CRISPR/Cas9-induced site-specific DNA double-strand breaks (DSBs) can be repaired by homology-directed repair (HDR) or non-homologous end joining (NHEJ) pathways. Extensive efforts have been made to knock-in exogenous DNA to a selected genomic locus in human cells; which, however, has focused on HDR-based strategies and was proven inefficient. Here, we report that NHEJ pathway mediates efficient rejoining of genome and plasmids following CRISPR/Cas9-induced DNA DSBs, and promotes high-efficiency DNA integration in various human cell types. With this homology-independent knock-in strategy, integration of a 4.6 kb promoterless ires-eGFP fragment into the GAPDH locus yielded up to 20% GFP+ cells in somatic LO2 cells, and 1.70% GFP+ cells in human embryonic stem cells (ESCs). Quantitative comparison further demonstrated that the NHEJ-based knock-in is more efficient than HDR-mediated gene targeting in all human cell types examined. These data support that CRISPR/Cas9-induced NHEJ provides a valuable new path for efficient genome editing in human ESCs and somatic cells.

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The ubiquitin-like modifier (UBL) family has recently generated much interest in the scientific community, as it is implicated to play important regulatory roles via novel protein-protein modification. FAT10 (diubiquitin) belongs to this family of proteins, comprising two ubiquitin-like moieties fused in tandem, and has been implicated to be involved in the maintenance of spindle integrity during mitosis. As FAT10 may play a role in the regulation of genomic stability, we examined if there is an association between FAT10 expression and hepatocellular carcinoma (HCC) or other cancers. Northern blot analyses revealed upregulation of FAT10 expression in the tumors of 90% of HCC patients. In situ hybridization as well as immunohistochemistry utilizing anti-FAT10 antibodies localized highest FAT10 expression in the nucleus of HCC hepatocytes rather than the surrounding immune and non-HCC cells. FAT10 expression was also found to be highly upregulated in other cancers of the gastrointestinal tract and female reproductive system. In conclusion, we demonstrated upregulation of FAT10 expression in various gastrointestinal and gynecological cancers. Its overexpression is unrelated to the general increase in protein synthesis or a general immune/ inflammatory response to cancer. Rather, FAT10 may modulate tumorigenesis through its reported interaction with the MAD2 spindle-assembly checkpoint protein.

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OBJECTIVES Maternal deficiency of the omega-3 fatty acid, docosahexaenoic acid (DHA), has been associated with perinatal depression, but there is evidence that supplementation with eicosapentaenoic acid (EPA) may be more effective than DHA in treating depressive symptoms. This trial tested the relative effects of EPA- and DHA-rich fish oils on prevention of depressive symptoms among pregnant women at an increased risk of depression. STUDY DESIGN We enrolled 126 pregnant women at risk for depression (Edinburgh Postnatal Depression Scale score 9–19 or a history of depression) in early pregnancy and randomly assigned them to receive EPA-rich fish oil (1060 mg EPA plus 274 mg DHA), DHA-rich fish oil (900 mg DHA plus 180 mg EPA), or soy oil placebo. Subjects completed the Beck Depression Inventory (BDI) and Mini-International Neuropsychiatric Interview at enrollment, 26–28 weeks, 34–36 weeks, and at 6–8 weeks’ postpartum. Serum fatty acids were analyzed at entry and at 34–36 weeks’ gestation. RESULTS One hundred eighteen women completed the trial. There were no differences between groups in BDI scores or other depression endpoints at any of the 3 time points after supplementation. The EPA-and DHA-rich fish oil groups exhibited significantly increased post-supplementation concentrations of serum EPA and serum DHA respectively. Serum DHA- concentrations at 34–36 weeks were inversely related to BDI scores in late pregnancy. CONCLUSION EPA-rich fish oil and DHA-rich fish oil supplementation did not prevent depressive symptoms during pregnancy or postpartum.

