From LED screens to genes: The effects of blue light on aging and m6A methylation in fruit flies

By Pooja Toshniwal PahariaDec 7 2023Reviewed by Danielle Ellis, B.Sc.

In a recent study published in PNAS Nexus, researchers created Drosophila models using multi-omics profiles to elucidate the biological mechanisms and effects of everyday low-intensity blue light exposure (BLE). They also explored the role of N6-methyladenosine (m6A) methylation in blue light-induced phenotypes.

Background

LEDs have transformed contemporary living, yet the health, cognition, and aging risks associated with continuous exposure to artificial blue light remain unknown. BLE has been related to retinal cell damage, circadian disturbance, mental health problems, hastened aging, and brain dementia. Exposure to high-intensity blue light can result in reactive oxygen species (ROS) accumulation, apoptosis, and increased mortality. The chemical mechanisms underlying the effects of exposure to low-intensity blue light remain unknown. The m6A function in blue light-mediated abnormalities is also unknown.

About the study

The present study examined age- and BLE-induced m6A ribonucleic acid (RNA) methylome reprogramming in a Drosophila model.

The objective was to evaluate the effects of blue light exposure on Drosophila melanogaster adults, a model organism. After eclosion, the researchers retrieved eggs from colonies preserved on a photoperiodic 12-hour white light and 12-hour darkness (LD) cycle. Subsequently, the eggs were transferred to a climate chamber kept on a photoperiodic cycle. The flux density of blue light was adjusted to 30-50 molm2/s.

The team obtained five omics datasets, each with four groups. Each group had three biological duplicates for methylated ribonucleic acid immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) and five biological replicates to quantify the untargeted metabolome by liquid chromatography-mass spectrometry (LC-MS).

Poly(A)-RNA-seq libraries were created from adult male heads and F1-generation adult masculine flies, followed by poly(A)-MeRIP-seq libraries from whole adult masculine flies. The researchers used multiomics techniques to explore the effects of BLE in the model organism, Drosophila melanogaster.

A range of Drosophila models was constructed with varying daily BLE durations and studied for their transcriptome, m6A epi transcriptomic, and metabolomic profiles. In total, 11,350 genes were extracted from the samples and used in future studies. The global RNA profiles of entire flies were analyzed using MeRIP-seq input data and compared to head RNA-seq data. The DD25 flies' cumulative curve deviated somewhat due to a lower fraction of highly expressed genes.

The researchers also observed the expression of genes related to m6A and N6,2′-O-dimethyladenosine (m6Am). Untargeted metabolomic quantification was conducted on the same fly samples used in this investigation as MeRIP-seq. Blue light exposure may be crucial for circadian rhythm entrainment; thus, the researchers examined the integrative genomics viewer (IGV) paths of biological clock-associated genes involved in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway.

They used quantitative reverse transcription-polymerase chain reaction (RT-qPCR) to verify the relative messenger RNA (mRNA) expression levels of several genes of interest in adult male flies.

Western blotting was used to evaluate the relative protein expression levels of target rapamycin (TOR) and period circadian regulator (PER) genes in the same adult male flies. The researchers created recombinant Mettl3- and fl(2)d-RNAi Drosophila strains and S2 cell lines to explore the effects of changes in 5′ untranslated region (UTR)-enhanced m6A methylation levels caused by age, BLE, or other causes.

Results

In Drosophila, blue light (BL) causes metabolomic and m6A epi-transcriptomic reprogramming associated with aging. The m6A methylation sites concentrated in Drosophila transcripts' 5′ UTRs indicated high specificity for age and were altered by exposure to blue light. The findings showed that 5′ UTR-enhanced m6A methylation regulated the aging-related TOR and biological clock-associated PER genes.

Long-term exposure to blue light and aging triggered directed transcriptome, metabolomic, and m6A epi-transcriptomic reprogramming in entire adult flies, indicating that blue light exposure had a considerable influence on adult neural functioning at the transcriptional level. The team argued that age-induced m6A epi-transcriptomic reprogramming enriched by 5′ UTR affects the fate of age-associated mRNA molecules and worsens aging phenotypes.

The transcriptomic profiling analysis indicated that BLE may induce cephalic nervous system injury, whereas blue light exposure and aging produce metabolomic reprogramming in adult flies. DESeq2 discovered 517 differentially expressed genes (DEGs), of which most were identified between downregulated BD10 and BD25 heads.

The researchers found a link between m6A-related genes, 5′ UTR-enhanced m6A epi-transcriptomic regulation, age-related genes, and the Drosophila aging phenotype. As a feedback reaction, the team postulated a biological mechanism for lowered 5′ UTR-enhanced mRNA m6A methylation levels generated by aging, which might affect age-related gene fate and further worsen aging processes.

Conclusion

Overall, the study findings showed that BLE could reprogram Drosophila and change gene expression regulation associated with neural processes. BLE may change the 5′ UTR-enhanced m6A methylation with significant age specificity, impacting aging-related and circadian rhythm-associated genes.

Long-term BLE resulted in more reprogramming in multiomics profiles in BD25 and DD25 flies than in BD10 and DD10 flies. The high-resolution m6A epi transcriptomic mapping results showed that Drosophila mRNA m6A methylation was significantly 5′ UTR-enhanced and changeable with age.