Relogio, A. | bioRxiv Science

bioRxiv2024

Single-cell variations of circadian clock and immune gene expression in microglia and neurodegeneration

We investigated the diurnal rhythmicity of gene expression in microglia, the resident macrophages of the brain, in health and disease. Using RNA sequencing and single-cell analysis by RNAscope, we examined wild-type mice and the R6/2 transgenic mouse model of Huntingtons disease (HD). Our findings suggest context-dependent rhythmic gene expression in microglia, exhibiting substantial variability between individual cells and brain regions over 24 hours. Notably, we observed loss of rhythmic gene expression of key clock genes in microglia from symptomatic but not presymptomatic R6/2 mice. Moreover, we identified de novo 24-hour rhythmic gene expression and altered diurnal patterns of immune-related genes associated with neurodegenerative diseases in microglia from symptomatic R6/2 mice. Our findings suggest circadian reprogramming of microglia in the context of neurodegeneration.

neuroscience↗

bioRxiv2018

Systematic analysis of mouse genome reveals distinct evolutionary and functional properties among circadian and ultradian genes

In living organisms, biological clocks regulate 24 h (circadian) molecular, physiological, and behavioral rhythms to maintain homeostasis and synchrony with predictable environmental changes. Harmonics of these circadian rhythms having periods of 8 hours and 12 hours (ultradian) have been documented in several species. In mouse liver, harmonics of the 24-hour period of gene transcription hallmarked genes oscillating with a frequency two or three times faster than the circadian circuitry. Many of these harmonic transcripts enriched pathways regulating responses to environmental stress and coinciding preferentially with subjective dawn and dusk. We hypothesized that these stress anticipatory genes would be more evolutionarily conserved than background circadian and non-circadian genes. To investigate this issue, we performed broad computational analyses of genes/proteins oscillating at different frequency ranges across several species and showed that ultradian genes/proteins, especially those oscillating with a 12-hour periodicity, are more likely to be of ancient origin and essential in mice. In summary, our results show that genes with ultradian transcriptional patterns are more likely to be phylogenetically conserved and associated with the primeval and inevitable dawn/dusk transitions.

bioinformatics↗