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681.
笑对人生
(2022-10-07 22:00):
#paper doi: 10.1038/s41467-022-30033-z. Reference-free cell type deconvolution of multi-cellular pixel-resolution spatially resolved transcriptomics data. Nat Commun. 2022 Apr 29;13(1):2339.
空间转录组技术能够揭示组织内不同区域的细胞转录谱特征,对理解组织的细胞生物学功能具有重要意义。然而,目前空间转录组技术存在一定的局限性,一是基于测序的空间转录组技术分辨率较低,无法达到真正的单细胞水平,二是基于原位杂交或显微成像的空间转录组技术检测的RNA数量有限且价格昂贵。
为了解决上述的问题,科学家开发了一系列整合单细胞转录组数据和空间转录组的算法,用于预测多细胞空间分辨率(multi-cellular pixel-resolution)下的细胞类型和复原单个细胞的完整转录表达谱。SPOTlight主要是利用来自单细胞转录组数据(scRNA-seq)的细胞类型标记基因矩阵,基于种子非负向矩阵分解方法对空间转录组的捕获位置(spot)进行细胞类型去卷积。RCTD需要利用scRNA-seq中每种细胞类型所有marker基因的表达均值作为参考数据的输入,用于建立能够反映spot内每种细胞贡献的概率统计模型,进而预测细胞类型及其比例。SpatialDWLS首先使用来自scRNAseq的细胞类型特征基因去做GSEA富集,然后利用阻尼最小二乘法(dampened weighted least squares)算法推断spot的细胞类型组成。然而,以上的这些方法均依赖于合适的scRNAseq数据,受成本、技术和生物学差异等因素的影响较大。尽管目前已公布了众多的健康人器官或组织图谱文章,但也可能存在批次效应和异质性问题。此外,基于液滴的scRNAseq需要对组织进行解离和捕获,可能会导致scRNAseq鉴定细胞类型和空间转录组不一致的问题。基于以上种种原因,有必要开发一种无需参考数据的spot细胞类型解卷积方法。
STdeconvolve是一个无需单细胞参考数据即可对空间转录组数据进行细胞类型反卷积的软件包。STdeconvolve的核心算法是隐狄利克雷分配模型(Latent Dirichlet Allocation,LDA)。LDA是自然语言处理中被普遍使用的一种统计模型,可以用于发现文档集(documents)中潜在的主题(latent topics),并最终以概率分布的形式输出。当LDA应用到空间转录组数据时,则以多细胞空间分辨率下的基因表达计数矩阵(count matrix)作为输入,进而推断每种细胞类型(主题)的转录表达谱和每种细胞类型的占比。无论是在模拟的ST数据,还是在不同分辨率的空间转录组数据(10X Visium、DBiT-seq和Slide-seq),STdeconolve都能够有效地复原组织内某一细胞类型的转录表达谱信息以及在原分辨率下的每种细胞占比。当存在匹配的单细胞参考数据集时,STdeconolve的细胞类型反卷积性能与其他依赖参考数据的软件相当。而当缺乏匹配数据集时,STdeconolve的性能更优。文章中的性能评价指标是均方根误差(Root Mean Square Error,RMSE),RMSE可用于表示模型预测中产生的误差大小,一般来说,RMSE越小,表示模型的预测能力越好。
Abstract:
Recent technological advancements have enabled spatially resolved transcriptomic profiling but at multi-cellular pixel resolution, thereby hindering the identification of cell-type-specific spatial patterns and gene expression variation. To address this challenge, …
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Recent technological advancements have enabled spatially resolved transcriptomic profiling but at multi-cellular pixel resolution, thereby hindering the identification of cell-type-specific spatial patterns and gene expression variation. To address this challenge, we develop STdeconvolve as a reference-free approach to deconvolve underlying cell types comprising such multi-cellular pixel resolution spatial transcriptomics (ST) datasets. Using simulated as well as real ST datasets from diverse spatial transcriptomics technologies comprising a variety of spatial resolutions such as Spatial Transcriptomics, 10X Visium, DBiT-seq, and Slide-seq, we show that STdeconvolve can effectively recover cell-type transcriptional profiles and their proportional representation within pixels without reliance on external single-cell transcriptomics references. STdeconvolve provides comparable performance to existing reference-based methods when suitable single-cell references are available, as well as potentially superior performance when suitable single-cell references are not available. STdeconvolve is available as an open-source R software package with the source code available at https://github.com/JEFworks-Lab/STdeconvolve .
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682.
笑对人生
(2022-10-07 00:02):
#paper doi: 10.1038/nbt.3344. PMID: 26372948. Comprehensive analysis of cancer-associated somatic mutations in class I HLA genes. Nat Biotechnol. 2015 Nov;33(11):1152-8. 主要组织相容性复合物(major histocompatibility complex,MHC)是一群紧密连锁并呈现高度多态性的基因群的统称。MHC编码的蛋白通常称为MHC分子或MHC抗原。MHC的发现源自异种移植产生免疫排斥反应。研究表明,脊椎动物都具有MHC抗原,但它们的命名并不相同。人的MHC抗原称为人类白细胞抗原(human leucocyte antigen,HLA)。编码HLA的DNA序列为6号染色体短臂上一段长度约为3600kb的区域。该区域含有224个基因座,每个基因座又分别含有众多等位基因,是目前人类已知的基因多态性最丰富的区域。HLA的生物学功能包括参与抗原呈递,制约细胞间相互识别和诱导免疫应答等。HLA主要分成三类,MHC I类分子几乎在集体所有细胞中表达,能够被CD8+ T细胞识别;MHC II类分子主要表达在抗原呈递细胞(APC),能够被CD4+T细胞识别;MHC III类分子包括补体系统的成分和与炎症相关的分子,例如C4、TNF和热休克蛋白。肿瘤细胞自身能够表达与正常细胞不同的抗原,称为肿瘤新生抗原(neoantigen)。新生抗原属于肿瘤特异性抗原(tumor specific antigen,TSA)。为了让TSA不被免疫细胞发现,肿瘤细胞会通过让HLA基因发生杂合性缺失(LOH)、下调HLA基因表达(突变)和分泌PD-L1来隐藏自身。既往的研究表明,体细胞HLA基因的突变增加是导致HLA功能缺失的重要原因。基于NGS的全外显子测序技术(WES)因性价比高和能有效检测几乎所有基因的突变,目前在临床和科研肿瘤基因组检测得到广泛应用。然而,由于HLA基因序列单一和高GC含量的序列特点,利用WES进行HLA分型仍旧存在不少挑战。为此,本研究开发了一个名为POLYSOLVER(POLYmorphic loci reSOLVER)的高精确度HLA分型算法,适用于低覆盖度的WES数据。该算法在7930位癌症患者的WES数据得到验证,并在检测体细胞HLA基因突变表现出高的灵敏度和特异度。
Abstract:
Detection of somatic mutations in human leukocyte antigen (HLA) genes using whole-exome sequencing (WES) is hampered by the high polymorphism of the HLA loci, which prevents alignment of sequencing reads …
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Detection of somatic mutations in human leukocyte antigen (HLA) genes using whole-exome sequencing (WES) is hampered by the high polymorphism of the HLA loci, which prevents alignment of sequencing reads to the human reference genome. We describe a computational pipeline that enables accurate inference of germline alleles of class I HLA-A, B and C genes and subsequent detection of mutations in these genes using the inferred alleles as a reference. Analysis of WES data from 7,930 pairs of tumor and healthy tissue from the same patient revealed 298 nonsilent HLA mutations in tumors from 266 patients. These 298 mutations are enriched for likely functional mutations, including putative loss-of-function events. Recurrence of mutations suggested that these 'hotspot' sites were positively selected. Cancers with recurrent somatic HLA mutations were associated with upregulation of signatures of cytolytic activity characteristic of tumor infiltration by effector lymphocytes, supporting immune evasion by altered HLA function as a contributory mechanism in cancer.
