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Lan, T.

Publications and source records attributed to Lan, T..

At least 19 recordsLinked to original sources

RamiGlyph Captures Microglial Morphological Diversity and Predicts Functional States in Ischemia Reperfusion and Amyloid Pathology

Microglia are resident immune cells of the central nervous system, whose ramified processes rapidly remodel in response to injury. However, how to capture subtle morphological changes and whether functional state can be predicted from morphology remain open questions. Here, we present RamiGlyph, a contrastive learning framework integrating topological and structural features, trained on more than 20,000 reconstructed microglia. RamiGlyph not only distinguishes physiological and pathological states of microglia but also generalizes to neuronal cell type classification. Projection of microglia morphological embeddings revealed a continuum rather than discrete classes, from which a morphology score was derived to quantify dynamic process remodeling. To link morphology with function, Gromov Wasserstein optimal transport was used to align unpaired morphological and functional data across stages of ischemia reperfusion injury and amyloid pathology. These alignment results enable prediction of microglial functional states using RamiGlyph embeddings alone, with prediction reliability increasing upon cell aggregation. In summary, RamiGlyph provides a robust framework for resolving continuous microglial morphological variation and linking morphology to functional states across acute and chronic neuropathological contexts.

bioinformatics↗

A single-cell transcriptome atlas of the barley root apical meristem uncovers conserved and divergent roles of HvWOX5

Single-cell approaches have transformed plant developmental biology; however, cell-type-resolved resources for cereals remain limited. Here, we present a single-cell transcriptome atlas of the barley root apical meristem (RAM), which resolves 24 transcriptionally distinct cell populations. We assigned major root cell identities by integrating marker gene validation using Hybridization Chain Reaction (HCR) RNA fluorescence in situ hybridization and spatial transcriptomics with cross-species comparisons of published root atlases. Pseudotime analysis reconstructed developmental trajectories from the quiescent center to differentiating tissues, supporting the spatial and developmental organization of the atlas. We further demonstrated the utility of this resource by identifying HvWOX5 expression in the quiescent center and metaxylem and showing that HvWOX5 loss-of-function mutants displayed reduced root and meristem lengths, altered stem cell niche homeostasis, and disrupted metaxylem organization. Taken together, this atlas provides a framework for dissecting barley root development and identifies HvWOX5 as a key regulator of RAM organization and metaxylem patterning.

Plant Biology↗

A neural circuit mechanism for abstract free choice

Making abstract free choices, such as arbitrary decisions between comparable options formed independently of specific motor plans, is central to everyday behavior. Yet, the neural mechanisms underlying free choice remain poorly understood. Using a delayed-response paradigm (N=80), we dissociated abstract goal selection (color choice) from later motor response mapping. We found that freely chosen goals elicit slower responses and lower goal-switching costs than instructed goals. We developed a hierarchical attractor network model in which symmetry-breaking attractor dynamics drive free goal selection, and conjunctive representations translate these abstract goals into motor output. Freely chosen goals converged on less extreme fixed points than instructed ones, accounting for their slower, more variable responses. Consistent with our model, human EEG activity (N=30) sequentially encoded goal, conjunctive, and response representations, with conjunctive representations specifically coupled to behavioral variability. Our findings offer plausible circuit-level mechanisms for how abstract free choices are made and translated into action. HighlightsO_LIFree-instructed differences persist when goal selection and response mapping are dissociated C_LIO_LIAbstract free choices elicit reduced goal-switching costs relative to instructed ones C_LIO_LISymmetry-breaking attractor dynamics explain behavioral signatures of free choice C_LIO_LIEEG signals sequentially encode abstract goal, conjunctive, and response representations C_LIO_LIConjunctive representations, but not goal or response, were coupled to behavior C_LI

neuroscience↗

Endothelin-1 signaling regulates chamber-specific mouse atrial cardiomyocyte cytokinesis and polyploidy