Aneuploidy is a key process in tumorigenesis. Dysfunction of the mitotic spindle checkpoint proteins has been implicated as a cause of aneuploidy in cells. We have previously reported that FAT10, a member of the ubiquitin-like modifier family of proteins, is overexpressed in several gastrointestinal and gynecological cancers. Here we show that FAT10 interacts with MAD2, a spindle checkpoint protein, during mitosis. Notably, we show that localization of MAD2 at the kinetochore during the prometaphase stage of the cell cycle was greatly reduced in FAT10-overexpressing cells. Furthermore, compared with parental HCT116 cells, fewer mitotic cells were observed after double thymidine-synchronized FAT10-overexpressing cells were released into nocodazole for more than 4 h. Nonetheless, when these double thymidine-treated cells were released into media, a similar number of G 1 parental and FAT10-overexpressing HCT116 cells was observed throughout the 10-h time course. Additionally, more nocodazole-treated FAT10-overexpressing cells escape mitotic controls and are multinucleate compared with parental cells. Significantly, we observed a higher degree of variability in chromosome number in cells overexpressing FAT10. Hence, our data suggest that high levels of FAT10 protein in cells lead to increased mitotic nondisjunction and chromosome instability, and this effect is mediated by an abbreviated mitotic phase and the reduction in the kinetochore localization of MAD2 during the prometaphase stage of the cell cycle. Genetic instability is an important phenomenon that underlies tumorigenesis. Chromosome instability (CIN)2 involving gains and loss of chromosomes has been found to occur in most malignancies, whereas microsatellite instability, which occurs at the nucleotide level, is less commonly observed in cancers (1). Two forms of CIN, namely structural instability and numerical instability (aneuploidy), can be observed in various tumors. Genes responsible for CIN in human cancers include those involved in the condensation of chromosomes, cohesion of sister chromatids, formation of microtubules, and kinetochore structure and function as well as mitotic "checkpoint" genes that monitor the proper progression through the cell cycle (1, 2).MAD2 (mitotic arrest-deficient 2) is a key mitotic spindle checkpoint protein whose primary role is to ensure that all of the chromosomes are properly attached to the mitotic spindle before the onset of anaphase (3). It is activated by associating with unattached kinetochores. Activated MAD2 binds to Cdc20 and prevents the anaphase-promoting complex from ubiquitylating securin. As a result, anaphase is delayed until all of the kinetochores are attached by microtubules and the chromosomes are properly aligned along the metaphase plate (4 -6). MAD2 is an essential gene, and MAD2 Ϫ/Ϫ mice die in utero (7). Loss of one allele of MAD2 has been reported to result in premature anaphase and CIN in mammalian cells (8). Dysregulation of MAD2 has been implicated in various cancers. Reduced expression of ...

Various reports have implicated the virally encoded HBx protein as a cofactor in hepatocarcinogenesis. However, direct evidence of the role of HBx as a promoter of oncogenesis in response to an initiating factor such as DNA damage remains inadequate. Here, we report the effects of HBx in HepG2 cells exposed to UV light-induced DNA damage. HBx expression was found not to affect the morphology, viability, and cell cycle/apoptotic profiles or DNA repair machinery of untreated cells. Nonetheless, upon UV treatment, HBx protein levels increased concomitantly with p53 levels. Both HBx and p53 proteins were found to interact and colocalize primarily in the nucleus. The binding of HBx to p53 modulated (but did not inhibit) the transcriptional activation function of p53. Notably, HBx-expressing cells exhibited increased sensitivity to UV damage, resulting in greater G 2 /M arrest and apoptosis of these cells. Additionally, these cells displayed a reduced DNA repair capacity in response to UV damage. In conclusion, this work suggests that DNA damage may be an initiating factor in hepatocarcinogenesis and that HBx may act as the promoting factor by inhibiting DNA repair. In hepatitis B virus-infected hepatocytes, a chronic infection may present the opportunity for such a DNA-damaging event to occur, and accumulated errors caused by the inhibition of DNA repair by HBx may result in oncogenesis.

SummaryTumor necrosis factor-alpha (TNF-a) plays important roles in chronic inflammation-associated tumorigenesis but the mechanisms involved remain poorly understood. Previously, we reported that high levels of FAT10 led to chromosomal instability that is mediated by an abbreviated mitotic phase. Here, we show that TNF-a induces FAT10 gene expression through TNF receptor 1 (TNFR1) and activates the NF-kB pathway in HCT116 and SW620 cells. TNF-a treatment also leads to an abbreviated mitotic phase that can be reversed by inhibiting FAT10 expression. This abbreviated mitotic phase is correlated with a TNF-a-induced reduction in the kinetochore localization of MAD2 during prometaphase which, again, can be reversed by inhibiting FAT10 gene expression. There is greater variability of chromosome numbers in HCT116 and SW620 cells treated with TNF-a than in untreated cells, which can be reversed by the introduction of short hairpin RNA (shRNA) against FAT10. The more stable chromosome numbers in HCT116 cells expressing FAT10 shRNA can revert to greater variability with the addition of a mutant FAT10 that is not recognized by the FAT10 shRNA. Upon TNF-a stimulation, higher cell death is observed when FAT10 expression is inhibited by shRNA. These data strongly suggest that FAT10 plays an important role in mediating the function of TNF-a during tumorigenesis by inducing cell cycle deregulation and chromosomal instability, and by inhibiting apoptosis.