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683.
笑对人生
(2022-10-06 00:00):
#paper doi: 10.1038/nmeth.2883. PyClone: statistical inference of clonal population structure in cancer. Nat Methods. 2014 Apr;11(4):396-8.
恶性肿瘤的发生往往起源于一个癌变细胞(即肿瘤是由单克隆发育而来的)。癌变细胞在细胞增殖的过程中,由于变异或外界因素的压力选择,可能会产生在基因和表型方面与母细胞存在较大差异的子细胞。当这些具有相同遗传特点的子细胞逐渐形成一个细胞群体时,就称为是一个亚克隆。体细胞的突变是随机的,因此一个肿瘤块可能存在不同的克隆或亚克隆细胞。PyClone是一个基于分层贝叶斯的统计推断模型来分析癌症中克隆群体结构的软件。PyClone适用于多样本深度测序的体细胞突变数据,推断克隆群体时主要评估了细胞普遍性(prevalences),并解释了由于片段拷贝数变异(segmental copy-number changes)和正常细胞污染(normal-cell contamination)引起的等位基因不平衡。本研究还利用单细胞测序验证了PyClone推断克隆和亚克隆细胞群体的准确性。
Abstract:
We introduce PyClone, a statistical model for inference of clonal population structures in cancers. PyClone is a Bayesian clustering method for grouping sets of deeply sequenced somatic mutations into putative …
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We introduce PyClone, a statistical model for inference of clonal population structures in cancers. PyClone is a Bayesian clustering method for grouping sets of deeply sequenced somatic mutations into putative clonal clusters while estimating their cellular prevalences and accounting for allelic imbalances introduced by segmental copy-number changes and normal-cell contamination. Single-cell sequencing validation demonstrates PyClone's accuracy.
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684.
笑对人生
(2022-10-05 00:01):
#paper doi: 10.1186/s13059-016-0893-4. DeconstructSigs: delineating mutational processes in single tumors distinguishes DNA repair deficiencies and patterns of carcinoma evolution. Genome Biol. 2016 Feb 22;17:31.
突变信号(或突变特征)(mutational signature)首次提出来自Alexandrov LB, et al. Nature, 2013.的一项研究,当时利用非负矩阵分解(Non-negative matrix factorization,NMF)算法共发现21种mutational signature,每个signature包含96种不同三核苷酸突变(96 trinucleotide contexts)。最近来自science的研究报道了58种未被识别的mutational signature(Degasperi A, Science. 2022.)。与以往的研究相比,本研究开发的deconstructSigs包能够对单个肿瘤样本分析由环境暴露、DNA损伤修复异常和诱变等引起的突变信号。目前cosmic网站(https://cancer.sanger.ac.uk/signatures/)已经根据不同变异类型分成四大类signatures,分别是SBS Signature(Single base substitutions,95种亚signature)、DBS Signature(Doublet Base Substitution,11种亚signature)、ID Signatures(Small insertions and deletions,18种亚signature)和CN Signatures(Copy Number Variantions,24种亚signature)。deconstructSigs包的分析步骤包括(1)利用mut.to.sigs.input构建输入文件。(2)利用whichSignatures进行Signature 预测。这里提到的NMF是一种用于发现数据特征的算法,之前在图像识别领域很常用,较其他PCA或SVD等算法相比,保证了矩阵元素为非负(在大多数应用场景种负值元素大多数是无意义的)。NMF的基本思想是对于任意给定的一个非负矩阵V,其能够寻找到一个非负矩阵W和一个非负矩阵H,满足条件V=W*H,从而将一个非负的矩阵分解为左右两个非负矩阵的乘积。V分解为矩阵W和H的过程需要不断地迭代,直至矩阵W和H收敛才停止。V矩阵中每一列代表一个观测(observation),每一行代表一个特征(feature),比如RNAseq的样本(列)和基因(行)的表达矩阵;W矩阵称为基矩阵(行列式的值不等于0,就是基矩阵),H矩阵称为系数矩阵或权重矩阵。这时用系数矩阵H代替原始矩阵,就可以实现对原始矩阵进行降维,得到数据特征的降维矩阵,从而减少存储空间。
Abstract:
BACKGROUND: Analysis of somatic mutations provides insight into the mutational processes that have shaped the cancer genome, but such analysis currently requires large cohorts. We develop deconstructSigs, which allows the …
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BACKGROUND: Analysis of somatic mutations provides insight into the mutational processes that have shaped the cancer genome, but such analysis currently requires large cohorts. We develop deconstructSigs, which allows the identification of mutational signatures within a single tumor sample.RESULTS: Application of deconstructSigs identifies samples with DNA repair deficiencies and reveals distinct and dynamic mutational processes molding the cancer genome in esophageal adenocarcinoma compared to squamous cell carcinomas.CONCLUSIONS: deconstructSigs confers the ability to define mutational processes driven by environmental exposures, DNA repair abnormalities, and mutagenic processes in individual tumors with implications for precision cancer medicine.
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685.
笑对人生
(2022-10-03 23:59):
#paper doi: 10.1038/s41416-022-01913-4. Comprehensive assessment of actionable genomic alterations in primary colorectal carcinoma using targeted next-generation sequencing. Br J Cancer. 2022 Oct;127(7):1304-1311.
