Biology subjects

Nolan, P. M.

Publications and source records attributed to Nolan, P. M..

8 recordsLinked to original sources

bioRxiv2024

ZFHX3 plays a role in pain and cautious-like behaviours in mice

A missense mutation in zinc finger homeobox-3 (ZFHX3) gene is known to alter circadian rhythms and metabolism. ZFHX3 is highly expressed in the central nucleus of amygdala and so we investigated whether female and male Zfhx3Sci-/+ mice have impaired pain, fear, anxiety-like, and cautious-like behaviours as these behaviours which are associated with the central nucleus of the amygdala. Using mechanical and thermal sensitivity test, the fear conditioning test and the light-dark box test, we found that female Zfhx3Sci-/+ mice have hypoalgesia to mechanical stimulus while hyperalgesia to heat stimulus. Additionally, both female and male Zfhx3Sci-/+ display reduction of cautious-like behaviour. While neither female and male Zfhx3Sci-/+ mice showed a difference in fear conditioning or anxiety-like behaviour, we have demonstrated for the first time that ZFHX3 is involved in pain and cautious behaviours. HighlightsO_LIFemale and male Zfhx3Sci/+ mice displayed less cautious-like behaviour C_LIO_LIZfhx3Sci/+ female mice had hypoalgesia to noxious mechanical stimulus C_LIO_LIZfhx3Sci/+ female mice had hyperalgesia to noxious heat stimulus C_LI

animal behavior and cognition↗

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↗

bioRxiv2023

Deficient synaptic neurotransmission results in a persistent sleep-like cortical activity across vigilance states in mice

Growing evidence suggests that brain activity during sleep, as well as sleep regulation, are tightly linked with synaptic function and network excitability at the local and global levels. We previously reported that a mutation in synaptobrevin 2 (Vamp2) in restless (rlss) mice results in a marked increase of wakefulness and suppression of sleep, in particular REM sleep (REMS) as well as increased consolidation of sleep and wakefulness. In the current study, using finer-scale in vivo electrophysiology recordings, we report that spontaneous cortical activity in rlss mice during NREM sleep (NREMS) is characterised by an occurrence of abnormally prolonged periods of complete neuronal silence (OFF-periods), often lasting several seconds, similar to the burst suppression pattern typically seen under deep anaesthesia. Increased incidence of prolonged network OFF-periods was not specific to NREMS, but also present in REMS and wake in rlss mice. Slow-wave activity (SWA) was generally increased in rlss mice, while higher frequencies including theta-frequency activity were decreased, further resulting in diminished differences between vigilance states. The relative increase in SWA after sleep deprivation was attenuated in rlss mice, suggesting either that rlss mice experience persistently elevated sleep pressure, or, alternatively, that the intrusion of sleep-like patterns of activity into awake state diminishes the accumulation of sleep drive. We propose that deficit in global synaptic neurotransmitter release leads to state inertia, reflected in an abnormal propensity of brain networks to enter and remain in a persistent default state resembling coma or deep anaesthesia.

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↗

bioRxiv2022

A missense mutation in zinc finger homeobox-3 (ZFHX3) impedes growth and alters metabolism and hypothalamic gene expression in mice.

A protein altering variant in the gene encoding zinc finger homeobox-3 (ZFHX3) has recently been associated with lower BMI in a human genome-wide association study. We investigated metabolic parameters in mice harbouring a missense mutation in Zfhx3 (Zfhx3Sci/+) and looked for altered in situ expression of transcripts that are associated with energy balance in the hypothalamus to understand how ZFHX3 may influence growth and metabolic effects. One year old male and female Zfhx3Sci/+ mice weighed less, had shorter body length, reduced fat mass, smaller mesenteric fat depots, and lower circulating insulin, leptin, and insulin-like growth factor-1 (IGF1) concentrations than Zfhx3+/+ littermates. In a second cohort of 9 - 20-week-old males and females, Zfhx3Sci/+ mice ate less than wildtype controls, in proportion to body weight. In a third cohort of female-only Zfhx3Sci/+ and Zfhx3+/+ mice that underwent metabolic phenotyping from 6 - 14 weeks old, Zfhx3Sci/+ mice weighed less and had lower lean mass and energy expenditure, but fat mass didnt differ. We detected increased expression of somatostatin, and decreased expression of growth hormone-releasing hormone and growth hormone-receptor mRNAs in the arcuate nucleus (ARC). Similarly, ARC expression of orexigenic neuropeptide Y was decreased and ventricular ependymal expression of orphan G protein-coupled receptor Gpr50 was decreased. We demonstrate for the first time an energy balance effect of the Zfhx3Sci mutation, likely by altering expression of key ARC neuropeptides to alter growth, food intake and energy expenditure.

physiology↗

bioRxiv2021

Comprehensive phenotypic analysis of the Dp1Tyb mouse strain reveals a broad range of Down Syndrome-related phenotypes

Down syndrome (DS), trisomy 21, results in many complex phenotypes including cognitive deficits, heart defects and craniofacial alterations. Phenotypes arise from an extra copy of human chromosome 21 (Hsa21) genes. However, causative genes remain mostly unknown. Animal models enable identification of these genes and pathological mechanisms. The Dp1Tyb mouse model of DS has an extra copy of 63% of Hsa21-orthologous mouse genes. Here, we comprehensively phenotype Dp1Tyb mice and find wide-ranging DS-like phenotypes including aberrant megakaryopoiesis, reduced bone density, and deficits in memory, locomotion, hearing and sleep. Thus, Dp1Tyb mice are an excellent model for studies of many complex DS phenotypes.

genetics↗

bioRxiv2020

Aberrant synaptic release underlies sleep/wake transition deficits in a mouse Vamp2 mutant

Sleep-wake transitions are modulated through extensive subcortical networks although the precise roles of their individual components remain elusive. Using forward genetics and in vivo electrophysiology, we identified a recessive mouse mutant line characterised by a reduced propensity to transition between all sleep states while a profound loss in total REM sleep time was evident. The causative mutation, an Ile102Asn substitution in VAMP2, was associated with substantial synaptic changes while in vitro electrophysiological investigations with fluorescence imaging revealed a diminished probability of vesicular release in mutants. We conclude that the synaptic efficiency of the entire subcortical brain network determines the likelihood that an animal transitions from one vigilance state to the next.

neuroscience↗

bioRxiv2019

Loss of Bardet-Biedl syndrome proteins causes synaptic aberrations in principal neurons

Bardet-Biedl syndrome (BBS), a ciliopathy, is a rare genetic condition characterised by retina degeneration, obesity, kidney failure and cognitive impairment. In spite of a progress made in general understanding of BBS aetiology, the molecular mechanism of cognitive impairment remains elusive. Here we report that loss of Bardet-Biedl syndrome proteins causes synaptic dysfunction in principal neurons providing possible explanation for cognitive impairment phenotype in BBS patients. Using synaptosomal proteomics and immunocytochemistry we demonstrate the presence of Bbs in postsynaptic density of hippocampal neurons. Loss of Bbs results in the significant reduction of dendritic spines in principal neurons of Bbs mice models. Furthermore, we demonstrate that spine deficiency correlates with events that destabilize spine architecture, such as, impaired spine membrane receptors signalling known to be involved in the maintenance of dendritic spines. Finally, we show that voluntary exercise rescues spine deficiency in the neurons. Based on our data, we propose a model in which Bbs proteins, similar to their function in primary cilia, regulate trafficking of signalling receptors into and out of the membrane of dendritic spines, thus providing the basis for synaptic plasticity.

cell biology↗