Biology subjects

Gururajan, A.

Publications and source records attributed to Gururajan, A..

5 recordsLinked to original sources

bioRxiv2025

Cumulative pregnancy and postnatal environmental exposures impact social behaviour in male mice associated with epigenetic, ribosomal, and immune dysregulation

Environmental exposures across critical developmental windows can significantly influence brain development and contribute to the pathogenesis of neurodevelopmental disorders (NDDs). Emerging clinical evidence suggests that cumulative environmental factors during early development result in more pronounced disease phenotypes in offspring. Here, we developed a triple-hit model using C57Bl/6JAusb mice to examine the cumulative effects of antenatal social stress, antenatal chronic high-fat diet consumption, and postnatal poly(I:C) exposure on neurodevelopmental outcomes in offspring. Male triple-hit offspring displayed autism-like social deficits and an overall increased susceptibility to neurodevelopmental behavioural alterations in adulthood compared to male non-stressed controls. Conversely, these behavioural changes were not observed amongst female triple-hit offspring. Single-cell RNA (scRNA) transcriptomic and bulk proteomic sequencing were performed in male triple-hit offspring across peripheral blood immune cells and brain tissue. scRNA sequencing in microglia, astrocytes, and oligodendrocytes revealed dysregulation in critical glial cell processes, ribosomal functions, and chromatin remodelling. Similar functional themes were observed across peripheral blood macrophages, neutrophils, and naive B cells - displaying immune and ribosomal dysregulation at the transcriptional level. Proteomics pathway enrichment analyses revealed significantly reduced protein abundance in ribosomal biogenesis, translation, and chromatin remodelling functions in both peripheral blood immune cells and brain tissue. We also observed synaptic dysfunction in the blood and brain proteome. Overall, using our unique triple-hit model, we demonstrate that multiple early life environmental exposures drive NDD-associated behaviours in a sex-specific manner; and is associated with overlapping central and peripheral molecular mechanisms that have clinical relevance to NDD pathogenesis.

developmental biology↗

bioRxiv2024

High fat diet consumption and social instability stress impair stress adaptation and maternal care in C57Bl/6 mice

Poor maternal diet and psychosocial stress represent two environmental factors that can significantly impact maternal health during pregnancy. While various mouse models have been developed to study the relationship between maternal health and offspring development, few incorporate multiple sources of stress that mirror the complexity of human experiences. Maternal high-fat diet (HF) models in rodents are well-established, whereas maternal psychosocial stress models are still emerging. The social instability stress (SIS) paradigm, serves as a chronic and unpredictable form of social stress. To evaluate the combined effects of a poor maternal diet and social stress on maternal health and behaviour, we developed a novel maternal stress model in adult female C57Bl/6 mice. We observed that all HF+ mice demonstrated rapid weight gain, elevated fasting blood glucose levels and impaired glucose tolerance independent of the presence (+) or absence (-) of SIS. Behavioural testing revealed anxiety-like behaviors remained across all groups prior to pregnancy. However, we did observe a trend of poorer nest quality among all HF+ mice compared to HF-mice following nest building testing. Unlike the other HF+ and HF-stress groups, which exhibited significantly reduced plasma ACTH and corticosterone levels following SIS exposure, we did not observe this reduction in HF+/SIS+ females. In addition, HF+/SIS+ females demonstrated significant postpartum maternal neglect, resulting in fewer numbers of live offspring. These findings suggest that prolonged maternal HF diet consumption, coupled with SIS, places a significant burden on the maternal stress response system, resulting in reduced parental investment and negative postpartum behaviour towards offspring.

animal behavior and cognition↗

bioRxiv2022

Quiet wakefulness: The influence of intraperitoneal and intranasal oxytocin on sleep-wake behaviour and neurophysiology in rats.