这是一篇设计思路较为简单的原发结直肠癌体细胞突变检测文章,检测项目包括SNV(单核苷酸变异)、small INDELS(小的插入或缺失)、CNV(拷贝数变异)、TMB(肿瘤突变负荷)和microsatellite status(微卫星状态)。使用基于扩增子的靶向二代测序技术,设计靶向测序panel为428 cancer-related genes。使用的测序平台为Ion Proton sequencer using the Ion PI chip。临床样本的主要信息为澳大利亚队列,575份原发CRC(结肠腺癌)的FFPE样本,按取样部位划分,45.6%来自右侧colon(结肠),剩下54.4%来自左侧结肠。该篇文章主要的亮点是在对突变数据进行解读时,始终围绕着临床用药进行对比或探讨。主要值得关注的发现包括(1)在MSI-H的CRCs,BRAF是突变频率最高的原癌基因,占比为71%,其次是抑癌基因RNF43(63%)、KMT2C(50%)、APC(48%)、FAT1(48%)、ATM(39%)和ARID1A(39%)。在MSS的CRC中,APC和TP53是突变频率最高的抑癌基因,占比分别是74%和67%,突变频率最高的原癌基因是KRAS(47%)、PIK3CA(21%)和BRAF(13%)。413基因的拷贝数变异图谱也发现了MSI-H和MSS间存在差异。(2)MSI-H组患者的TMBs中位值显著高于MSS组。左侧结肠,只有5.6%是MSI-H,右侧结肠,1/3是MSI-H。47%的MSI-H患者存在至少一种loss of function(功能丧失)的突变导致ICIs治疗不佳。在MSS且RAS/RAF野生型突变的CRC患者中,59%含有至少一个可采取anti-EGFR靶向治疗的actionable mutation。actionable mutation理解为目前具有明确治疗策略的突变。随着NGS高通量测序的普及,肿瘤基因检测会报告大量的突变,其中包含具有临床意义的突变,而这些突变又包括可评估预后的突变、目前已经有批准的或正在临床试验的靶向药基因突变。(3)根据生物标志物(未找到具体标准),对复发晚期(III或IV)的CRC患者,分成6类,分别是MSI、On-label、On-label plus Off-label、Off-label、WT-RAS/RAF和WT-RAS/RAF plus Off-label。这里的on-label是指按药物包装上标注的适应症使用,off-label意为超出所标注的适应症用药。
Abstract:
BACKGROUND: The clinical utility of comprehensive genomic profiling (CGP) for guiding treatment has gradually become the standard-of-care procedure for colorectal carcinoma (CRC). Here, we comprehensively assess emerging targeted therapy biomarkers …
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BACKGROUND: The clinical utility of comprehensive genomic profiling (CGP) for guiding treatment has gradually become the standard-of-care procedure for colorectal carcinoma (CRC). Here, we comprehensively assess emerging targeted therapy biomarkers using CGP in primary CRC.METHODS: A total of 575 primary CRCs were sequenced by ACTOnco® assay for genomic alterations, tumour mutational burden (TMB), and microsatellite instability (MSI).RESULTS: Eighteen percent of patients were detected as MSI-High (MSI-H), and the remaining cases were classified as microsatellite stable (MSS). Driver mutation prevalence in MSS CRCs were APC (74%), TP53 (67%), KRAS (47%), PIK3CA (21%) and BRAF (13%). The median TMBs for MSI-H and MSS patients were 37.8 mutations per mega base (mut/Mb) and 3.9 mut/Mb, respectively. Forty-seven percent of MSI-H CRC harboured at least one loss-of-function mutations in genes that may hamper immune checkpoint blockade. Among MSS RAS/RAF wild-type CRCs, 59% had at least one actionable mutation that may compromise the efficacy of anti-EGFR therapy. For late-stage CRC, 51% of patients are eligible for standard care actionability and the remaining 49% could be enrolled in clinical trials with investigational drugs.CONCLUSIONS: This study highlights the essential role of CGP for identifying rational targeted therapy options in CRC.
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686.
颜林林
(2022-10-03 11:15):
#paper doi:10.1038/s41398-022-02189-1 Translational Psychiatry, 2022, The phenotypic spectrum and genotype-phenotype correlations in 106 patients with variants in major autism gene CHD8. 这篇论文的研究主题,是CHD8基因突变与表型的关系。该基因在既往研究中已被报道与孤独症(autism)有关。这是一篇系统性综述,收集并整理了来自17篇论文的病例数据,对其中有CHD8突变信息的病例,还联系相应医生,对临床信息进行了补充完整。结合所收集的表型信息,与突变谱进行关联分析。对于部分开展了甲基化检测的病例,还进行了表观特征的分析,找到与CHD8单倍体剂量不足(haploinsufficiency)相关的修饰。这是一篇针对某个已知疾病相关基因,进行深入研究的很好范例。此研究还提供了在线网站,允许提交关于CHD8的新临床数据,使共同推动与之相关的孤独症研究和诊疗探索。
Abstract:
CHD8, a major autism gene, functions in chromatin remodelling and has various roles involving several biological pathways. Therefore, unsurprisingly, previous studies have shown that intellectual developmental disorder with autism and …
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CHD8, a major autism gene, functions in chromatin remodelling and has various roles involving several biological pathways. Therefore, unsurprisingly, previous studies have shown that intellectual developmental disorder with autism and macrocephaly (IDDAM), the syndrome caused by pathogenic variants in CHD8, consists of a broad range of phenotypic abnormalities. We collected and reviewed 106 individuals with IDDAM, including 36 individuals not previously published, thus enabling thorough genotype-phenotype analyses, involving the CHD8 mutation spectrum, characterization of the CHD8 DNA methylation episignature, and the systematic analysis of phenotypes collected in Human Phenotype Ontology (HPO). We identified 29 unique nonsense, 25 frameshift, 24 missense, and 12 splice site variants. Furthermore, two unique inframe deletions, one larger deletion (exons 26-28), and one translocation were observed. Methylation analysis was performed for 13 patients, 11 of which showed the previously established episignature for IDDAM (85%) associated with CHD8 haploinsufficiency, one analysis was inconclusive, and one showing a possible gain-of-function signature instead of the expected haploinsufficiency signature was observed. Consistent with previous studies, phenotypical abnormalities affected multiple organ systems. Many neurological abnormalities, like intellectual disability (68%) and hypotonia (29%) were observed, as well as a wide variety of behavioural abnormalities (88%). Most frequently observed behavioural problems included autism spectrum disorder (76%), short attention span (32%), abnormal social behaviour (31%), sleep disturbance (29%) and impaired social interactions (28%). Furthermore, abnormalities in the digestive (53%), musculoskeletal (79%) and genitourinary systems (18%) were noted. Although no significant difference in severity was observed between males and females, individuals with a missense variant were less severely affected. Our study provides an extensive review of all phenotypic abnormalities in patients with IDDAM and provides clinical recommendations, which will be of significant value to individuals with a pathogenic variant in CHD8, their families, and clinicians as it gives a more refined insight into the clinical and molecular spectrum of IDDAM, which is essential for accurate care and counselling.