Cardiomyocyte (CM) maturation is a central process in postnatal heart development accompanied by profound structural, metabolic, and cell cycle changes. One hallmark of this maturation program is CM polyploidy that is closely associated with the loss of cardiac regenerative capacity. Most insights into ploidy regulation have come from studies of ventricular CMs, whereas the spatiotemporal dynamics and molecular regulation of atrial CM polyploidy remain poorly understood. We show that CM polyploidy in the postnatal mouse heart is highly chamber-specific, with >90% of ventricular CMs are polyploid, compared with [~]30% of left atrial (LA) CMs and [~]15% of right atrial (RA) CMs. These chamber-specific differences correlate with their differential susceptibility to cytokinesis failure and are regulated, at least in part, by endocardial cells. Mechanistically, we identify the endocardial/endothelial-derived factor EDN1 as a postnatally enriched signal in the LA compared with the RA. EDN1 can act directly on primary aCMs to inhibit cytokinesis, in part by suppressing Wnt signaling. Consistently, inhibition of Edn1 signaling in vivo using Bosentan reduced CM cytokinesis failure specifically in the LA. Altogether, our findings reveal a previously unrecognized role for endothelial-myocardial crosstalk in regulating chamber-specific CM polyploidy through Edn1 signaling.

developmental biology↗

Telomeric repeat distribution and chromosomal evolution in the slipper orchid genus Paphiopedilum

The chromosomal mechanisms responsible for the extraordinary diversity in chromosome number and karyotype structure in Paphiopedilum remain incompletely resolved, particularly the processes by which extensive dysploid variation has arisen in the apparent absence of polyploidy. Telomeric repeats provide informative cytogenetic markers for reconstructing chromosome evolution because their typically terminal localization and repetitive nature can retain signatures of breakage, fusion, and repair. To address the chromosomal evolutionary problem in Paphiopedilum, telomeric repeat distribution was examined in 41 species representing all major taxonomic sections (phylogenetic lineages) using fluorescence in situ hybridization (FISH). In addition to conventional terminal telomeres, diverse interstitial telomeric repeat (ITR) patterns were detected, including centromeric, pericentromeric, and subtelomeric arrays, as well as rare chromosome ends lacking detectable telomeric signals. Classification of these patterns into twelve chromosomal types, interpreted in a phylogenetic context, suggests that telomere-associated and chromosome structural processes have contributed to karyotype diversification, including centric fission, subtelomeric rearrangement, repeat amplification, and potentially centric fusion, with different processes predominating among lineages. In some sections, such as Pardalopetalum, these types resolve into internally consistent patterns often dominated by terminal localization with recurrent subtelomeric expansion, providing a clear cytogenetic signature of lineage-specific telomere repeat dynamics, whereas other sections exhibit greater within-section heterogeneity in both signal position and intensity. These results provide a coherent cytogenetic framework for dysploid chromosome evolution in Paphiopedilum and identify telomeric repeat dynamics as an important contributor to karyotype diversification in the genus.

plant biology↗

FLOWERING LOCUS T1 is a pleiotropic regulator of reproductive development, plant longevity, and source-sink relations in barley

Source-sink interactions play a critical but mechanistically underexplored role in coordinating reproductive output and longevity in plants. Here, we investigated the role of FT1, the barley homolog of the florigen FLOWERING LOCUS T (FT), in regulating source (leaf) and sink (inflorescence) development and metabolism. Using ft1 knock-out mutants in the spring barley cultivar Golden Promise, which carries a mutated ppd-H1 allele, and in an introgression line with a wild-type Ppd-H1 allele, we show that Ppd-H1 primarily regulates the timing of inflorescence development and flowering through FT1, whereas variation in tiller number and leaf size is determined by the genetic background. ft1 mutants exhibited reduced determinacy of both leaf and inflorescence meristems, resulting in increased leaf and spikelet numbers and size, but severely reduced inflorescence fertility, altered senescence patterns, and significantly extended plant longevity. The ft1 mutants exhibited a strong transcriptional reprogramming of genes involved in both the light and dark reactions of photosynthesis in the leaf, alongside an upregulation of genes associated with carbon catabolism and stress responses in the leaf and inflorescence. Elevated soluble sugar and starch levels in ft1 inflorescences indicated that the impaired development and fertility of ft1 inflorescences were not caused by carbon limitation, but instead reflected a reduced sink strength. Our work reveals that FT1 coordinates the development of vegetative and reproductive meristems and organs with plant physiology and metabolism, thereby regulating source-sink relationships and balancing plant longevity with reproductive output.

