origin of the relevant glutamatergic inputs for ketamine-elicited synaptic and behavioral effects, we used a combination of opto- and chemogenetics. We found that ketamine rescues stress-induced reduction in excitatory strength at medial prefrontal cortex and ventral hippocampus inputs to NAc D1-MSNs. Chemogenetically preventing ketamine-evoked plasticity at those unique inputs to the NAc reveals a ketamine-operated input-specific control of hedonic behavior. These results establish that ketamine rescues stress-induced anhedonia via cell-type-specific adaptations as well as information integration in the NAc via discrete excitatory synapses.

neuroscience↗

bioRxiv2023

Impaired motor-to-sensory transformation mediates auditory hallucinations

Distinguishing reality from hallucinations requires efficient monitoring of agency. It has been hypothesized that a copy of motor signals, termed efference copy (EC) or corollary discharge (CD), suppresses sensory responses to yield a sense of agency; impairment of the inhibitory function leads to hallucinations. However, how can the sole absence of inhibition yield positive symptoms of hallucinations? We hypothesize that selective impairments in functionally distinct signals of CD and EC during motor-to-sensory transformation cause the positive symptoms of hallucinations. In an electroencephalography (EEG) experiment with a delayed articulation paradigm in schizophrenic patients with (AVHs) and without auditory verbal hallucinations (non-AVHs), we found that preparing to speak without knowing the contents (general preparation) did not suppress auditory responses in both patient groups, suggesting the absent of inhibitory function of CD. Whereas, preparing to speak a syllable (specific preparation) enhanced the auditory responses to the prepared syllable in non-AVHs, whereas AVHs showed enhancement in responses to unprepared syllables, opposite to the observations in the normal population, suggesting that the enhancement function of EC is not precise in AVHs. A computational model with a virtual lesion of an inhibitory inter-neuron and disproportional sensitization of auditory cortices fitted the empirical data and further quantified the distinct impairments in motor-to-sensory transformation in AVHs. These results suggest that broken CD plus noisy EC causes erroneous monitoring on the imprecise generation of internal auditory representation and yields auditory hallucinations. Specific impairments in functional granularity of motor-to-sensory transformation mediate positivity symptoms of agency abnormality in mental disorders.

neuroscience↗

bioRxiv2023

CHPF boosts proliferation and invasion of clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (ccRCC) is a malignant tumor most commonly seen in the urinary system, featuring quick progression, invasive behavior, frequent recrudesce, and bad prognosis, whereas Chondroitin polymerizing factor (CHPF) is an essential glycosyl transferase of biosynthesis involved chondroitin sulphate. But the relationship between the two has not been fully understood so far. The present research will probe into the relationship between CHPF and ccRCC. MethodsExplore the CHPF expression level in renal ccRCC tissues through bioinformatics analysis of The Cancer Genome Atlas (TCGA) and the real-time quantitative polymerase chain reaction detection system (qPCR); acquire relevant clinical data from the TCGA data-base and use Kaplan-Meier survival analysis to verify the relevance of CHPF expression to the clinical prognosis of ccRCC patients; then, effectively silence CHPF in ccRCC 786-O cells by a lentivirus-mediated approach; next, observe the effects of CHPF on tumor cell proliferation, cell cycle progression, and apoptosis. ResultsIn ccRCC tissues, CHPF expression has been significantly upregulated; the higher expression, the shorter survival of ccRCC patients. CHPF downregulation in the 786-O cell can effectively hold back the proliferation, apoptosis and cycle of cancer cells. ConclusionBased on the above results, we arrive at a conclusion that CHPF expression contributes markedly to the development of human ccRCC cells. Therefore, CHPF may act as a potential prognostic marker of ccRCC and provide a new target for ccRCC treatment. Simple SummaryChondroitin polymerizing factor (CHPF) is an important glycosyltransferase involved in the biosynthesis of chondroitin sulfate, which is thought to have some pro-carcinogenic effects. However, the role and mechanism of CHPF in clear cell renal cell carcinoma (ccRCC) have not been reported. The aim of this study was to investigate the relationship between CHPF and ccRCC. In this study, we found that CHPF was highly expressed in ccRCC and knocking out CHPF can greatly inhibit the proliferation and cell cycle progression of ccRCC and accelerate its apoptosis, suggesting that CHPF can predict the prognosis of ccRCC and a potential target for treatment.