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687.
笑对人生
(2022-10-02 23:49):
#paper doi: 10.1016/j.omtn.2021.12.009. Computational elucidation of spatial gene expression variation from spatially resolved transcriptomics data.Mol Ther Nucleic Acids. 2021 Dec 11;27:404-411.
尽管由于技术限制,空间转录组(spatial transcriptomics,ST)无法实现真正的单细胞空间转录组,然而,相对于single cell transcriptomics,ST却可以提供重要的细胞空间位置信息。识别空间变异基因(Spatially Variable Gene,SVGs),即找到表达与空间位置相关的基因,是ST数据分析的重要内容之一。SVGs有助于系统地分析特定位置细胞状态、推断细胞间通讯,确定空间组织病理表型与基因表达的关系。与对不同区域直接做差异表达分析方法不同的是,高可变基因分析能够揭示跨区域间的类梯度表达模式变化,例如癌变区和非癌区之间的过渡区域表达模式。本综述系统且详细地总结了目前最前沿的识别SVGs工具及其背后涉及的算法。作者根据算法原理,将SVGs工具分为三大类,分别是基于统计学模型、基于机器学习和基于空间网格。作者认为,目前大多数方法都存在运存消耗过大和输出的统计显著性p值为0过多的问题,此外,缺乏对各个工具相比较的评价指标。这里提到莫兰指数(Moran‘s I),它是一种评价空间自相关(spatial autocorrelation)的统计学方法,来源于地理学。Moran’s I 的取值范围在-1到1之间,Moran’s I>0表示空间正相关,值越大,空间相关性越明显。Moran’s I<0表示空间负相关性,值越小,空间差异越大。否则,Moran’s I=0,空间呈随机性。
Abstract:
Recent advances in spatially resolved transcriptomics (SRT) have revolutionized biological and medical research and enabled unprecedented insight into the functional organization and cell communication of tissues and organs i. Identifying …
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Recent advances in spatially resolved transcriptomics (SRT) have revolutionized biological and medical research and enabled unprecedented insight into the functional organization and cell communication of tissues and organs i. Identifying and elucidating gene spatial expression variation (SE analysis) is fundamental to elucidate the SRT landscape. There is an urgent need for public repositories and computational techniques of SRT data in SE analysis alongside technological breakthroughs and large-scale data generation. Increasing efforts to use techniques in SE analysis have been made. However, these attempts are widely scattered among a large number of studies that are not easily accessible or comprehensible by both medical and life scientists. This study provides a survey and a summary of public resources on SE analysis in SRT studies. An updated systematic overview of state-of-the-art computational approaches and tools currently available in SE analysis are presented herein, emphasizing recent advances. Finally, the present study explores the future perspectives and challenges of techniques in SE analysis. This study guides medical and life scientists to look for dedicated resources and more competent tools for characterizing spatial patterns of gene expression.
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688.
颜林林
(2022-10-02 15:26):
#paper doi:10.1186/s12859-022-04948-9 BMC Bioinformatics, 2022, Visualizing the knowledge structure and evolution of bioinformatics. 这篇文章用了一些生物信息学中常用的数据分析方法和可视化方法,来研究生物信息学学科本身。对过去几十年所发表的相关论文摘要文本的分析,展示了一些研究模式变迁过程(如从纯理论性的模型计算到堆机器学习模型)以及相应的知识结构的变化过程。思路上很新颖,正文中以UMAP点图展示知识结构的方式也很有创意。
Abstract:
BACKGROUND: Bioinformatics has gained much attention as a fast growing interdisciplinary field. Several attempts have been conducted to explore the field of bioinformatics by bibliometric analysis, however, such works did …
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BACKGROUND: Bioinformatics has gained much attention as a fast growing interdisciplinary field. Several attempts have been conducted to explore the field of bioinformatics by bibliometric analysis, however, such works did not elucidate the role of visualization in analysis, nor focus on the relationship between sub-topics of bioinformatics.RESULTS: First, the hotspot of bioinformatics has moderately shifted from traditional molecular biology to omics research, and the computational method has also shifted from mathematical model to data mining and machine learning. Second, DNA-related topics are bridge topics in bioinformatics research. These topics gradually connect various sub-topics that are relatively independent at first. Third, only a small part of topics we have obtained involves a number of computational methods, and the other topics focus more on biological aspects. Fourth, the proportion of computing-related topics hit a trough in the 1980s. During this period, the use of traditional calculation methods such as mathematical model declined in a large proportion while the new calculation methods such as machine learning have not been applied in a large scale. This proportion began to increase gradually after the 1990s. Fifth, although the proportion of computing-related topics is only slightly higher than the original, the connection between other topics and computing-related topics has become closer, which means the support of computational methods is becoming increasingly important for the research of bioinformatics.CONCLUSIONS: The results of our analysis imply that research on bioinformatics is becoming more diversified and the ranking of computational methods in bioinformatics research is also gradually improving.
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689.
笑对人生
(2022-10-01 23:59):
#paper doi: 10.1038/s41586-018-0414-6. RNA velocity of single cells. Nature. 2018 Aug;560(7719):494-498.
