目的:头颅定位侧位片评估种植支抗辅助的口内Ⅲ类牵引和传统合垫基托式口外前方牵引，纠正单侧唇腭裂患儿因上颌骨发育不足而导致的骨性Ⅲ类错合的效果。方法:2018年3月至2020年10月，广州市妇女儿童医疗中心口腔正畸科用随机数字表法将单侧完全性唇腭裂患儿54例[男24例，女30例，年龄8~12(11.09±1.35)岁]分为3组：传统合垫基托式口外前方牵引组(A组)、种植支抗辅助口内Ⅲ类牵引组(B组)、对照组，每组18例。在矫治开始前(T1)及结束后(T2)分别拍摄头颅定位侧位片，通过Dolphin软件进行颌骨、牙齿以及软组织测量，将头影指标进行组间比较。结果:A组和B组牵引时间分别为(10.51±1.33)个月和(9.20±1.45)个月( P＝0.146)。A组和B组A点平均前移4.08 mm和4.83 mm，ANB角(上牙槽座点A至鼻根点N连线与鼻根点至下牙槽座点B连线构成角)和Wits值(Ao点与Bo点间距离)与对照组比较，差异有统计学意义(均 P<0.01)，上颌骨前移在A组和B组间差异无统计学意义( P>0.05)。B组U6-VRmx平均增加0.46 mm，U1-pp平均增加0.63 mm，均明显小于A组(均 P<0.001)，提示种植支抗辅助的口内Ⅲ类牵引能减少磨牙前移和上颌切牙唇倾。 结论:种植支抗辅助的口内Ⅲ类牵引能明显减少磨牙前移和上颌切牙唇倾等不利的牙齿移动。

染色质拓扑相关结构域(topological associated domain，TAD)是基因组三维结构和转录调控的基本单位。相邻TAD以特征序列边界间隔，形成相对独立的功能域，TAD内部基因的转录受到共同调控，而TAD间彼此互不影响。TAD结构的改变与多种疾病的发生密切相关。本文对TAD的重要组成、特性、对疾病发生的影响及常用的染色质互作研究方法进行综述。

Altered three-dimensional architecture of chromatin influences various genomic regulators and subsequent gene expression in human cancer.However,knowledge of the topological rearrangement of genomic hierarchical layers in cancer is largely limited.Here,by taking advantage of in situ Hi-C,RNA-sequencing,and chromatin immunoprecipitation sequencing(ChIP-seq),we investigated structural reorganization and functional changes in chromosomal compartments,topologically associated domains(TADs),and CCCTC binding factor(CTCF)-mediated loops in gallbladder cancer(GBC)tissues and cell lines.We observed that the chromosomal compartment A/B switch was correlated with CTCF binding levels and gene expression changes.Increased inter-TAD interactions with weaker TAD boundaries were identified in cancer cell lines relative to normal controls.Furthermore,the chromatin short loops and cancer unique loops associated with chromatin remodeling and epithelial-mesenchymal transition activation were enriched in cancer compared with their control counterparts.Cancer-specific enhancer-promoter loops,which contain multiple transcription factor binding motifs,actedas a central element to regulate aberrant gene expression.Depletion of individual enhancers in each loop anchor that connects with promoters led to the inhibition of their corresponding gene expressions.Collectively,our data offer the landscape of hierarchical layers of cancer genome and functional alterations that contribute to the development of GBC.

The spatial organization of the genome plays an important role in the regulation of gene expression.However,the core structural features of animal genomes,such as topologically associated domains (TADs) and chromatin loops,are not prominent in the extremely compact Arabidopsis genome.In this study,we examine the chromatin architecture,as well as their DNA methylation,histone modifications,accessible chromatin,and gene expression,of maize,tomato,sorghum,foxtail millet,and rice with genome sizes ranging from 0.4 to 2.4 Gb.We found that these plant genomes can be divided into mammalian-like A/B compartments.At higher resolution,the chromosomes of these plants can be further partitioned to local A/B compartments that reflect their euchromatin,heterochromatin,and polycomb status.Chromatins in all these plants are organized into domains that are not conserved across species.They show similarity to the Drosophila compartment domains,and are clustered into active,polycomb,repressive,and intermediate types based on their transcriptional activities and epigenetic signatures,with domain border overlaps with the local A/B compartment junctions.In the large maize and tomato genomes,we observed extensive chromatin loops.However,unlike the mammalian chromatin loops that are enriched at the TAD border,plant chromatin loops are often formed between gene islands outside the repressive domains and are closely associated with active compartments.Our study indicates that plants have complex and unique 3D chromatin architectures,which require further study to elucidate their biological functions.

Cho and colleagues uncover a novel mechanism of transcriptional repression of MYC which attributes a tumor-suppressive role to the neighboring PVT1 promoter, and shed light on recurrent chromosomal rearrangements within the MYC locus.In human cells, chromatin is three-dimensionally organized into discrete self-interacting units called topologically associating domains (TADs). TADs are generally preserved across cell lineages and their boundaries are enriched for binding sites of ubiquitous architectural proteins (e.g., CTCF, cohesins, etc.). These domain boundaries are referred to as chromatin "insulators" as they confine enhancer activity within specified TADs. Dynamic looping interactions within a TAD scaffold, or intra-TAD loops, enable finer regulation of enhancer-promoter pairs in different tissue types1.

