Biology subjects

Rajebhosale, P.

Publications and source records attributed to Rajebhosale, P..

4 recordsLinked to original sources

bioRxiv2024

Diversification of Dentate Gyrus Granule Cell Subtypes is Regulated by Neuregulin1 Nuclear Back Signaling.

Neuronal heterogeneity is a defining feature of the developing mammalian brain, but the mechanisms regulating the diversification of closely related cell types remain elusive. In this study, we investigated the heterogeneity of dentate gyrus (DG) granule cells (GCs) and the influence of a psychosis associated V321L mutation in Neuregulin1 (Nrg1) on GC subtype composition. Using morpho-electric characterization, single-nucleus gene expression, and chromatin accessibility profiling, we identified distinct morphological and molecular features of typical GCs and a rare subtype known as semilunar granule cells (SGCs). The V321L mutation disrupts Nrg1 nuclear back-signaling, resulting in an overabundance of SGC-like cells. We discovered pseudotime gene expression trajectories suggesting the potential for GC-to-SGC transitions, supported by the accessibility of SGC-specific genes in other GCs. Intriguingly, we found an increase in SGC-marker expression over the adolescence to adulthood transition window in wild-type mice, coinciding with a decline in Nrg1 nuclear back-signaling capacity. This suggests that intact Nrg1 signaling suppresses SGC-like fate acquisition, and that its natural downregulation may underlie the emergence of SGC-like cells during postnatal development. Similarly, a pathological block of nuclear back signaling by the V321L mutation in Nrg1, may result in acquisition of the SGC-like fate due to loss of the repressive mechanisms maintained by intact nuclear back signaling. Our findings reveal a novel role for Nrg1 in maintaining DG cell-type composition and suggest that disrupted subtype regulation may contribute to disease-associated changes in DG GC morphology and function. Understanding these mechanisms provides new insights into mechanisms of cell-type diversity and its potential role in psychiatric pathology.

neuroscience↗

bioRxiv2022

Psychosis-associated Valine to Leucine mutation in Neuregulin1 disrupts expression of a schizophrenia susceptibility gene network within the hippocampus and alters adult hippocampal neurogenesis.

Neuregulin1 (Nrg1) signaling is critical for aspects of neuronal development and function from fate specification to synaptic plasticity. Type III Nrg1 is a synaptic protein which engages in bi-directional signaling with its receptor ErbB4. Forward signaling engages ErbB4 phosphorylation, whereas back signaling engages two known mechanisms: 1. local axonal PI3K-AKT signaling, and 2. cleavage by gamma secretase resulting in cytosolic release of the intracellular domain (ICD), which can traffic to the nucleus (Bao, Wolpowitz et al. 2003, Hancock, Canetta et al. 2008). To dissect the contribution of these alternate signaling strategies to neuronal development we generated a transgenic mouse with a missense mutation (V321L) in the Nrg1 transmembrane domain that disrupts nuclear back signaling with minimal effects on forward signaling or local back-signaling and was previously found to be associated with psychosis (Walss-Bass, Liu et al. 2006). We combined RNA sequencing, retroviral fate mapping of neural stem cells, behavioral analyses, and various network analyses of transcriptomic data to investigate the effect of disrupting Nrg1 nuclear back-signaling in the dentate gyrus (DG) of male and female mice. The V321L mutation impairs nuclear translocation of the Nrg1 ICD and alters gene expression in the DG. V321L mice show reduced stem cell proliferation, altered cell cycle dynamics, fate specification defects, and dendritic dysmorphogenesis. Orthologs of known schizophrenia (SCZ)-susceptibility genes were dysregulated in the V321L DG. These genes coordinated a larger network with other dysregulated genes. WGCNA and protein-interaction network analyses revealed striking similarity between DG transcriptomes of V321L mouse and humans with schizophrenia. SIGNIFICANCE STATEMENTSynaptic contact is predicted to be a regulator of the generation of nuclear signaling by Nrg1. Here we show that a schizophrenia-associated mutation in Nrg1 disrupts its ability to communicate extracellular signals to the neuronal genome which results in altered expression of a gene network enriched for orthologs of schizophrenia-susceptibility genes. The striking overlap in functional and molecular alterations between a single rare homozygous missense mutation (V321L) and schizophrenia patient data (complex polygenic and environmental burden) underscores potential convergence of rare and common variants on the same cellular and molecular phenotypes. Furthermore, our data indicate that the evolutionarily conserved gene networks that form the basis for this risk are necessary for coordinating neurodevelopmental events in the DG.

neuroscience↗

bioRxiv2021

Basal forebrain cholinergic neurons are part of the threat memory engram

Although the engagement of cholinergic signaling in threat memory is well established (Knox, 2016a), our finding that specific cholinergic neurons are requisite partners in a threat memory engram is likely to surprise many. Neurons of the basal forebrain nucleus basalis and substantia innominata (NBM/SIp) comprise the major source of cholinergic input to the basolateral amygdala (BLA), whose activation are required for both the acquisition and retrieval of cued threat memory and innate threat response behavior. The retrieval of threat memory by the presentation of the conditioning tone alone elicits acetylcholine (ACh) release in the BLA and the BLA-projecting cholinergic neurons manifest immediate early gene responses and display increased intrinsic excitability for 2-5 hours following the cue-elicited memory response to the conditioned stimulus. Silencing cue-associated engram-enrolled cholinergic neurons prevents the expression of the defensive response and the subset of cholinergic neurons activated by cue is distinct from those engaged by innate threat. Taken together we find that distinct populations of cholinergic neurons are recruited to signal distinct aversive stimuli via the BLA, demonstrating exquisite, functionally refined organization of specific types of memory within the cholinergic basal forebrain.

neuroscience↗

bioRxiv2020

Acetylcholine is released in the basolateral amygdala in response to predictors of reward and enhances learning of cue-reward contingency

The basolateral amygdala (BLA) is critical for associating initially neutral cues with appetitive and aversive stimuli and receives dense neuromodulatory acetylcholine (ACh) projections. We measured BLA ACh signaling and principal neuron activity in mice during cue-reward learning using a fluorescent ACh sensor and calcium indicators. We found that ACh levels and activity of nucleus basalis of Meynert (NBM) cholinergic terminals in the BLA (NBM-BLA) increased sharply in response to reward-related events and shifted as mice learned the tone-reward contingency. BLA principal neuron activity followed reward retrieval and moved to the reward-predictive tone after task acquisition. Optical stimulation of cholinergic NBM-BLA terminal fibers during cue-reward learning led to more rapid learning of the cue-reward contingency. These results indicate that BLA ACh signaling carries important information about salient events in cue-reward learning and provides a framework for understanding how ACh signaling contributes to shaping BLA responses to emotional stimuli.

neuroscience↗