本研究首次将RNA速率(RNA velocity)这一概念引入单细胞转录组测序数据科学中,即利用新生(未剪切)和成熟(剪切)mRNA相对丰度变化来评估基因剪切和降解的速率。此外,研究者运用该概念揭示了小鼠胚胎海马组织和人类胚胎大脑中细胞转录动力学特征,表明了RNA速率在单细胞数据科学中的应用价值。RNA速率的发现:在真核生物中,细胞核的DNA首先经过转录形成初级mRNA(或未成熟mRNA),接着需要经过加工(可变剪接)才产生成熟的mRNA。在这个过程中,细胞内就可能存在不同状态的mRNAs。传统转录组测序的mRNA富集方法是利用带有oligo(dT)的磁珠对mRNA进行分离纯化。本研究通过对不同技术平台的单细胞转录组测序数据进行read检查发现,存在15-25%的reads包含内含子序列(内含子序列在mRNA加工成熟过程会被切掉,在成熟mRNA一般不会存在)。基于这些reads的内含子序列和对应外显子序列可认为它们代表的是未剪接的mRNAs前体。
RNA速率中未剪接(unspliced)和剪接(spliced)事件的预测公式(微积分方程):du/dt=α(t)-β(t)u(t),ds/dt=β(t)u(t)-γ(t)s(t),α表示转录速率,β表示剪接速率,s表示剪切mRNAs分子数,t表示时间,u表示未剪切的mRNA分子数,γ表示降解的速率。RNA速率是由unspliced mRNA形成spliced mRNA和mRNA降解两个事件的动态平衡来决定的。对于给定某个基因的,利用unspliced和spliced分子数可以建立一个线性回归模型,本文将其定义为steady-state model。在这个方程拟合直线上的细胞认为具有正速度(unspliced更占优),细胞处于下方则具有负速度(降解更占优),若在直线上,就处于稳态。
Abstract:
RNA abundance is a powerful indicator of the state of individual cells. Single-cell RNA sequencing can reveal RNA abundance with high quantitative accuracy, sensitivity and throughput. However, this approach captures …
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RNA abundance is a powerful indicator of the state of individual cells. Single-cell RNA sequencing can reveal RNA abundance with high quantitative accuracy, sensitivity and throughput. However, this approach captures only a static snapshot at a point in time, posing a challenge for the analysis of time-resolved phenomena such as embryogenesis or tissue regeneration. Here we show that RNA velocity-the time derivative of the gene expression state-can be directly estimated by distinguishing between unspliced and spliced mRNAs in common single-cell RNA sequencing protocols. RNA velocity is a high-dimensional vector that predicts the future state of individual cells on a timescale of hours. We validate its accuracy in the neural crest lineage, demonstrate its use on multiple published datasets and technical platforms, reveal the branching lineage tree of the developing mouse hippocampus, and examine the kinetics of transcription in human embryonic brain. We expect RNA velocity to greatly aid the analysis of developmental lineages and cellular dynamics, particularly in humans.
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690.
颜林林
(2022-10-01 23:28):
#paper doi:10.1186/s12896-022-00758-2 BMC Biotechnology, 2022, A new method for screening acute/chronic lymphocytic leukemia: dual-label time-resolved fluorescence immunoassay. 本文根据既往研究发现,锁定两个蛋白 S100A8 和 LRG1,作为白血病的早期发现生物标志物,使用 TRFIA(时间分辨的荧光免疫分析,该方法最早出现于2002年左右,参考doi: 10.1016/S0167-7012(01)00352-9 的文章)技术进行高灵敏度的检测,由此建立白血病的外周血早筛方法。本文对此筛查方法,在不同浓度的样本中(包括批间实验)进行了技术验证,并在120例健康人+59例白血病患者中进行了临床验证。
Abstract:
BACKGROUND: Lymphocytic leukemia (LL) is a primary malignant tumor of hematopoietic tissue, which seriously affects the health of children and the elderly. The study aims to establish a new detection …
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BACKGROUND: Lymphocytic leukemia (LL) is a primary malignant tumor of hematopoietic tissue, which seriously affects the health of children and the elderly. The study aims to establish a new detection method for screening acute/chronic LL using time-resolved fluorescence immunoassay (TRFIA) via quantitative detection of S100 calcium binding protein A8 (S100A8) and leucine-rich alpha-2-glycoprotein 1 (LRG1) in serum.METHODS: Here a sandwich TRFIA was optimized and established: Anti-S100A8/LRG1 caputre antibodies immobilized on 96-well plates captured S100A8/LRG1, and then banded together with the anti-S100A8/LRG1 detection antibodies labeled with Europium(III) (Eu3+)/samarium(III) (Sm3+) chelates. Finally time resolved fluorometry measured the fluorescence intensity.RESULTS: The sensitivity of S100A8 was 1.15 ng/mL(LogY = 3.4027 + 0.4091 × LogX, R2 = 0.9828, P < 0.001, dynamic range: 2.1-10,000 ng/mL), and 3.2 ng/mL for LRG1 (LogY = 3.3009 + 0.4082 × LogX, R2 = 0.9748, P < 0.001, dynamic range: 4.0-10,000 ng/mL). The intra-assay and inter-assay CVs were low, ranging from 5.75% to 8.23% for S100A8 and 5.30% to 9.45% for LRG1 with high specificity and affinity in serum samples. Bland-Altman plots indicated TRFIA and ELISA kits have good agreement in clinical serum samples. Additionally, the cutoff values for S100A8 and LRG1 were 1849.18 ng/mL and 588.08 ng/mL, respectively.CONCLUSION: The present TRFIA method could be used for the quantitative detection of S100A8 and LRG1 in serum, and it has high sensitivity, accuracy and specificity. Clinically, this TRFIA method could be suitable for screening of LL via the quantitative detection of S100A8 and LRG1.
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691.
龙海晨
(2022-10-01 21:58):
#paper Rowold D, Garcia-Bertrand R, Calderon S, Rivera L, Benedico DP, Alfonso Sanchez MA, Chennakrishnaiah S, Varela M, Herrera RJ. At the southeast fringe of the Bantu expansion: genetic diversity and phylogenetic relationships to other sub-Saharan tribes. Meta Gene. 2014 Oct 2;2:670-85. doi: 10.1016/j.mgene.2014.08.003. PMID: 25606451; PMCID: PMC4287857. 这是一篇研究撒哈拉以南的非洲的部落扩张的文章,介绍这篇文章,主要是因为咱们群里是多学科融合,我觉得咱们可以逐步开展合作。一般来说,研究几个文明的关系,通常可能从考古,人文,文化方面。这篇文章是通过对基因的分析研究来论证一个种族部落文明的迁徙发展的。通过对基因的研究分析,画出了班图人发源,迁徙,发展的路线。相当于把基因研究、数据分析运用在人文研究方面做出某些论证。咱们群里也可以试着开展合作。
Abstract:
Here, we present 12 loci paternal haplotypes (Y-STR profiles) against the backdrop of the Y-SNP marker system of Bantu males from the Maputo Province of Southeast Africa, a region believed …
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Here, we present 12 loci paternal haplotypes (Y-STR profiles) against the backdrop of the Y-SNP marker system of Bantu males from the Maputo Province of Southeast Africa, a region believed to represent the southeastern fringe of the Bantu expansion. Our Maputo Bantu group was analyzed within the context of 27 geographically relevant reference populations in order to ascertain its genetic relationship to other Bantu and non Bantu (Pygmy, Khoisan and Nilotic) sub-equatorial tribes from West and East Africa. This study entails statistical pair wise comparisons and multidimensional scaling based on YSTR Rst distances, network analyses of Bantu (B2a-M150) and Pygmy (B2b-M112) lineages as well as an assessment of Y-SNP distribution patterns. Several notable findings include the following: 1) the Maputo Province Bantu exhibits a relatively close paternal affinity with both east and west Bantu tribes due to high proportion of Bantu Y chromosomal markers, 2) only traces of Khoisan (1.3%) and Pygmy (1.3%) markers persist in the Maputo Province Bantu gene pool, 3) the occurrence of R1a1a-M17/M198, a member of the Eurasian R1a-M420 branch in the population of the Maputo Province, may represent back migration events and/or recent admixture events, 4) the shared presence of E1b1b1-M35 in all Tanzanian tribes examined, including Bantu and non-Bantu groups, in conjunction with its nearly complete absence in the West African populations indicate that, in addition to a shared linguistic, cultural and genetic heritage, geography (e.g., east vs. west) may have impacted the paternal landscape of sub-Saharan Africa, 5) the admixture and assimilation processes of Bantu elements were both highly complex and region-specific.
