Optimization and quality control of genome-wide Hi-C library preparation.

Highest-throughput chromosome conformation capture (Hi-C) is one of the key assays for genome- wide chromatin interaction studies. It is a time-consuming process that involves many steps and many different kinds of reagents, consumables, and equipments. At present, the reproducibility is unsatisfactory. By optimizing the key steps of the Hi-C experiment, such as crosslinking, pretreatment of digestion, inactivation of restriction enzyme, and in situ ligation etc., we established a robust Hi-C procedure and prepared two biological replicates of Hi-C libraries from the GM12878 cells. After preliminary quality control by Sanger sequencing, the two replicates were high-throughput sequenced. The bioinformatics analysis of the raw sequencing data revealed the mapping-ability and pair-mate rate of the raw data were around 90% and 72%, respectively. Additionally, after removal of self-circular ligations and dangling-end products, more than 96% of the valid pairs were reached. Genome-wide interactome profiling shows clear topological associated domains (TADs), which is consistent with previous reports. Further correlation analysis showed that the two biological replicates strongly correlate with each other in terms of both bin coverage and all bin pairs. All these results indicated that the optimized Hi-C procedure is robust and stable, which will be very helpful for the wide applications of the Hi-C assay.

POU2F2-oriented network promotes human gastric cancer metastasis.

BACKGROUND AND AIMS: Aberrant upregulation of POU2F2 expression has been discovered in metastatic gastric cancer (GC). However, the mechanisms underlying the aberrant upregulation and the potential functions of POU2F2 remain uncertain. DESIGN: The role and mechanism of POU2F2 in GC metastasis were investigated in gastric epithelial cells, GC cell lines and an experimental metastasis animal model by gain of function and loss of function. Upstream and downstream targets of POU2F2 were selected by bioinformatics and identified by luciferase reporter assay, electrophoretic mobility shift assay and chromatin immunoprecipitation PCR. The influence of miR-218 on its putative target genes (POU2F2, ROBO1 and IKK-ß) and GC metastasis was further explored via in vitro and in vivo approaches. RESULTS: Increased POU2F2 expression was detected in metastatic GC cell lines and patient samples. POU2F2 was induced by the activation of nuclear factor (NF)-κB and, in turn, regulated ROBO1 transcription, thus functionally contributing to GC metastasis. Finally, miR-218 was found to suppress GC metastasis by simultaneously mediating multiple molecules in the POU2F2-oriented network. CONCLUSIONS: This study demonstrated that NF-κB and the SLIT2/ROBO1 interaction network with POU2F2 as the central part may exert critical effects on tumour metastasis. Blocking the activation of the POU2F2-oriented metastasis network using miR-218 precursors exemplified a promising approach that sheds light on new strategies for GC treatment.

Construction of CTCF degradation cell line by CRISPR/Cas9 mediated genome editing.

The CCCTC-binding factor (CTCF) is the main insulator protein described in vertebrates. It plays fundamental roles during diverse cellular processes. CTCF gene knockout mice led to death during embryonic development. To further explore the functions of CTCF, we employed a CRISPR/Cas9-based genome engineering strategy to in-frame insert the mitosis-special degradation domain (MD) of cyclin B into the upstream open reading frame of CTCF gene. Fusion protein is designed to degrade during mitosis leaded by MD. As a control group, mutation of a single arginine (R42A) within the destruction box inactivates the MD leading to constitutive expression of MD*-CTCF. The homozygous clones were obtained via the screening by puromycin when coexpressed with puromycin resistence gene. The protein level of CTCF in MD-CTCF cell line was about 10% of wild-type cells throughout cell cycles by the analyses of Western blotting and immunofluorescence. There was no significant difference between MD*-CTCF cell line and wild type. Flow cytometry results showed prolonged G1 phase in MD-CTCF cell line. Taken together, we demonstrated the feasibility of efficiently inserting MD domain into genome with the CRISPR/Cas9 technology and reported the first CTCF-specific degradation human cell line.

[(99m)Tc-MDP wholebody bone imaging in evaluation of the characteristics of bone metastasis of primary lung cancer].

