Characterization of NDNF neurons in the mouse basolateral amygdala and in the primary motor cortex of a Huntington’s disease model

Mastrodicasa, Ylenia (2025): Characterization of NDNF neurons in the mouse basolateral amygdala and in the primary motor cortex of a Huntington’s disease model. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)

Abstract

The basolateral amygdala (BLA) and motor cortex (M1) are both important regions involved in the regulation of complex behaviours and both display distinct patterns of activity and cellular alterations in neurodegenerative and neuropsychiatric conditions. The BLA, is an integrative center within the amygdala, is known to regulate responses to both positive and negative stimuli by processing and modulating fear-related behaviours. While excitatory pyramidal neurons (PNs) make up most of the BLA, local inhibitory interneurons (INs) tightly control PNs activity and thus are essential in shaping BLA responses to aversive stimuli. In this study, we explore the role of neuron-derived neurotrophic factor (NDNF)-positive INs within BLA microcircuits, focusing on their activity in response to fear-related behaviours. Using in vivo Ca2+ imaging, we identified two distinct ensembles of BLANdnf neurons which show opposite activity patterns during contextual fear conditioning and exposure to the predator odour trimethylthiazoline (TMT). Optogenetic loss-of-function studies indicate that BLANdnf neuron activity promotes freezing behaviour in response to aversive stimuli, suggesting a functional role in mediating fear responses. Additionally, monosynaptic tracing reveals significant inputs from the cortical amygdala (CoA) to BLANdnf neurons, emphasising their involvement in processing odour-induced fear. Parallel to this study, we examined the role of NDNF INs in the primary motor cortex (M1) within the context of Huntington’s disease (HD), a hereditary neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms linked to progressive neurodegeneration in the cortex and striatum. In the R6/2 mouse model of HD, we used single-nuclei RNA sequencing (snRNA-seq), ex vivo patch clamp recordings, and in vivo two-photon Ca2+ imaging to investigate how NDNF INs contribute to local circuitry dysfunction over the course of HD. Transcriptomic analysis revealed that key genes associated with NDNF IN markers are downregulated at advanced disease stages in R6/2 mice compared to wild-type controls. Patch-clamp experiments indicated an increased action potential (AP) firing rate in NDNF INs within the M1 of R6/2 mice, while synaptic transmission appeared unaffected. Two-photon imaging during a running wheel task revealed increased Ca2+ activity in NDNF INs specifically at the onset of locomotion in HD mice, suggesting that these neurons may impact motor control circuits by influencing transitions between different behavioural states. In summary, this work highlights the diverse roles that NDNF INs play in modulating neural circuitry across different brain regions and contexts, from fear processing in the BLA to motor function in the M1. In the BLA, NDNF INs influence responses to negative stimuli, potentially shaping behaviour through differential activity patterns in response to fear conditioning. In the M1, NDNF INs exhibit hyperexcitability in the context of HD, which may exacerbate cortical network dysfunction as the disease progresses. These findings emphasise the importance of local inhibitory circuits in maintaining region-specific excitatory-inhibitory balance and suggest that NDNF INs may be important in both behavioural modulation and neurodegenerative diseases.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Basolateral amygdala, motor cortex, NDNF, fear, anxiety, Huntington's disease, interneurons, optogenetics, animal behavior, calcium imaging, RNA sequencing, electrophysiology
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Graduate School of Systemic Neurosciences (GSN)
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 29. April 2025
• 1. Bericht­erstatter:in: Klein, Rüdiger