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692.
小擎子
(2022-09-30 23:54):
#paper doi:10.1016/j.cell.2022.09.005 Cell, 2022, Pan-cancer analyses reveal cancer-type-specific fungal ecologies and bacteriome interactions。新鲜出炉的首个泛癌症真菌生物组图谱。35种癌症,17401个样本(组织,血液,血浆)。文章发现,细菌在肿瘤微生物组中优于真菌.但宏基因组的生物信息学分析,确实可以支持样本里真菌的存在。文章也用染色体显色的方法在癌组织中可视化了人类肿瘤里的真菌,并发现真菌会有癌症类型特异性的定位模式。真菌染色主要在胰腺癌,乳腺癌和卵巢癌中存在,但是大部分都定位在黑色素瘤和肺癌里的巨噬细胞。文献还使用了无监督分类揭示真菌共生驱动的真菌-细菌-免疫簇.这种免疫簇可以区分免疫反应亚型。
Abstract:
Cancer-microbe associations have been explored for centuries, but cancer-associated fungi have rarely been examined. Here, we comprehensively characterize the cancer mycobiome within 17,401 patient tissue, blood, and plasma samples across …
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Cancer-microbe associations have been explored for centuries, but cancer-associated fungi have rarely been examined. Here, we comprehensively characterize the cancer mycobiome within 17,401 patient tissue, blood, and plasma samples across 35 cancer types in four independent cohorts. We report fungal DNA and cells at low abundances across many major human cancers, with differences in community compositions that differ among cancer types, even when accounting for technical background. Fungal histological staining of tissue microarrays supported intratumoral presence and frequent spatial association with cancer cells and macrophages. Comparing intratumoral fungal communities with matched bacteriomes and immunomes revealed co-occurring bi-domain ecologies, often with permissive, rather than competitive, microenvironments and distinct immune responses. Clinically focused assessments suggested prognostic and diagnostic capacities of the tissue and plasma mycobiomes, even in stage I cancers, and synergistic predictive performance with bacteriomes.
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693.
小W
(2022-09-30 23:53):
#paper https://doi.org/10.1038/s41573-022-00538-9 The expanding role for small molecules in immuno-oncology. 发表在 Nat Rev Drug Discov (2022). 的一篇小分子在免疫肿瘤中应用的综述文章。从靶向致瘤途径的药物 、 靶向代谢途径 、 小分子ICIs 三个方向,分别描述 了用于直接刺激抗肿瘤免疫反应的不同靶点小分子的发现 、 优缺点、成药 、 临床试验 进展等。本文对 不同机理小分子药物的展望 以及 各靶点的临床试验进展 , 还是挺有意思的。
Abstract:
The advent of immune checkpoint inhibition (ICI) using antibodies against PD1 and its ligand PDL1 has prompted substantial efforts to develop complementary drugs. Although many of these are antibodies directed …
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The advent of immune checkpoint inhibition (ICI) using antibodies against PD1 and its ligand PDL1 has prompted substantial efforts to develop complementary drugs. Although many of these are antibodies directed against additional checkpoint proteins, there is an increasing interest in small-molecule immuno-oncology drugs that address intracellular pathways, some of which have recently entered clinical trials. In parallel, small molecules that target pro-tumorigenic pathways in cancer cells and the tumour microenvironment have been found to have immunostimulatory effects that synergize with the action of ICI antibodies, leading to the approval of an increasing number of regimens that combine such drugs. Combinations with small molecules targeting cancer metabolism, cytokine/chemokine and innate immune pathways, and T cell checkpoints are now under investigation. This Review discusses the recent milestones and hurdles encountered in this area of drug development, as well as our views on the best path forward.
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694.
cellsarts
(2022-09-30 23:43):
#paper DOI 10.1074/jbc.M111.293795 Crystal Structure of Human -Galactosidase
STRUCTURAL BASIS OF GM1 GANGLIOSIDOSIS AND MORQUIO B DISEASES* author: Umeharu Ohto , THE JOURNAL OF BIOLOGICAL CHEMISTRY January 13, 2012 人β -半乳糖苷酶的晶体结构
GM1神经节肥瘦症和Morquio B是常染色体隐性遗传与神经退行性疾病相关的溶酶体积储病, 这些疾病是因溶酶体缺乏β -半乳糖苷酶引起的,β -半乳糖苷酶缺乏导致β -半乳糖苷酶底物---GM1神经节苷和角蛋白硫酸盐---的积累分别导致了侏儒症和骨骼异常。缺乏 β -半乳糖苷酶会导致溶酶体储存性疾病。文章首次报道了人类β -半乳糖苷酶的晶体结构。人类β -半乳糖苷酶是由TIM 催化结构域和两个β -折叠结构域所组成人类β -半乳糖苷酶突变可分为直接影响配体识别的突变、蛋白质内部核心突变、或位于蛋白质表面的突变。文章探讨了这一些结构突变与:对溶酶体储存疾病的关系。
IF:4.000Q2
The Journal of biological chemistry,
2012-Jan-13.
DOI: 10.1074/jbc.M111.293795
PMID: 22128166
Abstract:
G(M1) gangliosidosis and Morquio B are autosomal recessive lysosomal storage diseases associated with a neurodegenerative disorder or dwarfism and skeletal abnormalities, respectively. These diseases are caused by deficiencies in the …
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G(M1) gangliosidosis and Morquio B are autosomal recessive lysosomal storage diseases associated with a neurodegenerative disorder or dwarfism and skeletal abnormalities, respectively. These diseases are caused by deficiencies in the lysosomal enzyme β-d-galactosidase (β-Gal), which lead to accumulations of the β-Gal substrates, G(M1) ganglioside, and keratan sulfate. β-Gal is an exoglycosidase that catalyzes the hydrolysis of terminal β-linked galactose residues. This study shows the crystal structures of human β-Gal in complex with its catalytic product galactose or with its inhibitor 1-deoxygalactonojirimycin. Human β-Gal is composed of a catalytic TIM barrel domain followed by β-domain 1 and β-domain 2. To gain structural insight into the molecular defects of β-Gal in the above diseases, the disease-causing mutations were mapped onto the three-dimensional structure. Finally, the possible causes of the diseases are discussed.
