Biology subjects

Harwell, C. C.

Publications and source records attributed to Harwell, C. C..

5 recordsLinked to original sources

bioRxiv2025

Mu opioid receptor mRNA and protein localization across the rat and mouse habenula

The habenula (Hb) has high intensity mu opioid binding and receptor (MOR) expression. It contains medial and lateral subdivisions (MHb and LHb, respectively), yet the details of MOR localization across these regions remains debated. MHb and LHb participate in largely non-overlapping neural circuits, therefore accurately resolving MOR expression across them is critical for understanding how MOR ligands impact behaviors. Here we utilized in situ hybridization (ISH) and immunocytochemistry (ICC) to systematically map Oprm1 mRNA and MOR protein throughout the habenular complex. We studied rat and mouse tissue to evaluate expression across two common research species. We also performed parallel mapping in Oprm1-Venus/Venus mice. Importantly, we found mRNA and protein in both MHb and LHb in both species. In rat, 39 {+/-} 3% and 21 {+/-} 4% of cells expressed Oprm1 in MHb and LHb, respectively. These proportions were greater in mouse: 57 {+/-} 1% (MHb) and 32 {+/-} 4% (LHb). Oprm1 puncta per positive cell were greater in MHb compared to LHb for both rat and mouse (p < 0.0001). The highest intensity labeling was localized along the lateral edge of the MHb for all methods. ICC showed MOR localized to fibers and somata in both regions. In LHb, MOR labeling was most dense in intermediate sections along the anterior-posterior (AP) axis. In rats we also observed greater labeling in dorsal LHb at intermediate AP levels and medial LHb more posteriorly. These results indicate that both MHb and LHb can contribute to MOR mediated actions through their respective circuits. Key PointsO_LIMu opioid receptor mRNA and protein are expressed in both the medial and lateral habenulae in rat and mouse. C_LIO_LIIn the medial habenula, most mu opioid receptor mRNA and protein was detected along its lateral border. C_LIO_LIAcross samples, Oprm1+ cells in the MHb contained more mRNA puncta per cell compared to lateral habenula cells. C_LI

neuroscience↗

bioRxiv2023

Developmental origin and local signals cooperate to determine septal astrocyte identity

Astrocyte specification during development is influenced by both intrinsic and extrinsic factors, but the precise contribution of each remains poorly understood. Here we show that septal astrocytes from Nkx2.1 and Zic4 expressing progenitor zones are allocated into non-overlapping domains of the medial (MS) and lateral septal nuclei (LS) respectively. Astrocytes in these areas exhibit distinctive molecular and morphological features tailored to the unique cellular and synaptic circuit environment of each nucleus. Using single-nucleus (sn) RNA sequencing, we trace the developmental trajectories of cells in the septum and find that neurons and astrocytes undergo region and developmental stage-specific local cell-cell interactions. We show that expression of the classic morphogens Sonic hedgehog (Shh) and Fibroblast growth factors (Fgfs) by MS and LS neurons respectively, functions to promote the molecular specification of local astrocytes in each region. Finally, using heterotopic cell transplantation, we show that both morphological and molecular specifications of septal astrocytes are highly dependent on the local microenvironment, regardless of developmental origins. Our data highlights the complex interplay between intrinsic and extrinsic factors shaping astrocyte identities and illustrates the importance of the local environment in determining astrocyte functional specialization.

neuroscience↗

bioRxiv2023

A developmentally defined population of neurons in the lateral septum controls responses to aversive stimuli

When interacting with their environment, animals must balance exploratory and defensive behavior to evaluate and respond to potential threats. The lateral septum (LS) is a structure in the ventral forebrain that calibrates the magnitude of behavioral responses to stress-related external stimuli, including the regulation of threat avoidance. The complex connectivity between the LS and other parts of the brain, together with its largely unexplored neuronal diversity, makes it difficult to understand how defined LS circuits control specific behaviors. Here, we describe a mouse model where the deletion of the transcriptional regulator Prdm16 in cells with a common developmental origin (Nkx2.1-lineage) results in the almost complete ablation of neurons from this lineage in the LS. Using a combination of single-nucleus RNA sequencing, histological and electrophysiological methods and behavioral analyses, we discovered that Crhr2-expresssing neurons are specifically affected in mutant mice, resulting in connectivity and electrophyisiological defects. This neuronal population is specifically activated in stressful contexts, and its removal results in increased exploratory behavior, even under stressful conditions. Our study extends the current knowledge about how defined neuronal populations within the LS can evaluate contextual information to select appropriate behavioral responses. This is a necessary step towards understanding the crucial role that the LS plays in neuropsychiatric conditions where defensive behavior is dysregulated, such as anxiety and aggression disorders.

neuroscience↗

bioRxiv2021

Transcriptional profiling of sequentially generated septal neuron fates

The septum is a ventral forebrain structure known to regulate innate behaviors. During embryonic development, septal neurons are produced in multiple proliferative areas from neural progenitors following transcriptional programs that are still largely unknown. Here, we use a combination of single cell RNA sequencing, histology and genetic models to address how septal neuron diversity is established during neurogenesis. We find that the transcriptional profiles of septal progenitors change along neurogenesis, coinciding with the generation of distinct neuron types. We characterize the septal eminence, a spatially distinct and transient proliferative zone composed of progenitors with distinctive molecular profiles, proliferative capacity and fate potential compared to the rostral septal progenitor zone. We show that Nkx2.1-expressing septal eminence progenitors give rise to neurons belonging to at least three morphological classes, born in temporal cohorts that are distributed across different septal nuclei in a sequential fountain-like pattern. Our study provides insight into the molecular programs that control the sequential production of different neuronal types in the septum, a structure with important roles in regulating mood and motivation.

neuroscience↗

bioRxiv2020

Cortical ChAT+ neurons co-transmit acetylcholine and GABA in a target- and brain-region specific manner

The cerebral cortex contains neurons that express choline acetyltransferase (ChAT) and are a potential local source of acetylcholine. However, the neurotransmitters released by cortical ChAT+ neurons and their synaptic connectivity are unknown. We show that the nearly all cortical ChAT+ neurons are specialized VIP+ interneurons that release GABA strongly onto other inhibitory interneurons and acetylcholine sparsely onto layer 1 interneurons and other VIP+/ChAT+ interneurons. This differential transmission of ACh and GABA based on the postsynaptic target neuron is reflected in VIP+/ChAT+ interneuron pre-synaptic terminals, as quantitative molecular analysis shows that only a subset of these are specialized to release acetylcholine. In addition, we identify a separate, sparse population of non-VIP ChAT+ neurons in the medial prefrontal cortex with a distinct developmental origin that robustly release acetylcholine in layer 1. These results demonstrate both cortex-region heterogeneity in cortical ChAT+ interneurons and target-specific co-release of acetylcholine and GABA.

neuroscience↗