Differential expression of natural antisense transcripts during liver development in embryonic mice

The seeds of its regulation: Natural antisense transcripts as single-gene control switches in neurodegenerative disorders

Several proteins play critical roles in vulnerability or resistance to neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and frontotemporal dementia (FTD). Regulation of these proteins is critical to maintaining healthy neurohomeostasis. In addition to transcription factors regulating gene transcription and microRNAs regulating mRNA translation, natural antisense transcripts (NATs) regulate mRNA levels, splicing, and translation. NATs' roles are significant in regulating key protein-coding genes associated with neurodegenerative disorders. Elucidating the functions of these NATs could prove useful in treating or preventing diseases. NAT activity is not restricted to mRNA translation; it can also regulate DNA (de)methylation and other gene expression steps. NATs are noncoding RNAs (ncRNAs) encoded by DNA sequences overlapping the pertinent protein genes. These NATs have complex structures, including introns and exons, and therefore bind their target genes, precursor mRNAs (pre-mRNAs), and mature RNAs. They can occur at the 5'- or 3'-ends of a mRNA-coding sequence or internally to a parent gene. NATs can downregulate translation, e.g., microtubule-associated protein tau (MAPT) antisense-1 gene (MAPT-AS1), or upregulate translation, e.g., β-Amyloid site Cleaving Enzyme 1 (BACE1) antisense gene (BACE1-AS). Regulation of NATs can parallel pathogenesis, wherein a "pathogenic" NAT (e.g., BACE1-AS) is upregulated under pathogenic conditions, while a "protective" NAT (e.g., MAPT-AS1) is downregulated under pathogenic conditions. As a relatively underexplored endogenous control mechanism of protein expression, NATs may present novel mechanistic targets to prevent or ameliorate aging-related disorders.

Analysis of gene expression changes during lipid droplet formation in HepG2 human liver cancer cells

Fatty liver is a condition of excessive triglyceride accumulation in hepatocytes. Additionally, hepatocytes exhibit a high degree of fat droplet accumulation during excessive alcohol consumption and metabolic syndrome. However, the molecular mechanisms involved in fat droplet formation remain unknown. The present study used an in vitro fatty liver formation model of the human liver cancer cell line, HepG2, to comprehensively search for fat droplet formation-related genes, and which exhibit changes in expression during fat droplet formation. Microarray analysis with extracted total RNA determined the genes that are involved in fat droplet formation and their expression was confirmed using quantitative polymerase chain reaction following the culture of the HepG2 cells in culture medium containing 0, 50, 200 and 500 µM of oleic acid for 24 h. The results revealed 142 genes demonstrating increased expression levels by >2.0-fold with oleic acid treatment and 426 genes demonstrating decreased expression levels. Perilipin 2 (PLIN2) was estimated as the gene most closely associated with fatty liver. Lipid droplet formation in the HepG2 cells induced by oleic acid led to the upregulation of PLIN2 in a concentration-dependent manner. On the whole, the findings of the present study indicate the involvement of genes in oleic acid-induced lipid droplet formation in HepG2 cells; PLIN2 in particular may play a crucial role in this process.

Characteristics of Antisense Transcript Promoters and the Regulation of Their Activity

Recently, an increasing number of studies on natural antisense transcripts have been reported, especially regarding their classification, temporal and spatial expression patterns, regulatory functions and mechanisms. It is well established that natural antisense transcripts are produced from the strand opposite to the strand encoding a protein. Despite the pivotal roles of natural antisense transcripts in regulating the expression of target genes, the transcriptional mechanisms initiated by antisense promoters (ASPs) remain unknown. To date, nearly all of the studies conducted on this topic have focused on the ASP of a single gene of interest, whereas no study has systematically analyzed the locations of ASPs in the genome, ASP activity, or factors influencing this activity. This review focuses on elaborating on and summarizing the characteristics of ASPs to extend our knowledge about the mechanisms of antisense transcript initiation.