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695.
林李泽强
(2022-09-30 23:42):
#paper doi:10.1073/pnas.1910666116,PNAS, 2019, Population-based neuroimaging reveals traces of childbirth in the maternal brain.
这项利用神经成像和机器学习(大脑年龄分析范式),分析了来自the UK Biobank的12021名中年女性的大脑结构特征,结果表明,与未分娩的同龄人相比,产妇大脑老化证据较少(即产妇展现出更'年轻'的大脑)。分娩(生育)和“看起来更年轻”的大脑之间的关系不受常见的基因变异或相关的混杂因素影响。结果表明,胎次可能涉及神经变化,可能会影响女性晚年的大脑老化,当然这需要更进一步的纵向研究确认。这项研究的结果还是相当有意思,与我们平时的认知(生多孩子的人‘老得快’)是截然相反。
IF:9.400Q1
Proceedings of the National Academy of Sciences of the United States of America,
2019-10-29.
DOI: 10.1073/pnas.1910666116
PMID: 31615888
Abstract:
Maternal brain adaptations have been found across pregnancy and postpartum, but little is known about the long-term effects of parity on the maternal brain. Using neuroimaging and machine learning, we …
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Maternal brain adaptations have been found across pregnancy and postpartum, but little is known about the long-term effects of parity on the maternal brain. Using neuroimaging and machine learning, we investigated structural brain characteristics in 12,021 middle-aged women from the UK Biobank, demonstrating that parous women showed less evidence of brain aging compared to their nulliparous peers. The relationship between childbirths and a "younger-looking" brain could not be explained by common genetic variation or relevant confounders. Although prospective longitudinal studies are needed, the results suggest that parity may involve neural changes that could influence women's brain aging later in life.
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696.
Arwen
(2022-09-30 23:41):
#paper doi:https://doi.org/10.48550/arXiv.2202.02000,Cross-Modality Multi-Atlas Segmentation via Deep Registration and Label Fusion 基于多图谱的分割技术是医学影像分割问题中一个比较有效的方法。一般来说,多图谱技术通过将多个图谱非线性配准到个体图像,并将对应的图谱分割图变换到个体图像空间,并利用融合算法融合多图谱分割图得到个体图像的分割图。但是,传统的多图谱分割技术受限两点:一是配准过程计算量太大,二是标签融合算法会影响到最终分割图的精度。这篇文章构建了两个神经网络,一个网络用于生成形变场,将图谱映射到个体空间,另一个网络用于计算各个图谱分割标签的融合权重,用于后续的分割图融合。不过这篇文章做的一般,我个人觉得不咋地。配准网络部分明明使用scaling and squaring算法就可以生成合理的形变场,非要做没啥必要的创新,应该就是强行扩充文章内容吧。
arXiv,
2022.
DOI: 10.48550/arXiv.2202.02000
Abstract:
Multi-atlas segmentation (MAS) is a promising framework for medical image segmentation. Generally, MAS methods register multiple atlases, i.e., medical images with corresponding labels, to a target image; and the transformed …
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Multi-atlas segmentation (MAS) is a promising framework for medical image segmentation. Generally, MAS methods register multiple atlases, i.e., medical images with corresponding labels, to a target image; and the transformed atlas labels can be combined to generate target segmentation via label fusion schemes. Many conventional MAS methods employed the atlases from the same modality as the target image. However, the number of atlases with the same modality may be limited or even missing in many clinical applications. Besides, conventional MAS methods suffer from the computational burden of registration or label fusion procedures. In this work, we design a novel cross-modality MAS framework, which uses available atlases from a certain modality to segment a target image from another modality. To boost the computational efficiency of the framework, both the image registration and label fusion are achieved by well-designed deep neural networks. For the atlas-to-target image registration, we propose a bi-directional registration network (BiRegNet), which can efficiently align images from different modalities. For the label fusion, we design a similarity estimation network (SimNet), which estimates the fusion weight of each atlas by measuring its similarity to the target image. SimNet can learn multi-scale information for similarity estimation to improve the performance of label fusion. The proposed framework was evaluated by the left ventricle and liver segmentation tasks on the MM-WHS and CHAOS datasets, respectively. Results have shown that the framework is effective for cross-modality MAS in both registration and label fusion.
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697.
Ricardo
(2022-09-30 23:32):
#paper doi:https://doi.org/10.48550/arXiv.2202.03563,Aladdin: Joint Atlas Building and Diffeomorphic Registration Learning with Pairwise Alignment 图谱构建和图像配准是医学影像分析中的重要任务,但是图谱估计和无参形变的计算需要极高的计算代价。此外,以前的图谱构建方法通常计算模糊图谱和每个单独的图像之间的相似度驱动模型优化,这可能会增加预估的图谱和个体图像之间配准的难度,因为预估的模糊图谱相比个体图像不具有更清楚的解剖结构。这篇文章基于forward model从多个角度约束了图谱的生成空间,并做了充足的理论分析。但是由于模型较为复杂,并且涉及所有图像的同时优化,所以不太适合3d图像数据,目前还只是在2d图像数据上做实验。
arXiv,
2022.
DOI: 10.48550/arXiv.2202.03563
Abstract:
Atlas building and image registration are important tasks for medical image analysis. Once one or multiple atlases from an image population have been constructed, commonly (1) images are warped into …
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Atlas building and image registration are important tasks for medical image analysis. Once one or multiple atlases from an image population have been constructed, commonly (1) images are warped into an atlas space to study intra-subject or inter-subject variations or (2) a possibly probabilistic atlas is warped into image space to assign anatomical labels. Atlas estimation and nonparametric transformations are computationally expensive as they usually require numerical optimization. Additionally, previous approaches for atlas building often define similarity measures between a fuzzy atlas and each individual image, which may cause alignment difficulties because a fuzzy atlas does not exhibit clear anatomical structures in contrast to the individual images. This work explores using a convolutional neural network (CNN) to jointly predict the atlas and a stationary velocity field (SVF) parameterization for diffeomorphic image registration with respect to the atlas. Our approach does not require affine pre-registrations and utilizes pairwise image alignment losses to increase registration accuracy. We evaluate our model on 3D knee magnetic resonance images (MRI) from the OAI-ZIB dataset. Our results show that the proposed framework achieves better performance than other state-of-the-art image registration algorithms, allows for end-to-end training, and for fast inference at test time.
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698.