plant biology↗

A mobile circular DNA element drives memory-related processes in mice

Extrachromosomal circular DNAs (ecDNAs) are double stranded, closed loop DNA molecules that act independently of the genome. Here we report the discovery of a brain-enriched ecDNA, ecCldn34d, that regulates the transcriptional state of plasticity-related genes and is temporally associated with the stability of fear memories. ecDNA therefore represents a novel class of mobile DNA elements that are involved in experience-dependent neuroadaptation.

neuroscience↗

Local translation of circular RNAs is required for synaptic activity and memory

Circular RNAs (circRNAs) are enriched in synapses and implicated in cognitive processes, and recent studies have shown that circRNAs can encode micropeptides, which suggests that there may be novel synaptic proteoforms in the brain that await discovery. Here we report widespread learning-induced local circRNA translation in the prefrontal cortex of male C57BL/6 mice. More than 1500 synapse-enriched circRNAs contain active IRES elements, with 842 interacting with the ribosome and 241 exhibiting direct evidence of activity-induced translation. We discovered a synapse-enriched micropeptide (P1) that is derived from a single exon circRNA, the mRNA host of which encodes an enzyme associated with protein repair. Although P1 is only a third of the size of the full-length protein, it is locally expressed, enzymatically active, and interacts with plasticity-related proteins, including CaMKII. In addition to direct effects on synaptic activity, targeted P1 knockdown impairs whereas its overexpression enhances fear extinction memory. These findings shed new light on the dark proteome in the brain and reveal local circRNA translation as a novel mechanism of plasticity and memory.

neuroscience↗

Elastase mediated white matter damage in cerebral small vessel disease: Microglia - neutrophils pas de deux

Cerebral small vessel disease (CSVD) leads to an extensive white matter damage associated with cognitive decline, yet the underlying damaging mechanisms remain incompletely understood. Here we established a positive correlation between plasma levels of serine proteinase elastase ELANE and periventricular white matter hyperintensity (PV-WMH) in a cohort of CSVD patients. In a CSVD murine model induced by bilateral carotid artery stenosis (BCAS), upregulated ELANE was detected both in microglia and peripheral blood neutrophils. Genetic ELANE deficiency significantly alleviated oligodendrocyte loss, thereby reducing white matter lesions (WMLs) as well as ameliorating sensorimotor and cognitive impairments in BCAS mice. In vitro studies demonstrated that ELANE triggered time-dependent and dose-dependent oligodendrocyte lineage cell death. Bone marrow transplantation showed that ELANE from microglia and peripheral blood both contributed to WML development and BCAS-induced neurological deficits. Mechanistically, ELANE, accumulated by oligodendrocytes, cleaved the phosphodiesterase domain of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase). Pharmacological inhibition of ELANE with Sivelestat reduced oligodendrocyte loss and WMLs leading to the restoration of white matter integrity and neurological improvements in BCAS mice. In post-mortem brain specimens of CSVD patients ELANE accumulated within WMLs being predominantly localized in microglia (and hence defined as microglial ELANE) rather than in the brain-infiltrating neutrophils. We therefore posit microglial ELANE as an instigator of whiter matter injury in CSVD and suggest its potential therapeutic relevance.

neuroscience↗

From Flowering Time to High Temperature Resilience: PHOTOPERIOD 1 (PPD-H1) Controls Spike Fertility through Improving Stress Resistance and Energy Metabolism under High Ambient Temperatures

