Glia-to-interneuron conversion in the postnatal mouse cerebral cortex

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Interneurons modulate and synchronise local network activity, which is essential for establishing balance of excitatory-inhibitory activity in the brain. Defects among distinct interneuron populations are associated with numerous neuropsychiatric disorders. Engineering induced neurons (iNs) from other resident brain cells emerges as an innovative strategy to replace lost or dysfunctional neurons and restore function in brain regions devoid of intrinsic regenerative capacity. In this study, I aimed at generating glia-derived interneuron-like cells in the postnatal mouse cerebral cortex via transcription factor-mediated lineage reprogramming.

Here, I showed that Ascl1SA6, a phospho-site mutant form of Ascl1 in which six serine-proline sites subject to phosphorylation were mutated, exhibited enhanced neurogenic activity during in vivo glia-to-neuron conversion. In addition, co-expression of Ascl1SA6 together with other reprogramming factors, such as Bcl2 or Dlx2, boosted the reprogramming efficiency and generated a remarkable proportion of GABAergic-like iNs. A fraction of Ascl1SA6 and Bcl2-derived iNs acquired hallmarks of parvalbumin (PV) interneurons, such as the expression of PV interneuron-specific markers as well as acquisition of fast-spiking firing properties. Using robust fate-mapping strategies, I unambiguously demonstrated that iNs originated from glial cells, with astrocytes being the main starting cell population from which iNs were generated. Finally, I found that PV-like iNs were missing some morphological and molecular features of mature endogenous PV interneurons. Aiming at promoting iNs maturation, I developed a strategy to selectively activate iNs upon inducible chemogenetic stimulation, opening new avenues to study activity-dependent modulation of iNs during lineage reprogramming.

Taken together, this study sheds light on the molecular cues and regulatory mechanisms necessary to induce glial fate switch towards an interneuron identity in the postnatal mouse cerebral cortex. Hence, this work provides solid basis for future work aiming at replacing dysfunctional fast-spiking PV interneurons as an innovative therapeutic approach to treat neuropsychiatric disorders.

Date of Award1 Feb 2024
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorBenedikt Berninger (Supervisor) & Juan Burrone (Supervisor)

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