Biology subjects

Saha, P. K.

Publications and source records attributed to Saha, P. K..

5 recordsLinked to original sources

bioRxiv2025

Fast Ripple-Delta Coupling as Early Biomarker for Post-Traumatic Epileptogenesis in Repetitive Brain Injury

Traumatic brain injury (TBI) can induce post-traumatic epilepsy (PTE), but early biomarkers for epileptogenesis are lacking. We used a repetitive diffuse TBI (rdTBI) model in mice with continuous video-EEG monitoring up to 4[1/2] months post-injury to investigate electrographic biomarkers before and during post-traumatic seizure development. 25% of mice developed post-traumatic seizures with highly variable latency (5-126 days post-injury). Most significantly, we identified fast ripple-delta DOWN state coupling as an early biomarker that was detectable at 4 days post-TBI and appeared before seizure onset in all seizure-experiencing mice. This EEG signature distinguished seizure-experiencing from seizure-free TBI mice with high specificity. Power spectrum analysis revealed elevated delta and theta power, reduced physiological fast oscillations (alpha, beta, gamma) and increased pathological high-frequency oscillations (fast ripples) in seizure-experiencing animals, indicating network hyperexcitability. Spike analysis showed that while TBI itself increased cortical excitability, seizure onset triggered a dramatic further escalation in interictal activity. These electrographic signatures were remarkably consistent across all seizure-experiencing animals regardless of single or recurrent seizure pattern. Our results demonstrate that fast ripple-delta coupling represents a promising early biomarker detectable at 4 days post-TBI, before seizure onset, offering potential for early identification of post-traumatic seizure susceptibility. Importantly, this biomarker identified all seizure-prone animals regardless of whether they developed single or recurrent seizures, suggesting shared underlying mechanisms and clinical relevance for any post-traumatic seizure occurrence. These findings emphasize the utility of temporal EEG analysis for detecting early electrographic changes in post-traumatic epileptogenesis and may inform future intervention strategies. Key PointsO_LIFast ripple-delta DOWN state coupling was detectable as early as 4 days post-TBI and appeared before seizure onset in seizure-experiencing mice, representing the first early biomarker that can stratify animals for epileptogenesis risk during the critical latent period. C_LIO_LIDelta and theta power increased while alpha, beta and gamma power decreased in all seizure-experiencing mice post-TBI, creating a consistent electrographic signature regardless of whether animals developed single or recurrent seizures. C_LIO_LIFast ripples were elevated and gamma-to-HFO ratios were reduced in seizure-experiencing mice, reflecting network hyperexcitability shift and potential inhibitory dysfunction that preceded seizure onset. C_LIO_LISeizure onset triggered a 3-fold escalation in spike activity, while baseline spike differences between TBI and pre-seizure mice were not significant, highlighting the limitation of spike counts alone as predictive biomarkers during the latent period. C_LIO_LIElectrographic signatures were almost similar across all seizure patterns (single and recurrent), suggesting shared underlying mechanisms of network dysfunction, though larger studies are needed to determine if biomarkers can predict seizure frequency in addition to seizure susceptibility. C_LI

neuroscience↗

bioRxiv2022

Circadian clock control of MRTF-SRF signaling suppresses beige adipocyte thermogenic recruitment

The morphological transformation of adipogenic progenitors into mature adipocytes requires dissolution of cytoskeleton driven by progressive loss of MRTF-SRF activity. Circadian clock confers temporal control in adipogenic differentiation, and MRTF-SRF inhibits beige adipocyte development. Here we identify that key components of the actin cytoskeleton-MRTF/SRF signaling cascade are direct transcriptional targets of circadian clock, and a clock-MRTF/SRF regulatory axis suppresses beige adipocyte thermogenic recruitment. Genetic loss- or gain-of-functions of the core clock regulator, Brain and Muscle Arnt-like 1 (Bmal1), altered actin cytoskeleton organization, cell shape and SRF activity. Genes involved in actin dynamic-MRTF-SRF pathway display diurnal expression profiles in beige adipose tissue, with identification of Bmal1 direct transcriptional regulation. Using beige adipocyte-selective genetic models together with pharmacological approaches, we demonstrate that Bmal1 inhibits beige adipogenesis and thermogenic capacity via the MRTF-SRF pathway. Selective ablation of Bmal1 induced beigeing, whereas its targeted overexpression attenuated the beige thermogenic program resulting in obesity. Collectively, our findings define a novel circadian clock control in actin cytoskeleton-MRTF-SRF signaling that suppresses beige adipogenesis to maintain metabolic homeostasis.