High ambient temperature (HT) impairs reproductive development and grain yield in temperate crops. To ensure reproductive success under HT, plants must maintain developmental stability. However, the mechanisms integrating plant development and temperature resilience are largely unknown. Here, we demonstrate that PHOTOPERIOD 1 (PPD-H1), homologous to PSEUDO RESPONSE REGULATOR genes of the Arabidopsis circadian clock, controls developmental stability in response to HT in barley. We analyzed HT responses in independent introgression lines with either the ancestral wild-type Ppd-H1 allele or the natural ppd-h1 variant, selected in spring varieties to delay flowering and enhance yield under favourable conditions. HT delayed inflorescence development and reduced grain number in ppd-h1 mutant lines, while the wild-type Ppd-H1 genotypes accelerated reproductive development and showed a stable grain set under HT. Using a CRISPR/Cas9-induced ppd-h1 mutant, we confirmed that the CCT domain of Ppd-H1 controls developmental stability, but not clock gene expression. Transcriptome and phytohormone analyses in developing leaves and inflorescences revealed increased stress gene expression and abscisic acid levels in the leaf and inflorescence of the natural and induced mutant ppd-h1 lines. Furthermore, the mutant ppd-h1 lines downregulated photosynthesis-and energy metabolism-related genes, and reduced auxin and cytokinin levels in the inflorescence, which impaired anther and pollen development. By contrast, in the wild-type Ppd-H1 plants, the transcriptome and phytohormone levels and anther and pollen development remained stable under HT. Our findings suggest that Ppd-H1 enhances stress resistance and energy metabolism, thereby stabilizing reproductive development, floret fertility and grain set under HT.

plant biology↗

How Error Correction Affects PCR Deduplication: A Survey Based on UMI Datasets of Short Reads

Next-Generation Sequencing (NGS) data is widely utilised for various downstream applications in bioinformatics, and numerous techniques have been developed for PCR-deduplication and error-correction to eliminate bias and errors introduced during the sequencing. This study first-time provides a joint overview of recent advances in PCR-deduplication and error-correction on short reads. In particular, we utilise UMI-based PCR-deduplication strategies and sequencing data to assess the performance of the solely-computational PCR-deduplication approaches and investigate how error correction affects the performance of PCR-deduplication. Our survey and comparative analysis reveal that the deduplicated reads generated by the solely-computational PCR-deduplication and error-correction methods exhibit substantial differences and divergence from the sets of reads obtained by the UMI-based deduplication methods. The existing solely-computational PCR-deduplication and error-correction tools can eliminate some errors but still leave hundreds of thousands of erroneous reads uncorrected. All the error-correction approaches raise thousands or more new sequences after correction which do not have any benefit to the PCR-deduplication process. Upon these discoveries, we offer practical suggestions to enhance the existing computational approaches for improving the quality of short-read sequencing data.

bioinformatics↗

CLAVATA signalling shapes barley inflorescence architecture by controlling activity and determinacy of shoot apical and rachilla meristems

Grasses exhibit a large variety of diverse inflorescence architectures, from complex branched inflorescences in Oryzeae (rice) to simple spike-type inflorescences in Triticeae (e.g. barley, wheat). Inflorescence architecture depends on shape, longevity and determinacy of meristems that direct growth of the main rachis and lateral branches, but how individual meristem activities are determined and integrated within complex inflorescences is not yet understood. We found that activity of distinct meristems in the barley inflorescence is coordinated by a signalling pathway comprising the receptor like kinase Hordeum vulgare CLAVATA1 (HvCLV1) and the secreted CLAVATA3/ENDOSPERM SURROUNDING REGION (CLE)-family peptide FON2- LIKE CLE PROTEIN1 (HvFCP1). HvFCP1 interacts with HvCLV1 to promote spikelet formation but restricts inflorescence meristem and rachilla meristem proliferation. Hvfcp1 or Hvclv1 mutants generate branched inflorescences with additional rows of spikelets and supernumerary florets. Transcriptome analysis reveals that HvFCP1/HvCLV1 signalling controls inflorescence branching through the regulation of trehalose-6-phosphate synthesis and sugar transport. Our discoveries reveal the potential to engineer barley inflorescence architecture by manipulating regulation of distinct meristem activities.

plant biology↗

Turn `noise' to signal: accurately rectify millions of erroneous short reads through graph learning on edit distances

