Molecular cloning and characterization of the germ cell-related nuclear orphan receptor in chickens

hsa_circ_001653 up-regulates NR6A1 expression and elicits gastric cancer progression by binding to microRNA-377

NEW FINDINGS

What is the central question of this study? Does hsa_circ_001653 influence the development of gastric cancer (GC) and if so how? What is the main finding and its importance? Bioinformatics analysis revealed the presence of differentially expressed hsa_circ_001653 in GC and adjacent normal tissues, and this was strongly related to the pathology of patients with GC. Knockdown of hsa_circ_001653 suppressed the proliferation, invasion and migration of GC cells, while inducing cell apoptosis via miR-377-mediated NR6A1 inhibition. The effect of hsa_circ_001653 and miR-377 on tumour growth in GC was further confirmed in vivo.

ABSTRACT

Gastric cancer (GC) is one of the leading causes of human mortality through malignant tumours. Circular RNAs (circRNAs) have been identified as binding to microRNAs (miRNAs) to modulate the progression of tumours. This study explores the role of hsa_circ_001653, a newly identified circRNA, in the development of GC. hsa_circ_001653 expression was measured in 86 paired normal and tumour tissues surgically resected from GC patients. Cross-talk between hsa_circ_001653 and microRNA-377 (miR-377)/nuclear receptor subfamily 6, group A, member 1 (NR6A1) was assessed using bioinformatics analysis, dual-luciferase reporter assay, Ago2 immunoprecipitation and western blot analysis. A series of functional experiments were carried out to elucidate the role of hsa_circ_001653 in GC cell proliferation, invasion, migration and apoptosis, and its underlying molecular mechanisms. Nude mice were inoculated with GC cells for in vivo analysis. hsa_circ_001653 was found to be an up-regulated circRNA in GC tissues and cells. Down-regulation of hsa_circ_001653 inhibited GC cell proliferation, migration and invasion, while stimulating cell apoptosis. hsa_circ_001653 was found to bind to miR-377, which targeted NR6A1 and repressed its expression. Inhibition of miR-377 and overexpression of NR6A1 restored the proliferation, migration and invasion in GC cells lacking hsa_circ_001653. Furthermore, inhibition of hsa_circ_001653 attenuated tumour growth in nude mice inoculated with GC cells. Collectively, the demonstration that hsa_circ_001653 exerts its anticancer effects by regulating the miR-377-NR6A1 axis increases our understanding of gastric cancer pathophysiology. The findings uncover new potential therapeutic targets for GC.

The avian-specific small heat shock protein HSP25 is a constitutive protector against environmental stresses during blastoderm dormancy

Small heat shock proteins (sHSPs) range in size from 12 to 42 kDa and contain an α-crystalline domain. They have been proposed to play roles in the first line of defence against various stresses in an ATP-independent manner. In birds, a newly oviposited blastoderm can survive several weeks in a dormant state in low-temperature storage suggesting that blastoderm cells are basically tolerant of environmental stress. However, sHSPs in the stress-tolerant blastoderm have yet to be investigated. Thus, we characterised the expression and function of sHSPs in the chicken blastoderm. We found that chicken HSP25 was expressed especially in the blastoderm and was highly upregulated during low-temperature storage. Multiple alignments, phylogenetic trees, and expression in the blastoderms of Japanese quail and zebra finch showed homologues of HSP25 were conserved in other avian species. After knockdown of chicken HSP25, the expression of pluripotency marker genes decreased significantly. Furthermore, loss of function studies demonstrated that chicken HSP25 is associated with anti-apoptotic, anti-oxidant, and pro-autophagic effects in chicken blastoderm cells. Collectively, these results suggest avian HSP25 could play an important role in association with the first line of cellular defences against environmental stress and the protection of future embryonic cells in the avian blastoderm.

Gene expression and DNA methylation status of chicken primordial germ cells

DNA methylation reprogramming of primordial germ cells (PGCs) in mammals establishes monoallelic expression of imprinting genes, maintains retrotransposons in an inactive state, inactivates one of the two X chromosomes, and suppresses gene expression. However, the roles of DNA methylation in chickens PGCs are unknown. In this study, we found a 1.5-fold or greater difference in the expression of 261 transcripts when comparing PGCs and chicken embryonic fibroblasts (CEFs) using an Affymetrix GeneChip Chicken Genome Array. In addition, we analyzed the methylation patterns of the regions ~5-kb upstream of 261 sorted genes, 51 of which were imprinting homologous loci and 49 of which were X-linked homologous loci in chicken using the MeDIP Array by Roche NimbleGen. Seven hypomethylated and five hypermethylated regions within the 5-kb upstream regions of 261 genes were found in PGCs when compared with CEFs. These differentially methylated regions were restrictively matched to differentially expressed genes in PGCs. We also detected 203 differentially methylated regions within imprinting and X-linked homologous regions between male PGCs and female PGCs. These differentially methylated regions may be directly or indirectly associated with gene expression during early embryonic development, and the epigenetic difference could be evolutionally conserved between mammals and birds.