cell biology↗

bioRxiv2020

Ubc9 deletion in adipocytes causes lipoatrophy in mice

ObjectiveWhite adipose tissue (WAT) expansion regulates energy balance and overall metabolic homeostasis. WAT absence or loss occurring through lipodystrophy and lipoatrophy contributes to the development of dyslipidemia, hepatic steatosis, and insulin resistance. We previously demonstrated the sole small ubiquitin-like modifier (SUMO) E2-conjuguating enzyme Ubc9 represses human adipocyte differentiation. Germline and other tissue-specific deletions of Ubc9 frequently cause lethality in mice. As a result, the role of Ubc9 during WAT development remains unknown. MethodsTo determine how Ubc9 impacts body composition and energy balance, we generated adipocyte-specific Ubc9 knockout mice (Ubc9a-KO). CRISPR/Cas9 gene editing inserted loxP sites flanking exons 3 and 4 at the Ubc9 locus. Subsequent genetic crosses to AdipoQ-Cre transgenic mice allowed deletion of Ubc9 in white and brown adipocytes. We measured multiple metabolic endpoints that describe energy balance and carbohydrate metabolism in Ubc9a-KO and littermate controls during postnatal growth. ResultsTo our surprise, Ubc9a-KO mice developed hyperinsulinemia and hepatic steatosis. Global energy balance defects emerged from dysfunctional WAT marked by pronounced local inflammation, loss of serum adipokines, hepatomegaly, and near absence of major adipose tissue depots. We observed progressive lipoatrophy that commences in the early adolescent period. ConclusionsOur results demonstrate that Ubc9 expression in mature adipocytes is essential for maintaining WAT expansion. Deletion of Ubc9 in fat cells compromised and diminished adipocyte function that provoked WAT inflammation and ectopic lipid accumulation in the liver. Our findings reveal an indispensable role for Ubc9 during white adipocyte expansion and endocrine control of energy balance.

developmental biology↗

bioRxiv2020

Loss of Bone Morphogenetic Protein-binding Endothelial Regulator Causes Insulin Resistance

Accumulating evidence suggests chronic inflammation of metabolic tissues plays a causal role in obesity-induced insulin resistance. Yet, how specific endothelial factors exert impacts in metabolic tissues remains undefined. Bone morphogenetic protein (BMP)–binding endothelial regulator (BMPER) adapts endothelial cells to inflammatory stress in diverse organ microenvironments. Here we demonstrate BMPER is a driver of insulin sensitivity. Inducible knockout (iKO) of BMPER causes hyperinsulinemia, glucose intolerance and insulin resistance without increasing inflammation in metabolic tissues. Interestingly, BMPER can directly activate insulin signaling, which requires its internalization and interaction with Niemann-Pick C1 (NPC1), an integral membrane protein that transports intracellular cholesterol. These results suggest the endocrine function of the vascular endothelium maintains glucose homeostasis. Of potential clinical significance, the delivery of BMPER recombinant protein or its overexpression significantly alleviates insulin resistance and hyperglycemia in high-fat diet (HFD)-fed mice and Leprdb/db (db/db) diabetic mice. We conclude that BMPER exhibits therapeutic potential for the treatment of diabetes.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pathology↗

bioRxiv2019

3dSpAn: an interactive software for 3D segmentation and analysis of dendritic spines

Three dimensional segmentation and analysis of dendritic spines involve two major challenges: 1) how to segment individual spines from the dendrites and 2) how to quantitatively assess the morphology of individual spines. We developed a software named 3dSpAn to address these two issues by implementing our previously published 3D multiscale opening algorithm in shared intensity space and using effective morphological features for individual dendritic spine plasticity analysis. 3dSpAn consists of four modules: Preprocessing and ROI selection, Intensity thresholding and seed selection, Multiscale segmentation and Quantitative morphological feature extraction. We show the results of segmentation and morphological analysis for different observation methods, including in vitro and ex vivo imaging with confocal microscopy, and in vivo samples, using high-resolution two-photon microscopy. The software is freely available, the source code, windows installer, the software manual and video tutorial can be obtained from: https://sites.google.com/view/3dSpAn/.

neuroscience↗