Although the per-base erring rate of NGS is very low at 0.1% to 0.5%, the percentage/probability of erroneous reads in a short-read sequencing dataset can be as high as 10% to 15% or in the number of millions. Correction of these wrongly sequenced reads to retrieve their huge missing value will improve many downstream applications. As current methods correct only some of the errors at the cost of introducing many new errors, we solve this problem by turning erroneous reads into their original states, without bringing up any non-existing reads to keep the data integrity. The novelty of our method is originated in a computable rule translated from PCR erring mechanism that: a rare read is erroneous if it has a neighbouring read of high abundance. With this principle, we construct a graph to link every pair of reads of tiny edit distances to detect a solid part of erroneous reads; then we consider them as training data to learn the erring mechanisms to identify possibly remaining hard-case errors between pairs of high-abundance reads. Compared with state-of-the-art methods on tens of datasets of UMI-based ground truth, our method has made a remarkably better performance under 19 metrics including two entropy metrics that measure noise levels in a dataset. Case studies found that our method can make substantial impact on genome abundance quantification, isoform identification, SNP profiling, and genome editing efficiency estimation. For example, the abundance level of the reference genome of SARS-CoV-2 can be increased by 12% and that of Monkeypox can be boosted by 52.12% after error correction. Moreover, the number of distinct isomiRs is decreased by 31.56%, unveiling there are so many previously identified isomiRs that are actually sequencing errors. Author summaryDetecting short-read sequencing errors and correcting the related erroneous reads is a long-standing problem in bioinformatics. Current error correction algorithms correct only small parts of the errors but simultaneously introduce thousands of non-existing sequences. We present a new method to rectify erroneous reads under 300 bp produced by PCR-involved miRNA-sequencing, small RNA sequencing, or paired-end RNA sequencing, regardless of platform or sample type. Our method is the first kind considering the PCR erring mechanism and machine learning technique to improve sequencing data quality by turning millions of erroneous short reads into their original state without bringing up any non-existing sequences into the read set. Our error correction method can make a significant impact on a wide range of cutting-edge downstream applications. The observations and advantages in the case studies lay down strong evidence to question the accuracies of current downstream research outcomes and open new avenues to conduct downstream analysis whenever short-read data are adopted.

bioinformatics↗

LEAFY interacts with WHEAT ORTHOLOG OF APO1 to regulate spikelet number per spike in wheat

In wheat, the transition of the inflorescence meristem to a terminal spikelet (IM[->]TS) determines the spikelet number per spike (SNS), an important yield component. In this study, we demonstrate that the plant-specific transcription factor LEAFY (LFY) physically and genetically interacts with WHEAT ORTHOLOG OF APO1 (WAPO1) to regulate SNS and floret development. Loss-of-function mutations in either or both genes result in significant and similar reductions in SNS, as a result of a reduction in the rate of spikelet meristems formation per day. SNS is also modulated by significant genetic interactions between LFY and SQUAMOSA MADS-box genes VRN1 and FUL2, which promote the IM[->]TS transition. Single-molecule fluorescence in-situ hybridization revealed a down-regulation of LFY and up-regulation of the SQUAMOSA MADS-box genes in the distal part of the developing spike during the IM[->]TS transition, supporting their opposite roles in the regulation of SNS in wheat. Concurrently, the overlap of LFY and WAPO1 transcription domains in the developing spikelets contributes to normal floret development. Understanding the genetic network regulating SNS is a necessary first step to engineer this important agronomic trait. SUMMARY STATEMENTThe plant specific transcription factor LEAFY plays an important role in the regulation of the number of spikelets per spike in wheat.

plant biology↗

G6PD Maintains Redox Homeostasis and Biosynthesis in LKB1-Deficient KRAS-Driven Lung Cancer

Cancer cells depend on nicotinamide adenine dinucleotide phosphate (NADPH) to combat oxidative stress and support reductive biosynthesis. One major NAPDH production route is the oxidative pentose phosphate pathway (committed step: glucose-6-phosphate dehydrogenase, G6PD). Alternatives exist and can compensate in some tumors. Here, using genetically-engineered lung cancer model, we show that ablation of G6PD significantly suppresses KrasG12D/+;Lkb1-/-(KL) but not KrasG12D/+;p53-/- (KP) lung tumorigenesis. In vivo isotope tracing and metabolomics revealed that G6PD ablation significantly impaired NADPH generation, redox balance and de novo lipogenesis in KL but not KP lung tumors. Mechanistically, in KL tumors, G6PD ablation caused p53 activation that suppressed tumor growth. As tumor progressed, G6PD-deficient KL tumors increased an alternative NADPH source, serine-driven one carbon metabolism, rendering associated tumor-derived cell lines sensitive to serine/glycine depletion. Thus, oncogenic driver mutations determine lung cancer dependence on G6PD, whose targeting is a potential therapeutic strategy for tumors harboring KRAS and LKB1 co-mutations.