OBJECTIVE: To explore the image characteristics of bone metastasis of primary lung carcinoma. METHODS: Whole-body bone imaging ((99)Tc(m)-MDP) was performed in 258 patients with pathologically proven lung carcinoma. The rate of bone metastasis, distribution of the metastatic lesions and their characteristics were analyzed. RESULTS: Among the 258 cases, 142 patients developed bone metastasis. The overall rate of bone metastasis was 55.0%. The metastases located in axial skeleton were 49.6%, appendicular skeleton 36.0%, trunk bones of the axial skeleton 48.4%, and appendicular girdle skeleton 31.4%. Ribs, thoracic vertebrae, ilium and lumbar vertebrae had a higher rate of bone metastasis, higher than 20%, respectively. 1252 lesions were detected including 406 at the left side of the body, 387 in the axial skeleton and 459 at the right side of the body. There was no significant difference in terms of number of lesions between left side and right side (chi(2) = 3.3, P = 0.072). 1224 bone metastatic foci (97.8%) were presented as strong radioactive, 26 (2.1%) mixed lesion, and 2 (0.2%) low radioactive. According to the shape of the lesions, there were 810 punctate lesions (71.5%), 159 (14.0%) lump form, 108 (9.5%) strip form and 56 (4.9%) lamellar form. The accumulative bone metastasis rate was 28.7% for the patients with one to three lesions. The metastasis rate decreased gradually with the increasing number of metastatic lesions. CONCLUSION: Bone metastasis is very common in patients with lung cancer. Most bone metastases are characterized by strong radioactive and earlier punctate form, often occurs in the trunk bones of axial skeleton or appendicular girdles. The distribution of earlier metastases has not obvious regularity, and advanced bone metastases are often concurrent, multiple and multiform, widely and randomly distributed in the body.

Epigenetics recording varied environment and complex cell events represents the origin of cellular aging.

Although a relationship between epigenetics and aging phenotypic changes has been established, a theoretical explanation of the intrinsic connection between the epigenetics and aging is lacking. In this essay, we propose that epigenetic recording of varied cell environment and complex history could be an origin of cellular aging. Through epigenetic modifications, the environment and historical events can induce the chromatin template into an activated or repressive accessible structure, thereby shaping the DNA template into a spectrum of chromatin states. The inner nature of diversity and conflicts born by the cell environment and its historical events are hence recorded into the chromatin template. This could result in a dissipated spectrum of the chromatin state and chaos in overall gene expression. An unavoidable degradation of epigenome entropy, similar to Shannon entropy, would be consequently induced. The resultant disorder in epigenome, characterized by corrosion of epigenome entropy as reflected in chromatin template, can be stably memorized and propagated through cell division. Furthermore, the hysteretic nature of epigenetics responding to the emerging environment could exacerbate the degradation of epigenome entropy. As well as stochastic errors, we propose that outside entropy (or chaos) derived from the varied environment and complex cell history, gradually input and imprinted into the chromatin via epigenetic modifications, would lead inevitably to cellular aging, the extent of which could be aggravated by hysteresis of epigenetics without error erasing and correction.

Coordinated regulation of IFITM1, 2 and 3 genes by an IFN-responsive enhancer through long-range chromatin interactions.

Interferon-induced transmembrane protein (IFITM) 1, 2 and 3 genes encode a family of interferon (IFN)-induced transmembrane proteins that block entry of a broad spectrum of pathogens. However, the transcriptional regulation of these genes, especially whether there exist any enhancers and their roles during the IFN induction process remain elusive. Here, through public data mining, episomal luciferase reporter assay and in vivo CRISPR-Cas9 genome editing, we identified an IFN-responsive enhancer located 35kb upstream of IFITM3 gene promoter upregulating the IFN-induced expression of IFITM1, 2 and 3 genes. Chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA) and luciferase reporter assay demonstrated that signal transducers and activators of transcription (STAT) 1 bound to the enhancer with the treatment of IFN and was indispensable for the enhancer activity. Furthermore, using chromosome conformation capture technique, we revealed that the IFITM1, 2 and 3 genes physically clustered together and constitutively looped to the distal enhancer through long-range interactions in both HEK293 and A549 cells, providing structural basis for coordinated regulation of IFITM1, 2 and 3 by the enhancer. Finally, we showed that in vivo truncation of the enhancer impaired IFN-induced resistance to influenza A virus (IAV) infection. These findings expand our understanding of the mechanisms underlying the transcriptional regulation of IFITM1, 2 and 3 expression and its ability to mediate IFN signaling.