CircRNA (circ_0008057) promotes uremic serum-mediated proliferation and migration of vascular smooth muscle cells via miR-370/PLk1 signaling pathway

In order to explore the mechanism of gefitinib-acquired resistance in lung cancer, a new biomarker has been developed for early clinical diagnosis and intervention; human NSCLC (Non-Small Cell Lung Cancer) cell lines H292 (denoted as H292S) and PC9 (denoted as PC9S) were used to establish gefitinibresistant NSCLC cell lines H292 and PC9 models. CCK-8 (Cell Counting Kit-8) method was used to test the drug resistance of the cells. circRNAs (circular RNAs) that were differentially expressed before and after resistance were screened by RNA sequencing technology. The effects of circSETD3 overexpression and interference on the sensitivity of gefitinib was observed to analyze the nuclear localization of circSETD3 and verify the interaction between circSETD3-miR-520h-ABCG2. The results showed that the most significant change in differential expression of human NSCLC cell lines before and after drug resistance was hsa_circ_0000567, that is, circSETD3, which is mainly present in the cytoplasm. In H292S and PC9S, compared with the negative control group, the cell proliferation ability of the overexpression group was significantly increased, and the apoptosis ability was significantly decreased. In H292R and PC9R, compared with the negative control group, the proliferation ability of the interference group was significantly decreased, and the apoptosis ability was significantly increased. Overexpression of circSETD3 to H292S and PC9S, the expression of ABCG2 increased significantly. Also, the expression of ABCG2 decreased significantly after transfection with miR-520h mimics. H292R and PC9R interfered with circSETD3, the expression of ABCG2 decreased significantly. Moreover, the expression of ABCG2 increased significantly after transfection with miR-520h inhibitor. In conclusion, circSETD3 can be used as a novel biomarker for lung cancer. It relieves miR-520h degradation of the transporter ABCG2 by down-regulating the miR-520h expression, causing gefitinib to be pumped out of the cell.

Position effect variegation and epigenetic modification of a transgene in a pig model

Sequences proximal to transgene integration sites are able to regulate transgene expression, resulting in complex position effect variegation. Position effect variegation can cause differences in epigenetic modifications, such as DNA methylation and histone acetylation. However, it is not known which factor, position effect or epigenetic modification, plays a more important role in the regulation of transgene expression. We analyzed transgene expression patterns and epigenetic modifications of transgenic pigs expressing green fluorescent protein, driven by the cytomegalovirus (CMV) promoter. DNA hypermethylation and loss of acetylation of specific histone H3 and H4 lysines, except H4K16 acetylation in the CMV promoter, were consistent with a low level of transgene expression. Moreover, the degree of DNA methylation and histone H3/H4 acetylation in the promoter region depended on the integration site; consequently, position effect variegation caused variations in epigenetic modifications. The transgenic pig fibroblast cell lines were treated with DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine and/or histone deacetylase inhibitor trichostatin A. Transgene expression was promoted by reversing the DNA hypermethylation and histone hypoacetylation status. The differences in DNA methylation and histone acetylation in the CMV promoter region in these cell lines were not significant; however, significant differences in transgene expression were detected, demonstrating that variegation of transgene expression is affected by the integration site. We conclude that in this pig model, position effect variegation affects transgene expression.

Transgene insertion affects transcription and epigenetic modification of flanking host sequence in transgenic pigs

Transgenic technology has been used for years to study gene function, produce important proteins, and generate models for the study of human diseases. However, the efficiency of producing transgenic animal lines that retain normal function is extremely low. The low efficiency can be mainly attributed to the integrated transgene. A further understanding of the effects of transgene integration on transcription and epigenetic modification of the host genome would improve the transgenic efficiency. Therefore, we utilized three transgenic pigs produced by SCNT expressing GFP, to identify alterations of transcription, DNA methylation and histone acetylation resulting from integration of the GFP gene. Multiple copies of the transgene integrated into a single site of the three transgenic pigs were verified by TAIL—PCR and the integration sites were different in each pig. We observed that the integrated transgene frequently resulted in significantly low transcription of flanking sequences in various tissues of transgenic pigs in comparison with wild—type pigs. Corresponding with the low transcription, DNA hypermethylation and loss of acetylation of histone H3 and H4 were detected. Our results demonstrate that the abnormal transcription and epigenetic modification of sequences flanking the transgene were not correlated with the expression of the transgene. However, the disturbance caused by the insertion of the transgene, was dependent upon the integration site. This suggests that some sequences in the host genome could permit integration and expression of transgene without causing defects in the host.

427 INTEGRATION SITE ANALYSIS IN TRANSGENIC PIGS BY THERMAL ASYMMETRIC INTERLACED (TAIL)-PCR AND JUNCTION PCR

Transgenic animals have been used to study gene function, produce important proteins, xenotransplantation donor, and generate models for the study of human diseases. Recent progress in animal cloning has provided an attractive alternative to improve transgenic efficiency, through the combination of transfection and somatic cell nuclear transfer (SCNT). However, when transgenic animals are produced by SCNT using randomly transfected cells as donor, the integration sites of transgene cannot be predicted. Many methods on the basis of genome walking have been demonstrated to clone transgene integration sites but they are either complicated or inefficient. In the study, we report a PCR-based method, thermal asymmetric interlaced PCR (TAIL-PCR), which relies on a series of 3 nested PCR reactions with transgene specific, designed with melting temperature of about 64, and arbitrary degenerate primers, by control of annealing temperature to efficiently reduce the nonspecific amplification to clone the integration sites in transgenic pigs by SCNT. Junction PCR combined with transgene-specific and integration site primers was performed to confirm the integration sites. Three integration sites were found (1 mapped on chromosome 4; the other 2 met a significant match in the pig expressed sequence tag database) in 2 founder transgenic pigs. Junction PCR resulted in specific amplification bands to identify the integration sites, and segregation of the integration sites was also detected in subsequent progeny by junction PCR analysis. We also used junction PCR combining with transgene-specific 5′ and 3′ integration site primers to analyze zygosity of the integration sites. Besides the specific amplification bands amplifying by transgene specific and integration site primers, bands amplified by 5′ and 3′ integration site primers were obtained to determine the heterozygosity of integration site. In conclusion, this strategy can be efficiently employed to clone transgene integration site and determine zygosity. This work was supported by grant from the State Transgenic Research Programme of China (Grant No. 2008ZX08006-002).