genetics↗

bioRxiv2023

Evolution of the gene regulatory network of body axis by enhancer hijacking in amphioxus

A central goal of evolutionary developmental biology is to decipher the evolutionary pattern of gene regulatory networks (GRNs) that control morphogenesis during embryonic development, and the underlying molecular mechanism of the GRNs evolution. The Nodal signaling that governs the body axes of deuterostomes exhibits a conserved GRN orchestrated principally by Nodal, Gdf1/3 and Lefty. Despite that the GRN retains a conserved function in deuterostomes, the expression patterns of Gdf1/3 and Nodal are derived in cephalochordate amphioxus, implying a specific rewiring of the GRN in this lineage. Here we examined the regulatory mechanism and evolution of this GRN in amphioxus by functional genetic manipulations. We found that while the amphioxus Gdf1/3 orthologue shows nearly no expression during embryogenesis, its duplicate Gdf1/3-like linking to Lefty is zygotically expressed in a similar pattern as Lefty. Mutant and transgenic analyses revealed that Gdf1/3 is no longer crucial for amphioxus axial development. Instead, Gdf1/3-like assumes this responsibility, likely through hijacking Lefty enhancers. We also showed that amphioxus Nodal has become an indispensable maternal factor to compensate for the loss of maternal Gdf1/3 expression. We therefore demonstrated a case that the evolution of an ancestral GRN could be triggered by enhancer hijacking events. This pivotal event has allowed the emergence of a new GRN in the extant amphioxus, presumably evolving through a stepwise process. The co-expression of Gdf1/3-like and Lefty achieved by shared regulatory region may have provided developmental robustness during body axis formation in extant amphioxus, which provides a selection-based hypothesis for the phenomena called developmental system drift.

evolutionary biology↗

bioRxiv2023

Evaluation of population structure inferred by principal component analysis or the admixture model

Principal component analysis (PCA) is commonly used in genetics to infer and visualize population structure and admixture between populations. PCA is often interpreted in a way similar to inferred admixture proportions, where it is assumed that individuals belong to one of several possible populations or are admixed between these populations. We propose a new method to assess the statistical fit of PCA (interpreted as a model spanned by the top principal components) and to show that violations of the PCA assumptions affect the fit. Our method uses the chosen top principal components to predict the genotypes. By assessing the covariance (and the correlation) of the residuals (the differences between observed and predicted genotypes), we are able to detect violation of the model assumptions. Based on simulations and genome wide human data we show that our assessment of fit can be used to guide the interpretation of the data and to pinpoint individuals that are not well represented by the chosen principal components. Our method works equally on other similar models, such as the admixture model, where the mean of the data is represented by linear matrix decomposition.

genetics↗

bioRxiv2023

High-resolution Dynamic Human Brain Neural Activity Recording Using 3T MRI

Despite extensive research over decades, a non-invasive technique capable of capturing neural activities in the human brain with high spatiotemporal resolution is still lacking. The recently proposed direct imaging of neuronal activity (DIANA) using ultrahigh-field magnetic resonance imaging (MRI) has shown promise, but the translation from anesthetized mice to awake humans poses a significant challenge. Here we present Time Resolved ImaGing of Global Electroneurophysiological Record (TRIGGER), a novel technique that enables the direct detection of neural activity in the awake human brain using 3T MRI. In 18 participants, visual responses were captured at 5-mm spatial resolution and 1.4-ms temporal resolution. Importantly, the delay in stimulus presentation reliably corresponded to the latency of neural responses on a millisecond scale. Furthermore, when stimuli were presented to one visual field, the responses in two hemispheres exhibited the expected time difference. This non-invasive mapping approach holds the potential to elucidate neural dynamics underlying human brain function and disorders.

neuroscience↗