IntroductionExogenous administration of the neuropeptide oxytocin exerts diverse effects on various neurobehavioural processes, including sleep and wakefulness. Since oxytocin can enhance attention to social and fear-related environmental cues, it should promote arousal and wakefulness. However, as oxytocin can attenuate stress, reduce activity, and elicit anxiolysis, oxytocin might also prime the brain for rest and promote sleep. At present, little research has comprehensively characterised the neuropsychopharmacology of oxytocin-induced effects on sleep-wake behaviour and no reconciliation of these two competing hypotheses has been proposed. MethodsThis study explored the effects of oxytocin on sleep-wake outcomes using radiotelemetry-based polysomnography in adult male and female Wistar rats. Oxytocin was administered via intraperitoneal (i.p.; 0.1, 0.3 and 1 mg{middle dot}kg-1) and intranasal (i.n.; 0.06, 1, 3 mg{middle dot}kg-1) routes. Caffeine (i.p. and i.n.; 10 mg{middle dot}kg-1) was administered as a wake-promoting positive control. To ascertain mechanism of action, pre-treatment experiments with the oxytocin receptor (OXTR) antagonist L-368,899 (i.p.; 5 mg{middle dot}kg-1) followed by oxytocin (i.p.; 1 mg{middle dot}kg-1) were also conducted. ResultsIn both male and female rats, i.p. oxytocin promoted quiet wakefulness at the cost of suppressing active wakefulness, NREM and REM sleep. Several i.p. oxytocin-induced sleep-wake effects were mediated by OXTR binding. In contrast, i.n. oxytocin did not alter most sleep-wake outcomes at any dose tested. Both i.p. and i.n. caffeine demonstrated wake-promoting effects. ConclusionsThese findings help reconcile competing hypotheses of oxytocin-induced effects on sleep-wake behaviour: i.p. oxytocin promotes quiet wakefulness--a state of restful environmental awareness compatible with both oxytocins anxiolytic effects and its enhancement of processing complex stimuli.

animal behavior and cognition↗

bioRxiv2021

Sex-specific transcriptomic and epitranscriptomic signatures of PTSD-like fear acquisition.

Our understanding of the molecular pathology of posttraumatic stress disorder (PTSD) is rapidly evolving and is being driven by advances in sequencing techniques. Conventional short-read RNA sequencing (RNA-seq) is a central tool in transcriptomics research that enables unbiased gene expression profiling. With the recent emergence of Oxford Nanopore direct RNA-seq (dRNA-seq), it is now also possible to interrogate diverse RNA modifications, collectively known as the epitranscriptome. Here, we present our analyses of the male and female mouse amygdala transcriptome and epitranscriptome, obtained using parallel Illumina RNA-seq and Oxford Nanopore dRNA-seq, associated with the acquisition of PTSD-like fear induced by Pavlovian cued-fear conditioning. We report significant sex-specific differences in the amygdala transcriptional response during fear acquisition, and a range of shared and dimorphic epitranscriptomic signatures. Differential RNA modifications are enriched among mRNA transcripts associated with neurotransmitter regulation and mitochondrial function, many of which have been previously implicated in PTSD. Very few differentially modified transcripts are also differentially expressed, suggesting an influential, expression-independent role for epitranscriptional regulation in PTSD-like fear-acquisition. Overall, our application of conventional and newly developed methods provides a platform for future work that will lead to new insights into and therapeutics for PTSD.

neuroscience↗

bioRxiv2021

Epitranscriptomic Dysregulation in Stress-induced Psychopathologies

To date, over 100 different chemical modifications to RNA have been identified. Collectively known as the epitranscriptome, these modifications function to regulate RNA stability and as such, represent another mechanistic layer of post-transcriptional gene regulation. N6-methyladenosine (m6A) is the most common RNA modification in the mammalian brain and has been implicated in a number of processes relevant to neurodevelopment, brain function and behaviour. Here, following brief descriptions on epitranscriptomic mechanisms, we will review the literature on the potential functions of the m6A-methylome in fine-tuning gene expression which include prescribing localisation of transcripts in distal compartments as well as interactions with microRNAs and long non-coding RNAs. We will then discuss findings from rodent and human studies for stress-induced disorders - major depression and post-traumatic stress disorder - which support a hypothesis for a dysregulation of the m6A-methylome and the m6A-machinery in the pathophysiology. To support this, we have included a bioinformatic analysis of publicly available single-cell RNA-sequencing and bulk transcriptomics datasets which suggests an altered m6A-methylome as a consequence of dysregulated cell- and regionally-specific expression of key enzymes involved in the writing, reading and erasing of m6A. We hope this review will generate further interest in the field of epitranscriptomics, opening up new lines of research into its involvement in psychiatric disorders.

neuroscience↗