Interactions between chromatin segments play a large role in functional genomic assays and developments in genomic interaction detection methods have shown interacting topological domains within the genome. Among these methods, Hi-C plays a key role. Here, we present the Genome Interaction Tools and Resources (GITAR), a software to perform a comprehensive Hi-C data analysis, including data preprocessing, normalization, and visualization, as well as anal-ysis of topologically-associated domains (TADs). GITAR is composed of two main modules: (1) HiCtool, a Python library to process and visualize Hi-C data, including TAD analysis; and (2) processed data library, a large collection of human and mouse datasets processed using HiCtool. HiCtool leads the user step-by-step through a pipeline, which goes from the raw Hi-C data to the computation, visualization, and optimized storage of intra-chromosomal contact matrices and TAD coordinates. A large collection of standardized processed data allows the users to compare different datasets in a consistent way, while saving time to obtain data for visualization or additional analyses. More importantly, GITAR enables users without any programming or bioin-formatic expertise to work with Hi-C data. GITAR is publicly available at http://genomegitar.org as an open-source software.

目的 比较种植支抗压低上颌前牙时,不同植入部位种植钉的稳定性.方法 选取需压低上颌前牙的正畸治疗患者90例,其中A组30例于上颌中切牙间唇侧植入1枚种植钉;B组30例于上颌中切牙与侧切牙间唇侧各植入1枚种植钉;另C组30例,于上颌侧切牙与尖牙间唇侧各植入1枚种植钉.比较三种不同植入部位种植钉的松动率.结果 A组松动率为33.33％,B组松动率为11.67％,C组松动率为15.00％.三种不同植入部位种植钉松动率的两两比较,A组松动率高于B组,有统计学意义(P＜0.05).A组松动率高于C组,有统计学意义(P＜0.05).B组和C组松动率的比较,无统计学意义(P＞0.05).结论 使用种植支抗压低上颌前牙时,植入于上颌中切牙与侧切牙间唇侧或上颌侧切牙与尖牙间唇侧,稳定性均优于植入于上颌中切牙间唇侧.

染色质在细胞核内的缠绕、折叠及其在细胞核内的空间排布是真核生物染色质构型的主要特征.在经典DNA探针荧光原位杂交显微观察的基础上,基于新一代测序技术的Hi-C及ChIA-PET染色质构型捕获技术已经被广泛应用于动物及植物细胞核染色质构型的研究中,并以新的角度定义了包括:染色体(质)域(chromosome territory)、A/B染色质区室(compartment A/B)、拓扑偶联结构域(topological associated domains,TADs)、染色质环(chromatin loops)等在内的多个更为精细的染色质构型.利用以上两种主流技术,越来越多的植物物种染色质构型特征被鉴定、分析和比较.本文系统分析和总结了近年来以植物细胞为模型的细胞核染色构型领域取得的重要成果,包括各级染色质构型特征的组成、建立机制和主要影响因素等.在此基础上,分析了目前研究植物染色质构型技术的瓶颈和突破性的技术进展,并对后续研究主要关注的问题和研究内容进行了展望,以期为相关领域的研究提供更多的理论参考和依据.

染色体的空间交互作用被视为影响基因表达调控的重要因素,高通量染色体构象捕获(high-throughput chromosome conformation capture,Hi-C)技术已成为3D基因组学中探索染色体空间交互作用的主要实验手段之一.随着Hi-C样本数据的持续累积以及分析处理流程复杂度的不断提升,基于生物信息学的Hi-C数据分析对探究基因表达的时空调控机制而言,是机遇也是挑战.本文从生物信息学角度,综合阐述了Hi-C的国内外研究现状及发展动态,包括数据标准化、多级结构分析、数据可视化以及三维建模,重点剖析了多级结构中的A/B区室(A/B compartments)、拓扑相关域(topological associated domains,TADs)和染色质环(chromain looping),在此基础上分析了该方向未来可能的研究热点及发展趋势,以期为将基因表达调控的探索从传统线性空间进一步拓展到三维结构空间提供支持.

Chromatins are not randomly packaged in the nucleus and their organization plays important roles in transcription regulation,which is best studied in the mammalian models.Using in situ Hi-C,we have compared the 3D chromatin architectures of rice mesophyll and endosperm,foxtail millet bundle sheath and mesophyll,and maize bundle sheath,mesophyll and endosperm tissues.We found that their global A/B compartment partitions are stable across tissues,while local A/B compartment has tissue-specific dynamic associated with differential gene expression.Plant domains are largely stable across tissues,while new domain border formations are often associated with transcriptional activation in the region.Genes inside plant domains are not conserved across species,and lack significant co-expression behavior unlike those in mammalian TADs.Although we only observed chromatin loops between gene islands in the large genomes,the maize loop gene pairs' syntenic orthologs have shorter physical distances in small genome monocots,suggesting that loops instead of domains might have conserved biological function.Our study showed that plants' chromatin features might not have conserved biological functions as the mammalian ones.