钟鸣
(2022-09-30 22:51):
#paper doi:10.1128/IAI.71.11.6192-6198.2003 , infection and immunity, 2003, Genetic basis for the structural difference between Streptococcus pneumoniae serotype 15B and 15C capsular polysaccharides
肺炎链球菌血清型众多,血清型的不同取决于荚膜结构,且荚膜在激发免疫反应时占主导作用,因此血清型间缺少交叉保护作用。对肺炎球菌荚膜形成机制的深入了解有助于指导疫苗的开发。
此前有报道称血清型15B与15C会相互转化,这里,作者通过比较这两种血清型的荚膜编码基因,发现编码O-乙酰转移酶的基因中TA序列重复数量不同决定该酶是否有完全活性,进而导致荚膜结构不同。而TA数量的可变性,正是两种血清型可以相互转化的原因。
作者将荚膜结构不同的原因定位到了具体的基因,感觉是大道至简的规律。也为其他细菌的荚膜研究提供了参考和借鉴。
Abstract:
In a search for the genetic basis for the structural difference between the related Streptococcus pneumoniae capsular serotypes 15B and 15C and for the reported reversible switching between these serotypes, …
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In a search for the genetic basis for the structural difference between the related Streptococcus pneumoniae capsular serotypes 15B and 15C and for the reported reversible switching between these serotypes, the corresponding capsular polysaccharide synthesis (cps) loci were investigated by keeping in mind that at the structural level, the capsules differ only in O acetylation. The cps locus of a serotype 15B strain was identified, partially PCR amplified with primers based on the related serotype 14 sequence, and sequenced. Sequence analysis revealed, among other open reading frames, an intact open reading frame (designated cps15bM) whose product, at the protein level, exhibited characteristics of previously identified acetyltransferases. Genetic analysis of the corresponding region in a serotype15C strain indicated that the same gene was present but had a premature stop in translation. Closer analysis indicated that the serotype 15B gene contained a short tandem TA repeat consisting of eight TA units. In serotype 15C, this gene contained nine TA units that resulted in a frameshift and a truncated product. Genetic analysis of 17 serotype 15B and 15C clinical isolates revealed a perfect correlation between the serotype and the length of the short tandem repeat in the putative O-acetyltransferase gene. The number of TA repeating units varied between seven and nine in the various isolates. Together, the data strongly suggest that the structural difference between serotypes 15B and 15C is based on variation in the short tandem TA repeat in the O-acetyltransferase gene and that the transition between serotypes is due to slipped-strand mispairing with deletion or insertion of TA units in the cps15bM gene.
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699.
林海onrush
(2022-09-30 22:25):
#paper arXiv, 2209.00796 (2022) , Diffusion Models: A Comprehensive Survey of Methods and Applications, Diffusion model在诸多领域都有着优异的表现,并且考虑到不同领域的应用中diffusion model产生了不同的变形,论文系统地介绍了diffusion model的应用研究,其中包含如下领域:计算机视觉,NLP、波形信号处理、多模态建模、分子图建模、时间序列建模、对抗性净化。工作的主要贡献总结如下:新的分类方法:我们对扩散模型和其应用提出了一种新的、系统的分类法。具体将模型分为三类:采样速度增强、最大似然估计增强、数据泛化增强。进一步地,将扩散模型的应用分为七类:计算机视觉,NLP、波形信号处理、多模态建模、分子图建模、时间序列建模、对抗性净化。全面地概述了现代扩散模型及其应用,展示了每种扩散模型的主要改进,和原始模型进行了必要的比较,并总结了相应的论文。扩散模型的基本思想是正向扩散过程来系统地扰动数据中的分布,然后通过学习反向扩散过程恢复数据的分布,这样就了产生一个高度灵活且易于计算的生成模型。
arXiv,
2022.
DOI: 10.48550/arXiv.2209.00796
Abstract:
Diffusion models are a class of deep generative models that have shown impressive results on various tasks with a solid theoretical foundation. Despite demonstrated success than state-of-the-art approaches, diffusion models …
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Diffusion models are a class of deep generative models that have shown impressive results on various tasks with a solid theoretical foundation. Despite demonstrated success than state-of-the-art approaches, diffusion models often entail costly sampling procedures and sub-optimal likelihood estimation. Significant efforts have been made to improve the performance of diffusion models in various aspects. In this article, we present a comprehensive review of existing variants of diffusion models. Specifically, we provide the taxonomy of diffusion models and categorize them into three types: sampling-acceleration enhancement, likelihood-maximization enhancement, and data-generalization enhancement. We also introduce the other generative models (i.e., variational autoencoders, generative adversarial networks, normalizing flow, autoregressive models, and energy-based models) and discuss the connections between diffusion models and these generative models. Then we review the applications of diffusion models, including computer vision, natural language processing, waveform signal processing, multi-modal modeling, molecular graph generation, time series modeling, and adversarial purification. Furthermore, we propose new perspectives pertaining to the development of generative models. Github: this https URL.
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700.
洪媛媛
(2022-09-30 22:09):
#paper https://doi.org/10.2144/04372ST03 BioTechniques 37:226-231 (August 2004). AutoDimer: a screening tool for primer-dimer and hairpin structures.这篇文章关于AutoDimer软件,可以分析多重引物之间的dimer和引物自身的hairpin,介绍了软件的序列输入格式、需要输入的参数、比对算法原理和输出的参数和score意义。
Abstract:
The ability to select short DNA oligonucleotide sequences capable of binding solely to their intended target is of great importance in developing nucleic acid based detection technologies. Applications such as …
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The ability to select short DNA oligonucleotide sequences capable of binding solely to their intended target is of great importance in developing nucleic acid based detection technologies. Applications such as multiplex PCR rely on primers binding to unique regions in a genome. Competing side reactions with other primer pairs or template DNA decrease PCR efficiency. Freely available primer design software such as Primer3 screens for potential hairpin and primer-dimer interactions while selecting a single primer pair. The development of multiplex PCR assays (in the range of 5 to 20 loci) requires the screening of all primer pairs for potential cross-reactivity. However, a logistical problem results due to the number of total number of comparisons required. Comparing the primer set for a 10-plex assay (20 total primer sequences) results in 210 primer-primer combinations that must be screened. The ability to screen sets of candidate oligomers rapidly for potential cross-reactivity reduces overall assay development time. Here we report the application of a familiar sliding algorithm for comparing two strands of DNA in an overlapping fashion. The algorithm has been employed in a software package wherein the user can compare multiple sequences in a single computational run. After the screening is completed, a score is assigned to potential duplex interactions exceeding a user-defined threshold. Additional criteria of predicted melting temperature (Tm) and free energy of melting (ΔG) are included for further ranking. Sodium counterion and total stand concentrations can be adjusted for the Tm and ΔG calculations. The predicted interactions are saved in a text file for further evaluation.
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