Biology subjects

Bafna, A.

Publications and source records attributed to Bafna, A..

3 recordsLinked to original sources

bioRxiv2024

The dynamic gene regulatory landscape of the mouse brain in response to sleep deprivation

Sleep deprivation (SD) negatively impacts nearly all brain functions including cognition, memory consolidation and metabolism. However, the gene regulatory networks that underlie these biological effects are not well understood. In order to identify these networks, we conducted a multiomic analysis to analyse how gene expression, chromatin accessibility, enhancer activity and DNA methylation change with acute SD in mice. By studying three brain regions involved in different aspects of sleep - the cortex (CTX), dentate gyrus (DG), and suprachiasmatic nucleus (SCN) - we found that the effects of SD on the multiome varied widely, impacting physiological processes specific to each area, from spine formation in the dentate gyrus to neuropeptide release in the SCN. Our integrated analysis showed that distinct brain region-specific networks of regulatory factors dynamically alter the epigenomic landscape in response to SD to orchestrate transcriptional responses. These findings provide new understanding of the regulatory grammar encoded within the genome, which enables a general physiological signal like SD to produce unique effects in a tissue-specific context.

neuroscience↗

bioRxiv2023

Loss of zinc finger homeobox-3 (ZFHX3) affects rhythmic gene transcription in mammalian central clock

The mammalian suprachiasmatic nucleus (SCN), situated in the ventral hypothalamus, directs daily cellular and physiological rhythms across the body. The SCN clockwork is a self-sustaining transcriptional-translational feedback loop (TTFL) that in turn co-ordinates the expression of clock-controlled genes (CCGs) directing circadian programmes of SCN cellular activity. In the mouse, the transcription factor, ZFHX3 (zinc finger homeobox-3), is necessary for the development of the SCN and influences circadian behaviour in the adult. The molecular mechanisms by which ZFHX3 affects the SCN at transcriptomic and genomic levels are, however, poorly defined. Here, we used chromatin immunoprecipitation sequencing (ChIP-seq) to map the genomic localization of ZFHX3 binding sites in SCN chromatin. To test for function, we then conducted comprehensive RNA sequencing at six distinct times-of-day to compare the SCN transcriptional profiles of control and ZFHX3-conditional null mutants. We show that the genome-wide occupancy of ZFHX3 occurs predominantly around gene transcription start sites (TSS), co-localizing with known histone modifications, and preferentially partnering with clock transcription factors (CLOCK, BMAL1) to regulate clock gene(s) transcription. Correspondingly, we show that the conditional loss of ZFHX3 in the adult has a dramatic effect on the SCN transcriptome, including changes in the levels of transcripts encoding elements of numerous neuropeptide neurotransmitter systems while attenuating the daily oscillation of the clock TF Bmal1. Furthermore, various TTFL genes and CCGs exhibited altered circadian expression profiles, consistent with an advanced in daily behavioural rhythms under 12h light-12h dark conditions. Together, these findings reveal the extensive genome-wide regulation mediated by ZFHX3 in the central clock that orchestrates daily timekeeping in mammals.

neuroscience↗

bioRxiv2022

Dynamic modulation of genomic enhancer elements in the suprachiasmatic nucleus mediates daily timekeeping in mammals

The mammalian suprachiasmatic nucleus (SCN), located in the ventral hypothalamus, is crucial for synchronising and resetting all cellular rhythms in accordance with critical environmental and visceral cues. Consequently, the systematic regulation of spatiotemporal gene transcription in the SCN is vital for daily timekeeping. Here, we sought to identify SCN enriched gene regulatory elements that enable temporal gene expression using histone-ChIP-seq. We found a vast majority of SCN enhancers not only exhibit robust 24-hour rhythmic modulation in H3K27ac occupancy, but also possess canonical E-box (CACGTG) motif, potentially influencing downstream cycling gene expression. In parallel, we conducted RNA-Seq at six distinct times to establish enhancer-gene relationships in the SCN. Surprisingly, around 35% of cycling H3K27ac abundance is seen adjacent to rhythmic gene transcripts, often preceding the rise in mRNA levels. We also noted that enhancers encompass non-coding actively transcribing enhancer RNAs (eRNAs), that in turn oscillate along with cyclic histone acetylation to direct gene transcription. Taken together, these findings shed light on genome-wide pre-transcriptional regulation operative in the central clock that enables its orchestration of daily timekeeping mechanisms in mammals.

genomics↗