Cajal-Retzius cells (CRs) are a neuronal population that play a central role in the development and wiring of the cerebral cortex and hippocampus. A remarkable property of CRs is their transient lifespan. Indeed, in mice, they almost completely disappear between the first and third postnatal weeks, with the exception of a subset of hippocampal CRs persisting into adulthood and integrating into hippocampal circuits. To date, the prevailing hypothesis is that their death is consequence of an atypical depolarizing response to GABAA receptors activation. Indeed, in most neurons the polarity of GABAA receptor-mediated responses shifts from depolarizing to hyperpolarizing around birth, reflecting the upregulation of the chloride extruder KCC2. This phenomenon does not occur in CRs, which maintain strikingly low levels of KCC2 expression. However, the molecular mechanisms underlying CR programmed death remain to be elucidated. Similarly, the precise function and connectivity of persistent hippocampal CRs remain unknown. In this project, we have developed two in vivo experimental approaches to begin to address these two questions. First, we showed that in utero injections of adeno-associated viruses (AAV), in combination with doxycycline administration, can be used to achieve a spatiotemporally controlled transgene expression in hippocampal CRs. This lays the foundation for future experiments expressing recombinant KCC2 in postnatal CRs, to elucidate its potential involvement in their fate. Next, we developed a method based on in utero AAV infection combined with postnatal stereotaxic infection of recombinant herpes simplex virus (HSV) to perform anterograde transsynaptic tracing of persistent CRs. This pilot study represents a fundamental step forward in identifying CR postsynaptic targets and in better understanding their contribution to hippocampal function.

Survival and synaptic integration of Cajal Retzius neurons in the hippocampus

QUESTORI, BEATRICE
2023/2024

Abstract

Cajal-Retzius cells (CRs) are a neuronal population that play a central role in the development and wiring of the cerebral cortex and hippocampus. A remarkable property of CRs is their transient lifespan. Indeed, in mice, they almost completely disappear between the first and third postnatal weeks, with the exception of a subset of hippocampal CRs persisting into adulthood and integrating into hippocampal circuits. To date, the prevailing hypothesis is that their death is consequence of an atypical depolarizing response to GABAA receptors activation. Indeed, in most neurons the polarity of GABAA receptor-mediated responses shifts from depolarizing to hyperpolarizing around birth, reflecting the upregulation of the chloride extruder KCC2. This phenomenon does not occur in CRs, which maintain strikingly low levels of KCC2 expression. However, the molecular mechanisms underlying CR programmed death remain to be elucidated. Similarly, the precise function and connectivity of persistent hippocampal CRs remain unknown. In this project, we have developed two in vivo experimental approaches to begin to address these two questions. First, we showed that in utero injections of adeno-associated viruses (AAV), in combination with doxycycline administration, can be used to achieve a spatiotemporally controlled transgene expression in hippocampal CRs. This lays the foundation for future experiments expressing recombinant KCC2 in postnatal CRs, to elucidate its potential involvement in their fate. Next, we developed a method based on in utero AAV infection combined with postnatal stereotaxic infection of recombinant herpes simplex virus (HSV) to perform anterograde transsynaptic tracing of persistent CRs. This pilot study represents a fundamental step forward in identifying CR postsynaptic targets and in better understanding their contribution to hippocampal function.
2023
Survival and synaptic integration of Cajal Retzius neurons in the hippocampus
Neuroscience
hippocampus
mouse
viral infection
transynaptic tracing
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12608/71590