cancer biology↗

The genome and population genomics of allopolyploid Coffea arabica reveal the diversification history of modern coffee cultivars

Coffea arabica, an allotetraploid hybrid of C. eugenioides and C. canephora, is the source of approximately 60% of coffee products worldwide, and its cultivated accessions have undergone several population bottlenecks. We present chromosome-level assemblies of a di-haploid C. arabica accession and modern representatives of its diploid progenitors, C. eugenioides and C. canephora. The three species exhibit largely conserved genome structures between diploid parents and descendant subgenomes, with no obvious global subgenome dominance. We find evidence for a founding polyploidy event 350,000-610,000 years ago, followed by several pre-domestication bottlenecks, resulting in narrow genetic variation. A split between wild accessions and cultivar progenitors occurred [~]30.5 kya, followed by a period of migration between the two populations. Analysis of modern varieties, including lines historically introgressed with C. canephora, highlights their breeding histories and loci that may contribute to pathogen resistance, laying the groundwork for future genomics-based breeding of C. arabica.

genomics↗

Large-scale population genomics of Malayan pangolins reveals deep diversification and a new species

BackgroundArchipelagos and oceanic islands often present high percentage of endemism due to rapid speciation. The Malayan pangolin is a species distributing at both mainland (southern Yunnan, China) and oceanic islands via Malayan peninsula, which may result in deep differentiation among populations. In-depth investigation of population structure and genetic consequences for such species is of vital importance for their protection and conservation, practically for the critically endangered Malayan pangolin that is suffering from poaching, illegal trade, and habitat loss. ResultsHere we carried out a large-scale population genomic analysis for Malayan pangolins, and revealed three highly distinct genetic populations in this species, two of which are now being reported for the first time. Based on multiple lines of genomic and morphological evidence, we postulate the existence of a new pangolin species (Manis_1). Genetic diversity and recent inbreeding were both at a moderate level for both Malayan pangolins and Manis_1, but mainland Malayan pangolins presented relatively lower genetic diversity, higher inbreeding and fitness cost than island populations. ConclusionsWe found extremely deep and graded differentiation in Malayan pangolins, with two newly discovered genetic populations and a new pangolin species that is closely related to the Philippine pangolin than the typical Malayan pangolin, but a distant relative of the Indian pangolin. Anthropogenic factors did not significantly weaken the basis of genetic sustainability for Malayan pangolins, but mainland Malayan pangolins should be paid more attention for conservation due to higher genetic risks than island populations.

genomics↗

Population genomics reveals extensive inbreeding and purging of mutational load in wild Amur tigers

The inbreeding is a big threat for the persistence of genetic diversity in small and isolated populations of endangered species. The homozygous genome could exacerbate inbreeding depression by introducing homozygous deleterious alleles in the population. However, purging of inbreeding loads as they become homozygotes in small populations could alleviate the depression. The Amur tiger (Panthera tigris altaica) is typically exists in small population living in forests in Northeast Asia and is among the most endangered animals on the planet with great symbolic significance of conservation. By comparing with captive individuals, we revealed substantially higher and more extensive inbreeding in the wild Amur tiger population (FROH=0.51) than in captive Amur tigers (FROH=0.26). We further found much less mutational loads in wild populations when compared with captive Amur tigers. However, the frequency of loss of function and deleterious nonsynonymous mutations inside ROH regions are much lower than that in non-ROH regions in both wild and captive Amur tigers, indicating the purging may had occurred in both populations but much effective in the wild population. In addition, we found the average frequency of deleterious alleles was much lower than that of neutral alleles in the wild population, indicating that the purifying selection contributed to the purging of mutational loads in the wild Amur tigers. These findings provide valuable genome-wide evidence to support the making of future conservation plans of wild Amur tigers.

genomics↗